Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #20 on: November 07, 2018, 03:00:34 PM »
Here is a link to the raw scans.

https://we.tl/t-cZDL23E8Qu

I'm not sure how many versions of the PTMV there were. There are scans for 930-02 and 930-03. I don't have scans for 930-01.
« Last Edit: November 07, 2018, 03:16:14 PM by Gold »


beatnik

Re: Light Beam Meters - Neumann PTMV
« Reply #21 on: November 07, 2018, 03:36:37 PM »
Awesome. Thanks a lot Paul

abbey road d enfer

Re: Light Beam Meters - Neumann PTMV
« Reply #22 on: November 11, 2018, 07:23:54 AM »
I have a set of light beam PPM meters in a Neumann SP66 mastering console. I had another set in previous MT66 which is almost the same as an SP66. I could never get them calibrated where I trusted them. 
What's wrong with the calibration? You should be able to do a simple comparison with a trusted meter on steady tones. Maybe they are calibrated at +6dBu (the German broadcast standard of the time). Or is it the response to transients? Do you have other peak-meters you van compare with? Specs for PPM's have evolved over the years, particularly the attack time, which was originally 10ms, gradually shifted to 1ms, and now to zero (True-PPM). That makes a lot of difference in terms of what the eye perceives.
At Barclay studios we made comparisons, since we had all sorts of meters available (we had lightbeam meters - probably Neumann - in the transcription desks, Moving-coil PPM's in the Neve desk, VU-meters in the API desk, bargarphs in the cutting room, and a 30 LED prototype I had built. We ended up concluding they all gave different indications as soon as there were transients in the program. We didn't pursue with the prototype because it was felt that, since it did not agree with any of the other established systems, we could not impose our own standard.
Anyway, the Neve PPM's were recognized as the most usable, followed by the VU meters.
Only one guy favored the Neumann lightbeams, having worked all his professional life with them. OTOH, he did not have to make  big decisions, since his work was copying tapes to tapes.
Me, having been a 2-week chicken at the time, I was comfortable enough with my LED meters and used them regularly  in my recording studio and in the consoles I built at the time.
Now I'm happy with the true PPM's in my DAW.

I recently discovered a Neumann factory calibration procedure for the PTMV amplifiers. I also found a calibration procedure for the meter unit. I’m having someone restore them. The PTMV has nuvistors and that is out of my wheelhouse.

I can’t wait to see a properly calibrated light beam meter. I’ve never seen one before. I don’t imagine anyone under say 60 years old has ever seen a properly calibrated one.
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Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #23 on: November 12, 2018, 01:09:40 AM »
I think the calibration problem was that if I adjusted 0% to minimum deflection and 100%  to the red line then 0VU didn’t match up  at +4 dBu. Each channel was different too. That was about 15 years ago so I don’t exactly remember.

There are a lot of calibration points. I’d like to see what one looks like when calibrated to factory specs before I decide if I like it or not.

I like VU meters. I’ve been using mechanical PPM ‘s driven with a board that is more German than British.  They are okay but I have an RTW plasma PPM that I like better. I’m going to use that in my main console instead of the mechanical PPM’s.

The light beam meters are built into the Neumann SP66. I want that restored to original condition. It ‘s a great sounding and looking console IMO. 

abbey road d enfer

Re: Light Beam Meters - Neumann PTMV
« Reply #24 on: November 12, 2018, 06:53:04 AM »
I think the calibration problem was that if I adjusted 0% to minimum deflection and 100%  to the red line then 0VU didn’t match up  at +4 dBu.
Calibrating at nominal level is the first step in the calibration process. However, adjustment of other parameters interact with it; it is often necessary to redo the initial level calibration, sometimes several times. It's a lengthy and tedious procedure.

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I like VU meters.
I respect your opinion, but would you agree they are almost useless in a digital environment? I tend to look at them as decorative signal presence indicators.  :)

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   I have an RTW plasma PPM that I like better. I’m going to use that in my main console instead of the mechanical PPM’s.
That makes sense IMO.

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The light beam meters are built into the Neumann SP66. I want that restored to original condition.
The meters are probably the most difficult in that endeavour.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #25 on: November 12, 2018, 11:17:25 AM »
Calibrating at nominal level is the first step in the calibration process. However, adjustment of other parameters interact with it; it is often necessary to redo the initial level calibration, sometimes several times. It's a lengthy and tedious procedure.

As I remember no matter what I did something didn’t seem right.  It wasn’t subtle like being picky about integration time.

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I respect your opinion, but would you agree they are almost useless in a digital environment? I tend to look at them as decorative signal presence indicators.  :)

They are obviously useless for seeing overs but still just as useful for judging how the audio will hit a mechanical transducer like a speaker.

abbey road d enfer

Re: Light Beam Meters - Neumann PTMV
« Reply #26 on: November 12, 2018, 12:35:15 PM »
As I remember no matter what I did something didn’t seem right.  It wasn’t subtle like being picky about integration time.
There are a few components in them that are prone to drifting; when they do, the log amp goes all over the place. Finding which is defective is sometimes uneasy. IIRC, they had to be sent back to the factory; even the french distributor was not properly equipped (competent?) to service them.

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They are obviously useless for seeing overs but still just as useful for judging how the audio will hit a mechanical transducer like a speaker.
If you mean they are a rough indicator of how loud it will sound, I agree; that's their raison d'etre, but it's been demonstrated often enough that the perception of loudness is not a simple matter and that it takes a quite complex analysis to achieve proper measurement of perceived loudness.
If you mean that a VU-meter can give a useful indication of how a loudspeaker is stressed, that is far drom the reality; the mechanisms are very complex. A VU-meter may indicate roughly the electrical power delivered to the loudspeaker, that's about it.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Gold

Re: Light Beam Meters - Neumann PTMV
« Reply #27 on: November 12, 2018, 01:21:26 PM »
There are a few components in them that are prone to drifting; when they do, the log amp goes all over the place. Finding which is defective is sometimes uneasy. IIRC, they had to be sent back to the factory; even the french distributor was not properly equipped (competent?) to service them.

That’s why I gave it to an ace tech who is familiar with this old stuff. He’s calibrated them before many times.

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If you mean they are a rough indicator of how loud it will sound, I agree; that's their raison d'etre, but it's been demonstrated often enough that the perception of loudness is not a simple matter and that it takes a quite complex analysis to achieve proper measurement of perceived loudness.

No, I use my ears for that.

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If you mean that a VU-meter can give a useful indication of how a loudspeaker is stressed, that is far drom the reality; the mechanisms are very complex. A VU-meter may indicate roughly the electrical power delivered to the loudspeaker, that's about it.

That’s what I mean. The integration time of a VU meter more closely approximates the breakup behavior of cheap speakers. I wouldn’t use them if I was designing drivers but I get very useful information out of them. I say this from experience. YMMV.