Re: small signal NPN transitor for muting microphone


"Walter Harley"
>
> The schematic would be more clear if it read from left to right, instead
> of right to left as it presently does. If I understand what the OP is
> trying to do, the microphone is the signal source; normally, the
> microphone drives the preamp, and the OP is attempting to mute it by
> shorting its output to ground via the transistor.
>
> If the microphone is indeed a dynamic (coil) type, as indicated on the
> schematic, then its output is AC with very little DC component, with
> magnitude on the order of 10mV.
>
> You're right that I'm wrong, though. It would mute the negative-going
> part of the wave, if the signal were strong enough.


** It will MUTE the ENTIRE wave.

Build the cct if you still doubt that !!!!!



> Indeed, it would mute it regardless of the base voltage, because of the
> collector-base diode being forward-biased. It's horribly distorted,
> though.


** Completely wrong.

When the switch is open, the transistor has a very low *resistance* from C
to E - smoothly muting the audio signal.

When the switch is closed, the transistor is biased off.




......... Phil




.

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