Relay Interface - Fender Trem and Reverb Control

Hey all.

I’ve had a hunt so apologies if this is covered somewhere…

Im using the relay switch but I can’t for the life of me work out how to switch off the reverb and trem separately on a fender amp (tonemaster specifically)

Ive tried multiple different combinations of ring engaged, tip engaged etc.
Tried using a TS and TRS

I can get it to turn off both together, but no one or the other like the Footswitch does that comes with the amp

Any ideas?!

Just looked at the Tonemaster Footswitch. It looks similar to the footswitch used for the Fender Blues Deluxe Reissue which I’m having the same problem with.

It looks like these amps do not use TRS for their switching but use a TR cable with 2 diodes in the switcher in reverse position from each other. The 2 footswitches select the appropriate diode which switches amp.

It looks like all you can do is have a custom cable made that includes the diodes or get a custom converter box made which also includes the diodes. I’ve asked quite a few custom cable / switcher companies and no luck so far.

You would think with the popularity of these amps there would be some kind of solution available.

@james Any chance of a converter box to allow switching of these amps?

I tried googling for a schematic and found this:


from Fender Footswitch Schematic Help

and also https://www.reddit.com/r/diypedals/comments/qupit0/fender_tone_master_amp_footswitch_rebuild/

Based on this, it looks like it functions the same way. There’s only so many ways you can switch with a TRS cable and passive switcher - either with Tip/Ring to ground, or with a resistor ladder.

But, if it is based on this:


then I don’t think there’s any easy way to mod it. Soldering a diode across from Ring to Tip will solve one part. but for the other part, you’ll need to cut a trace and solder another diode which I don’t think is feasible.

I’m pretty sure it’s like the second drawing you posted.

I’ve done some more googling and it seems like it can be done with a custom cable

“These amps have some circuitry in the footswitch that would need to be replicated. The solution only requires a custom made Y cable (all TR plugs) that includes a couple of diodes. The two diodes will be commonly connected to the Tip of the amp end with each diode running individually to one Tip of the two switcher ends. One diode should have the cathode pointing towards its switcher end and the other diode should have the anode pointing towards its switcher end. Any typical diode with a 0.7v forward drop should work for this.”

Does this make any sense? Would it require 2 Relay Interfaces to do the job?

A single relay interface will work because there are 2 relays - one on the tip and the other on the ring.

This wiring should work for the custom table:

TRS side to the Relay switcher.

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Just in case this helps anyone - I had Goodwood Audio make a custom cable for my BDRI and it works perfectly.

Goodwood Audio was extremely helpful and if anyone shows them the above sketch (thanks James!) I’m sure they could help you out.

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