Date   

Re: Looking for sensitive audio RMS meter

Kerry Burns
 

Hello Chris



I have an older 3400A.  It works well for most audio measurements ( and beyond, up to 10 MHz), but the lowest range is 1mV so probably not sensitive enough for sub 1uV work.   



Kerry



From: <TekScopes@groups.io> on behalf of bhome1959 <bhome@sympatico.ca>
Reply to: <TekScopes@groups.io>
Date: Tuesday, 11 May 2021 at 12:41 pm
To: <TekScopes@groups.io>
Subject: Re: [TekScopes] Looking for sensitive audio RMS meter



Hi Liam,

I would love a 3457A!



Anyone have a HP 3400A? That would completely suit Bob's requirements. BTW, I am also looking for one of those that works. I bought one on fleabay and it has serious problems.



-Chris


Re: Looking for sensitive audio RMS meter

Tom Lee
 

Because "Bob's your uncle" (only makes sense if you're from the UK).

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 5/10/2021 19:42, cheater cheater wrote:
On Tue, May 11, 2021 at 4:41 AM bhome1959 <bhome@sympatico.ca> wrote:
Hi Liam,
I would love a 3457A!

Anyone have a HP 3400A? That would completely suit Bob's requirements. BTW, I am also looking for one of those that works. I bought one on fleabay and it has serious problems.
Why does everyone keep on calling me Bob? What the heck...




Re: Type 519 -- Why 125 ohms?

Tom Lee
 

The 519 has no vertical amp (as I'm sure you know), so the input signal has to drive the CRT's distributed deflection plates directly. The deflection structure looks like a transmission line, basically, and has a characteristic impedance of 125 ohms.

So, your next question would be, "Why is the deflection structure 125 ohms?" The answer to that is that you'd actually like it to be fairly high so that you can deliver the deflection voltage (about 10V per cm) at reasonably low power. At 125 ohms, you're already taking quite a bit of power to deflect it. 50 ohms would be painful.

Why not much higher than 125 ohms? Because it's hard to construct -- and fit into the CRT -- a deflection structure with a much higher impedance, since Zo = sqrt(L/C). And even if you could pull off that trick, plumbing for, say, a 300 ohm impedance is no easy task by itself. The geometric mean of 50 and 300 just happens to be about 125 ohms (for small values of 125). That's somewhat of a coincidence, but not entirely.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 5/10/2021 18:54, Sean Turner wrote:
Pondering the beast that is sitting in my lab got me thinking, why 125 ohm? Does anyone know of the history of why this was chosen? I haven't been able to find much about this, so insights are appreciated!

Sean




Re: Looking for sensitive audio RMS meter

n4buq
 

Dunno. Sounds better than "cheater"?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "cheater cheater" <cheater00social@gmail.com>
To: TekScopes@groups.io
Sent: Monday, May 10, 2021 9:42:32 PM
Subject: Re: [TekScopes] Looking for sensitive audio RMS meter

On Tue, May 11, 2021 at 4:41 AM bhome1959 <bhome@sympatico.ca> wrote:

Hi Liam,
I would love a 3457A!

Anyone have a HP 3400A? That would completely suit Bob's requirements.
BTW, I am also looking for one of those that works. I bought one on
fleabay and it has serious problems.
Why does everyone keep on calling me Bob? What the heck...






Re: Looking for sensitive audio RMS meter

 

On Tue, May 11, 2021 at 4:41 AM bhome1959 <bhome@sympatico.ca> wrote:

Hi Liam,
I would love a 3457A!

Anyone have a HP 3400A? That would completely suit Bob's requirements. BTW, I am also looking for one of those that works. I bought one on fleabay and it has serious problems.
Why does everyone keep on calling me Bob? What the heck...


Re: Looking for sensitive audio RMS meter

 

On Tue, May 11, 2021 at 3:20 AM Liam Perkins <hifi@telus.net> wrote:

I just lit up the 3457s with inputs shorted and they pass self-test. One of
them has Opt 007 which I -think- might be the 7th digit option but it's a
slog thru about 5lbs of manual to sort that for certain.
You started here saying tens of uV now you're into nVs which is a place
that ought to have a gate saying, "Abandon Hope All Ye Who Enter". Read a
slew of Jim Williams app notes from, I think, Analog Devices and start
buying coffee in 2 and 5lb tins because you're gonna need 'em nested like
Russian dolls.
What -are- you wanting to do ?
I want to be able to measure total noise down to -110 dBV, or possibly
-130 dBV if possible. This means resolving single microvolts and
tenths of microvolts.

On Mon, May 10, 2021 at 7:05 PM Bill Perkins <hifi@telus.net> wrote:

The 465A is an about 1960 design and isn't even in the ballpark

On Mon, May 10, 2021 at 6:46 PM Göran Krusell <mc1648pp@gmail.com> wrote:

hp 465 A amplifier!









Re: Looking for sensitive audio RMS meter

 

Hi Liam,
I would love a 3457A!

Anyone have a HP 3400A? That would completely suit Bob's requirements. BTW, I am also looking for one of those that works. I bought one on fleabay and it has serious problems.

-Chris


Re: Looking for sensitive audio RMS meter

 

On Tue, May 11, 2021 at 3:21 AM Liam Perkins <hifi@telus.net> wrote:

I'm going thru a PAR CR-4A LNA for a guy in Germany who wants to use it as
an effects box with his synth'. There are a couple of YTs by another guy
over there who loves his and has it make the God Awfullest noises you ever
heard, and he loves it. I think those guy get a kick out torturing
germanium . . .
You've got to be kidding me...

Anyways, this preamp looks like it wouldn't be too bad for my use.

On Mon, May 10, 2021 at 7:05 PM George Kerber <gk5220@gmail.com> wrote:

Sorry about that. Best bet is to check out eBay listings for 323. It's
probably really pricey when purchased directly from Ballantine (I was about
$700 new in the 1970's). I was surprised to see it on their website.

FFT spectrum analyzer is perfect for noise measurements. You get the
spectrum and total noise level number if needed. I use a, not so portable,
HP 35665A. A good low noise preamp such as PAR 113 is a good complement to
any RMS meter or FFT analyzer.

George

On Mon, May 10, 2021 at 5:41 PM cheater cheater <cheater00social@gmail.com
wrote:

Hi George,

On Tue, May 11, 2021 at 1:58 AM George Kerber <gk5220@gmail.com> wrote:

Bob,
Actually I'm the one looking for the volt meter :-)

You might consider a HP distortion analyzer such as this one:
http://www.barrytech.com/hewlett-packard/analyzers/hp339a.html
https://www.ebay.com/itm/233587661597?hash=item3662e8db1d:g:KrMAAOSwiGBevSVB

I love the fact that it's got a dBV display which is what I'd like to
be doing my measurements in anyways (it's for audio equipment).

Also, a Ballantine 323 True RMS analog AC voltmeter. Only measure to
300
uV.
https://www.ballantinelabs.com/323/
https://www.ebay.com/itm/384146432011?hash=item5970e9600b:g:j8MAAOSwcXBgk0HN

Thanks, any clue how much the Ballantine 323 costs? They don't have
any prices on their website. However, ebay shows units going for sub
$100 which is pretty great.

Any chance of being able to convert its scale to dBV? I would love to
not have to pull out a calculator every time I measure something.

Both are somewhat portable.

An HP 3561A 100kHz FFT spectrum analyzer would probably meet your spec,
it's portable, but really hard to lug around.
I'm afraid it might be way too large for me. Always liked how it
looks, but it's just not practical in my circumstances, and also I'm
not looking for a spectrum analyzer.

On Tue, May 11, 2021 at 2:35 AM George Kerber <gk5220@gmail.com> wrote:

You might also consider soundcard-based FFT for rms and spectrum
measurements to 100kHz and a laptop. There are a lot of choices and
price
ranges. One professional package is by Pioneer Hill Software:
https://www.spectraplus.com/ Very nice, but $$$.

Another is Spectrum Lab, by DL4YHF Spectrum Lab (Audio Signal
Analyser).
I
have played with it a little, but it has a very steep learning curve.

George
I'm looking for a meter to measure total noise level, rather than its
spectrum. I agree that FFT measurements are useful in their own right.

I'm on a short budget. If I had the money I'd just buy Audio Precision.













Re: Looking for sensitive audio RMS meter

 

On Tue, May 11, 2021 at 2:46 AM Göran Krusell <mc1648pp@gmail.com> wrote:

hp 465 A amplifier!
Unfortunately, at 25 uV self-noise, the HP 465 A won't be helpful in
measuring noise on the order of 1uV.


Re: Type 519 -- Why 125 ohms?

Harvey White
 

IIRC, that's the impedance, or close to it, of twisted pair non shielded cable.

Harvey

On 5/10/2021 9:54 PM, Sean Turner wrote:
Pondering the beast that is sitting in my lab got me thinking, why 125 ohm? Does anyone know of the history of why this was chosen? I haven't been able to find much about this, so insights are appreciated!

Sean





Re: Type 519 -- Why 125 ohms? Zo formula

Jeff Kruth
 

Hi Sean!A reasonable swag is that it is about the top end of coax impedance, hard to make a higher Z as OD of inner conductor gets vanishingly small. 73Jeff Kruth In a message dated 5/10/2021 9:54:24 PM Eastern Standard Time, sdturne@q.com writes: 
Pondering the beast that is sitting in my lab got me thinking, why 125 ohm? Does anyone know of the history of why this was chosen? I haven't been able to find much about this, so insights are appreciated! Sean


Re: TM-500 Test Module Question

Jared Cabot
 

Ok, I just updated the photo album with a description of the fix for future reference. This should make it clear how to perform the fix.

Let's call it a 'service update', just like you find with all good test equipment... :)


https://groups.io/g/TekScopes/album?id=263748


Re: Chaining power supplies together.

Torch
 

At the risk of being branded a philistine, not all Chinese power supplies are completely useless or disposable. I bought one of the early Korad KA3305P units and have been quite satisfied with it. Effectively 3 power supplies in 1, and the two variable 31V, 5.1A outlets can be chained in series or parallel with the push of a button. IE: it can deliver 62V @ 5.1A or 31V @10.2A.

I did a tear down at the time, which can be seen here: https://www.eevblog.com/forum/testgear/inside-the-new-korad-ka3305p-linear-psu/


Type 519 -- Why 125 ohms?

Sean Turner
 

Pondering the beast that is sitting in my lab got me thinking, why 125 ohm? Does anyone know of the history of why this was chosen? I haven't been able to find much about this, so insights are appreciated!

Sean


Re: Looking for sensitive audio RMS meter

Liam Perkins
 

I'm going thru a PAR CR-4A LNA for a guy in Germany who wants to use it as
an effects box with his synth'. There are a couple of YTs by another guy
over there who loves his and has it make the God Awfullest noises you ever
heard, and he loves it. I think those guy get a kick out torturing
germanium . . .

On Mon, May 10, 2021 at 7:05 PM George Kerber <gk5220@gmail.com> wrote:

Sorry about that. Best bet is to check out eBay listings for 323. It's
probably really pricey when purchased directly from Ballantine (I was about
$700 new in the 1970's). I was surprised to see it on their website.

FFT spectrum analyzer is perfect for noise measurements. You get the
spectrum and total noise level number if needed. I use a, not so portable,
HP 35665A. A good low noise preamp such as PAR 113 is a good complement to
any RMS meter or FFT analyzer.

George

On Mon, May 10, 2021 at 5:41 PM cheater cheater <cheater00social@gmail.com
wrote:

Hi George,

On Tue, May 11, 2021 at 1:58 AM George Kerber <gk5220@gmail.com> wrote:

Bob,
Actually I'm the one looking for the volt meter :-)

You might consider a HP distortion analyzer such as this one:
http://www.barrytech.com/hewlett-packard/analyzers/hp339a.html
https://www.ebay.com/itm/233587661597?hash=item3662e8db1d:g:KrMAAOSwiGBevSVB

I love the fact that it's got a dBV display which is what I'd like to
be doing my measurements in anyways (it's for audio equipment).

Also, a Ballantine 323 True RMS analog AC voltmeter. Only measure to
300
uV.
https://www.ballantinelabs.com/323/
https://www.ebay.com/itm/384146432011?hash=item5970e9600b:g:j8MAAOSwcXBgk0HN

Thanks, any clue how much the Ballantine 323 costs? They don't have
any prices on their website. However, ebay shows units going for sub
$100 which is pretty great.

Any chance of being able to convert its scale to dBV? I would love to
not have to pull out a calculator every time I measure something.

Both are somewhat portable.

An HP 3561A 100kHz FFT spectrum analyzer would probably meet your spec,
it's portable, but really hard to lug around.
I'm afraid it might be way too large for me. Always liked how it
looks, but it's just not practical in my circumstances, and also I'm
not looking for a spectrum analyzer.

On Tue, May 11, 2021 at 2:35 AM George Kerber <gk5220@gmail.com> wrote:

You might also consider soundcard-based FFT for rms and spectrum
measurements to 100kHz and a laptop. There are a lot of choices and
price
ranges. One professional package is by Pioneer Hill Software:
https://www.spectraplus.com/ Very nice, but $$$.

Another is Spectrum Lab, by DL4YHF Spectrum Lab (Audio Signal
Analyser).
I
have played with it a little, but it has a very steep learning curve.

George
I'm looking for a meter to measure total noise level, rather than its
spectrum. I agree that FFT measurements are useful in their own right.

I'm on a short budget. If I had the money I'd just buy Audio Precision.










Re: Looking for sensitive audio RMS meter

Liam Perkins
 

I just lit up the 3457s with inputs shorted and they pass self-test. One of
them has Opt 007 which I -think- might be the 7th digit option but it's a
slog thru about 5lbs of manual to sort that for certain.
You started here saying tens of uV now you're into nVs which is a place
that ought to have a gate saying, "Abandon Hope All Ye Who Enter". Read a
slew of Jim Williams app notes from, I think, Analog Devices and start
buying coffee in 2 and 5lb tins because you're gonna need 'em nested like
Russian dolls.
What -are- you wanting to do ?

On Mon, May 10, 2021 at 7:05 PM Bill Perkins <hifi@telus.net> wrote:

The 465A is an about 1960 design and isn't even in the ballpark

On Mon, May 10, 2021 at 6:46 PM Göran Krusell <mc1648pp@gmail.com> wrote:

hp 465 A amplifier!






Re: Looking for sensitive audio RMS meter

Liam Perkins
 

The 465A is an about 1960 design and isn't even in the ballpark

On Mon, May 10, 2021 at 6:46 PM Göran Krusell <mc1648pp@gmail.com> wrote:

hp 465 A amplifier!






Re: Looking for sensitive audio RMS meter

George Kerber
 

Sorry about that. Best bet is to check out eBay listings for 323. It's
probably really pricey when purchased directly from Ballantine (I was about
$700 new in the 1970's). I was surprised to see it on their website.

FFT spectrum analyzer is perfect for noise measurements. You get the
spectrum and total noise level number if needed. I use a, not so portable,
HP 35665A. A good low noise preamp such as PAR 113 is a good complement to
any RMS meter or FFT analyzer.

George

On Mon, May 10, 2021 at 5:41 PM cheater cheater <cheater00social@gmail.com>
wrote:

Hi George,

On Tue, May 11, 2021 at 1:58 AM George Kerber <gk5220@gmail.com> wrote:

Bob,
Actually I'm the one looking for the volt meter :-)

You might consider a HP distortion analyzer such as this one:
http://www.barrytech.com/hewlett-packard/analyzers/hp339a.html
https://www.ebay.com/itm/233587661597?hash=item3662e8db1d:g:KrMAAOSwiGBevSVB

I love the fact that it's got a dBV display which is what I'd like to
be doing my measurements in anyways (it's for audio equipment).

Also, a Ballantine 323 True RMS analog AC voltmeter. Only measure to 300
uV.
https://www.ballantinelabs.com/323/
https://www.ebay.com/itm/384146432011?hash=item5970e9600b:g:j8MAAOSwcXBgk0HN

Thanks, any clue how much the Ballantine 323 costs? They don't have
any prices on their website. However, ebay shows units going for sub
$100 which is pretty great.

Any chance of being able to convert its scale to dBV? I would love to
not have to pull out a calculator every time I measure something.

Both are somewhat portable.

An HP 3561A 100kHz FFT spectrum analyzer would probably meet your spec,
it's portable, but really hard to lug around.
I'm afraid it might be way too large for me. Always liked how it
looks, but it's just not practical in my circumstances, and also I'm
not looking for a spectrum analyzer.

On Tue, May 11, 2021 at 2:35 AM George Kerber <gk5220@gmail.com> wrote:

You might also consider soundcard-based FFT for rms and spectrum
measurements to 100kHz and a laptop. There are a lot of choices and price
ranges. One professional package is by Pioneer Hill Software:
https://www.spectraplus.com/ Very nice, but $$$.

Another is Spectrum Lab, by DL4YHF Spectrum Lab (Audio Signal Analyser).
I
have played with it a little, but it has a very steep learning curve.

George
I'm looking for a meter to measure total noise level, rather than its
spectrum. I agree that FFT measurements are useful in their own right.

I'm on a short budget. If I had the money I'd just buy Audio Precision.






Re: Looking for sensitive audio RMS meter

Göran Krusell
 

hp 465 A amplifier!


Re: Looking for sensitive audio RMS meter

 

Hi George,

On Tue, May 11, 2021 at 1:58 AM George Kerber <gk5220@gmail.com> wrote:

Bob,
Actually I'm the one looking for the volt meter :-)

You might consider a HP distortion analyzer such as this one:
http://www.barrytech.com/hewlett-packard/analyzers/hp339a.html
https://www.ebay.com/itm/233587661597?hash=item3662e8db1d:g:KrMAAOSwiGBevSVB
I love the fact that it's got a dBV display which is what I'd like to
be doing my measurements in anyways (it's for audio equipment).

Also, a Ballantine 323 True RMS analog AC voltmeter. Only measure to 300 uV.
https://www.ballantinelabs.com/323/
https://www.ebay.com/itm/384146432011?hash=item5970e9600b:g:j8MAAOSwcXBgk0HN
Thanks, any clue how much the Ballantine 323 costs? They don't have
any prices on their website. However, ebay shows units going for sub
$100 which is pretty great.

Any chance of being able to convert its scale to dBV? I would love to
not have to pull out a calculator every time I measure something.

Both are somewhat portable.

An HP 3561A 100kHz FFT spectrum analyzer would probably meet your spec,
it's portable, but really hard to lug around.
I'm afraid it might be way too large for me. Always liked how it
looks, but it's just not practical in my circumstances, and also I'm
not looking for a spectrum analyzer.

On Tue, May 11, 2021 at 2:35 AM George Kerber <gk5220@gmail.com> wrote:

You might also consider soundcard-based FFT for rms and spectrum
measurements to 100kHz and a laptop. There are a lot of choices and price
ranges. One professional package is by Pioneer Hill Software:
https://www.spectraplus.com/ Very nice, but $$$.

Another is Spectrum Lab, by DL4YHF Spectrum Lab (Audio Signal Analyser). I
have played with it a little, but it has a very steep learning curve.

George
I'm looking for a meter to measure total noise level, rather than its
spectrum. I agree that FFT measurements are useful in their own right.

I'm on a short budget. If I had the money I'd just buy Audio Precision.

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