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Paul E. Schoen
Guest
Guest
Fri Feb 12, 2010 3:18 am
"David Eather" <eather_at_tpg.com.au> wrote in message
news:VMOdnQ-MerwJIe7WnZ2dnUVZ_tP_fwAA_at_supernews.com...
Quote:
Paul E. Schoen wrote:
I had one of those cheap cassette recorders, and it worked OK. But I had
an 8-track tape player in my car and I wanted to be able to record, so I
built an AC bias circuit (I think mine was 40 kHz), using a circuit that
I found in an old databook. It incorporated the RIAA non-linear
amplitude curve as well. I also made a device which used a cheap
turntable and crystal pickup, with two J-FET (2N3819) linear amplifiers
and VU meters.
Didn't all that stuff make the car hard to drive?
I had one of those cheap cassette recorders, and it worked OK. But I had
an 8-track tape player in my car and I wanted to be able to record, so I
built an AC bias circuit (I think mine was 40 kHz), using a circuit that
I found in an old databook. It incorporated the RIAA non-linear
amplitude curve as well. I also made a device which used a cheap
turntable and crystal pickup, with two J-FET (2N3819) linear amplifiers
and VU meters.
Didn't all that stuff make the car hard to drive?
Not at all. My car was a 1965 Chevy Malibu that was good on the curves.
Most importantly, it had a Class A driver :)
Paul
pimpom
Guest
Guest
Fri Feb 12, 2010 9:04 am
Paul E. Schoen wrote:
Quote:
"David Eather" <eather_at_tpg.com.au> wrote in message
news:VMOdnQ-MerwJIe7WnZ2dnUVZ_tP_fwAA_at_supernews.com...
Paul E. Schoen wrote:
I had one of those cheap cassette recorders, and it worked
OK. But
I had an 8-track tape player in my car and I wanted to be
able to
record, so I built an AC bias circuit (I think mine was 40
kHz),
using a circuit that I found in an old databook. It
incorporated
the RIAA non-linear amplitude curve as well. I also made a
device
which used a cheap turntable and crystal pickup, with two
J-FET
(2N3819) linear amplifiers and VU meters.
Didn't all that stuff make the car hard to drive?
Not at all. My car was a 1965 Chevy Malibu that was good on the
curves. Most importantly, it had a Class A driver :)
Was the driver good on curves _inside_ the car?
news:VMOdnQ-MerwJIe7WnZ2dnUVZ_tP_fwAA_at_supernews.com...
Paul E. Schoen wrote:
I had one of those cheap cassette recorders, and it worked
OK. But
I had an 8-track tape player in my car and I wanted to be
able to
record, so I built an AC bias circuit (I think mine was 40
kHz),
using a circuit that I found in an old databook. It
incorporated
the RIAA non-linear amplitude curve as well. I also made a
device
which used a cheap turntable and crystal pickup, with two
J-FET
(2N3819) linear amplifiers and VU meters.
Didn't all that stuff make the car hard to drive?
Not at all. My car was a 1965 Chevy Malibu that was good on the
curves. Most importantly, it had a Class A driver :)
Was the driver good on curves _inside_ the car?
Jon Kirwan
Guest
Guest
Wed Feb 17, 2010 5:28 am
On Thu, 11 Feb 2010 17:51:27 +1000, David Eather
<eather_at_tpg.com.au> wrote:
Quote:
snip
It is not a big stress. You can always use the junk-box transformer and
if it really isn't suitable replace it latter. For your consideration -
the RMS power of even compressed samples of music is only about 20% of
the peak.
There are a few variations on that figure. RCA did a lot of research in
the area and found that Radio broadcasts of compressed FM signals of
"Rock Music" - an undefined term, was the most demanding at 15%. Some
companies are trying to redefine that. IRF who call the same figure 1/8
of max power (12.5%) - which just happens to make their newest audio
mosfets look really good. It might be the other way around. They may
really believe it, and designed the mosfets to match. I forget where but
some group stated the 20% figure with respect to new modern music
styles. IIRC they were regarded as technically competent in the area and
had no axe to grind or wheelbarrow to push - so I filed the info away.
In any case an overestimate leads to a more conservative design and 5%
is not much. I'd be wary of definition of "modern music" too - badly
played organ music can be a stream of full amplitude waveforms that only
change in frequency at random intervals.
I'd use the junk box transformer and forget about allowing for the
electricity company slackness and just choose good sized caps that are a
reasonable price. I think a learning experience allows for a little
compromise.
It is not a big stress. You can always use the junk-box transformer and
if it really isn't suitable replace it latter. For your consideration -
the RMS power of even compressed samples of music is only about 20% of
the peak.
There are a few variations on that figure. RCA did a lot of research in
the area and found that Radio broadcasts of compressed FM signals of
"Rock Music" - an undefined term, was the most demanding at 15%. Some
companies are trying to redefine that. IRF who call the same figure 1/8
of max power (12.5%) - which just happens to make their newest audio
mosfets look really good. It might be the other way around. They may
really believe it, and designed the mosfets to match. I forget where but
some group stated the 20% figure with respect to new modern music
styles. IIRC they were regarded as technically competent in the area and
had no axe to grind or wheelbarrow to push - so I filed the info away.
In any case an overestimate leads to a more conservative design and 5%
is not much. I'd be wary of definition of "modern music" too - badly
played organ music can be a stream of full amplitude waveforms that only
change in frequency at random intervals.
I'd use the junk box transformer and forget about allowing for the
electricity company slackness and just choose good sized caps that are a
reasonable price. I think a learning experience allows for a little
compromise.
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
I take a little issue with your use of terms in this phrase,
"RMS power of even compressed samples of music is only about
20% of the peak." Power is average and I don't think RMS
applies to power. Volts-to-power is a squared-phenomenon. So
are amps-to-power. RMS makes sense for those two. But power
is an average (integrated Joules divided by time.)
So I believe I have to interpret your meaning as suggesting
that the short-term power required (also an average of some
ill-defined kind, I suppose) when playing music can be a
factor of 5 times more than its long-term average power. You
also mentioned a figure as low as 12.5%, which would suggest
a factor of 8 used as a margin instead of 5.
But a requirement to support short-term power levels is
really just a compliance requirement on the power supply
rails, isn't it?
So put another way, if I wanted a long-term average of 10W
output and I wanted the extra margins required to support the
worst case estimate of a factor of 8 for short-term power
bursts, then I'd need to design rails that support a voltage
compliance level substantially higher. The parts would need
to withstand it, too. And because of the much higher rail
voltages that need to be dropped most of the time, the output
BJTs would need to have just that much more capacity to
dissipate.
Or put still another way, assuming that my output swing at
the output stage emitters cannot exceed a magnitude of 15V
and that everything is sized for dissipating 10W, does this
mean the amplifier is a 10W amplifier that can support a peak
of 14W=(15^2/(2*
)? (Which isn't so good, considering your
comments above regarding "music?")
What is meant when one says, '10 watts?'
This gets worse when I consider the class of operation,
doesn't it? I mean, class-B might be specified as 10W into 8
ohms, but wouldn't that be 20W into 4 ohms? But if class-A,
it's pretty much 10W no matter what?
I'm beginning to imagine amplifiers should be specified as to
their peak output voltage compliance into 8, 6, and 4 ohms;
instantaneous and sustained without damage to the unit. For
example, 35V into 8 ohms instantaneous, 15V sustained. Or
80W instantaneous, 15W sustained. That way, someone might
have some knowledge about how well it might handle _their_
music at, say, 15W average power. And could compare that
against another unit specified as 20V into 8 ohms, 15V
sustained.
How does one know what they are buying? What a headache.
Jon
Jon Kirwan
Guest
Guest
Wed Feb 17, 2010 5:30 am
On Tue, 16 Feb 2010 20:28:30 -0800, I wrote:
Quote:
20V into 8 ohms, 15V sustained.
I mean "20V instantaneous into 8 ohms, 15V sustained."
Jon
Paul E. Schoen
Guest
Guest
Wed Feb 17, 2010 10:20 pm
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Quote:
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
I take a little issue with your use of terms in this phrase,
"RMS power of even compressed samples of music is only about
20% of the peak." Power is average and I don't think RMS
applies to power. Volts-to-power is a squared-phenomenon. So
are amps-to-power. RMS makes sense for those two. But power
is an average (integrated Joules divided by time.)
So I believe I have to interpret your meaning as suggesting
that the short-term power required (also an average of some
ill-defined kind, I suppose) when playing music can be a
factor of 5 times more than its long-term average power. You
also mentioned a figure as low as 12.5%, which would suggest
a factor of 8 used as a margin instead of 5.
But a requirement to support short-term power levels is
really just a compliance requirement on the power supply
rails, isn't it?
So put another way, if I wanted a long-term average of 10W
output and I wanted the extra margins required to support the
worst case estimate of a factor of 8 for short-term power
bursts, then I'd need to design rails that support a voltage
compliance level substantially higher. The parts would need
to withstand it, too. And because of the much higher rail
voltages that need to be dropped most of the time, the output
BJTs would need to have just that much more capacity to
dissipate.
Or put still another way, assuming that my output swing at
the output stage emitters cannot exceed a magnitude of 15V
and that everything is sized for dissipating 10W, does this
mean the amplifier is a 10W amplifier that can support a peak
of 14W=(15^2/(2*
)? (Which isn't so good, considering your
comments above regarding "music?")
What is meant when one says, '10 watts?'
This gets worse when I consider the class of operation,
doesn't it? I mean, class-B might be specified as 10W into 8
ohms, but wouldn't that be 20W into 4 ohms? But if class-A,
it's pretty much 10W no matter what?
I'm beginning to imagine amplifiers should be specified as to
their peak output voltage compliance into 8, 6, and 4 ohms;
instantaneous and sustained without damage to the unit. For
example, 35V into 8 ohms instantaneous, 15V sustained. Or
80W instantaneous, 15W sustained. That way, someone might
have some knowledge about how well it might handle _their_
music at, say, 15W average power. And could compare that
against another unit specified as 20V into 8 ohms, 15V
sustained.
How does one know what they are buying? What a headache.
Yes, as an extension of what (I think) Mark Twain said, there are lies,
damn lies, statistics, and specifications. Then there is the matter of
testing. An amplifier is a complex entity and its performance depends on
the power supply, the load, its components, environmental conditions, and
the nature of the signal being applied. So it may seem fair to level the
playing field by testing with a pure sine wave at certain frequencies and
determining that it maintains a certain level of maximum distortion without
overheating or shutting down over an extended period of time in a
controlled environment.
But in real life there are many more factors involved, and the actual
performance in an individual situation may vary widely. Power is indeed an
average function, but the ability to provide power involves efficiency and
a duty-cycle rated function of maximum temperature of components, and also
the ability of the power supply to maintain a certain voltage level for
long enough to "ride out" brief peaks in the signal of typical music.
The power that can be supplied to various loads depends largely on
impedance matching. But most solid state amplifiers are capable of
supplying a certain amount of current, so if it is optimized for eight
ohms, it may be able to provide even less continuous power at 4 ohms, but
possibly more peak power.
You have brought up some good points. But for most purposes, an amplifier
rated conservatively at 10W continuous power should be plenty for home
music listening. When pushed beyond its normal limits, much depends on how
the amplifier handles overloads, and your personal threshold of annoyance
when the inevitable distortion occurs.
Paul
Jon Kirwan
Guest
Guest
Wed Feb 17, 2010 11:10 pm
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
<paul_at_peschoen.com> wrote:
Quote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
I take a little issue with your use of terms in this phrase,
"RMS power of even compressed samples of music is only about
20% of the peak." Power is average and I don't think RMS
applies to power. Volts-to-power is a squared-phenomenon. So
are amps-to-power. RMS makes sense for those two. But power
is an average (integrated Joules divided by time.)
So I believe I have to interpret your meaning as suggesting
that the short-term power required (also an average of some
ill-defined kind, I suppose) when playing music can be a
factor of 5 times more than its long-term average power. You
also mentioned a figure as low as 12.5%, which would suggest
a factor of 8 used as a margin instead of 5.
But a requirement to support short-term power levels is
really just a compliance requirement on the power supply
rails, isn't it?
So put another way, if I wanted a long-term average of 10W
output and I wanted the extra margins required to support the
worst case estimate of a factor of 8 for short-term power
bursts, then I'd need to design rails that support a voltage
compliance level substantially higher. The parts would need
to withstand it, too. And because of the much higher rail
voltages that need to be dropped most of the time, the output
BJTs would need to have just that much more capacity to
dissipate.
Or put still another way, assuming that my output swing at
the output stage emitters cannot exceed a magnitude of 15V
and that everything is sized for dissipating 10W, does this
mean the amplifier is a 10W amplifier that can support a peak
of 14W=(15^2/(2*)? (Which isn't so good, considering your
comments above regarding "music?")
What is meant when one says, '10 watts?'
This gets worse when I consider the class of operation,
doesn't it? I mean, class-B might be specified as 10W into 8
ohms, but wouldn't that be 20W into 4 ohms? But if class-A,
it's pretty much 10W no matter what?
I'm beginning to imagine amplifiers should be specified as to
their peak output voltage compliance into 8, 6, and 4 ohms;
instantaneous and sustained without damage to the unit. For
example, 35V into 8 ohms instantaneous, 15V sustained. Or
80W instantaneous, 15W sustained. That way, someone might
have some knowledge about how well it might handle _their_
music at, say, 15W average power. And could compare that
against another unit specified as 20V into 8 ohms, 15V
sustained.
How does one know what they are buying? What a headache.
Yes, as an extension of what (I think) Mark Twain said, there are lies,
damn lies, statistics, and specifications. Then there is the matter of
testing. An amplifier is a complex entity and its performance depends on
the power supply, the load, its components, environmental conditions, and
the nature of the signal being applied. So it may seem fair to level the
playing field by testing with a pure sine wave at certain frequencies and
determining that it maintains a certain level of maximum distortion without
overheating or shutting down over an extended period of time in a
controlled environment.
But in real life there are many more factors involved, and the actual
performance in an individual situation may vary widely. Power is indeed an
average function, but the ability to provide power involves efficiency and
a duty-cycle rated function of maximum temperature of components, and also
the ability of the power supply to maintain a certain voltage level for
long enough to "ride out" brief peaks in the signal of typical music.
The power that can be supplied to various loads depends largely on
impedance matching. But most solid state amplifiers are capable of
supplying a certain amount of current, so if it is optimized for eight
ohms, it may be able to provide even less continuous power at 4 ohms, but
possibly more peak power.
You have brought up some good points. But for most purposes, an amplifier
rated conservatively at 10W continuous power should be plenty for home
music listening. When pushed beyond its normal limits, much depends on how
the amplifier handles overloads, and your personal threshold of annoyance
when the inevitable distortion occurs.
Paul
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
I take a little issue with your use of terms in this phrase,
"RMS power of even compressed samples of music is only about
20% of the peak." Power is average and I don't think RMS
applies to power. Volts-to-power is a squared-phenomenon. So
are amps-to-power. RMS makes sense for those two. But power
is an average (integrated Joules divided by time.)
So I believe I have to interpret your meaning as suggesting
that the short-term power required (also an average of some
ill-defined kind, I suppose) when playing music can be a
factor of 5 times more than its long-term average power. You
also mentioned a figure as low as 12.5%, which would suggest
a factor of 8 used as a margin instead of 5.
But a requirement to support short-term power levels is
really just a compliance requirement on the power supply
rails, isn't it?
So put another way, if I wanted a long-term average of 10W
output and I wanted the extra margins required to support the
worst case estimate of a factor of 8 for short-term power
bursts, then I'd need to design rails that support a voltage
compliance level substantially higher. The parts would need
to withstand it, too. And because of the much higher rail
voltages that need to be dropped most of the time, the output
BJTs would need to have just that much more capacity to
dissipate.
Or put still another way, assuming that my output swing at
the output stage emitters cannot exceed a magnitude of 15V
and that everything is sized for dissipating 10W, does this
mean the amplifier is a 10W amplifier that can support a peak
of 14W=(15^2/(2*
)? (Which isn't so good, considering your
comments above regarding "music?")
What is meant when one says, '10 watts?'
This gets worse when I consider the class of operation,
doesn't it? I mean, class-B might be specified as 10W into 8
ohms, but wouldn't that be 20W into 4 ohms? But if class-A,
it's pretty much 10W no matter what?
I'm beginning to imagine amplifiers should be specified as to
their peak output voltage compliance into 8, 6, and 4 ohms;
instantaneous and sustained without damage to the unit. For
example, 35V into 8 ohms instantaneous, 15V sustained. Or
80W instantaneous, 15W sustained. That way, someone might
have some knowledge about how well it might handle _their_
music at, say, 15W average power. And could compare that
against another unit specified as 20V into 8 ohms, 15V
sustained.
How does one know what they are buying? What a headache.
Yes, as an extension of what (I think) Mark Twain said, there are lies,
damn lies, statistics, and specifications. Then there is the matter of
testing. An amplifier is a complex entity and its performance depends on
the power supply, the load, its components, environmental conditions, and
the nature of the signal being applied. So it may seem fair to level the
playing field by testing with a pure sine wave at certain frequencies and
determining that it maintains a certain level of maximum distortion without
overheating or shutting down over an extended period of time in a
controlled environment.
But in real life there are many more factors involved, and the actual
performance in an individual situation may vary widely. Power is indeed an
average function, but the ability to provide power involves efficiency and
a duty-cycle rated function of maximum temperature of components, and also
the ability of the power supply to maintain a certain voltage level for
long enough to "ride out" brief peaks in the signal of typical music.
The power that can be supplied to various loads depends largely on
impedance matching. But most solid state amplifiers are capable of
supplying a certain amount of current, so if it is optimized for eight
ohms, it may be able to provide even less continuous power at 4 ohms, but
possibly more peak power.
You have brought up some good points. But for most purposes, an amplifier
rated conservatively at 10W continuous power should be plenty for home
music listening. When pushed beyond its normal limits, much depends on how
the amplifier handles overloads, and your personal threshold of annoyance
when the inevitable distortion occurs.
Paul
It sure has been an education, so far. Now I am beginning to
understand the technical motivation for LOTS of rails and the
ability to select between them (perhaps automatically) in
those fancy-pants amplifier designs; dropping in (or out)
stacked BJTs as needed. Though I am loathe to even attempt
thinking more about them.
.....
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
Jon
pimpom
Guest
Guest
Thu Feb 18, 2010 10:02 pm
Jon Kirwan wrote:
Quote:
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
.............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
.............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at
mains frequency.
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for
Class B. Add some mAs for the driver stages. That's slightly more
than 0.25A each for diodes in full-wave rectification. The
ubiquitous 1N4002 to 1N4007 rated for 1 Amp diodes will do fine.
They differ only in the maximum reverse voltage ratings and cost
almost the same. As a matter of convenience, I stock only the
1000-volt 1N4007. At less than 2 cents US each retail, I buy them
in batches of hundreds at a time.
Quote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple
and load regulation. I divide the full supply dc voltage with the
current at maximum output. This gives the equivalent dc load as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the order
of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
Jon Kirwan
Guest
Guest
Thu Feb 18, 2010 10:54 pm
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
<pimpom_at_invalid.invalid> wrote:
Quote:
Jon Kirwan wrote:
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at
mains frequency.
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at
mains frequency.
Thanks. That had certainly crossed my mind as I was writing.
I just wanted to be sure I hadn't missed something important.
Quote:
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for
Class B. Add some mAs for the driver stages. That's slightly more
than 0.25A each for diodes in full-wave rectification. The
ubiquitous 1N4002 to 1N4007 rated for 1 Amp diodes will do fine.
They differ only in the maximum reverse voltage ratings and cost
almost the same. As a matter of convenience, I stock only the
1000-volt 1N4007. At less than 2 cents US each retail, I buy them
in batches of hundreds at a time.
Class B. Add some mAs for the driver stages. That's slightly more
than 0.25A each for diodes in full-wave rectification. The
ubiquitous 1N4002 to 1N4007 rated for 1 Amp diodes will do fine.
They differ only in the maximum reverse voltage ratings and cost
almost the same. As a matter of convenience, I stock only the
1000-volt 1N4007. At less than 2 cents US each retail, I buy them
in batches of hundreds at a time.
I pull them out of CFL lamps before disposal. So they are
"free" to me. I've quite a few, now. 1200V PIV, I think.
Way overkill. But free. I'll use them.
Quote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple
and load regulation. I divide the full supply dc voltage with the
current at maximum output. This gives the equivalent dc load as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the order
of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple
and load regulation. I divide the full supply dc voltage with the
current at maximum output. This gives the equivalent dc load as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the order
of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
So I'm settled on those particulars, now. The only thing I
don't have, right now, are the caps. Well, maybe. I just
found a 2.2mF, 35V cap. So that gives me one. I've got all
kinds of 200V caps, up to about 470uF. But still looking for
one more 'something close' on the order of 35-50V. I'll keep
looking through the junk box some more. Might turn up
another one.
If so, I then need to figure out all the mounting stuff for
the hardware. I have the AC plugs and grommets and fuse
holders. I can also pull a transorb out of the junk box
(from those CFL lamps, again.) The transformer doesn't have
any brackets or mounting holes in the laminated steel core so
I will have to fashion one from a simple strap of metal,
drilled out. Then to wire it all up and do the smoke test
and verify the output, with and without a load on it.
There and done, I'm ready to move on.
Thanks,
Jon
pimpom
Guest
Guest
Thu Feb 18, 2010 11:59 pm
Jon Kirwan wrote:
Quote:
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
Rules of thumb are often based on previous mathematical
derivations, as it was in this case. However, after having done
umpteen calculations where absolute precision is not needed, the
novelty wears off after some time and one tends to be satisfied
with being able to intuitively predict the outcome within a per
cent or so without actually putting anything on paper. It's been
firmly etched in my mind for 40 years that 1000uF has a reactance
of 1.5815 ohms (usually taken as 1.6) at 100Hz (twice the mains
frequency here) and I quickly derive Xc for other values from
that within a second. Then I mentally divide the equivalent DC
resistance of a load (not necessarily an audio amplifier) with
that reactance and have a good idea of what to expect in terms of
ripple voltage amplitude, regulation, DC voltage, peak diode
current, rms transformer current, etc.
Heck, it's past 4 am over here. Time for bed. Bye.
Paul E. Schoen
Guest
Guest
Fri Feb 19, 2010 12:24 am
"pimpom" <pimpom_at_invalid.invalid> wrote in message
news:hlk96n$6g8$1_at_news.albasani.net...
Quote:
Jon Kirwan wrote:
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at mains
frequency.
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for Class B.
Add some mAs for the driver stages. That's slightly more than 0.25A each
for diodes in full-wave rectification. The ubiquitous 1N4002 to 1N4007
rated for 1 Amp diodes will do fine. They differ only in the maximum
reverse voltage ratings and cost almost the same. As a matter of
convenience, I stock only the 1000-volt 1N4007. At less than 2 cents US
each retail, I buy them in batches of hundreds at a time.
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at mains
frequency.
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for Class B.
Add some mAs for the driver stages. That's slightly more than 0.25A each
for diodes in full-wave rectification. The ubiquitous 1N4002 to 1N4007
rated for 1 Amp diodes will do fine. They differ only in the maximum
reverse voltage ratings and cost almost the same. As a matter of
convenience, I stock only the 1000-volt 1N4007. At less than 2 cents US
each retail, I buy them in batches of hundreds at a time.
At one time I had two reels of 5000 each of 1N4004 that I got surplus, but
I sold most of them. I also have a bag of about 1000 pieces of 1N4003. So I
have pretty much a lifetime supply. Either one is OK for 120 VAC mains and
perfect for lower voltage applications. But now my new designs are mostly
SMT. I was going to keep the thru holes and use the "free" parts I had, but
I figured that the labor cost of inserting, soldering, and clipping leads
on 6 diodes on 40 boards might be more than the $0.06 each for the S1G SMT
diodes. Once a commitment is made to SMT it is usually cost-effective to
use as many such parts as possible. I never fully analyzed it, though. I
figure about 2 minutes for the six diodes. At $60/hr, or $1/minute, I spend
$2/board for the leaded parts. The SMT assembly is probably $0.05 per part,
so I spend a total of $0.66 per board.
Quote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple and load
regulation. I divide the full supply dc voltage with the current at
maximum output. This gives the equivalent dc load as seen by the power
supply. In the sample design under consideration, that's roughly 30 ohms
on each side of the split supply. Calculate the reactance of the filter
capacitor at the pulsating dc frequency which is twice the mains
frequency for full-wave. My rule of thumb is to get an R/Xc ratio of the
order of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
Some time ago I came up with a rule of thumb of 1000 uF per amp, and I
revised that to 2000 uF per amp. I used an RC time constant of 8 mSec
between peaks for a 37% discharge from peak which holds the approximate RMS
value, and for a typical 8 VDC power supply at 1 amp R=8 ohms. So C =
..008/8 = 1000 uF. But two time constants gives only 13% discharge so 2000
uF is much better. For a 16 VDC supply, 1000 uF is OK, and as the voltage
doubles the required capacitance is halved. So for most low voltage
applications, 1000 to 2000 uF per amp is reasonable, and easy to remember.
Of course, if you enjoy mathematical analysis, you can spend time working
out effects of winding resistance and capacitor ESR and acceptable ripple.
Or you can just use LTSpice. But if I need a quick and dirty junkbox power
supply, 1000 uF/amp is good enough to grab and go.
For example, using LTSpice, I find a 12.6 V transformer and I want to make
a 12 VDC power supply at 1 amp. Using a 1000 uF capacitor and a 12 ohm
load, my output is 13.3 V which has a peak of 16.1 V and drops to 10.4 V,
which is a 35% drop as predicted. With 2000 uF it drops to 12.6 VDC so my
output is high enough to provide the 12 VDC I wanted with a regulator. Of
course there are line variations and transformer regulation, but not bad
for a quick estimate.
If I wanted 24 VDC, and I had a 25.2 V transformer, a 1000 uF capacitor
gives me a minimum of 26 VDC for a regulator with a little bit of headroom.
Now I actually add a simple emitter follower voltage regulator with a
2N3055 and two 12 V zeners and a diode in series, with 220 ohms and a 100
uF cap. I get an output of 24.18 VDC which varies from 23.99 VDC to 24.30
VDC. Adding the regulator improves the minimum voltage excursion on the
1000 uF main filter capacitor to 27.6 VDC.
Since I was originally designing for just such a regulated power supply, my
"grab-and-go" estimates for main filter capacitors seems to work out quite
well. And I found it more fun to build and test the circuit using LTSpice
rather than with math. Filter capacitors of this size are typically -20% /
+80% tolerance, so chances are the results will be even better than
expected.
Paul
Jon Kirwan
Guest
Guest
Fri Feb 19, 2010 7:19 am
On Fri, 19 Feb 2010 04:17:22 +0530, "pimpom"
<pimpom_at_invalid.invalid> wrote:
Quote:
Jon Kirwan wrote:
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
Rules of thumb are often based on previous mathematical
derivations, as it was in this case.
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at the
pulsating dc frequency which is twice the mains frequency for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
Rules of thumb are often based on previous mathematical
derivations, as it was in this case.
Don't mistake me. All I meant to say is that I _am_ new and
therefore took a slower approach, not having developed the
well worn ruts from good experience as you have done. And
that I enjoyed seeing your way of cutting through it.
Quote:
However, after having done
umpteen calculations where absolute precision is not needed, the
novelty wears off after some time and one tends to be satisfied
with being able to intuitively predict the outcome within a per
cent or so without actually putting anything on paper.
umpteen calculations where absolute precision is not needed, the
novelty wears off after some time and one tends to be satisfied
with being able to intuitively predict the outcome within a per
cent or so without actually putting anything on paper.
I think I clearly understood exactly that from your writing.
Quote:
It's been
firmly etched in my mind for 40 years that 1000uF has a reactance
of 1.5815 ohms (usually taken as 1.6) at 100Hz (twice the mains
frequency here) and I quickly derive Xc for other values from
that within a second. Then I mentally divide the equivalent DC
resistance of a load (not necessarily an audio amplifier) with
that reactance and have a good idea of what to expect in terms of
ripple voltage amplitude, regulation, DC voltage, peak diode
current, rms transformer current, etc.
Heck, it's past 4 am over here. Time for bed. Bye.
firmly etched in my mind for 40 years that 1000uF has a reactance
of 1.5815 ohms (usually taken as 1.6) at 100Hz (twice the mains
frequency here) and I quickly derive Xc for other values from
that within a second. Then I mentally divide the equivalent DC
resistance of a load (not necessarily an audio amplifier) with
that reactance and have a good idea of what to expect in terms of
ripple voltage amplitude, regulation, DC voltage, peak diode
current, rms transformer current, etc.
Heck, it's past 4 am over here. Time for bed. Bye.
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
Jon
Paul E. Schoen
Guest
Guest
Fri Feb 19, 2010 8:43 am
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:buasn5pd2p5vs3uppunegtjcq8rfk8f3m1_at_4ax.com...
Quote:
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
I can't speak for pimpom but I don't think any offense has been taken.
There are many ways to approach any problem and sometimes "quick and dirty"
is appropriate while other times a careful mathematical approach
considering all factors is required. There are some areas of mathematics
where my eyes glaze over and it becomes gobble-de-gook, while I can design
a circuit in my head and visualize currents and voltages and waveforms
which can then be verified and improved by using a tool such as LTSpice.
Previous to that I would rely on actual breadboard circuits and using test
equipment (with a good understanding of its limitations) to see how it
performs.
Also, I think this thread has about run its course, and it may be time to
start a new one. It has now morphed into power supply design (as it applies
to audio amps), and it seems to be more suited to sci.electronics.design.
You may consider yourself a beginner but your theoretical knowledge and
mathematical analysis is beyond the range of basics. It seems that your
lack of direct experience and practical "knack" will soon pass as you build
and test a hands-on circuit.
My main criticism would be that you tend to limit yourself too much by
using scavenged parts and freebies in a junkbox. I tend to do that myself,
and often wind up with an inferior design or one that acts abnormally
because perhaps a part is damaged or is not really the best choice given
the wide range of new devices available. And, unless your budget is
severely crimped, you can order new parts with guaranteed specs that will
result in a more predictable and satisfactory outcome, and if it is a
worthwhile design, others may use the same parts and benefit from your
work.
I have an old power supply right here that I built when I was in high
school and I've been itching to rebuild it to be more useful. But it has a
pair of 2N1540 transistors and a pair of 2N554 and two 450 uF 50 V metal
can capacitors and an RT-204 "Selenium Rectifier Type" transformer and a
1N2976B stud mount 12V zener, and the meters are 0-10 VDC and 0-3 Amps. I
no longer have the schematic and what I've been able to trace does not seem
to make much sense to me now. It is nicely packaged in a Bud Portacab but
I'd really like to have at least 0-15 VDC and more like 5 amps and better
regulation and current limiting rather than the crude 3 amp fuse it has
now. So should I use these old obsolete parts (those are Germanium
transistors!), and make compromises to get it working again or should I
design from scratch and make it do what I really want or do I just put it
back in the junk pile and buy what I'd like for a hundred bucks or so? If I
could just get it working OK in a few hours I could live with the limited
output, and maybe I could add a x2 switch so I can get 0-20V with the same
meter, or I could make a new scale and change the internal resistor, or...
so I wind up with one or two days work and I talk myself out of it again...
Paul
Jon Kirwan
Guest
Guest
Fri Feb 19, 2010 10:30 am
On Thu, 18 Feb 2010 18:24:21 -0500, "Paul E. Schoen"
<paul_at_peschoen.com> wrote:
Quote:
"pimpom" <pimpom_at_invalid.invalid> wrote in message
news:hlk96n$6g8$1_at_news.albasani.net...
Jon Kirwan wrote:
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at mains
frequency.
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for Class B.
Add some mAs for the driver stages. That's slightly more than 0.25A each
for diodes in full-wave rectification. The ubiquitous 1N4002 to 1N4007
rated for 1 Amp diodes will do fine. They differ only in the maximum
reverse voltage ratings and cost almost the same. As a matter of
convenience, I stock only the 1000-volt 1N4007. At less than 2 cents US
each retail, I buy them in batches of hundreds at a time.
At one time I had two reels of 5000 each of 1N4004 that I got surplus, but
I sold most of them. I also have a bag of about 1000 pieces of 1N4003. So I
have pretty much a lifetime supply. Either one is OK for 120 VAC mains and
perfect for lower voltage applications. But now my new designs are mostly
SMT. I was going to keep the thru holes and use the "free" parts I had, but
I figured that the labor cost of inserting, soldering, and clipping leads
on 6 diodes on 40 boards might be more than the $0.06 each for the S1G SMT
diodes. Once a commitment is made to SMT it is usually cost-effective to
use as many such parts as possible. I never fully analyzed it, though. I
figure about 2 minutes for the six diodes. At $60/hr, or $1/minute, I spend
$2/board for the leaded parts. The SMT assembly is probably $0.05 per part,
so I spend a total of $0.66 per board.
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple and load
regulation. I divide the full supply dc voltage with the current at
maximum output. This gives the equivalent dc load as seen by the power
supply. In the sample design under consideration, that's roughly 30 ohms
on each side of the split supply. Calculate the reactance of the filter
capacitor at the pulsating dc frequency which is twice the mains
frequency for full-wave. My rule of thumb is to get an R/Xc ratio of the
order of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
Some time ago I came up with a rule of thumb of 1000 uF per amp, and I
revised that to 2000 uF per amp. I used an RC time constant of 8 mSec
between peaks for a 37% discharge from peak which holds the approximate RMS
value, and for a typical 8 VDC power supply at 1 amp R=8 ohms. So C =
.008/8 = 1000 uF. But two time constants gives only 13% discharge so 2000
uF is much better. For a 16 VDC supply, 1000 uF is OK, and as the voltage
doubles the required capacitance is halved. So for most low voltage
applications, 1000 to 2000 uF per amp is reasonable, and easy to remember.
news:hlk96n$6g8$1_at_news.albasani.net...
Jon Kirwan wrote:
On Wed, 17 Feb 2010 16:20:40 -0500, "Paul E. Schoen"
paul_at_peschoen.com> wrote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:kvlmn5dhciv4c51a0au32qi52rjnl67sro_at_4ax.com...
Okay. I'm back to the power supply, again. (I'm convinced
that my junkbox unit will work fine -- I think it can hold
maybe 18V minimum under load on each rail. Which seems more
than enough headroom for 12.7V, plus output stage overhead.
....
............<snip>.............
Now, I want axial leaded diodes for the bridge. From
simulating a load of 8 ohms, 1kHz, average power of 10W, and
my secondary winding resistance of 2.6 ohms, I'm finding that
each diode suffers under a quarter watt of dissipation. So,
any recommendations about diodes? Obviously, for a one-off,
cost is not really an issue. How important is 'fast
recovery'? (Outside of its impact on dissipation.) Seems
that anything with 100V or better for reverse voltage
standoff, 1/4 watt or better, should work. Leakage probably
isn't that important (except against as it may add to
dissipation.)
Fast recovery is not important here since the diodes work at mains
frequency.
10W sinusoidal into 8 ohms = 1.58A peak = 0.503A dc average for Class B.
Add some mAs for the driver stages. That's slightly more than 0.25A each
for diodes in full-wave rectification. The ubiquitous 1N4002 to 1N4007
rated for 1 Amp diodes will do fine. They differ only in the maximum
reverse voltage ratings and cost almost the same. As a matter of
convenience, I stock only the 1000-volt 1N4007. At less than 2 cents US
each retail, I buy them in batches of hundreds at a time.
At one time I had two reels of 5000 each of 1N4004 that I got surplus, but
I sold most of them. I also have a bag of about 1000 pieces of 1N4003. So I
have pretty much a lifetime supply. Either one is OK for 120 VAC mains and
perfect for lower voltage applications. But now my new designs are mostly
SMT. I was going to keep the thru holes and use the "free" parts I had, but
I figured that the labor cost of inserting, soldering, and clipping leads
on 6 diodes on 40 boards might be more than the $0.06 each for the S1G SMT
diodes. Once a commitment is made to SMT it is usually cost-effective to
use as many such parts as possible. I never fully analyzed it, though. I
figure about 2 minutes for the six diodes. At $60/hr, or $1/minute, I spend
$2/board for the leaded parts. The SMT assembly is probably $0.05 per part,
so I spend a total of $0.66 per board.
I'm expecting to use caps on the order of perhaps 2.2mF 50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad I
can make it while seeing what that means for the output. And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of ripple and load
regulation. I divide the full supply dc voltage with the current at
maximum output. This gives the equivalent dc load as seen by the power
supply. In the sample design under consideration, that's roughly 30 ohms
on each side of the split supply. Calculate the reactance of the filter
capacitor at the pulsating dc frequency which is twice the mains
frequency for full-wave. My rule of thumb is to get an R/Xc ratio of the
order of 50 for a medium quality amp. Your choice of 2200uF agrees well
with this.
Some time ago I came up with a rule of thumb of 1000 uF per amp, and I
revised that to 2000 uF per amp. I used an RC time constant of 8 mSec
between peaks for a 37% discharge from peak which holds the approximate RMS
value, and for a typical 8 VDC power supply at 1 amp R=8 ohms. So C =
.008/8 = 1000 uF. But two time constants gives only 13% discharge so 2000
uF is much better. For a 16 VDC supply, 1000 uF is OK, and as the voltage
doubles the required capacitance is halved. So for most low voltage
applications, 1000 to 2000 uF per amp is reasonable, and easy to remember.
Okay.
Quote:
Of course, if you enjoy mathematical analysis, you can spend time working
out effects of winding resistance and capacitor ESR and acceptable ripple.
out effects of winding resistance and capacitor ESR and acceptable ripple.
I suppose what I don't enjoy is taking on faith "rules" or
"prepared charts" I'm handed. So I do the math once or
twice, just to verify and make sure I have a small sense of
understanding about the whys and wherefores. (And I enjoy
the math practice, from time to time.)
Quote:
Or you can just use LTSpice.
Once I feel I grasp the theory I will use LTspice a lot and
not give it that much thought later on. But isn't it better
to make sure, at least once
Quote:
But if I need a quick and dirty junkbox power
supply, 1000 uF/amp is good enough to grab and go.
supply, 1000 uF/amp is good enough to grab and go.
And I think I understand the details why. (Unless someone
expresses an interest, I won't dump it out here.)
Quote:
For example, using LTSpice, I find a 12.6 V transformer and I want to make
a 12 VDC power supply at 1 amp. Using a 1000 uF capacitor and a 12 ohm
load, my output is 13.3 V which has a peak of 16.1 V and drops to 10.4 V,
which is a 35% drop as predicted. With 2000 uF it drops to 12.6 VDC so my
output is high enough to provide the 12 VDC I wanted with a regulator. Of
course there are line variations and transformer regulation, but not bad
for a quick estimate.
a 12 VDC power supply at 1 amp. Using a 1000 uF capacitor and a 12 ohm
load, my output is 13.3 V which has a peak of 16.1 V and drops to 10.4 V,
which is a 35% drop as predicted. With 2000 uF it drops to 12.6 VDC so my
output is high enough to provide the 12 VDC I wanted with a regulator. Of
course there are line variations and transformer regulation, but not bad
for a quick estimate.
As I just wrote, once I've done it in the "forward direction"
and feel I understand the details well enough, once or twice,
just selecting rules to follow after that make sense. If
something doesn't feel right in the simulation, you can
always return to the fundamentals on paper to double-check.
But I don't like using a tool in a fashion where I have no
clue whatsoever how to check the work on my own, should I
decide to do so. Doesn't feel right. (You are past that
point, of course, so no problem there.)
Quote:
If I wanted 24 VDC, and I had a 25.2 V transformer, a 1000 uF capacitor
gives me a minimum of 26 VDC for a regulator with a little bit of headroom.
Now I actually add a simple emitter follower voltage regulator with a
2N3055 and two 12 V zeners and a diode in series, with 220 ohms and a 100
uF cap. I get an output of 24.18 VDC which varies from 23.99 VDC to 24.30
VDC. Adding the regulator improves the minimum voltage excursion on the
1000 uF main filter capacitor to 27.6 VDC.
Since I was originally designing for just such a regulated power supply, my
"grab-and-go" estimates for main filter capacitors seems to work out quite
well. And I found it more fun to build and test the circuit using LTSpice
rather than with math. Filter capacitors of this size are typically -20% /
+80% tolerance, so chances are the results will be even better than
expected.
gives me a minimum of 26 VDC for a regulator with a little bit of headroom.
Now I actually add a simple emitter follower voltage regulator with a
2N3055 and two 12 V zeners and a diode in series, with 220 ohms and a 100
uF cap. I get an output of 24.18 VDC which varies from 23.99 VDC to 24.30
VDC. Adding the regulator improves the minimum voltage excursion on the
1000 uF main filter capacitor to 27.6 VDC.
Since I was originally designing for just such a regulated power supply, my
"grab-and-go" estimates for main filter capacitors seems to work out quite
well. And I found it more fun to build and test the circuit using LTSpice
rather than with math. Filter capacitors of this size are typically -20% /
+80% tolerance, so chances are the results will be even better than
expected.
Thanks. And I got it.
Jon
Jon Kirwan
Guest
Guest
Fri Feb 19, 2010 11:00 am
On Fri, 19 Feb 2010 02:43:12 -0500, "Paul E. Schoen"
<paul_at_peschoen.com> wrote:
Quote:
"Jon Kirwan" <jonk_at_infinitefactors.org> wrote in message
news:buasn5pd2p5vs3uppunegtjcq8rfk8f3m1_at_4ax.com...
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
I can't speak for pimpom but I don't think any offense has been taken.
news:buasn5pd2p5vs3uppunegtjcq8rfk8f3m1_at_4ax.com...
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
I can't speak for pimpom but I don't think any offense has been taken.
I wasn't sure and I knew I didn't want any mistake there. It
doesn't hurt to clarify, just in case.
Quote:
There are many ways to approach any problem and sometimes "quick and dirty"
is appropriate while other times a careful mathematical approach
considering all factors is required. There are some areas of mathematics
where my eyes glaze over and it becomes gobble-de-gook, while I can design
a circuit in my head and visualize currents and voltages and waveforms
which can then be verified and improved by using a tool such as LTSpice.
Previous to that I would rely on actual breadboard circuits and using test
equipment (with a good understanding of its limitations) to see how it
performs.
is appropriate while other times a careful mathematical approach
considering all factors is required. There are some areas of mathematics
where my eyes glaze over and it becomes gobble-de-gook, while I can design
a circuit in my head and visualize currents and voltages and waveforms
which can then be verified and improved by using a tool such as LTSpice.
Previous to that I would rely on actual breadboard circuits and using test
equipment (with a good understanding of its limitations) to see how it
performs.
I study some new piece of mathematics as often as I'm able.
It's the language of science, so to speak. And it is very
difficult to "read" a science paper with good understanding
without it. I'm slogging through a book on atmospheric and
oceanic fluid dynamics -- can't read a single decent science
paper on the subject without getting some understanding of
the basics, which I'm finding 'hard.' But I'm slogging
through it. Only way to get to the other end.
...............
Quote:
Also, I think this thread has about run its course, and it may be time to
start a new one.
start a new one.
I'm okay with that.
Quote:
It has now morphed into power supply design (as it applies
to audio amps), and it seems to be more suited to sci.electronics.design.
to audio amps), and it seems to be more suited to sci.electronics.design.
I think I'm closing in on the end of that section, now. I
think I know mostly what parts to use, and why to use them. I
suppose there is always another consideration to take, that I
might have missed. But fuse placement, transorb use, and a
few other details aren't that hard.
What I need to think about a little more is organizing the
approach towards the end-point. I need to explore several
different types of output stages, for learning's purpose. Not
because I'll need all of them in the end. Just to make sure
I've got the salient details understood. Then, I make a
decision there. Finally, I need to figure out how I'm going
to include a microcontroller and external volume control
widget that meets my _real_ needs and move forward from
there.
I'm planning a year for getting there. No rush.
A project after that is re-designing the front panel of a
microwave oven. But that is yet another story.
Quote:
You may consider yourself a beginner
I do.
Quote:
but your theoretical knowledge and
mathematical analysis is beyond the range of basics.
mathematical analysis is beyond the range of basics.
It's just like being good at typing fast. Useless, if you
don't have any idea what you want to write about. Great, if
you do.
So I can type? I need to get to the point where I have some
story worth telling.
Quote:
It seems that your lack of direct experience and practical
"knack" will soon pass as you build and test a hands-on circuit.
"knack" will soon pass as you build and test a hands-on circuit.
I can hope. I'm the kind that likes to "measure twice, cut
once," though.
When I designed my son's house, it was my _first_ ever
attempt. I had never studied a single architecture book,
never computed beam loading, etc. That was last spring.
Since then, I've discovered that there is ONLY ONE really
good book targeted squarely at people like me -- those
without prior, formal architecture training. (If interested,
I'd be glad to talk about that book.) I then did perform
those calculations and designed a gambrel roof I wanted for
the balloon framed structure and ran over to the planning
departments for an ear-full. I took into account the
required 80MPH side wind loads on the broadest side, with a
3' snow load at the same time, as well. And the rest. I
also read large sections of the NEC (adopted with slight
modifications by Oregon) and did my own Ufer ground for the
home (and a grounding well) and even had an interesting
discussion with the county electrician about what I
considered to be the stupidest part of the NEC -- the
allowance "as code" of a 20' #4 bare copper wire in the same
wet sponge cement as iron rebar. I chose NOT to do that. But
the funny part of the discussion was that the county official
broke protocol and started asking _me_ to help him understand
some problems he encountered!!! I was able to, by the way!
The result is fantastic. And worth the effort. And I
learned a lot, too.
But in no way did I want to build that darned thing twice!!
You better believe it! So I made VERY sure of every step and
asked for advice, even when people felt I should not be doing
this work myself. The gambrel roof is such a case, because
code required it to be signed off by a licensed professional.
Got that done, of course. But I did the work. All of it.
Quote:
My main criticism would be that you tend to limit yourself too much by
using scavenged parts and freebies in a junkbox.
using scavenged parts and freebies in a junkbox.
Well, this is part of a learning experience, right now. If
and when I decide to finalize and generate the final unit for
my daughter, in a year or so, I will use new parts and make
it more professional-looking. Right now, I'm not there.
Quote:
I tend to do that myself,
and often wind up with an inferior design or one that acts abnormally
because perhaps a part is damaged or is not really the best choice given
the wide range of new devices available. And, unless your budget is
severely crimped, you can order new parts with guaranteed specs that will
result in a more predictable and satisfactory outcome, and if it is a
worthwhile design, others may use the same parts and benefit from your
work.
and often wind up with an inferior design or one that acts abnormally
because perhaps a part is damaged or is not really the best choice given
the wide range of new devices available. And, unless your budget is
severely crimped, you can order new parts with guaranteed specs that will
result in a more predictable and satisfactory outcome, and if it is a
worthwhile design, others may use the same parts and benefit from your
work.
Hehe. Unless I get some of those "fake" parts that I saw
pimpom also discussing in a different thread! ;)
But of course I also take your point, too.
Quote:
I have an old power supply right here that I built when I was in high
school and I've been itching to rebuild it to be more useful. But it has a
pair of 2N1540 transistors and a pair of 2N554 and two 450 uF 50 V metal
can capacitors and an RT-204 "Selenium Rectifier Type"
school and I've been itching to rebuild it to be more useful. But it has a
pair of 2N1540 transistors and a pair of 2N554 and two 450 uF 50 V metal
can capacitors and an RT-204 "Selenium Rectifier Type"
(I extracted some selenium rectifiers from an old WW II radar
set. VR-150 tubes, as well. Selsyn motors. Lots of very
interesting stuff. I very much know what they look like!)
Quote:
transformer and a
1N2976B stud mount 12V zener, and the meters are 0-10 VDC and 0-3 Amps. I
no longer have the schematic and what I've been able to trace does not seem
to make much sense to me now. It is nicely packaged in a Bud Portacab but
I'd really like to have at least 0-15 VDC and more like 5 amps and better
regulation and current limiting rather than the crude 3 amp fuse it has
now. So should I use these old obsolete parts (those are Germanium
transistors!), and make compromises to get it working again or should I
design from scratch and make it do what I really want or do I just put it
back in the junk pile and buy what I'd like for a hundred bucks or so? If I
could just get it working OK in a few hours I could live with the limited
output, and maybe I could add a x2 switch so I can get 0-20V with the same
meter, or I could make a new scale and change the internal resistor, or...
so I wind up with one or two days work and I talk myself out of it again...
1N2976B stud mount 12V zener, and the meters are 0-10 VDC and 0-3 Amps. I
no longer have the schematic and what I've been able to trace does not seem
to make much sense to me now. It is nicely packaged in a Bud Portacab but
I'd really like to have at least 0-15 VDC and more like 5 amps and better
regulation and current limiting rather than the crude 3 amp fuse it has
now. So should I use these old obsolete parts (those are Germanium
transistors!), and make compromises to get it working again or should I
design from scratch and make it do what I really want or do I just put it
back in the junk pile and buy what I'd like for a hundred bucks or so? If I
could just get it working OK in a few hours I could live with the limited
output, and maybe I could add a x2 switch so I can get 0-20V with the same
meter, or I could make a new scale and change the internal resistor, or...
so I wind up with one or two days work and I talk myself out of it again...
Hehe. Well, I think I explained my perspective for now. I'm
just learning, at this stage, so the random parts are fine.
Same with the amplifier. I think I can learn _about_
amplifiers plenty good enough even if I'm using poor quality
parts. In fact, I might learn some diagnostic tricks along
the way, using them. And maybe get lost a few times, too.
But what the heck? That's a good way to learn, too.
Jon
pimpom
Guest
Guest
Fri Feb 19, 2010 7:25 pm
Jon Kirwan wrote:
Quote:
On Fri, 19 Feb 2010 04:17:22 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF
50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad
I
can make it while seeing what that means for the output.
And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage
with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at
the
pulsating dc frequency which is twice the mains frequency
for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
Rules of thumb are often based on previous mathematical
derivations, as it was in this case.
Don't mistake me. All I meant to say is that I _am_ new and
therefore took a slower approach, not having developed the
well worn ruts from good experience as you have done. And
that I enjoyed seeing your way of cutting through it.
However, after having done
umpteen calculations where absolute precision is not needed,
the
novelty wears off after some time and one tends to be
satisfied
with being able to intuitively predict the outcome within a
per
cent or so without actually putting anything on paper.
I think I clearly understood exactly that from your writing.
It's been
firmly etched in my mind for 40 years that 1000uF has a
reactance
of 1.5815 ohms (usually taken as 1.6) at 100Hz (twice the
mains
frequency here) and I quickly derive Xc for other values from
that within a second. Then I mentally divide the equivalent DC
resistance of a load (not necessarily an audio amplifier) with
that reactance and have a good idea of what to expect in terms
of
ripple voltage amplitude, regulation, DC voltage, peak diode
current, rms transformer current, etc.
Heck, it's past 4 am over here. Time for bed. Bye.
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
Jon
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
On Fri, 19 Feb 2010 02:20:29 +0530, "pimpom"
pimpom_at_invalid.invalid> wrote:
Jon Kirwan wrote:
I'm expecting to use caps on the order of perhaps 2.2mF
50V,
to be secure about the rails. But I expect to want to play
with that, once everything is working, to see just how bad
I
can make it while seeing what that means for the output.
And
then see if I can calculate a prediction that isn't too far
from those results, on paper.
I have my own rule of thumb here for acceptable levels of
ripple
and load regulation. I divide the full supply dc voltage
with
the
current at maximum output. This gives the equivalent dc load
as
seen by the power supply. In the sample design under
consideration, that's roughly 30 ohms on each side of the
split
supply. Calculate the reactance of the filter capacitor at
the
pulsating dc frequency which is twice the mains frequency
for
full-wave. My rule of thumb is to get an R/Xc ratio of the
order
of 50 for a medium quality amp. Your choice of 2200uF agrees
well
with this.
Thanks for your thinking on this. I used more mathy stuff to
get there, but I like your practical slice through all that.
It is easy to follow.
Rules of thumb are often based on previous mathematical
derivations, as it was in this case.
Don't mistake me. All I meant to say is that I _am_ new and
therefore took a slower approach, not having developed the
well worn ruts from good experience as you have done. And
that I enjoyed seeing your way of cutting through it.
However, after having done
umpteen calculations where absolute precision is not needed,
the
novelty wears off after some time and one tends to be
satisfied
with being able to intuitively predict the outcome within a
per
cent or so without actually putting anything on paper.
I think I clearly understood exactly that from your writing.
It's been
firmly etched in my mind for 40 years that 1000uF has a
reactance
of 1.5815 ohms (usually taken as 1.6) at 100Hz (twice the
mains
frequency here) and I quickly derive Xc for other values from
that within a second. Then I mentally divide the equivalent DC
resistance of a load (not necessarily an audio amplifier) with
that reactance and have a good idea of what to expect in terms
of
ripple voltage amplitude, regulation, DC voltage, peak diode
current, rms transformer current, etc.
Heck, it's past 4 am over here. Time for bed. Bye.
I didn't expect this and it all looks as though I may have
unintentionally implied something. If so, I hope you will
re-read what I wrote and understand that I'm merely
commenting upon my own painstaking processes, which are at
this point in time important steps for me to take, and in no
way commenting about anything you are saying (except perhaps
that I agree and otherwise like the way you thought about
it.) That's all there was there.
Thanks very much again,
Jon
If I seemed to be snapping at you, I apologise. I'd be less than
honest if I didn't admit that I was just a little bit irritated
at the time, but you weren't really the cause. I'd had a
frustrating day - no, make that a frustrating 2 weeks plus - from
being given the runaround by a component manufacturer. That and
the fact that I'm not a native user of English may have made me
sound more abrupt than I meant to be. Again, I apologise.
You and I are very similar in that I also like to dissect all the
little bits and pieces of any new ground I'm venturing into. But
I suspect that your keen desire to analyse everything in minute
detail, and the fact that you're probably better at that than a
lot of people here with more experience in applied electronics,
has put off more than one of the regulars in this NG.
elektroda.net NewsGroups Forum Index - Electronic for beginners - Discussing audio amplifier design -- BJT, discrete
