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Re: [ARSCLIST] Peter Copeland on RCA Victor recordings (1941)

Prentice, Will wrote: 
I don't think Peter's reference to Victor's multiple limiters and the
Wireless World article are related. The article actually does cover
de-emphasis, stating "A system of pre-emphasis and compensation with
what has been termed the "orthacoustic characteristic" has recently been
developed..."

Regards

Will

Then this has nothing to do with recording phonograph records. This system was used only for 16-inch 33 1/3 RPM broadcast transcriptions. Part of the specifications include the minimum inner grove diameter of 8-inches. It was originally announced on Sept 15, 1939, and revisions were made to the spec sheet on March 30, 1942 and May 25, 1943 which is the version I have. These two revisions cover the mentioning of the NAB curve introduced in 1942 and the RCA Universal Lateral/Vertical pick-up and compensation filter introduced around those dates.

RCA did manufacture a Limiting Amplifier at that time, the 86-A, MI-11216, but it is designed to work at line level for the composite feed to a transmitter or recorder. It is rack mounted and takes an 8-inch high space. It would take a whole rack full of them to use independently on each mic. Additionally, each mic would have to be pre-amped and amped up into the limiter, and the output padded down to go to the mixer. They didn't do things internally in the board back in those days! The catalog also mentions a 96-AX Deluxe Limiting Amplifier but it is not included in the 1941 broadcast equipment catalog I have.

Mike Biel mbiel@xxxxxxxxx

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Michael Biel
Sent: 29 September 2008 20:14
To: ARSCLIST@xxxxxxxxxxxxxxxx
Subject: Re: [ARSCLIST] Peter Copeland on RCA Victor recordings (1941)

Prentice, Will wrote:
Doug and all

I've looked up this edition of Wireless World, but there's no mention
of
Victor's use of limiters I'm afraid. It's a short, 3 paragraph article
entitled "New Recording Characteristic: Reducing Noise Level"
describing
in general terms the idea behind pre-emphasis.

I think the key word here is the use of the word "level" in the headline. Since limiters adjust level, could he have misinterpreted it to mean that this EQ was adjusting levels? As we know now, a pre-emphasis properly works only if there is a calibrated reciprocal de-emphasis on the playback end. Consumer phonographs did not have actual de-emphasis circuits at that time, only professional turntables in broadcasting had them for the newly emerging Orthocoustic and NAB curves. Unlike Dolby and DBX, these units were completely passive. Was

Peter possibly claiming that RCA was using limiters as an active EQ, several decades in advance of Dolby? And what was the 1941 Wireless World article detailing? Orthocoustic had been announced back in 1938 for ETs. Was this a curve being used on commercial phonograph records or a belated article on Orthocoustic?
I don't recall discussing this with Peter, but others he worked with
on
a wider level may know his sources. George Brock-Nannestad, possibly?

Will

I agree. George, have you seen anything in the EMI papers that discuss this?

Mike Biel mbiel@xxxxxxxxx 
-----Original Message-----
From: Doug Pomeroy

The following from Copeland's manual has always puzzled me, and I
wonder
if anyone can shed light on the reference to "Victor's then-unique use of multiple
limiters (essentially one on each mike)", since I've never heard of this from any other
source. This may originate in Ref. 60, Wireless World (1941), which I have not
seen. RCA Victor may have experimented with limiters in 1941, but Copeland's
statement can leave the impression that this was common practice.

6.71 Various RCA characteristics
Ref. 60 (July 1941) is the earliest contemporary reference I have found which describes RCA Victor using pre-emphasis on its 78s, although the time constant was not given. Straight listening suggests the idea was tried somewhat earlier, and we saw in section 6.23 that Moyer wrote about RCA's Western Electric systems with pre- emphasis at 2500Hz (corresponding to 63.6 microseconds); but I am deeply sceptical. It seems to me far more likely that, if something which had been mastered direct-to-disc was reissued on microgroove, the remastering engineer would simply have treated everything the same. And I consider it likely that judging by "pure sound" clues, Victor's then-unique use of multiple limiters (essentially one on each mike), would itself have resulted in a "brighter" sound.
Doug Pomeroy

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