THD claims of audio signal generators

Bret Ludwig wrote:

dpierce@cartchunk.org wrote:
snip
Mr. Ludwig, it is clear that you're not in the least bit interested in
dealing with the content of the article. You never read the article,
that's apparent, and you're making a load of baseless assumptions
completely irrelevant rantings.

We obviously are not communicating too well.

You have made your own self contradictions quite clear. The
issue is not one of communications, but expertise, or the
obvious lack thereof.

Frankly my entire thesis is simpler than all this: some people like to
build tube amps!

No, you stated the following, quite clearly and unambiguously:

"Subjectively tube amps of a given specification often
(not always) sound better than solid state amps of
better spec. Russ Hamm proved it in 1973 with his
paper which appeared in JAES and it has not been
contradicted."

Nothing in your statement intimates anythong about building
tube amps. Nothing. That thesis, as you stated it above, has
been shown to be incorrect. And if you did read the original
Hamm article, clearly the major point he made failed to stick,
because it was all about the performance of the amplifier
under conditions of severe clipping.

 

[Pooh Bear]

Bret Ludwig wrote:

"Don't clip the amplifier" is easy to say, and tough to do.

No !

It's ridiculously simple in fact.

Graham

 

[Don Pearce]

On Fri, 06 Jan 2006 07:12:51 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

Stewart Pinkerton wrote:

Actually, it's a piece of piss if you're using CD as a source, since
you can set system gain to sit just below clipping for 0dB FS from the
CD. That's what I do with my '50 watt' Krell.

Very true.

If you knew the settings for the cutter lathe you could do the same for vinyl too,
despite some audiophools not understanding this point ( they think it has unlimited
dynamic range it seems ! ).

Graham

But it is different for every disc - the point with CD is that you can
set it once and forget it.

d

Pearce Consulting
http://www.pearce.uk.com

 

[Pooh Bear]

Bret Ludwig wrote:

"Don't clip the amplifier" is easy to say, and tough to do.

Wrong. It's easy if you know how.

Totally
avoiding amplifier clipping under any and all circumstnaces requires
either active power compression control (i.e. "Power Guard")

Not necessarilily. What's this 'power guard' anyway ? Some audiophoolery I expect.
Pro-audio amps have had signal limiters to avoid clipping for *decades*. Including
the cutting lathe amplifiers that made the vinyl !

or a
really, really, really big amplifier,

That helps for sure.

the very small signal performance
of which is usually suspect unless the amplifier is made extremely
heavy and hot and has a very high quiescent power draw. A 20 watt tube
amp that pulls 50 watts at full power is more efficient in practice
than a 250 watt solid state amp

That's a pure lie. Tube amplifiers are staggeringly inefficient.

First, Hamm's article by title states "transistors _can_ sound better than tubes",
which is sometimes true, not that they "always do" which we know to be false.

How do you know ? Personal bias ?

Graham

 

[Pooh Bear]

Don Pearce wrote:

On Fri, 06 Jan 2006 07:12:51 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:



Stewart Pinkerton wrote:

Actually, it's a piece of piss if you're using CD as a source, since
you can set system gain to sit just below clipping for 0dB FS from the
CD. That's what I do with my '50 watt' Krell.

Very true.

If you knew the settings for the cutter lathe you could do the same for vinyl too,
despite some audiophools not understanding this point ( they think it has unlimited
dynamic range it seems ! ).

Graham

But it is different for every disc - the point with CD is that you can
set it once and forget it.

CD makes it simpler for sure since there is a clearly defined 'brick wall'.

Just pointing out that vinyl doesn't have some supposed infinite headroom.

Graham

 

[Mr.T]

"Don Pearce" <donald@pearce.uk.com> wrote in message
news:43be1935.15291437@text.usenet.plus.net...

But it is different for every disc - the point with CD is that you can
set it once and forget it.

Since the cartridge you use has it's trackability limits, and the cutter
lathes also have their limits, there is still a finite limit to what you
will ever get from a vinyl disk. This can be ascertained.
OTOH, CD's have differing average levels, so you cannot "set and forget",
only ascertain the peak level setting for clipping for Dfs.
Admittedly the peak levels on all modern CD's come close to this, whereas
the peak levels for individual vinyl disks cover a wide range.
Knowing the maximum gain setting in both cases allows you to set a volume
control level below the maximum required for amplifier induced clipping
however.

MrT.

 

[Pooh Bear]

Bret Ludwig wrote:

Arny Krueger wrote:
snip
If you use them a lot, the tubes wear out.

This is why they still make'em.

There
are no proprietary parts that are likely to wear out with
normal use.

Tubes have always been proprietary parts. OK, you HP 200C has say a 6SN7 in
it. Which manufacturer's 6SN7 is the right one to use?

My experience is the box works with any of them. Probably one yields
best case distortion or dial tracking. I have never had it be an issue.

The tube-bigot lie here is that most ICs in good audio test equipment are
standard parts, or can be readily replaced with standard parts.

IIRC the 8903 has a proprietary diff amp that is close to unobtanium.
HP solid state RF gens use a lot of proprietary silicon-8640s are
slowly dropping, which is a shame, they are the low phase noise
solution even today. The Ollies couldn't copy this stuff on their own,
or they would-they need Western capital and management. Too bad, I'd
love seeing Agilent hoist by their own 35 year old petard!

Audio Precision test oscillators offer THD residuals in the 0.0006% region (
-104dB )

Not a toob in sight !

Graham

 

[Pooh Bear]

Arny Krueger wrote:

In fact audio generators with rediculously low residiuals have been made
using nothing more exotic than NE 5532s.

I may shortly be diving inside our AP test set ( backlight needs replacing )
.. Dunno what they use actually. Maybe some exotic PMI or AD parts in
selected places ?

Graham

 

[Pooh Bear]

"Mr.T" wrote:

"Don Pearce" <donald@pearce.uk.com> wrote in message
news:43be1935.15291437@text.usenet.plus.net...
But it is different for every disc - the point with CD is that you can
set it once and forget it.

Since the cartridge you use has it's trackability limits, and the cutter
lathes also have their limits, there is still a finite limit to what you
will ever get from a vinyl disk.

Spot on !

This can be ascertained.
OTOH, CD's have differing average levels, so you cannot "set and forget",
only ascertain the peak level setting for clipping for Dfs.

Not sure what you're saying. It's certainly easy to set up a listening system
that simply won't clip from a CD source. The *CD* may be clipped of course
but that's an entirely different matter.

Admittedly the peak levels on all modern CD's come close to this, whereas
the peak levels for individual vinyl disks cover a wide range.
Knowing the maximum gain setting in both cases allows you to set a volume
control level below the maximum required for amplifier induced clipping
however.

Correct.

Graham

 

[Arny Krueger]

"Bret Ludwig" <bretldwig@yahoo.com> wrote in message
news:1136496152.654232.244260@z14g2000cwz.googlegroups.com

"Don't clip the amplifier" is easy to say, and tough to
do.

Nonsense. People do it all the time.

Totally avoiding amplifier clipping under any and all
circumstnaces

A totally ludicrous goal. In the real world enough can be known about the
initial requirements that clipping can generally be avoided.

requires either active power compression
control (i.e. "Power Guard")

Compression is not a solution because it has its own set of audible
consequences.

or a really, really, really big amplifier,

By the ca. 1960 standards of tube bigots, really really big amplifers are
now readily available.

the very small signal performance of which
is usually suspect unless the amplifier is made extremely
heavy and hot and has a very high quiescent power draw.

Total nonsense.

A 20 watt tube amp that pulls 50 watts at full power is
more efficient in practice than a 250 watt solid state
amp that pulls 80 watts quiescent and 500 at full power
if either provides the same _subjective_ performance-even
though the solid state amp is more efficent for each watt
it puts out.

There's no way that a 20 watt tube amp can sound better than a 500 watt amp,
if the situation requires much more than 20 watts. While tube enthusiasts
like to posture about how their hobby-horse amps sound as good if not better
than far larger SS amps, back in the real world an hi fi amp that is
clipping sounds bad no matter what its active devices are.

First, Hamm's article by title states "transistors _can_
sound better than tubes", which is sometimes true, not
that they "always do" which we know to be false.

This is just more senseless posturing. Of course a sweeping generality can
be false under some situations. So what?

Either vacuum tubes or trnasistors can be used with good
results. However many people still prefer to use vacuum
tubes, at least under certain circumstances.

There are enough people listening to amplifiers that the "many people (who)
still prefer to use vacuum tubes" is a miniscule and shrinking minority.

However, I have not yet read this second Hamm paper, and
will endeavor to do so. It still won't make building tube
amps any less recreationally rewarding, though.

I thought this was about technology, not recreation.

 

[Arny Krueger]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43BE1873.38505D6B@hotmail.com

Stewart Pinkerton wrote:

Actually, it's a piece of piss if you're using CD as a
source, since you can set system gain to sit just below
clipping for 0dB FS from the CD. That's what I do with
my '50 watt' Krell.

Very true.

If you knew the settings for the cutter lathe you could
do the same for vinyl too, despite some audiophools not
understanding this point ( they think it has unlimited
dynamic range it seems ! ).

Setting levels for vinyl playback or transcription is similarly pretty easy.

Get a trackbility test LP such as the one from Hi Fi News and set levels so
that you can play the highest trackable segment while leaving a few dB for
headroom throrgh the electronics. It's really a similar thing to the
procedure that was suggested for a system with a CD player.

 

[Arny Krueger]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43BE1AAE.1567FBC0@hotmail.com

Bret Ludwig wrote:

"Don't clip the amplifier" is easy to say, and tough to
do.

Wrong. It's easy if you know how.

Totally
avoiding amplifier clipping under any and all
circumstnaces requires
either active power compression control (i.e. "Power
Guard")

Not necessarilily. What's this 'power guard' anyway ?

An electronic circuitry that backs off the amplifier's gain when the input
signal would tend to push it into clipping.

http://www.mcintoshlabs.com/mcprod/..%5Cdata%5Cbrochures%5CMC602br.pdf

"Power GuardŽ clipping protection. Power Guard ensures that the amplifier
will always deliver full power without causing clipping distortion. If an
amplifier channel is overdriven, Power Guard automatically reduces the input
volume just enough to keep distortion below 2% and prevent any clipping
distortion. Thanks to an optical resistor, Power Guard acts literally at the
speed of light, producing absolutely no audible side effects. An amplifier
with Power Guard will actually deliver clipping-free output well above its
rated power."

Some audiophoolery I expect. Pro-audio amps have had
signal limiters to avoid clipping for *decades*.
Including the cutting lathe amplifiers that made the
vinyl !

Vinyl bigots would die if they knew about all the work-arounds that were
routinely used in its production.

or a
really, really, really big amplifier,

That helps for sure.

the very small signal performance
of which is usually suspect unless the amplifier is made
extremely
heavy and hot and has a very high quiescent power draw.
A 20 watt tube amp that pulls 50 watts at full power is more efficient
in practice than a 250 watt solid state amp

That's a pure lie. Tube amplifiers are staggeringly
inefficient.

Bret is also implicitly claiming that a 20 watt tubed amp can sound as good
as a 500 watt amp when 500 watts would be required to avoid clipping. This
is complete and total nonsense.

First, Hamm's article by title states "transistors _can_
sound better than tubes", which is sometimes true, not
that they "always do" which we know to be false.

How do you know ? Personal bias ?

It's what the voices in his head tell him. I think he should unwrap the
aluminum foil from around his cranium.

 

[Arny Krueger]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43BE1F7F.A4E69E0F@hotmail.com

Arny Krueger wrote:

In fact audio generators with rediculously low
residiuals have been made using nothing more exotic than
NE 5532s.

Various construction projects like this have been published in the past,
including one by me. There was also a far more elaborate project by Cordell
that was published in Audio Magazine.

If one works with building audio generators of the traditional analog kind,
it turns out that the nonlinearity of the means used to stabilize the levels
is the major source of distortion, not the amplifier portion of the
oscillator. This is true whether a light bulb, a CdS opto-isolator, a
thermistor, a FET or a VCA is used. Been there and done that for all of
them.

I may shortly be diving inside our AP test set (
backlight needs replacing ) . Dunno what they use
actually. Maybe some exotic PMI or AD parts in selected
places ?

Maybe even discrete op amps, depending on the age.

One relevant parameter is the maximum amplitude that is provided. One
classic benchmark maximum output in the 10 vrms or +22 range. To provide
this at the generator's output terminals @600 ohms, you have to have a few
dB more at the op amp's output terminals.

You can't really do this with +/- 15 or +/- 18 supplies. One can stretch
NE5532s to +/- 22 but they tend to degrade over years.

The only high-voltage op amp chip that I know (one that shows signs of
hanging in with +/- 22) of is the OPA 604/2604. According to Doug Self,
they vastly underperform NE 5532s for nonlinear distortion.

Modern DAC chips are so good, and digital computation and function
management is so cheap and pervasive, that a modern sound card in a PC is
the most practical way to generate well-controlled sine waves these days.

It takes a lot of work to outperform a M-Audio Audiophile 24192 driven by
simple freeware software like Audacity and/or Audio Rightmark.

 

[Arny Krueger]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43BE1EE6.23E804B3@hotmail.com

Bret Ludwig wrote:

Arny Krueger wrote:
snip
If you use them a lot, the tubes wear out.

This is why they still make'em.

There
are no proprietary parts that are likely to wear out
with normal use.

Tubes have always been proprietary parts. OK, you HP
200C has say a 6SN7 in it. Which manufacturer's 6SN7 is
the right one to use?

My experience is the box works with any of them.
Probably one yields best case distortion or dial
tracking. I have never had it be an issue.

The tube-bigot lie here is that most ICs in good audio
test equipment are standard parts, or can be readily
replaced with standard parts.

IIRC the 8903 has a proprietary diff amp that is close
to unobtanium. HP solid state RF gens use a lot of
proprietary silicon-8640s are slowly dropping, which is
a shame, they are the low phase noise solution even
today. The Ollies couldn't copy this stuff on their own,
or they would-they need Western capital and management.
Too bad, I'd love seeing Agilent hoist by their own 35
year old petard!

Audio Precision test oscillators offer THD residuals in
the 0.0006% region ( -104dB )

I looped-back a little XP PC with an Audiophile 24192 in it the other day,
running the freeware Audio Rightmark Program. *All* spurious responses were
112 dB or better down (most in the -120 dB range), and THD+N was something
like -106 dB.

Not a toob in sight !

AFAIK toobed audio generators and analyzers never got within 2-3 orders of
magnitude of -106 dB residuals. Something like 0.05% midband, and 0.1% at 20
and 20 KHz was about as far as toobs got.

When the first generation SS audio test equipment like the HP 331-334
first hit the market, residuals *instantly* improved by like an order of
magnitude.

http://mywebpages.comcast.net/mnowlen/hp334a.htm

Heath made a cheap clone of this box (IM5258) that I was able to improve so
that it had mid-band residuals in the 0.001-0.003% range.

 

[Mr.T]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:43BE204E.80AFCA17@hotmail.com...

OTOH, CD's have differing average levels, so you cannot "set and
forget",
only ascertain the peak level setting for clipping for Dfs.

Not sure what you're saying.

Simply that the apparent SPL level will be different using different CD's in
a "set and forget" position regardless of Dfs.
I think it's simply bad terminology saying "set and forget". It is actually
ascertaing the *maximum* gain setting, and one *often* varies the system
gain below that level.

It's certainly easy to set up a listening system
that simply won't clip from a CD source.

Which I agreed with, vinyl too. Also FM etc.

The *CD* may be clipped of course

Nearly all are these days.

but that's an entirely different matter.

Quite so.

MrT.

 

Arny Krueger wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
Audio Precision test oscillators offer THD residuals in
the 0.0006% region ( -104dB )

I looped-back a little XP PC with an Audiophile 24192 in it the other day,
running the freeware Audio Rightmark Program. *All* spurious
responses were 112 dB or better down (most in the -120 dB range),
and THD+N was something like -106 dB.

Not a toob in sight !

AFAIK toobed audio generators and analyzers never got within 2-3
orders of magnitude of -106 dB residuals. Something like 0.05%
midband, and 0.1% at 20 and 20 KHz was about as far as toobs got.

The biggest problem with low residuals back then was not, in my
experience, wether they used tubes or solid state, rather on how well
the unit was stabilized. There was a Krohn-Hite tubed oscillator, as I
recall, that was easily capable of well below 0.003% , you just had to
let it sit there and stabilize. AT the same time, some of the GR solid
state oscillators, like the 1309, could be tuned to meet those kinds of
levels, and MIGHT have been capable of far better, but the amplitude
stabilization network just just too noisy: you'd watch the residual
bouncing around and every once in a while you'd see it drop a good
20 dB below its average for a brief period (about a second). Bang the
case, upset the filament in the bulb they used for stabilization, and
you'd see the residual go all over the place.

The real secret to low-residual oscillators came with much better ,
lower noise and faster responding loop stabilization. The original
ST1700
had an oscillator circuit not substantially different than whatever
else was
out there but had superior stabilization and that was the secret to
their
significantly lower residual.

 

[Pooh Bear]

Arny Krueger wrote:

When the first generation SS audio test equipment like the HP 331-334
first hit the market, residuals *instantly* improved by like an order of
magnitude.

http://mywebpages.comcast.net/mnowlen/hp334a.htm

Heath made a cheap clone of this box (IM5258) that I was able to improve so
that it had mid-band residuals in the 0.001-0.003% range.

Neat !

Do you fancy posting any more info about that ?

Graham

 

[Arny Krueger]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43BE7FF1.6BC88172@hotmail.com

Arny Krueger wrote:

When the first generation SS audio test equipment like
the HP 331-334 first hit the market, residuals
*instantly* improved by like an order of magnitude.

http://mywebpages.comcast.net/mnowlen/hp334a.htm

Heath made a cheap clone of this box (IM5258) that I
was able to improve so that it had mid-band residuals in
the 0.001-0.003% range.

Neat !

Do you fancy posting any more info about that ?

Once upon a time I wrote an outline of an article about it for Ed Dell, but
lost interest in his ragazine due to his negative stance on ABX before
getting much furhter with it.

I still have the modded 5258 packed away someplace. I fired it up about a
year ago and it still worked. It was a real POS compared to what I now do
with PCs. Hard to operate, limited reporting, relatively high residuals.

The mod development work revealed some interesting stuff.

One of the more significant zero-cost enhanments involved taking a grounding
problem out of the power supply circuit card that flooded the whole box with
low-level ripple. Bad land pattern design around the power supply caps.

Part of the mod involved replacing one or two discrete transistor stages
with 5534s.

I had to up the gain of the measurement circuits by about 20 dB to make the
lower residuals useful. There was a 10/20 dB gain boost switch that the mod
added.

I had to work over some time constants in the nulling circuit, and make them
change for the lower frequency ranges. That was controlled by a second added
front-panel switch.

The box was noisy because it had immense bandwidth - something like 4-5 MHz
at -3 dB. To get the lowest residuals a switchable low-pass filter was added
to the metering circuit.

 

[Stewart Pinkerton]

On Fri, 06 Jan 2006 07:12:51 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

Stewart Pinkerton wrote:

Actually, it's a piece of piss if you're using CD as a source, since
you can set system gain to sit just below clipping for 0dB FS from the
CD. That's what I do with my '50 watt' Krell.

Very true.

If you knew the settings for the cutter lathe you could do the same for vinyl too,
despite some audiophools not understanding this point ( they think it has unlimited
dynamic range it seems ! ).

Yes, but there's a massive variation in maximum groove velocity, from
say EMI 'Music for Pleasure' at one end, to the Sheffield Track and
Drum records at the other. Setting your system gain to avoid clipping
at 30cm/sec will make for very quiet listening to most commercial
output!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[Bret Ludwig]

Pooh Bear wrote:

Arny Krueger wrote:

In fact audio generators with rediculously low residiuals have been made
using nothing more exotic than NE 5532s.

I may shortly be diving inside our AP test set ( backlight needs replacing )
. Dunno what they use actually. Maybe some exotic PMI or AD parts in
selected places ?

Never actually worked on one BUT ....(at a prev employer) our Portable
One Plus had the same issue. I had read somewhere there was a Cherry
display which was pin compatible with the LCD (or at least very likely
there was) and have bitched often at the readability issues with the
LCD. It turned out there WAS and they (the metrology guys) used that
instead and it is far more readable IMO. A heads-up.

I'll try to find a part number for you. They sent a note to AP so they
may know.