Reverb Footswitch Mod

Some players would like their reverb to be footswitchable, so they can turn it off when using distortion or when using different time-based effects. I get emails and posts asking, “Can you convert the Fat footswitch to kill the reverb?”

Yes, you can, but then you lose the Fat function. Separating the the Fat button from the footswitch and wiring the footswitch to the reverb is more work, and starts to get complicated. And some people want both.

So here’s a quick-and-dirty way to add footswitchable reverb to your Blues Junior.

I’ve got a kit for that, in the Mod Kits and Services tab. It’s pretty simple — a jack, some high quality miniature coaxial cable… and that’s it.

Drill a 3/8 inch hole in the chassis next to the speaker and Fat footswitch jack. Connect the center conductor to the top lead of C19. Bend it around the lead, close to the circuit board. Connect the shield lead to the lower lead of C19. Solder both, using only enough heat to flow  the solder. Too much heat could dislodge the solder joint on the back of the board; an extreme amount could damage C19.

Click for larger image.

When you need reverb switching, plug a guitar cord and an on/off latching footswitch into the new jack. When the switch is closed, it grounds the output signal from the tank and silences the reverb.

Keep the cord as short as possible to avoid picking up hum.


  1. SCWhitmore says:

    Hi Bill, I would like to do this mod, but can you please clear up the guitarchord and on/off latching switch. All I need is a single button foot switch like the one I have for the Fat switch right?

    Shawn Whitmore

  2. SCWhitmore says:

    Thanks Bill, I realy enjoy your site. Gave me courage and confidence to do my own work on my amp. I also did the Twin stack mod. I did notice a difference. I look forword to doing more of you mods. Thanks Again. Shawn Whitmore

  3. skatevato422 says:

    Very easy to do and alot of fun, I used a live wire footswitch and it works fine. Next on the list is the bypass switch and a speaker change, Thanks Billm audio

  4. Vintage64 says:

    I’ve done this mod on a 2011 Limited Edition Tweed Blues Junior and it works great. There are however slight differences in this model’s reverb tank. The input and output sockets have changed from the style pictured above to a white plastic type and the wiring has changed. I originally soldered to the BLACK wire on the OUTPUT socket tab of the tank (as described above) but it did not work (No fault of Bills of course). On closer inspection I noticed that all the wiring colours were reversed. That is the centre pin tabs on both the INPUT and OUTPUT were wired throughout with BLUE wire and BLACK wire was used for the outer contacts. As the new plastic sockets are moulded with the tabs built in, it can be difficult to see at first which tab goes where. A tip is to look down the centre hole of the socket from the inside of the tank to locate the pressure plate that contacts the centre pin. Obviously this is the right tab to solder to regardless of the wire colour. After swapping to this tab that was connected to the BLUE wire on my tank it worked fine. I’m not sure if this wiring colour code is for the new models or if mine was just built on a Friday afternoon? Hope that helps anyone having the same problem. Thanks again Bill for great kits and mods.

  5. skatevato422 says:

    Will the reverb footswitch mod work on the the reverb tank on a hot rod deville?

  6. Hello, Bill!

    I’ve been looking for something like this for my Fender Supersonic 60 for a long time. Thank you very much for the idea. I’ll try it as soon as possible.

    I will try not to drill the reverb tank. Let my explain: In the photo number 5, I can see a hole in the tank next to the “contact arm”. Maybe I could send a cable through a hole like that, make the connections inside, and then add a female cable plug to the cable outside the tank. When I want to use the mod, I’d connect the footswitch to the female jack with a guitar cable.

    I think it would work the same. Am I right????? Am I missing anything? Maybe a lot of hum or something?

    I don’t have a machine to drill the hole, that’s why I’m planning to do this. What do you think?

    Thank you very much for the idea and for your time!

    And please, excuse my bad english.

    Very nice webpage!

    • bill says:

      Yes, you can just run a wire into the reverb tank and it will do the same thing. You should use shielded guitar cable or you will get hum.

  7. jacobbundren says:

    Is it just me or do I remember this page having a lot more photos and detail? Has something changed?

    • bill says:

      Yes, I replaced the old technique (installing a jack in the tank) with a new one because it’s far easier to drill the chassis than the tank. The effect of the reverb is the same.

  8. jacobbundren says:

    Is there any way to get ahold of the old way? or will this work on a blues deluxe also? i was looking forward to doing that this weekend. thanks bill!

    • bill says:

      On an original Blues Deluxe, you can put the jack across C17 or R33, whichever is more accessible. Test with an ohmmeter and you’ll find that one side of the resistor and/or the cap is grounded. The shield lead goes there; the center lead to the other side. This will ground out the return signal from the tank.

      On the Blues Deluxe Reissue, the components are C10 and R35.

  9. studiodunn says:

    This worked like a charm. I am having an issue with my aftermarket switch not working on the Fat side. I assume, from reading, that the LED is the issue, and since I can plug in a cheap Johnson switch and it works, well……….

    I was wondering if the Fat and reverb can be wired up to a Stereo jack? One less cable is always a welcomed subtraction.


    • bill says:

      Yes, you could run the cutoff wire to a stereo jack instead of the mono jack. The stereo footswitch jack we use for the Clean Boost might work in that application, but the run from the jack to the board would require shielding.

      • prof.sherrill says:

        I’ve done the basic kit and the TwinStack mod to my BJ and am very happy with the results. I’m thinking about doing this stereo Reverb/Fat switch mod but have some concerns about hum. If one was to switch the reverb with a stereo switch, would there be more hum than two single switches? And at what length of chord would hum begin to become a concern for a reasonable person?

        Also, when you say in the above comment “the run from the jack to the board would require shielding,” do you mean a TRS cable with additional shielding around all three wires within? I’ve never cut open a TRS cable. Is that standard?

        • bill says:

          You would use shielded wire for the run from the jack to the reverb input point shown above. Not TRS, just regular coaxial.

          It’s hard to say how much hum there would be; shorter is better and higher quality cable, like Mogami or Canare is a plus.

  10. max says:

    First thanks a lot for those great mods. I’ve modded my BJ serie II with some of your kits (cream board basic, presence, sparkle, standby) and I’m really happy with it. I now play with the amp I’ve always wanted : Small combo with a big round sound.

    I still have a small issue with the reverb (that’s why I’m posting here). When I turn the reverb volume down to cut it, there is still a little reverb queue when I play quick and short notes with a lot of transient. I thaught it was the pot so I changed it (and also cause I wanted the log feeling to it) but my problem remained. I think it’s just a consequence of the way the reverb is implemented on this circuit.

    Is my only solution to implement a “kill switch’ function like the one proposed here?
    And if the answer is yes, instead of putting a foot switch, do you think I could use the switch provided with the presence pot mod? I’m not willing to install your clean boost, so I have this switch inside the amp with no function.

    Of course, I’d be glad to have a better solution (no switch) to keep only one control (the pot) for the reverb instead of two (pot + switch). I thaught of reducing the gain stage of the return of the reverb, by changing R42 or R44 on the cream board if I’m right (but I don’t know for witch value). But you know this circuit and the consequence of mods better than me. I think I would then have to turn my pot a little upper to have the same reverb then, but I might also have some more “noise” in it no ?

    Anyway, thanks for any advice and thanks again for the great job you do here.

    • bill says:

      Try lifting one leg of C23 (cream board). That’s the treble bleed/bypass cap for the reverb control. It keeps the reverb from getting too dark as you turn down. In return, it lets a tiny amount of treble reverb bleed all the time. Maybe you can live without it.

  11. trav357 says:

    Is it possible to have the reverb turn off when the fat switch is engaged?? I would like to use a two button footswitch, one for fat and reverb off and one for clean boost. If not I will use a three button switch.