# help with channel switching mod.



## Church-Audio (Sep 27, 2014)

I have a vox ac15c1 that I have done a channel switching mod to. I am using some opto switches that use two fets and an led for switching much like a vactrol. I am switching two things simultaneously I installed a second master volume for the treble channel so that when you switch channels you have separate control. I am switching the input at the gain pot area after v1 grounding the unused pot out, and simply swapping out the master volume. I have tried isolating with coupling caps using resistors to ground to drain off access dc to no avail still get a click when I switch channels. I will post the chip that I am using sometime today when I dig it up. And the schematic with what I've done. It's driving me crazy I am beginning to think it's the chips that I am using. I am running from the 6 volt heater. There are two states with this dual double throw single pole switch arrangement power on one state contacts 1,2 closed 4,5 closed second state 2.3 closed 5,6 closed. When the ic chips see power they obviously change state. I'm thinking it could be a voltage spike in the turn on or power up side that is causing the click.


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## WCGill (Mar 27, 2009)

I have the same problem using relays and yes, it does drive you nuts and seemingly at times, there is no solution. Have you tried isolating the dual switching function to just one and then the other to determine if one switching action is causing grief?


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## nonreverb (Sep 19, 2006)

Clamping FETs on the signal lines like Mesa use.


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## epis (Feb 25, 2012)

Or do it as in SLO, no clicks at all, you would need separate 6.3V windings. I have built my own "vactrols" as well. It works without any issues.


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