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Subject: Re: Help needed with audio mute circuit
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Date: Thu, 19 Sep 2002 06:39:21 GMT
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> > a self-conducting jfet can shorten the output to gnd, but you will need
> > negative voltage bigger than the neg.output swing + Upinch-off to
> > put it into high impedance. Since there is not much current involved,
> > can do that with a voltage doubler circuit after your transformer. With
> > arrangement the quality will not suffer, as the signal is not passing
> > through the fet.
> Yes. Do you think that having a JFET sitting at the output is a problem?
> e.g. ESD. The thought of generating a negative bias voltage makes me
> uneasy :)
> > Really the relays are not an expensive option, you need only one relays
> > multiple channels if there are enough contacts and again you can power
> > with a separate rectifier from your transformer to switch before the
> > regulator starts to drop out.
> The problem is that this is a compact, low power design with a lot of
> so relay isn't really an option. Oh yeah, and price is a big issue as
> BJTs on the other hand are less a cent a piece.....
> There has to be a way.... isn't there?
1. BJTs need a positive voltage to make them conduct, which will not be
available for long when the device is unpowered.
2. BJT have a small offset voltage, which will be less than the normal bias,
but still substantial (50mV)
3. for higher output currents there is a rectifying action
there are some schematics on the website of Rane, as far as I remember it is
an analog delay which has this kind of output mute.
electronic hardware designer