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RE: Highest frequency presnt on LPs?

Posted by Werner (A) on September 23, 2009 at 07:10:50

In Reply to: Highest frequency presnt on LPs? posted by thekong on September 22, 2009 at 22:20:49:

Actually LP is a pretty treble-unfriendly medium. Here are a number of issues to ponder:

1) Cutter HF response is not very extended. The best seems to be the (rare) Ortofon DSS731, -5dB at 30kHz. The ubiquitous Neumann SX66 and SX74 were significantly worse. (Note that quad albums were cut at
half speed, hence the apparent response beyond 30kHz.)

2) The cutting process uses treble limiters, as too hot treble can burn the cutter's coils, something not tolerated in a commercial venture.

3) Many LPs since the early 80s, and even late 70s, were cut through a digital delay line (to allow the groove spacing computer to do its job). These delays typically sampled at 44.1kHz, 48kHz, 50kHz, thus hard-limiting the result to 22kHz, 24kHz, 25kHz.

4) The manufacturing process is lossy, with stamper wear manifestating earliest as pure treble loss.

5) Upon replay tracing and tracking errors cause a level of distortion that reaches 10% (!) at 20kHz with most cartridges.


In the past years I have done spectral analyses on many commercial LPs.

Very often this reveals a hard ridge in the range 20-24kHz, indicating a digital master or digital delay line. Sad but true.

In nearly all cases was it clear that the spectral response above 20kHz was dominated by the distorion components of the baseband signal.

I have seen one (1) commercial LP that has something at 30kHz that I cannot reduce to mere distortion. It is probably a studio artefact.

However, when testing Japanese direct-cut LPs made in the 70s the spectral analysis looks much cleaner and with a nice and continuous response out to 40kHz or so. So it can be done, but it is inlikely
to happen on a mass-produced commercial product.



And then you wake up and realise that your classmates of old ... are running most of the TV shows.

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