Re: [ARSCLIST] RIAA phono EQ and Neumann time constant

[Graham Newton <gn@xxxxxxxxxxxxxxxxxxxxx>]

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.

Don't think Eric... it is bad for you!

I think (there goes that thinking again!) Stephen Temmer  and Georg Neumann 
would roll over in their graves to hear some of this.

The cutter life problem was caused by the record characteristic pre-emphasis 
overdriving the cutter heads on things like cymbal crashes and other loud high 
frequency stuff.  This would burn out the cutter drive coil necessitating a 
VERY expensive repair on the cutting head.  There was a fuse supposedly to 
protect the head coil but the coil always protected the fuse!

Neumann and others developed high frequency limiters on their cutter drive 
amplifiers to prevent this from happening.

I have a hard time with Neumann doing something non-standard, particularly when 
the above method appeared to work successfully.

> 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.
And I suspect that people, even in an A-B comparison test, CANNOT hear that 
difference.

> I know there are many more things to think about, like the accuracy 
> of the cartridge frequency response, the cartridge loading, the vinyl
> wall stiffness, etc. and that the sum of potential errors in phono 
> reproduction is fairly inaccurate to begin with.
Errors big enough to drive a truck through.

> There's also the bigger unknown of whether the cutting lathe was 
> in or out of spec.
And in most cases, you would find the cutting system chain would not be 
precisely in spec on all it's components... but most were close enough that 
nobody doing a listening test could tell.  What about cumulative opposite 
errors in the chain where one effectively cancels the other?  The mind 
boggles... I'm going for an aspirin.

> I also know that most discs cut in Europe since the late 1960s were
> cut on Neumann lathes, but figuring out what was cut on Neumann lathes
> in the USA is more difficult - perhaps half of all lathes in the USA
> are Neumanns. [visually, you can identify a disc cut on a Scully 
> automatic lathe, but that's about it]
The evidence of the cutting lathe type can be seen in the run out where it 
forms a lock groove... and it only signifies the mechanical lathe that the 
cutting head was mounted on.

At RCA Victor in our stereo mastering suite, we had a Neumann lathe, with a 
Westrex 3D cutting head, driven by Haeco amplifiers from an Ampex tape deck 
equipped with a variable pitch/depth preview head.  We had RCA audio amplifiers 
driving LC-1A monitors and we managed to output a lot of award winning 
recordings with no concerns about being down 1 dB at 20 kHz!

> What do people on this list think about this Neumann lathe time constant
> and it's influence on RIAA playback accuracy?  Is it important, or not?
If any people are really worrying about this, I suggest you get back on your 
meds.  The number of grains of sugar in that spoonful you put in your morning 
coffee is more important!




... Graham Newton

--
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