From: Patent Tactics, George Brock-Nannestad

Richard Hess wrote and shortened Eric Jacobs' mail:

Hello, just a short input:

1) the actual modulation on the records, during mastering and from the 
finished record, is usually measured by the light-bandwidth (actually the 
width of the band of light) method originally according to Buchmann-Meyer 
(introduced into the US by Ben Bauer). That entirely bypasses the tracing 
loss and other losses in the stylus-groove interface. So, you may be certain 
that the test records are very close tolerance, but you must use an ELP in 
order to get the benefit.

2) I believe that the delay (phase) problem of having a mismatch between pre- 
and de-emphasis will be the predominant issue.

3) I worked my way through the various more or less official discussions on 
pre-and de-emphasis for a paper I gave at AES: "Pre- and De-Emphasis - A 
Forgotten Necessity", AES Convention Paper No. 5360, 110th Convention 2001 
May 12-15, Amsterdam. The sad conclusion (in a discussion of standardization) 
was that after the advent of the tone control, all standardization of this 
nature lost its relevance.

Kind regards,


> At 03:25 PM 2007-04-01, Eric Jacobs wrote:
> >Having a good understanding of the minimum error in the disc cutting
> >system (ie. just how flat a frequency response could be achieved, and
> >how accurate are the test discs used to calibrate the cutting systems)
> >will help make specifying minimum RIAA accuracy for reproduction less
> >arbitrary.  If disc cutting systems were accurate to 0.1 dB of RIAA
> >from 20 to 20 kHz when properly set up, then I think the Neumann
> >constant is worth looking into more deeply.  If disc cutting systems
> >were accurate to 1 dB of RIAA, then the Neumann time constant is a far
> >smaller consideration.
> >
> >I do believe it is a slippery slope to say that just because there are
> >many other elements in the reproduction chain that introduce far
> >bigger errors, we should ignore the potential influence of the Neumann
> >time constant - especially if the Neumann time constant could be easily
> >compensated for.
> Hello, Eric,
> I believe that we will be very lucky to be holding +/- 1dB from 20 to 
> 20 kHz with the tape component--in fact, holding +/- 1 dB from 50 to 
> 15 kHz across the board would have been quite excellent. In just ten 
> tapes from a major broadcaster known for their quality, I saw one 
> tape way outside +/- 1 dB at 15 kHz and each session varied within 
> the range while tapes from the same session were very close. These 
> were 15 in/s tapes.
> While that begs the issue of direct-to-disc recordings, I would 
> suggest that the vast majority of recordings made from perhaps 1950 
> until the end of the LP era were made via tape.
> Yes, it's a slippery slope and that's why I suggested that you 
> contribute an article about this to my blog where we can document all 
> of these little gotchas. It doesn't have to be long, but I will set 
> up a separate topic as I plan to add more tape ones in the future -- 
> or if you write it on your own website, I'll make a note of it and link to
> it.
> And oh, the chemistry issues. Tapes, like the plumbing in "The Money 
> Pit", are not getting better with age.
> Cheers,
> Richard