Temporary mute circuit to avoid gain stage popping?

[Frost]

Hi there,

I've got a guitar amp with a gain stage that can be switched in or out. Problem is, since it uses a series switch, the stage pops when I switch in or out. I'd use a shunt type switch but I'm unhappy with the tone degradation of the isolating resistors, etc.

Can anyone recommend a very temporary mute circuit to mute the output of the amp when the relay for the switching gets engaged? Can I use a 555 CMOS delay for this or a CD4049 as a flip-flop type circuit? Many thanks,

-Heiko

[Travis]

How about shunting with a power FET?  It should help you lose the clicks/pops and reduce or eliminate signal degradation.

[Frost]

Hey Travis,

Thanks for the suggestion. I spent all day yesterday banging my head into the wall trying to come up with a complex solution. I was not until I was brushing my teeth getting ready to hit the hay that I thought of what you suggested...using a transistor activated by the momentary switches that trigger the 74C373 to just shunt the signal in the amp to ground. Anyways, thanks again!

-Heiko

[Travis]

Frost, RG does something similar in his automatic mic muting article.

The photoFETs almost certainly can't handle the voltage you need, but the idea is there.

http://www.geofex.com/Article_Folders/automike/automike.htm

[Frost]

Hey Travis and everone else,

I'm using a 2N3904 NPN transistor to ground the signal in the amp at the entrance to the phase inverter. Is there a better transistor that you can recommend? I'm still getting a little bit of pop coming through...

Thanks,

-Heiko

[niftydog]

You're sure you're getting full saturation?

I've never done this, but I would hazard a guess that a MOSFET would do a better job.