[78-L] 1937 shellac test pressing outperforms audio CD

[Michael Biel]

Eric Jacobs wrote:
> I apologize in advance for cross posting.
>
> I couldn't help sharing this - I am regularly measuring 27.2 kHz 
> harmonics and occasionally as high as 43.6 kHz harmonics (violin)
> from a series of 1937 RCA Victor test pressings - nearly 72 years
> old.  I'm pretty fastidious about accurate cartridge loading, so 
> I don't think we're seeing ringing of the transducer.
>   

But they could be harmonic ringing of the mechanics of the cutter 
head--the other mechanical device in the chain.  You have to consider 
the source feeding the recording head--the microphones and amplifiers.  
If they were using RCA 44-BX Ribbon Velocity microphones, their top end 
is 13K to maybe 16K depending on the condition of the ribbon.  There 
also are limitations of the impedance matching transformer in the base 
of the microphone.  Then what are the top ends of the RCA pre-amps and 
amps in use in 1937?  I would think they would be rolling off by at 
least 20K if not lower.  We probably can't be sure even if we check the 
spec sheets because I doubt they were measuring any higher. 

While you are at it, I'd like to see what you measusre on Western 
Electrtic Wide Range Vertical Recordings such as used by World, 
Associated, and Muzak.  They claimed 13K around 1933-34.  I have a 
matched pair of World test pressings of the same broadcast on a lateral 
and a vertical, and while the lateral is great, the vertical IS better! 

I mentioned yesterday a 1932 Victor of Astaire with George Hall's orch 
on the Buddha CD "Time Capsule" which has highs that are unbelievable.  
Vince Giordano produced it.  I think this side was done off a vinyl test 
from the Victor Vintage series era, or maybe even a metal.  Victor and 
other companies routinely polished their masters or stampers with 
jeweler's rouge which probably removed the rough edges of the sound wave 
-- namely the high frequencies.  George Brock-Nannestad discovered a 
document at EMI that discussed Victor running a knurling tool thru the 
grooves to likewise smooth them out.  Remember those wear tests I 
mentioned yesterday?  Rough grooves wore out faster.  GOOD RECORDINGS 
wore out faster!!  There is evidence that Victor "dumbed down" their 
recordings, so it is important that you have access to those test 
pressings which might not have been compromised.  But maybe some of the 
things Victor was polishing off were cutter-head transient ringings. 

Mike Biel  mbielA at mbiel.com
> Never mind that we've invested nearly $60k in our analog disc 
> playback and digitization system, pushing the limits of what is 
> possible, but I was astounded by the recording quality and 
> performance of these particular discs that long preceeded modern 
> formats like magnetic tape and LP, let alone CD.
>
> For those who have the ability to measure this sort of thing,
> I can email 1-second and 2-second samples (24/96 WAVE files).
> For those that do not have access to a high-resolution spectrogram, 
> I can send jpegs taken from ours.  The WAVE files altogether are
> 2.3 MB - not especially large - but you should still make sure 
> that your email software and internet connection can handle email
> of this size.
>
>
> Eric Jacobs
>
> The Audio Archive, Inc.
> tel: 408.221.2128
> fax: 408.549.9867
> mailto:EricJ at TheAudioArchive.com
> http://www.TheAudioArchive.com
> Disc and Tape Audio Transfer Services and Preservation Consulting
>
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