THD as speced by the manufacturer is not the only measure of equipment
quality. For example, a lot of the HP equipment would meet spec near
their end of life or the end of life of their tubes. while Heathkit
equipment might meet spec only if routinely maintained.

HP's audio signal generators were renouned for their relatively high
power output, on the order of 1 watt for some models.

When you look at THD specs, you have to consider the whole operational
environment, including the power level, the impedance of the rated
load, and the frequency range.

Arny Krueger wrote:
THD as speced by the manufacturer is not the only measure of equipment
quality. For example, a lot of the HP equipment would meet spec near
their end of life or the end of life of their tubes. while Heathkit
equipment might meet spec only if routinely maintained.

The HP generators derived from the Model 200 will run forever, or at
least more than one human lifetime. There are no proprietary parts that
are likely to wear out with normal use. If needed the transformers and
the tuning capacitor could be repro'd for far less setup costs than
having a replacement IC taped out, masked and a run made such as would
be needed on many solid state units using proprietary ICs.

Everyone should own and care for one of these things. They were
manufactured until 1986 and represent the antithesis of all that is
wrong, immoral, indecent, and generally ****ed up in the electronics
business today. (And most will run on 220 balanced power with only a
flick of the voltage switch...)

Yes, I had a HP 220CD, if I remember the model number correctly. And it
was wonderful to look at inside. It got left behind on one of my moves.

Today, for practically any purpose that I can imagine in my home shop,
the audio output on my PC sound card rules. A decent voltmeter tells me
the output level.

wrote in message
ups.com


Today, for practically any purpose that I can imagine in
my home shop, the audio output on my PC sound card rules.

Most PC sound cards vastly outperform legacy audio signal generators, both
for low distortion and flatness. They also have excellent settling times.

A decent voltmeter tells me the output level.

The trick is finding an inexpensive one with good frequency response. My
best meters are Flukes (not cheap) or the ProTek 506 (flat enough but not
wonderful and still not exactly cheap).

Arny Krueger wrote:
wrote in message
ups.com


Today, for practically any purpose that I can imagine in
my home shop, the audio output on my PC sound card rules.

Most PC sound cards vastly outperform legacy audio signal generators, both
for low distortion and flatness. They also have excellent settling times.

A decent voltmeter tells me the output level.

The trick is finding an inexpensive one with good frequency response. My
best meters are Flukes (not cheap) or the ProTek 506 (flat enough but not
wonderful and still not exactly cheap).

No Arny, the trick is to ante up once and buy a good one from a first
or at least second tier manufacturer whose specs well eclipse the job
at hand. Second tier manufacturers are sometimes better because they
use off the shelf parts where Agilent and Tek used their fab
capabilities to make wonderful chips....that no longer exist. And they
are not making more.

If commodisumo PeeCee hardware were test grade National , Aeroflex,
Agilent and others would not be getting the hemmorhoid-splattering
prices they do for CompactPCI and VME/VXI hardware. A peecee is not a
core piece of test equipment. Yes you can do a few things with a sound
card, but a Audio Precision box is NOT a sound card in a fancy box.

"Bret Ludwig" wrote in message
oups.com
Arny Krueger wrote:
wrote in message
ups.com


Today, for practically any purpose that I can imagine in
my home shop, the audio output on my PC sound card
rules.

Most PC sound cards vastly outperform legacy audio
signal generators, both for low distortion and flatness.
They also have excellent settling times.

A decent voltmeter tells me the output level.

The trick is finding an inexpensive one with good
frequency response. My best meters are Flukes (not
cheap) or the ProTek 506 (flat enough but not wonderful
and still not exactly cheap).

No Arny, the trick is to ante up once and buy a good one
from a first or at least second tier manufacturer whose
specs well eclipse the job at hand.

Given that I mentioned a first tier vendor (apparently you never heard of
Fluke, Brat) I've got your "buy a good one" covered. Given that I mentioned
ProTek (apparently you never heard of them, either) I've got the lower tiers
covered as well.

BTW Brat, for your future reference, here's some much-needed info for you
about who Fluke is:

http://www.fluke.com/

On 4 Jan 2006 14:09:30 -0800, "Bret Ludwig"
wrote:


Arny Krueger wrote:
wrote in message
ups.com


Today, for practically any purpose that I can imagine in
my home shop, the audio output on my PC sound card rules.

Most PC sound cards vastly outperform legacy audio signal generators, both
for low distortion and flatness. They also have excellent settling times.

A decent voltmeter tells me the output level.

The trick is finding an inexpensive one with good frequency response. My
best meters are Flukes (not cheap) or the ProTek 506 (flat enough but not
wonderful and still not exactly cheap).

No Arny, the trick is to ante up once and buy a good one from a first
or at least second tier manufacturer whose specs well eclipse the job
at hand. Second tier manufacturers are sometimes better because they
use off the shelf parts where Agilent and Tek used their fab
capabilities to make wonderful chips....that no longer exist. And they
are not making more.

If commodisumo PeeCee hardware were test grade National , Aeroflex,
Agilent and others would not be getting the hemmorhoid-splattering
prices they do for CompactPCI and VME/VXI hardware. A peecee is not a
core piece of test equipment. Yes you can do a few things with a sound
card, but a Audio Precision box is NOT a sound card in a fancy box.

Nor does it contain tubes.................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Bret Ludwig" wrote in message
oups.com
Arny Krueger wrote:
THD as speced by the manufacturer is not the only
measure of equipment quality. For example, a lot of the
HP equipment would meet spec near their end of life or
the end of life of their tubes. while Heathkit equipment
might meet spec only if routinely maintained.

The HP generators derived from the Model 200 will run
forever, or at least more than one human lifetime.

If you use them a lot, the tubes wear out.

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?

If needed the transformers and the tuning
capacitor could be repro'd for far less setup costs than
having a replacement IC taped out, masked and a run made
such as would be needed on many solid state units using
proprietary ICs.

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.

"Arny Krueger" wrote in message
...
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?

Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Tim

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

On Wed, 4 Jan 2006 09:43:45 -0600, "Tim Williams"
wrote:

"Arny Krueger" wrote in message
...
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?

Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Tim

What a pile of nonsense!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:
snip
Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Tim

What a pile of nonsense!

I'm afraid it's true. Discrete power transistors vary much more than
tubes of a given type and manufacture run. That's why construction or
repair of high power solid state amps requires either factory-matched
sets or the use of a curve tracer to sort through piles of them.

Of course, the transistors come in N and P channel or NPN and PNP
types whereas tubes are not complementary. So it's apples vs. oranges.

Are apples or oranges better?

"RapidRonnie" wrote in message
ups.com
Jim Thompson wrote:
snip
Uh..!? Tubes from different manufacturers are
_massively_ better matched than any two transistors or
ICs from the _same batch_!

Tim

What a pile of nonsense!

I'm afraid it's true. Discrete power transistors vary
much more than tubes of a given type and manufacture run.

Not in terms of parameters that matter.

That's why construction or repair of high power solid
state amps requires either factory-matched sets or the
use of a curve tracer to sort through piles of them.

That would be a misapprehension on your part, Ronnie.

"RapidRonnie"


What a pile of nonsense!

I'm afraid it's true. Discrete power transistors vary much more than
tubes of a given type and manufacture run.


** Complete bull****.

Power BJTs from the same run are very nearly all identical.

They can be used in parallel just fine.


That's why construction or
repair of high power solid state amps requires either factory-matched
sets or the use of a curve tracer to sort through piles of them.


** You have NO idea what you are talking about.

A curve tracer is just about useless for power BJT matching where parallel
operation is needed.

You need a wide range Vbe / Ic match and that ideally means devices of the
same type, maker and batch.

With power tubes operated in parallel - mating up old and new or differing
brands leads to tears just the same as with BJTs.


Now, MOSFETS are another matter.

The laterals ( aka audio fets) match in parallel very nicely.

The verticals ( aka switching fets) are pigs.




......... Phil

On 4 Jan 2006 17:37:14 -0800, "RapidRonnie"
wrote:


Jim Thompson wrote:
snip
Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Tim

What a pile of nonsense!

I'm afraid it's true. Discrete power transistors vary much more than
tubes of a given type and manufacture run. That's why construction or
repair of high power solid state amps requires either factory-matched
sets or the use of a curve tracer to sort through piles of them.

Only because the design sucked in the first place (*). Probably
designed by a "tooobz" engineer ;-)

I have yet to see a single design that demonstrated the proper way to
do a stable A-B bias.

I know how but I ain't talking ;-)


Of course, the transistors come in N and P channel or NPN and PNP
types whereas tubes are not complementary. So it's apples vs. oranges.

Are apples or oranges better?

I like mixed fruit salad myself... apples, oranges, grapes, Kiwi, and
maybe some Pomegranate ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

"Tim Williams" wrote in message


"Arny Krueger" wrote in message
...

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?

Uh..!? Tubes from different manufacturers are
_massively_ better matched than any two transistors or
ICs from the _same batch_!

Thanks for permission to summarily dismiss any and all posts on
rec.audio.tubes mentioning equipment sonics dependent on brand of tube used.
;-)

As far as matching of SS parts goes, in practice parts matching is not the
issue for SS that it was for tubes. This is especially true of ICs.

Uh..!? Tubes from different manufacturers are
_massively_ better matched than any two transistors or
ICs from the _same batch_!

It usually takes several weeks into a new year before we
see things so remarkably clueless.

On Wed, 4 Jan 2006 09:43:45 -0600, "Tim Williams"
wrote:

"Arny Krueger" wrote in message
...
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?

Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Tim

That's totally backwards.

If you're talking about transconductance, *any* two small-signal
silicon transistors, even of different part numbers, will be better
matched than 99% of tube "matched pairs."

And after three months of use, the tubes will have drifted all over
the place, but the transistors won't.

And if you're talking differential offset voltage or drift of same,
the transistors beat the tubes by volts.

And you can't compare beta, bacause tubes don't have it.

John

"John Larkin" wrote in message
...
If you're talking about transconductance,

Ya, because they have that fun little exponential Vbe curve. Beta is to
transistors what Gm is to tubes and FETs, and you know it...

Tim

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

On Wed, 4 Jan 2006 10:37:27 -0600, "Tim Williams"
wrote:

"John Larkin" wrote in message
.. .
If you're talking about transconductance,

Ya, because they have that fun little exponential Vbe curve. Beta is to
transistors what Gm is to tubes and FETs, and you know it...

Tim

What - I mean, WHAT?

d

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

"Tim Williams" wrote in message

"John Larkin"
wrote in
message
...

If you're talking about transconductance,

Ya, because they have that fun little exponential Vbe
curve.

So far, so good.

Yes, and the Vbe curve relates very closely to the standard definition of
transconductance, right?

Beta is to transistors what Gm is to tubes and
FETs, and you know it...

Huh?

On Wed, 4 Jan 2006 10:37:27 -0600, "Tim Williams"
wrote:

"John Larkin" wrote in message
.. .
If you're talking about transconductance,

Ya, because they have that fun little exponential Vbe curve. Beta is to
transistors what Gm is to tubes and FETs, and you know it...

Tim

No, transistor Gm is to tube Gm as...

Good transistor design is beta independent, as good tube design is
tolerant of variations in transfer curves, grid current, and
transconductance.

John

Tim Williams wrote:
Ya, because they have that fun little exponential Vbe curve. Beta is to
transistors what Gm is to tubes and FETs, and you know it...

I've seen your posts here and elsewhere. They all seem to be of similar
quality. I have been designing, building and _listening to_ audio
amplifiers for about 60 years and the plain fact is that tube amps just
don't do a good job especially at very low or very high frequencies.
Almost acceptable THD is possible at 1 KHz matbe even up to 5 or 10 but
then maybe you can't hear anything above that.

Ted

On Wed, 4 Jan 2006 09:43:45 -0600, "Tim Williams"
wrote:

"Arny Krueger" wrote in message
...
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?

Uh..!? Tubes from different manufacturers are _massively_ better matched
than any two transistors or ICs from the _same batch_!

Utter bull****. In any normal application, IC matching is vastly
superior to valve matching.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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!

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.

My experience with several dozen HP 200's does not match yours.
Yes, they all oscillate, but amplitude stability and phase noise is
tube dependent.

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.

If you recall, the 8903 is a fairly rare beast in and of itself and
hardly
constitutes an example supporting your claim. I have an entire wall
of audio test equipment from HP, ST, Techron, GR, B&K, Leader,
and so on, and there's nary a proprietary IC in any one of them.

Now the exception is my old, trusty GR 1390B random noise
generator which uses a proprietary noise diode. if it goes, the
unit is worthless. WAIT! It's a vacuum tube, not an IC! Fancy that,
a proprietary, non-replaceable vacuum tube.

HP solid state RF gens use a lot of proprietary silicon-8640s

Lessee, HP 8640: signal generator with a range of 500 kHz to
500 MHz. Please explain how that is "audio test equipment."

wrote:

snip
My experience with several dozen HP 200's does not match yours.
Yes, they all oscillate, but amplitude stability and phase noise is
tube dependent.


i have probably just been lucky. Also I pay little attention to the
dial markings, I use my freq counter to set frequency. And I don't use
them for scope cal, there are precision level gens that are used for
that.

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.

If you recall, the 8903 is a fairly rare beast in and of itself


Oh no! They were sold by the truckload because they replaced the 339.
Then they went to *ucker in trade for....used 339s....because they
weren't. Potomac IIRC essentially cloned the 339, but in two boxes, a
gen and receive, and charged more for either than HP had for the 339.
So 8903s are common as sin. However, barring abuse, they run forever.

and
hardly
constitutes an example supporting your claim. I have an entire wall
of audio test equipment from HP, ST, Techron, GR, B&K, Leader,
and so on, and there's nary a proprietary IC in any one of them.

Now the exception is my old, trusty GR 1390B random noise
generator which uses a proprietary noise diode. if it goes, the
unit is worthless. WAIT! It's a vacuum tube, not an IC! Fancy that,
a proprietary, non-replaceable vacuum tube.

HP solid state RF gens use a lot of proprietary silicon-8640s

Lessee, HP 8640: signal generator with a range of 500 kHz to
500 MHz. Please explain how that is "audio test equipment."

Well, then I guess an FM tuner isn't an "audio unit".

Bret Ludwig wrote:
wrote:

snip
My experience with several dozen HP 200's does not match yours.
Yes, they all oscillate, but amplitude stability and phase noise is
tube dependent.

i have probably just been lucky.

I would take it , then, that you have not seen more than maybe a
couple of these units, yes? So, you hardly speak from a position
of authority. Having run an electronics calibration lab, and seen
quite a few, I might huimbly suggest my experience trumps yours.

Also I pay little attention to the
dial markings, I use my freq counter to set frequency.

Fine, but that doesn't deal with drift, amplitude instability, and all
the rest.

And I don't use
them for scope cal, there are precision level gens that are used for
that.

And how many of them are solid state

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.

If you recall, the 8903 is a fairly rare beast in and of itself

Oh no! They were sold by the truckload because they replaced the 339.
Then they went to *ucker in trade for....used 339s....because they
weren't.

You obviously missed my point, or chose to completely dance
around it with irrelevancies. The 8903 is merely ONE example
of audio test equipment. It is not representative of the realm of
equipment as you might suggest it does. Besides, you have
already demonstrated pretty narrow experience with HP200's,
and you did qualify your claims on the 8903 with "IIR," yes?
SO you have yet to provide any substantiation to your claim.

Potomac IIRC essentially cloned the 339, but in two boxes, a
gen and receive, and charged more for either than HP had for the 339.

How in any way, shape or form is this at all relevant?

So 8903s are common as sin. However, barring abuse, they run forever.

Which seems to contradict you earlier point.

I have an entire wall
of audio test equipment from HP, ST, Techron, GR, B&K, Leader,
and so on, and there's nary a proprietary IC in any one of them.

A point you failed to address.

Now the exception is my old, trusty GR 1390B random noise
generator which uses a proprietary noise diode. if it goes, the
unit is worthless. WAIT! It's a vacuum tube, not an IC! Fancy that,
a proprietary, non-replaceable vacuum tube.

A point you failed to address.

I should also add that of all the equipment I have, the tube0based
stuff has been the most difficult to support, because it's becoming
increasingly difficult to find suitable tubes, any ol' fire bottle just
won't do. But , even though the tubes ARE easy to extract, they
WILL have to be replaced at some point, absolute guarantee.

Whether or not any of the solid state units have proprietary parts
that will be hard to replace, I don't know: not a single one of them
has failed.

HP solid state RF gens use a lot of proprietary silicon-8640s

Lessee, HP 8640: signal generator with a range of 500 kHz to
500 MHz. Please explain how that is "audio test equipment."

Well, then I guess an FM tuner isn't an "audio unit".

Last time I checked, the part that an HP 8640 would test isn't.

"Bret Ludwig" wrote in message
oups.com
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.

Take it up with the manufacturer - its gratuitous.

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

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" wrote
in message

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.

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.

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" wrote
in message
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.

Arny Krueger wrote:
"Pooh Bear" 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.

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

Pooh Bear wrote:
Bret Ludwig wrote:

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

Not a toob in sight !

AP offers their oscillator only with their test set whgich starts at
about $7000-8000 new. A good used 200CD or its relatives is $25-50 in
working shape. Also, although the AP's gen is cleaner, it won't put the
level into the loads the HP will. And the HP will survive hobbyist and
student oopses for decades. With the AP you can kill it by walking over
a dry enough carpet and grabbing a test lead! I was a witness to that
one (it was the analyzer rather than the gen side that died-AP fixed it
gratis, but it was JUST back from cal.)

I may have given the wrong HP part number. (Didn't I say 204C? I think
that's right.) It's transistorized and does not contain a light bulb.

Arny Krueger wrote:

THD as speced by the manufacturer is not the only measure of equipment
quality. For example, a lot of the HP equipment would meet spec near
their end of life or the end of life of their tubes. while Heathkit
equipment might meet spec only if routinely maintained.

HP's audio signal generators were renouned for their relatively high
power output, on the order of 1 watt for some models.

When you look at THD specs, you have to consider the whole operational
environment, including the power level, the impedance of the rated
load, and the frequency range.


I had a version that used a pair of 6V6's for about 20 watts output.
It was built to test telephone lines and carrier current loops. Add the
right transformer to the output, and it made a great 120 VAC variable
frequency power supply. I had some of those large 24 VAC school clocks
and used one with the carrier loop generator to vary the speed f the
clock. Would would tell a pesky salesman he could have 15 minutes, then
I would turn up the frequency to only give him four or five minutes,
then slow it down and tell him his time was up, then point to the clock
over his head. They never caught on. ;-)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

As an aside Jim Williams of Linear Technology has written very
intelligent pieces on HP Wien-bridge oscillators and building an
improved solid state version. I doubt it is on the web but you may be
better at finding it than me.

"Bret Ludwig" wrote in message
oups.com...
As an aside Jim Williams of Linear Technology has written very
intelligent pieces on HP Wien-bridge oscillators and building an
improved solid state version. I doubt it is on the web but you may be
better at finding it than me.

I have it, actually. It's in a book published by Newnes, isn't it?