[ARSCLIST] Speed correction, was Re: [ARSCLIST] Can 78s sound better than LPs?

[Parker Dinkins <parker@xxxxxxxxxxxxxxxxx>]

According to my research, after WWII US power companies were synchronized,
with the nominal frequency maintained within +/- 0.5Hz.

See http://www.nscl.msu.edu/~daniel/back/yanczer/motordrv.html and
http://www.usace.army.mil/publications/armytm/tm5-689/c-2.pdf.

There is equipment available that provides a resolution of 0.02Hz. It then
becomes fairly easy to make **basic** (not definitive) speed corrections
using the hum signature. It's more difficult to find the hum signature on
professional, studio recordings, but presumably it's not as important in
those cases anyway.

---
Parker Dinkins
MasterDigital Corporation
CD Mastering + Audio Restoration
http://masterdigital.com



on 8/26/06 6:22 PM US/Central, Tom Fine at tflists@xxxxxxxxxxxxxxxxxxx
wrote:

> In fairness to most reputable manufacturers, their decks were set up to leave
> the factory running at 1 7/8 IPS. BUT, most cassette decks employ a belt drive
> somewhere in the works (and many consumer decks employ several belts and one
> motor). The net result is that the mechanics loosen up over time. Then the
> speed fluxuates. This can happen pretty soon after manufacture if the
> environment is temperature-varient and conducive to rubber deteriorating. Yeah
> cassettes, just not the highest of fi mediums! And we won't even discuss the
> typical portable cassette recorder, which was probably not accurate the day it
> was made (not talking about higher-end machines like the SuperScope or Nak).
> With home-made cassettes, I like to get the client in and have them control
> the speed adjust knob on my Nak MR-1 deck, to set the pitch where they're
> happy with it. It's interesting how many kids' recitals were recorded faster
> or slower than 1 7/8IPS, if one is to trust the client's sense of pitch. The
> same is true with old portable small-reel 3.75IPS machines, perhaps to an even
> greater extent. You get where you can tell if something is running slow or
> fast, just by the timbre of the voice or instrument.