[sdiy] tape loops, nagra tape machine erase head hack / AKA dummy load

[Anthony Bisset]

Hey Ken^All,

This is strange but switching out the record head for a .022uf cap seems
to work perfectly.  Anything larger than .033uf and I get a pitched whine
(especially .047 and above), anything smaller and the recording starts to
be filled with noise.

Is it appropriate to guess the bias oscillator is using the cap and
working okay?

What frequency are bias oscillators usually operating at... I was thinking
of filtering HF AC going to the erase head as opposed to switching it out...

When my Nagra tech gets back from NYC I'm sure he'll erase me.
-Anthony



On Thu, 6 Oct 2005, Ken Stone wrote:

> Quite often the erase head is used as the inductor in the bias oscillator,
> so as such it is essential. The only thing I would replace it with is
> another identical erase head. That way your circuitry should keep funtioning
> correctly
>
>
> >I'm having trouble disabling my nagra erase head.  After disconnecting the
> >erase head I've tried dummy resister loads between 10meg and 1k, but the
> >recorded sound volume rolls off far quicker than it should.  By the
> >second repeat, the sound is gone.  If I put tape over the erase head
> >and re-enable the erase head then we're in good shape.
> >
> >Do I need an inductive dummy load and if so, how do you calculate such a
> >thing?
> _______________________________________________________________________
> Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
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>
>