Driver to drive?

legg · May 26, 2012

On Fri, 25 May 2012 22:12:44 -0700, "Paul Hovnanian P.E."
<paul@hovnanian.com> wrote:

spamtrap1888 wrote:

On May 25, 7:28 pm, "Paul Hovnanian P.E." <p...@hovnanian.com> wrote:
I've got an axial lead polarized cap with the following markings:

1K
50V

Its about 0.1 in diam x 0.3 in long

Now, I've seen 1K as a picofarad value, which would make this a 1nF cap.
But this thing is big compared to other caps of this rating. A .001uF 1KV
ceramic is much smaller. And this doesn't make sense in the circuit its
in.

In other contexts, the K letter code defines the tolerance. But that
usually follows a three digit value code.

So, what is it that I'm looking at? The cap is bad, or I'd throw it on a
meter and figure it out.

I'm going to take a SWAG and say the K stands for Kemet.

Could there be more markings on the rest of the package, or have you
already removed it from the circuit?

Not yet removed. Its kind of stuffed between other components, so if there's
something on the bottom, I'll have to pull it to check. But I'd be
surprised to see the polarity and voltage marked on one side (along with
this mystery code) and the value marked on the other. They usually put all
these attribute markings together and part numbers elsewhere. That's what
makes me think the 1K is value.

Small parts will use the whole can. Romove one end to view full body.

RL

Paul Hovnanian P.E. · May 27, 2012

tm wrote:

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:qak0s7pmophl4v8uivt5ld1sv1dvmsrqnl@4ax.com...
On Fri, 25 May 2012 19:28:06 -0700, "Paul Hovnanian P.E."
paul@hovnanian.com> wrote:

I've got an axial lead polarized cap with the following markings:

Be thankful it has markings. I've seen parts with nothing marked on
them.

1K
50V
Its about 0.1 in diam x 0.3 in long

If it's polarized, that small, and only 50v rating, I would guess it's
an electrolytic (or possibly a tantalum) at 0.1uF 50V.

Now, I've seen 1K as a picofarad value,

It could also be in nano farads, making it a 1000nF or 0.1uF.

which would make this a 1nF cap. But
this thing is big compared to other caps of this rating. A .001uF 1KV
ceramic is much smaller. And this doesn't make sense in the circuit its
in.

ceramics are not polarized.

In other contexts, the K letter code defines the tolerance. But that
usually
follows a three digit value code.

So, what is it that I'm looking at? The cap is bad, or I'd throw it on a
meter and figure it out.

How do you know it's bad? If it leaked toxic brown goo, or sprayed
confetti everywhere, then it's probably an electrolyic. If it belched
toxic noxious fumes, it's a tantalum.
--

1000 nF is 1 uF

If it is shorted, it's probably a tantalum. If it's open, then aluminum
electrolytic.
If there was a fire, it's definitely tantalum.

Where is it in the circuit? Power supply, timing, filter???

Timing. Its in a circuit looking for more/less than 1800 RPM from an
ignition coil pickup. So I figure the ckt has a time constant of about
10mS.

That's what made me wonder about the 1K * 1pF interpretation. 1uF seems more
reasonable. Its shorted, but if its a tantalum (or whatever) its in a
current limited circuit. I don't see any external evidence of failure, but
things that go 'Bang' usually do so in low impedance circuits when they
short.

--
Paul Hovnanian mailto

aul@Hovnanian.com
------------------------------------------------------------------
This isn't right. This isn't even wrong. -- Wolfgang Pauli

Paul Hovnanian P.E. · May 27, 2012

Paul Hovnanian P.E. wrote:

spamtrap1888 wrote:

On May 25, 7:28Â pm, "Paul Hovnanian P.E." <p...@hovnanian.com> wrote:
I've got an axial lead polarized cap with the following markings:

1K
50V

Its about 0.1 in diam x 0.3 in long

Now, I've seen 1K as a picofarad value, which would make this a 1nF cap.
But this thing is big compared to other caps of this rating. A .001uF
1KV ceramic is much smaller. And this doesn't make sense in the circuit
its in.

In other contexts, the K letter code defines the tolerance. But that
usually follows a three digit value code.

So, what is it that I'm looking at? The cap is bad, or I'd throw it on a
meter and figure it out.

I'm going to take a SWAG and say the K stands for Kemet.

Could there be more markings on the rest of the package, or have you
already removed it from the circuit?

Not yet removed. Its kind of stuffed between other components, so if
there's something on the bottom, I'll have to pull it to check. But I'd be
surprised to see the polarity and voltage marked on one side (along with
this mystery code) and the value marked on the other. They usually put all
these attribute markings together and part numbers elsewhere. That's what
makes me think the 1K is value.

Its out now. Holding it with the (+) lead to the left, there are three lines
of markings:

+ NCC
+ 1K50V
+ @118

The '@' is actually a circle with letter 'M' in it.

--
Paul Hovnanian mailto

aul@Hovnanian.com
------------------------------------------------------------------
The Three Laws of Thermodynamics:
1) You can't win.
2) You can't break even.
3) You can't quit the game.

Tim Williams · May 27, 2012

"Paul Hovnanian P.E." <paul@hovnanian.com> wrote in message
news:tP6dnWMlbf2KEFzSnZ2dnUVZ_t6dnZ2d@posted.isomediainc...

Its out now. Holding it with the (+) lead to the left, there are three
lines
of markings:

+ NCC
+ 1K50V
+ @118

The '@' is actually a circle with letter 'M' in it.

Panasonic? They don't appear to advertise tantalums though.

Funny, NCC-Matsuo makes a "111" axial tantalum... don't suppose 118 was an
older series, rather than the date code one might expect there?

Anyway, it sounds like a M39003 spec dry tantalum, hermetically sealed. Not
as coveted as the M39006 wet slug types, unfortunately (which are mentioned
in either AoE or some LT appnotes as being extremely low leakage -- after a
sufficient soaking period -- and dangerously expensive!).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Jamie · May 29, 2012

Paul Hovnanian P.E. wrote:

William Sommerwerck wrote:

Might I ask whether it would be useful to determine what /type/ of
capacitor this is? That would go a long way in deciding its value.

We (the accumulated wisdom of s.e.d and s.e.r) seem to think its an aluminum
electrolytic. Long odds on a tantalum.

is it possibly a transient voltage suppresser (TVS diode)? They come in

polarized format and do have voltage and wattage mark in their part #?

The 1.5k series are 1500 watt units and the 50volt that was marked
may have been the zenering voltage...

THat value is found many times in automobile equipment to suppress the
load dumps.

Location of this component would tell alot about it. Like for example,
if it was across the DC bus line..

Just putting my two cents worth.

Jamie

Chieftain of the Carpet C · May 29, 2012

On Mon, 28 May 2012 19:50:37 -0700 (PDT), Tim Shoppa
<shoppa@trailing-edge.com> wrote:

On May 26, 1:14 am, "Paul Hovnanian P.E." <p...@hovnanian.com> wrote:
Tim Williams wrote:
Either 1uF, or the point is invisible making it 0.1?

Metal case something, or regular aluminum electrolytic? If it's not
aluminum then probably dry tantalum.

Tim

Looks like metal with a translucent, tan colored plastic covering. The
coloring could be due to aging. This thing (my truck) is about 35 years
old.

I'd vote for it being a film cap, 1K = 1000 pF = 1 nF = 0.001 uF, and
the polarizing mark indicates the outside foil.

Tim.

A far better job than the guy who guessed it at 1000 uF.

Yes, film caps are commonly marked this way as performance differs in
some circuits depending on which circuit element 'the outside foil' is
attached to.

Changes emission characteristics in some circuits too.

Tim Shoppa · May 29, 2012

On May 26, 1:14 am, "Paul Hovnanian P.E." <p...@hovnanian.com> wrote:

Tim Williams wrote:
Either 1uF, or the point is invisible making it 0.1?

Metal case something, or regular aluminum electrolytic? If it's not
aluminum then probably dry tantalum.

Tim

Looks like metal with a translucent, tan colored plastic covering. The
coloring could be due to aging. This thing (my truck) is about 35 years
old.

I'd vote for it being a film cap, 1K = 1000 pF = 1 nF = 0.001 uF, and
the polarizing mark indicates the outside foil.

Tim.

josephkk · May 29, 2012

On Fri, 25 May 2012 22:14:36 -0700, "Paul Hovnanian P.E."
<paul@hovnanian.com> wrote:

Tim Williams wrote:

Either 1uF, or the point is invisible making it 0.1?

Metal case something, or regular aluminum electrolytic? If it's not
aluminum then probably dry tantalum.

Tim

Looks like metal with a translucent, tan colored plastic covering. The
coloring could be due to aging. This thing (my truck) is about 35 years
old.

Talk about leaving out important information. For the era, 1 nF 50 V is
not unreasonable.

?-)

Jan Panteltje · Jun 1, 2012

Today a reply was posted by the researchers:
http://www.cl.cam.ac.uk/~sps32/microsemi_re.pdf

Tom Del Rosso · Jun 6, 2012

Jim Thompson wrote:

On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

--

Reply in group, but if emailing add one more
zero, and remove the last word.

Jim Thompson · Jun 6, 2012

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
<td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

Jim Thompson · Jun 6, 2012

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
<td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

The 10X impedance is a good rule-of-thumb for general hacking.

I tend to be an over-calculator, so I know every interaction.

I am blessed with an ability to "walk" circuits in my head and see
their functions (and faults) in a matter of seconds.

Pisses lots of people off, when I instantly say, "Can't be"

John Larkin · Jun 6, 2012

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
<td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

There's really no reason for that. The input impedance of a bipolar
transistor amp could be less than the output impedance of the previous
stage and you'd still get lots of gain. You'd be essentially
multiplying betas in successive stages.

In a simple chain of common-emitter amp stages, all biased at the same
current, without emitter degeneration, the 10:1 ratio isn't very
reasonable.

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

Jim Thompson · Jun 7, 2012

On Wed, 06 Jun 2012 16:49:55 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

There's really no reason for that. The input impedance of a bipolar
transistor amp could be less than the output impedance of the previous
stage and you'd still get lots of gain. You'd be essentially
multiplying betas in successive stages.

In a simple chain of common-emitter amp stages, all biased at the same
current, without emitter degeneration, the 10:1 ratio isn't very
reasonable.

Yup. And getting gain based on "multiplying betas" is an
unpredictable way to "design".

I'd probably go with an MC1552-style feedback triple to get
predictable voltage gain, but beef up the output to handle the speaker
load... although why not just roll a little power amp from the get-go?

I don't think "Dave" could cope with the usual bi-directional intercom
schemes.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice

josephkk · Jun 7, 2012

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
<td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

Well, i know of two ways to design multistage transistor amplifiers:
One starts at the beginning and starts with the required/desired input
impedance. That sets up the bias network and then the rest falls out
rather naturally. If the output voltage/current/impedance does not work
yet add another stage.
The second starts at the output requirements and proceeds to the input
requirements.
If there is noticeable excess gain in the system you can retune the stages
(with an eye toward reducing cost) or add global feedback. Global
feedback after three stages is rather risky.

?-)

Dave · Jun 7, 2012

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:72gts71tr6khe1r1tsmfghe2e8qnbt25b9@4ax.com...

On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

...Jim Thompson

Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave

Ian Field · Jun 7, 2012

"Dave" <db5151@hotmail.com> wrote in message
news:W4mdnZGyOIJJkkzSnZ2dnUVZ_qSdnZ2d@posted.internetamerica...

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote
in message news:72gts71tr6khe1r1tsmfghe2e8qnbt25b9@4ax.com...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly
higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing.
Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

...Jim Thompson

Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I
think it says a lot more about you than it does about me.

He seems to be ripping on a lot of people lately - and that's about as close
as he gets to posting on topic!

Jim Thompson · Jun 7, 2012

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" <db5151@hotmail.com> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:72gts71tr6khe1r1tsmfghe2e8qnbt25b9@4ax.com...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

...Jim Thompson

Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave

I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice

Jim Thompson · Jun 7, 2012

On Thu, 07 Jun 2012 13:42:13 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" <db5151@hotmail.com> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:72gts71tr6khe1r1tsmfghe2e8qnbt25b9@4ax.com...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous stage.
Similar. (The input impedance of the OP's stages are only slightly higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing. Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

...Jim Thompson

Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave

I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson

Ian Field · Jun 7, 2012

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:h042t7lutr0qrmfpma6v5v98ur9ncjioss@4ax.com...

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" <db5151@hotmail.com> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote
in
message news:72gts71tr6khe1r1tsmfghe2e8qnbt25b9@4ax.com...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:

Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave" <db5151@hotmail.com
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave

Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current
in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous
stage.
Similar. (The input impedance of the OP's stages are only slightly
higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing.
Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?

...Jim Thompson

Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I
think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything
as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave

I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

You declared war on JL by being a spitefull old fart.

Take care now - you're way past fighting on 2 fronts.

Driver to drive?

legg

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