[ARSCLIST] Fw: [78-l] ^ Distortion on a cassette tape

[steven c <stevenc@xxxxxxxxxxxxxx>]

Since ARSCLIST has all the serious magnetic tape expertise, perhaps you
can answer Norman's question (and I, or someone, can forward the solution
back over to 78-L...)

Steven C. Barr

----- Original Message ----- 
From: "Norman Field" <jazz@xxxxxxxxxxxxxxx>
To: "78-l" <78-L@xxxxxxxxxxxx>
Sent: Wednesday, June 21, 2006 1:10 PM
Subject: [78-l] ^ Distortion on a cassette tape


> OK, it's well off topic, but there's a lot of expert folks up here. And
I'm
> curious as to how this problem occurred.... somebody here may well know?
>
> This C90 cassette (of speech) was recorded on a faulty machine, in that it
> began very slow, & then ran slower & ever slower.
>
> In fact, it ended up so slow, that 32 minutes of one 45-minute side, when
> roughly re-pitched, ran for about 75 minutes!
>
> Of course, it started off like the Chipmunks... and ended up like
> hyper-active Chipmunks breathing practically pure helium & rushing around
in
> hopeless confusion... 8^}
>
> The starting speed, when roughly halved, gave perfectly acceptable
results,
> as was expected.
>
> But: as the speed fell & fell, finally requiring ~100% pitch reduction, a
> distortion gradually crept in.
>
> So that by the end, the voices were fragmentary & broken, sounding like a
> conversation half-heard in a dream, as it were. And totally
incomprehensible
> of course.
>
> Why should the material have become distorted?
>
> If the cells in the cassette recorder were losing voltage, that would
> account for it... but surely they'd never drive the motor for half an hour
> in that state?
>
> The only thing I can come up with is that the tape was somehow 'saturated'
> with signal, because it was passing far too slowly over the recording
head?
> And yet the modulation level on the tape was very low...
>
> Has anyone here come across such a phenomenon before?
>
> Previously, I've recovered stuff recorded on reel tape at 15/16 ips (~2.4
> cm/sec) when the lowest speed I have here is 3 3/4 ips (9.5 cm/sec), which
> requires a similar re-pitching, and it's been pretty well OK.
>
> Norman.
>
> P.S. At least I'm not charging my client for the 25% of the stuff I did
> manage to recover. We here on this list, many of us the 'progeny' of John
> R.T. Davies, don't like to be beaten! Come to that, I wonder what he would
> have done..?
>
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