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Re: [ARSCLIST] Victor shellac test pressing manufacturing question
On Friday, April 03, 2009 3:11 PM, Tom Fine wrote:
> As for the super-sonic frequencies, Eric, Mike had it right -- no
> microphones or audio transformers of those days would pass those
> frequencies, so anything up there is ringing or junk.
The current cartridge load is 600 Ohm. This works well for the
Lyra Helikon SL (0.220 mV output) which seems to prefer 600 - 1000
Ohm loads. However I think the Ortofon SPU Classic (0.200 mV output)
will need to run somewhere between 10 and 100 Ohm. I'm in the process
of making the appropriate cartridge load plug-ins and will test them
On a side note: I was hoping to find some 78 RPM coarse groove test
records with square waves, but I don't think such a beast was ever
made. The only 78s I seriously collect are test and calibration
records - these are great documents of historic EQs. The highest
frequency I've seen is the Victor-NBC Orthoacoustic calibration
disc with 10 kHz tones.
The good news is that the new AES 78 RPM test record has test tones
up to 30 kHz, which should be enough to excite ringing. For anyone
doing serious 78 RPM preservation work, the AES coarse groove test
record is a must.
The Audio Archive, Inc.
Disc and Tape Audio Transfer Services and Preservation Consulting