3 function footswitch - parts?

dilbert

Hi chaps,

I'm currently using a very simple valve preamp for recording at the moment. It's a Peavey 1U TG Raxx and there are three switches on the front panel which provide 'Bright', 'Thick' Tone adjustment and 'Gain Boost' capability. I am contemplating making these 'foot switchable' for live use.

To that end does anyone have any suggestions for parts to create a foot pedal to facilitate this mod or is there a 3 switch foot pedal available which might do the job?. 

Any suggestions or ideas would be appreciated.

Cheers.     

Sporky

There's a schematic here:

https://www.audioservicemanuals.com/p/Peavey/Peavey-TG/Peavey-TG-Raxx-Schematic-1.jpg

Looks like Thick is effectively a single pole, dual throw, Bright and Gain are effectively single pole, single throw.

You'd have to desolder the existing switches and make a hole for a cable.

dilbert

Cheers Andi, thanks for the heads up, much appreciated.

Sporky

I'd suggest waiting for an alternative opinion from someone who actually does this sort of thing, mind...

Danny1969

One issue unfortunately is taking the signal all the way out to the footswitch and back into the amp will add noise .. these is why amps generally use relays or signal detection rather than let the actual audio leave the amp. 

Relays can be brought in the same config as the switch's and have the benefit of a relaxed state ... meaning they will always be in the default state even if no footswitch is plugged in. 

So I would probably go ... small bit or veroboard bolted inside with the relays on it. If there's somewhere you can internally tap off the small DC voltage for the relays then great. If not put a battery in the footswitch enclosure. Then us a bit of mic cable and TRS connectors  ... common neg and switched +V got the relays to make them switch states 

ICBM

What Danny said - you can't just remotely control those functions by taking the switches out of the unit, because they're signal-path low-level switches and it will cause a (almost certainly unusably) large amount of noise, and also change the sound because even if you shield the cabling to try to keep the noise down, that will add a lot of capacitance.

You need to do it with relays and a control circuit. It can be done, but it's a lot of work. All three switches are actually SPSTs, which makes it easier - Thick doesn't need pin 2 of the switch connected, I'm not sure why they've done that (maybe just for PCB layout convenience).

dilbert

@Sporky & @Danny1969 many thanks for the helpful info, I wouldn't be doing it myself, but from what you have described it's not really worthwhile. I had a thought in my head that I could just relocate the switches to a box but obviously it's a bit more of a job than that and anyway, I seldom use the switches and  and as for the gain boost,....... isn't that what pedals are for?.   

Thanks again for your' time and advice, it's sincerely welcome in a scenario like this.