Re: [ARSCLIST] 1/4" audio tape digitizing

[Goran Finnberg <mastering@xxxxxxxxx>]

Richard Hess:

> My biggest concern is gap-loss in normal pro-machine 
> repro heads. I think that's probably the limiting factor.

Sorry no.

The wavelength on the tape stays the same irrespective of the
duplicating speed.

So when duplicating at 64X the original speed by running the binloop
master recorded at 3 3/4" speed at 240"/s then the replay gap in the
loop bin master machine isn´t any better than around 2 µM.

Which is the same gap width as is used on the Studer A80MR master maker
running the tape at 3 3/4" speed to get you to at least 16 kHz.

The losses occur in the inductance of the playback head at 2.5 mHy
resonating with the loading capacitance.

So you´ll see buffer amplifiers in the headstack with say 2" maximum of
unshielded wire connecting the replay head to the low capacitance input
buffer to get the LC resonance as far up as possible.

Normally the loading input resistor of the buffer amp is set to get you
some free eq loss compensation at approx 1.2 MHz to help compensate for
the spacing loss between the tape and the head due to the air that is
moved with the tape running past the head.

I know since I worked with professional duplicating of cassettes for
more than 15 years of my life and I rebuilt 6 Ampex BLM 200A from 32X
duplicating speed to 64X speeds and I had to figure out all the gotchas
myself.

No rocket science for sure since everything that goes at 1X speeds works
at 128X speed too.

-- 
Best,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering@xxxxxxxxx

Learn from the mistakes of others, you can never live long enough to
make them all yourself.    -   John Luther