Footswitches for Clean Boost/Fat Option

Here are some footswitches that have a TRS (tip, ring, sleeve) or stereo plug and two switches. Some have LEDs, but they won’t light because the Blues Junior senses the position of the switches by sending a -15 volt signal through the switches. When it’s grounded by the appropriate switch, the Fat or Clean Boost turns on. It’s possible that you could rewire one of the LED-equipped pedals by reversing the polarity of the LEDs and putting them in series with the switch. It may require a dropping resistor to prevent damage to the LED and too large a dropping resistor may prevent the amp from sensing the switch position.

I haven’t tested this modification, however, so you’re on your own.!Z0ivskAowsbjJ38WbW!W0w!/Marshall-P803-Twin-Footswitch-wLeadBoostChorus-s

You might be able to rewire the LEDs on this one by putting them in series with the switches, positive side to ground:
Here’s an inexpensive footswitch with a built-in 9V battery, so the LEDs work independently of the amp. Looks like a winner, reasonably priced:


  1. zoot suit says:

    how come fender doesn’t have a foot switch available for the blues junior. Although me personally, never have the amp off the fat switch.

    • bill says:

      Fender does have a footswitch available for the Blues Junior, but any simple on/off footswitch will work to control the Fat. The purpose of this section is to show some switches that will work with the modified stereo jack that controls the Fat switch and the Clean Boost.

      • don molenda says:

        ** you can assy a simple 2 switch footswitch using DPDT switches. one side for the effect the other to lite an LEd via a 9v batt in series with …say..2K resistor…adjust value for brightness… batt should lasta decent amt of time( use a 3mm LED.

      • Ian says:

        Hi Bill,
        are you sure that any simple on/off switch will do the “FAT” job? I tried many and it did not work. It seems that Fender did not make it so easy. The Fender Footswitch is ridiculously expensive. So I am looking for a cheap alternative.

        • bill says:

          Any simple mono on-off switch will work. If it has an LED, probably not.

        • uteowl says:

          I use my old Ampeg reverb on/off footswitch from my VT22 – almost 40 years old and it works like a charm.

        • Stephen T. says:

          Found a latched single switch from Signal-Flex. Model # SF2482 (they make a 2 switch also). Rather inexpensive at around $12.00 from a local music store. Works great, little red LED, thick metal case, full size thick rubber footpad, 9volt battery. Only needs any extra guitar cable you may have laying around.
          Brings the “FAT” on Right & Proper.
          Only downside may be that it has a modern modular look to it, In a battleship grey color. Nothing like a traditional Fender Jr. single switch. Not stealth technology by any means! Anyone looking to fly under the radar or into the Fender trad-image vibe, may wanna look elsewhere.
          All n’ all, very happy with it, no issues since purchase. And the seemingly-near-explosion proof case warms my heart.

  2. Sean says:

    Hey Bill

    Looking at the circuit diagram that came with my Blues Jr, I see the FAT with the switch is on it grounds the -15V through a 22k resistor, which gives a through-current of 0.6mA.

    I already have a footswitch with LEDs which i had previously disconnected so I thought I’d give it a go to connect the LEDs in series with the switch with no drop resistor (given the very low current), and I can tell you that the switch activates fine and the LED lights up, but it’s really dim.

    It’s still bright enough to see that it’s on in medium light conditions, although it’s a bit less clear if you’re trying to figure out if the switch is currently on or off from any distance away.

    I have a few common-or-garden LEDs in by box-of-bits and i tried them all with varying degrees of success – some barely light at all.

    I’ve kept brightest one on the FAT side of the switch.

    On the clean boost side though, even this LED does is very dim, so i’m guessing your circuit makes the ground connection on a through an even higher resistance, right?

    Since I don’t have your circuit schematic for the clean boost, is it possible you could advise me of the current draw to ground through the switch on the clean boost module? Or at least tell me the resistance value and I’ll do the math.

    I’m going to have to get a hold of some lower-current LEDs, and I want to make the right choice that will work fine on both sides.


    • bill says:

      The pull-up (-down?) resistor is 27K. Let me know how it turns out!

    • Moe says:

      I used a Roland footswitch. I put a LED in series with the switch. I got the LED in a 2 pack at Radio Shack and it was one for “automotive charger applications”. I think it might have an internal resister. I tried it either way till it lit and it is bright. I drilled a small hole on the footswitch housing an put a rubber grommet in and then the LED with a little silicone glue to secure it. I works graet. I use the amp and switch for my harmonicas.

  3. John says:

    I use the Fernder two button switch. It’s labeled REV and VIB, but I’ll make a new label to stick over the top. Looks great with the nice retro fender volume pedal!

  4. Bill,

    I love this website. I’ve done all the mods that I can do (anything non-soldering), but I’m still waiting for the Carling progressive standby switch to get to me (must be back ordered?). Will eventually be in contact about you doing some of your mods for me.

    Anyway, a couple of questions on this topic. I have a Vox VFS-2 Dual Footswitch that works with my little Pathfinder 15 that I like. I was wondering if it would work with the Blues Junior if I got the Clean Boost mod.

    Also, is there a way to have a footswitch for the reverb? Is that a mod you’re developing? I usually don’t like the spring reverb on amps. I installed a Ruby Reverb Unit and it’s growing on me quickly. However, I still have a couple of reverb pedals that I really like and would like to be able to use them with ease without also having the Ruby tank engaged.



  5. gegreene says:

    Hi Bill: I have a two button Vox switch for a Valvetronix VT30 Amp. Will this work?…Gary

  6. jonnymags says:

    I’d love to know if there was a mod to change the fat on/off footswitch jack to a reverb on/off jack!

    • bill says:

      I need to take pics of this, but it’s simple: Install a Switchcraft 11A 1/4 inch jack in the side of your reverb tank, being careful to clear the springs. Connect the center contact to the center of the output side’s RCA jack.

      Plug in an on/off footswitch with a shielded guitar cable. When the switch is on, it shorts the tank output signal to ground (which won’t damage anything). Keep the cable as short as possible to avoid hum.

  7. leslie says:

    Hey Bill I have put the mods in that I ordered they worked great.Also i bought the payne lab footswitch but it only works the clean boost.Do you have any idea why it won’t operate the fat switch? If you can help me out I would appreciate it …..Thanks

  8. leslie says:

    After I thought about it I figured ….duh!! it probabally has to be a stereo cable. I will get one Thank’s bill!!

  9. leslie says:

    Got my stereo cable today , everything work’s great …..Thank’s for all the mod’s Bill. I’m really satisfied with them all. Next up is the cathode follower mod!! The mod’s Make’s my amp sound really great,I highly recomend!!!!!

  10. bdr61 says:

    Dumb question… Hey Bill – you told me this once, sorry for asking again…. The left and right foot switch button, which is which? Thanks…

    • bill says:

      Most of the 2-button footswitches I’ve seen are wired so the left button controls the tip and the right button controls the ring of the stereo plug. So on the Blues Junior, the left button controls the Fat and the right is the Clean Boost.

  11. racktones says:

    Would it be logical to assume that there is nothing to stop taking a 2 button pedal with a large chassis

    and adding LEDs powered by a 9v, activated by the switches?

  12. TP says:

    Hi Bill
    got the clean boost with the new stereo jack recently. One question left: since I don’t have the presence control, I suppose I can cut the orange wire soldered to the stereo jack. Is that right?

    • bill says:

      Try grounding the orange wire for operation without the presence control.

      • TP says:

        Hi Bill
        Just finished installing the clean boost module with the stereo jack. And I built a nice footswitch with LEDs for each function. Works great, sounds great.
        What I found out, maybe interesting for other customers with no presence control:
        grounding the orange wire will leave the clean boost ON all the time, when there is no footswitch plugged into the stereo jack. Simply cutting the orange wire leaves the amp in non boosted mode, as long as there is no switch attached.

        Thanks again for all the great mods described on this page, it transfered my BJ into quite a boutique beauty soundwise. I did nearly every mod possible: bias, tone stack, twin stack, changed the coupling caps, power caps, Heyboer OT, cathode follower, MOD reverb tank, clean boost module, standby switch and last not least a Celestion G12-65.
        Sounds amazing and looks amazing too, as I got a Limited Edition Junior with the sunburst maple cabinet. (The only thing which could even top this gorgeous look, would be the gold panel, I saw once on one of your pages 😉

        • Q51 says:

          Hi TP,
          Did you install the LEDs without additional power (i.e. battery)? If so, would you share your schematic or a picture of your circuit for the rest of us?


  13. mfowler says:

    I just tried the Boss FS-5L footswitch for the stock Fat Boost and worked perfectly and has an LED that lights properly. It requires AAA batteries to light the LED. Boss has a double switch version (FS-6) that should work for the Fat/Clean Boost combination… it accepts a TRS plug for dual switch opertaion… requires a 9V battery. Also note that two FS-5L units can be physically connected together (like some kid’s building blocks) to make a double switch but that does not have a TRS input but you could make a y-end on the other end of a TRS. Once I get the Clean Boost mod I will do the latter since I already have an FS-5L.

  14. vovian says:

    Hi. Help me plz? I need a button “ Fat” on the top bar (‘Fat’ switch). Between “Treble” and “Vllume” potentiometers for my Fender Blues Junior amp. Where can I buy it?, Thank you/

  15. michele3b says:

    Bill–great great site. You deserve a major salute from every Fender tubie for realizing the potential of this little monster amp. Here’s a question I haven’t seen yet, although mflowler is getting close. The main value of this amp is, naturally, it’s size and weight. I started running two of these and never bothered with the fat switch before, but noticed that–especially on the BJIII, the fat boost is essentially a clean volume boost–at least it is on the one I got last week. So I’m wondering if there is a footswitch that will control the fat switch on 2 amps simultaneously–preferably with one switch. Thanks again for fixing this amp for all of us!

  16. michele3b says:

    Oh yeah–also, I have a Digitech FS3X footswitch (for a Jam Man) with a stereo out and was wondering if anyone knew whether it would be safe to try this on the BJ circuit–splitting into 2 monos to control the 2 amps–thanks again.

  17. geos says:

    Looks like this one is OOP (Out of Production) ( at least at “Music

    Any other known sources?
    The item is top of the list now.

  18. Patrick says:

    Regarding the Payne Labs footswitch, I bought one new via ebay, and it seems to be very well built with a solid housing and high quality switches. It works perfectly, and I recommend it.

    It measures 4.25″ W x 2.25″ L and is small enough to be conveniently secured along with a stereo cable behind the Velcro strap inside a Blues Junior. The switches are 2.75″ apart from center-to-center, which for me is far enough apart that I won’t hit them both by accident but close enough that I’m able to hit them both when I want to.

    Note that it does not come with the required 9V battery or stereo cable, so take that into account if price is an issue.

    The unit I received was labeled “FSGEN2BL” rather than “FSPV2B,” and when I asked about that, Ken at Payne Labs told me that they used to sell the same footswitch as both a generic and a Peavey-specific item, and have now decided to put the generic label on all of them. The page with the listing for the generic version is here:

  19. ddiggler says:

    I have custom switch that I made for sale…..

  20. tomabrown says:

    Hi All –

    Found this footswitch for the stereo plug mod controlling the Fat as well as Bill’s Clean boost mod. Made by VoodoMan Labs, it has red & green lights, runs on 9v battery or any 9v plugin, and works without any power. It is built great, fits into the velcro inside your BJ, and the red light runs the Fat side – appropriate – at least that’s how my BJ is wired.,shop.product_details/flypage,shop.flypage/product_id,307/category_id,11/manufacturer_id,0/option,com_virtuemart/Itemid,1/

    At 40 bucks, it seems quite reasonable to me.

    And btw – great mods Bill!

  21. Timbose says:

    You CAN use the 2 button fender footswitch from a Blues Deluxe… mine is a reissue version
    When using footswitch with the BD, one controls reverb, other is channel switching.
    HOWEVER when using it on the blues Junior, the FAT is controlled by the reverb button (LED DOES light up when activated) AND the reverb is uneffected (always whatever you have it dialed up to).
    The channel switch button does nothing – probably since the Junior is a single channel amp.

    So thats a strange fix since I now need something for the Blues Deluxe- BUT now I have chance to use the incorrect single channel switching foot switch I recently purchased by mistake for the BJ and use on the Blues Deluxe instead – should be good for my use since I never turn reverb off but will use the channel switch when soloing…fingers crossed!

  22. jamman95 says:

    Hi There! I just completed my Blues Junior mods. and did my first gig with it last night. I upgraded everything Bill offers for it, except for the OT, where I opted to go with the Mercury Magnets offering. In a word….AWESOME! Concerning the footswitch for the clean boost and fat boost….I use a BOSs FS6 and it works great! Not only a separate switch for both, but they are lighted when activated by an internal 9volt battery. I couldn’t be happier!!

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