Anyone ever done a relay on the input?

[eddie25]

I built an amp with a relay right on the input, switching between the grids of two channels. Perhaps obviously, it clicks when I switch channels. The weird thing is that I feel like I got this idea from an amp I had repaired in the past.

Anyhow, is this ever done? I tried all the standard tricks (grid leaks and caps almost everywhere) and do have coil diodes installed. The other relay is on the PI and is silent with the pre-PI master turned down. At this point I think it is just contact noise being amplified by the high gain circuit.

Would a better relay possibly hep? I'm using Axicom when it seems like Omron is the standard.

Any such thing as a simple muting circuit, or does anyone know of any amps that switch the input?

Thanks.

[Deric]

Got schematic?

[eddie25]

I don't.

Imagine 2 completely separate JCM800 Marshall preamps, with a relay switching between the very first grid (inputs) of each one (straight from the input jack), and also a relay switching between the two outputs from the Master Volume pot into the PI cap (this is the one that I think is fine). Both are connected to the same switch so they fire at the same time.

I should mention that I setup the relays so that the unused preamp is going to ground at both ends. And of course I tried a 1M across them as well.

[shoggoth]

If the two channels are completely separate and switched at the output, why not get rid of the input relay entirely? Just run the input to both grids simultaneously

[eddie25]

I will try that. I thought about this briefly, but the belief that I had seen this done along with the ease of putting a relay there and the idea that I wouldn't be stressing all the pre-amp tubes all the time caused it to slip my mind I guess.

Thanks.

[Rockwell666]

input is where a lot of noise is generated and amplified the most. like Shoggoth said, run the input into both channels and use a relay to switch between the two channel outputs into the master volume. no extra noise will amplified then.