[sdiy] coupler module

[Czech Martin]

Because I have more bipolar transistors on stock than
JFETS. But JEFTS may work also, perhaps the attenuation
is not that strong. Anyway, the  collector base
or drain gate junction must no be forward biased when
the transistor is supposed to be shut. All MOSFETS
without seperate bulk pin will have problems due to
the drain/ source-bulk diode.

Adding such a shut down transistor is an old trick
to fool measurement people when they try to 
measure idle noise (or similar) of DAC converters
and other circuits. Of course a short is dead silent.

The transition of the normal DAC noise floor to the
shut down noise floor seems to be very unpleasant
to the ears.

m.c.

> -----Original Message-----
> From: Glen [mailto:mclilith at charter.net]
> Sent: Dienstag, 26. August 2003 17:32
> To: Czech Martin; Fdi; synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] coupler module
> 
> 
> At 11:22 AM 8/26/03 , Czech Martin wrote:
> >The mute can perhaps be done with a simple bipolar 
> >transistor after a resistor.
> 
> Why not use a FET? It seems that most of the commercial 
> instruments I've
> seen use a FET--unless they actually use a relay for the 
> lower distortion,
> on-resistance, and noise.
> 
> later,
> Glen
> 
>