On Apr 29, 2010, at 11:25 AM, Richard L. Hess wrote:

> So, welcome to ARSC List and thanks for the posting.

Thank you Richard. I hope to learn from the List and contribute what I  
> Do you have any comments about why the 432 kHz bias of the ATR-100
> (and presumably the 400 kHz bias of the Sony APR 5000) is not
> recoverable?

I assume it's because of the short wavelengths involved. I don't have  
a technical explanation, but Jamie did tell me that he'd never been  
able to recover the bias from a tape recorded on an ATR-100.

In an earlier post you asked about staggered heads. If the bias is  
less than 90 kHz or so, then the bias signal can be recovered for each  
track directly from the audio capture (at 192kHz). If the bias is  
greater than 90kHz, it would have to downconverted through the Bias  
Mixer circuitry of the Plangent electronics. On our Plangent  
electronics the Bias Mixer is single channel (switchable to any of 4  
audio channels) so I would guess that a 2nd Bias Mixer would be needed  
so the bias of each track could be recovered separately. OR, the value  
of the interchannel delay of the staggered head could simple be  
applied to the processing. Perhaps Jamie could chime in.

David Glasser
Airshow Mastering
Boulder, CO
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