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Re: [ARSCLIST] Fwd: Peter Copeland on RCA Victor recordings (1941)
I've asked some of Peter's former research colleagues what his sources
of info on Victor's use of limiters might have been, and had the
following response from Adrian Tuddenham:
"No obvious written source of that information comes to mind.
From Blumlein's days in audio (if not before) the idea of a
self-limiting recording system without audible defects was a bit of a
'holy grail'.
Blumlein experimentd with reducing the field in the WE cutterhead to
counteract 'blasting' distortion from the inverse-square force which the
moving iron armature experienced on amplitude peaks (the idea was
abandoned because it could not be made to respond quickly enough). I
remember Peter commenting that it was impossible to overmodulate a
Blumlein moving coil cutterhead and the amplitude limit was usually set
by the geometry of the grooves and the limitations of the playback
device.
Peter's ear was incredibly sensitive to limiting (whether by machine or
by hand) and he could often unequivocally hear it when I didn't notice
it or was in some doubt. It is possible that he simply derived this
information from listening to the discs. I have no doubt that he would
not have made a statement like that unless he could quote the evidence
if challenged - and if the evidence were audible, I don't think there
would be much doubt that he would eventually be proven correct."
Regards
Will
-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Doug Pomeroy
Sent: 01 October 2008 14:39
To: ARSCLIST@xxxxxxxxxxxxxxxx
Subject: [ARSCLIST] Fwd: Peter Copeland on RCA Victor recordings (1941)
> From: Doug Pomeroy <pomeroyaudio@xxxxxxx>
> Date: September 30, 2008 8:51:10 PM EDT
> To: 78-list <78-l@xxxxxxxxxxxx>
> Subject: Re: Peter Copeland on RCA Victor recordings (1941)
>
> Clarification:
>
> I only mentioned that issue of Wireless World, because it is
> Copeland's
> Ref. 60, which he identifies at the head of the paragraph which
> includes
> the statement about Victor's use of limiters. Thanks for checking.
>
> Doug
>
>> Date: Mon, 29 Sep 2008 15:14:11 -0400
>> From: Michael Biel <mbiel@xxxxxxxxx>
>> Subject: Re: 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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