RCA Engineers Test Telefunken 12AX7 Tubes against Their 12AX7

kcline

Tube Audio Collector
From Dowd AWA Holding from TCA from Ludwell Sibley. In 1962 H. W. McCord Tube Engineer wrote an eight page " Coded Engineering Letter 653-#806" titled "Flicker Noise Test". Flicker noise is a very low frequency type noise. RCA was getting complaints about this. RCA compared RCA 12AX7 to the Telefunken 12AX7. and stated in the report as "usual Telefunken is our model", their 12AX7 was better then any RCA 12AX7 tested only nuvistors 6CW4 & 7895 came close. Testing procedure is very complicated and I do not have all of the report. Now RCA is not saying that the telefunken sounds better only that it tests better in the ficker noise testing. This paper was only read by tube engineering staff
 
Does it discuss the applications affected that were raising complaints?
 
From Dowd AWA Holding from TCA from Ludwell Sibley. In 1962 H. W. McCord Tube Engineer wrote an eight page " Coded Engineering Letter 653-#806" titled "Flicker Noise Test". Flicker noise is a very low frequency type noise. RCA was getting complaints about this. RCA compared RCA 12AX7 to the Telefunken 12AX7. and stated in the report as "usual Telefunken is our model", their 12AX7 was better then any RCA 12AX7 tested only nuvistors 6CW4 & 7895 came close. Testing procedure is very complicated and I do not have all of the report. Now RCA is not saying that the telefunken sounds better only that it tests better in the ficker noise testing. This paper was only read by tube engineering staff
what is flicker noise? I have read about it but please refresh my memory.
 
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Complaints from "manufactures of medical and geological recording systems and radio broadcasting and other high quality audio equipment. Flicker noise is of interest in the Sonobuoy nuvistor and the military is concerned with it in infrared detection equipment"
 
Complaints from "manufactures of medical and geological recording systems and radio broadcasting and other high quality audio equipment. Flicker noise is of interest in the Sonobuoy nuvistor and the military is concerned with it in infrared detection equipment"
Do you know the technical definition?
 
I do not have all 8 pages of this report just what Mr. Sibley posted in his article in TCA mag. All it says is Flicker noise is a very low frequency noise. Please note the quote "As usual" there must be other papers dealing with Tele 12AX7 where it was the best in whatever testing RCA was doing. The AWA Dowd archives is in no way complete, it was saved from being in the trash from the Harrison NJ tube engineering headquarters by Bro. Patrick Dowd and others. The late Bro. Dowd was a very well known tube collector.
 
kcline, I'm guessing the TCA reference isn't free on-line?

It's also not clear what vintage is the TCA reference, relative to the original 1962 RCA, and how or if TCA got permission to publish a (supposed) extract from the RCA doc, and hence whether a copy of the extract is public domain.
 
It's also not clear what vintage is the TCA reference, relative to the original 1962 RCA, and how or if TCA got permission to publish a (supposed) extract from the RCA doc, and hence whether a copy of the extract is public domain.

The USA has a specific fair-use exemption for such excerpts, so this would not run afoul of the copyright law. In addition, it doesn't matter if it is copyright or not, we, in the USA at any rate, have a right to make copies for our personal use. Beyond that, the original copyright holder (RCA) is long gone and it isn't clear who would even care to enforce those rights. Have you ever read of any lawsuit for hobbyists or engineers distributing 60 year-old technical papers? I sure haven't.

I can't track down the original paper, either.

Edit: removed computer paragraph, as after further researching that proved to be the wrong McCord. Still looking.
 
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In 1962 it could have been an analog computer, so, noise could be an issue.

Tubes were used as opamps for analog computers, true, but the modeling was done with substantial voltages not tiny ones.

Remember, the analog computer is about relative scale of the voltages, so one can use reasonable voltage levels, typically milliVolts to tens of milliVolts in the Philbrick application notes, and is not confined to tiny microvolt signals.

The 1/f noise would matter for DC amplifiers for things like thermocouples or scintillation detectors, but, again, not a typical application.

I can't find any McCord who worked in tubes. He's not mentioned in the RCA design guides. Could have been a one-off publication, of course.
 
"I'm guessing the TCA reference isn't free on-line?" As of now no. TCA Mags are not on line. TCA has a website http://www.tubecollectors.org/ I have no research on Mr. McCord but he was for sure an engineer with RCA. The paper I quoted from was inhouse only was never for outside eyes to see. When I quote I always state from the AWA-Dowd Archives a holding of the AWA. "I can't track down the original paper, either." It is all at the AWA museum near Rochester NY they do not have it online.
 
I have no research on Mr. McCord but he was for sure an engineer with RCA. The paper I quoted from was inhouse only was never for outside eyes to see.

My point was that H. W. McCord published no peer-reviewed papers, nor any papers in the RCA journal, nor has any citations in the RCA tube design books. At least none that I could find. And I looked. He's a mystery.
 
kcline, does that mean the except you have seen is a reference holding in the AWA Museum, or part of an article in a TCA magazine (and if so then which magazine vol/#) ?
 
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