Re: [ARSCLIST] Error concatenation (was RIAA phono EQ and Neumann time constant)

["Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>]

Hello, Eric,

This is indeed an interesting anomaly.

I think we need a catalog of off-standard calibration factors--and 
I'd be willing to make that a specific category on my blog ( 
www.richardhess.com/notes/ ). I accept guest articles should you be 
interested -- or I can point to your article.

HOWEVER, it is a very tiny error compared to what we're seeing in 
tape. There is a 4 dB at 16 kHz uncertainty in the cassette format 
which I believe I have fully documented (minus one uncertainty which 
sets the centre point of the anomaly--we know the two ends) at
http://richardhess.com/notes/2006/05/17/cassette-equalization-the-4-db-ambiguity-at-16-khz/

While the off-standard factors are probably not as large in reel tape 
as in cassettes, they, too, are larger than what you are discussing 
concerning discs. The good news about the tape variability in the 
disc chain is many (if not most) tapes had multi-frequency tones 
printed to them which would then be used to calibrate the playback 
machine prior to the disc cutting process.

A friend of mine and I think they may be as much as a 3-4 dB window 
in calibration tapes at 15-16 kHz after the NAB (NARTB) standard 
became a standard. Prior to that, there is even greater variability 
in tape. This is a down-the-road round-toit project for me as it 
involves a lot of fussy work in actually measuring several boxes of 
old, but unused, calibration tapes.

Cheers,

Richard

At 03:02 PM 2007-03-30, Eric Jacobs wrote:
> I've been thinking about the RIAA phono EQ curve, and realized that
> the majority of discs in Europe and many in the USA are cut on
> Neumann lathes.
>
> The Neumann lathes have a fourth time constant of 3.18 microseconds
> (50 kHz turnover) which was introduced around 1968 to increase
> cutter life.
>
> When a disc cut on a Neumann lathe is played back on an RIAA phono
> preamp, the frequencies between 10 kHz and 20 kHz are more rolled
> off than they should be.  Discs cut on a Neumann lathe will play
> -0.2 dB at 10.9 kHz and -0.64 dB at 20 kHz.  If your average phono
> preamp is -0.5 dB at 20 kHz, that means that you could be off by as
> much as -1 dB or more.

Richard L. Hess                   email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.