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[dsavitsk]

The circuit seems to work. It does not get rid of 100% of the thump, but it gets rid of enough that it no longer feels like it might hurt the speakers. At first, it seemed like it was causing some crackling on loud passages, but, if it was, it is gone now.

Thanks again amb. This is greatly appreciated.

-d

 

[amb]

Quote:

Originally Posted by dsavitsk The circuit seems to work. It does not get rid of 100% of the thump, but it gets rid of enough that it no longer feels like it might hurt the speakers.

Yeah, I didn't expect it to completely mute the transient for a couple of reasons:

1. The output impedance of your preamp is still fairly low even with that 68 ohm output resistor, and the JFET shunt to ground is not a perfect 0 ohms, so some bleed-through is unavoidable. If that resistor was a higher value then the muting effect would be improved, but I don't suggest changing it, because in general a low output impedance is a good thing.
2. The JFET starts its muting action as it gets power, and as I eluded to in a previous post, power is being turned on at the amp at the same time, so there is a very tiny window of time where a small glitch might still get through. This is a characteristic of this sort of circuit unless you could delay the amp power-up a bit.

At any rate, despite its shortcomings, it's cheap and reasonably effective, and should have no negative impact on the sound when not muting.

Quote:

Thanks again amb. This is greatly appreciated.

You're welcome.