Strymon Tech Corner #3 – Volume Pedal as an Expression Pedal

Posted by Terry

In this third edition of our tech corner series, I’ll explain a simple and easy way to use a volume pedal as an expression pedal. This cool little trick was shared with us by our good friend Chad. This article will be the last on expression pedals specifically, although there are many other interesting diy projects we can do in the future with the EXP input on Strymon gear.

If you’ve got a volume pedal hanging around that doesn’t get much use or better yet one already on your board, you can use it as an expression pedal with one special cable. It’s called a TRS (tip/ring/sleeve) insert cable and the purpose of this cable is normally to break out a TRS insert jack (commonly found in mixers) to the separate send and return signals. Luckily we can take advantage of this wiring to convert our volume pedal into a standard 1/4″ TRS equipped expression pedal.

One example of this type of insert cable is the Hosa STP-201 seen below.
1/4" TRS input cable

Once you have a TRS insert cable, simply plug the TRS plug into your exp input, the “ring” plug into the volume pedal input, and the “tip” plug into the volume pedal output. That’s all there is to it! Now you can use volume pedals like the popular Ernie Ball VP Jr or the new Dunlop DVP-1 as expression pedals for your Strymon gear and most other gear featuring expression pedal control. What is actually going on here is that we’re taking advantage of the design of a passive volume pedal and re-wiring it as an expression pedal with this cable. Note that your volume pedal needs to be passive, not active and the impedance (value of the resistance) in the volume pedal’s potentiometer isn’t critical. One thing that may be a little bit different about using the volume pedal as an expression is that if the volume pedal uses an audio taper potentiometer you won’t get a linear sweep of expression pedal values from toe to heel. In other words, much of the action will happen at one extreme of the pedal.

As you can see, the expression pedal schematic from Tech Corner #1
expression pedal schematic
is functionally identical to using a volume pedal with a TRS insert cable.
Schematic diagram for a volume pedal used as expression pedal

Here is a video walk-through:


Hopefully this has been a useful trick to get you rocking that expression pedal.

Happy shredding,
Terry

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40 Responses to “Strymon Tech Corner #3 – Volume Pedal as an Expression Pedal”

  1. andvari7 says:

    Wow. So that means that I could theoretically use a Morley PWB, which has the longest physical sweep of any pedal I have ever used, as an expression pedal. That would be spectacular, especially with the Lex.

  2. Terry says:

    Remember, it has to be a passive volume pedal. The Morley is active.

  3. Patrick says:

    Wow, sweet! Oh, and, nice boots.

  4. AR says:

    Yeah ok, not to be distracted, but what kind of boots are those?

  5. Patrick says:

    Would this work if I was using the expression pedal to control a 5k pot on a pedal? I had the pedal modded so that a certain knob is able to be expression controlable.

  6. iWhimsical says:

    Can I use this tip on El Cap?

  7. Terry says:

    Definitely! This will work for El Capistan, Brigadier, Orbit, Lex and TimeLine.

  8. Joshua Bredahl says:

    Does Strymon sell this TRS cable? If so how much?

  9. Terry says:

    Hi Joshua, no we don’t sell it but it’s readily available online. Thanks for reading :)

  10. Joshua Bredahl says:

    Thanks so much Terry! Man, ya’ll’s customer service is great! And fast! :)

  11. Ivan says:

    Hello!,
    Is there a way to have an expression pedal and a toggle pedal at the same time into the Timeline? Would love to do this expression trick and to also send tap tempo control into a separate external pedal because I feel like i could break the timeline by tapping it so much.
    Thank u!

  12. Ethan says:

    Hey there! No need to worry about breaking the switch, that’s what it’s there for! The expression pedal input will only do one thing at a time, so you’d need to choose either external tap or expression. Though you could use a midi controller to control your tap if you like. Hope this helps. :)

  13. Mattia says:

    I’would to buy an Ernie ball VP…it’s the same 250k or 25k?

  14. Terry says:

    Either should work with this trick.

  15. John says:

    Could you use an expression pedal to control the volume of a loop going? I have a midi controller that I use to trigger the looper

  16. Growen says:

    Hello,
    this is very interesting,
    but how to lower the 250K to 50K to suit the needs of an AXE FX for exemple (AXE FX accepts from 10K to 100K, but 250K is probably too much

  17. ansy williams says:

    Hi lowering the resistance of the pot is a bit difficult without completely ruining the taper, however i would imagine the AxeFx will actually accept the 250k definately worth a try. if it doesnt work the easiest thing would be to just change the pot. also there is no impedance in a resisitive circuit as it is suggested above. Impedance is a re-active measurement and requires a cap or inductor of some sort in the circiut.

  18. David says:

    Hi:

    I’m sure others may have tried this….but if not IT WORKS GREAT FOR ME.

    I have multiple Strymon pedals as well as pedals that work with an Ernie ball VP Jr as an expression controller.

    In addition to the Hosa STP-201/202.
    I added a HOSA YPP-308 cable … (Stereo 1/4″ Female to 2 Stereo 1/4″ Male Y-Cable)

    Which means I can use one Volume pedal to control 2 effects instead of a controller for each effect….it’s a little too late to worry about saving space on my board , but this helps a little. :)

  19. 96tele says:

    I am very pleased to know this as I prefer the Ernie Ball VP Jr to all the other pedals out there. One question: does the Hosa STP-201 come in shorter lengths?

  20. [...] interesante viene al investigar un poco y ver en el blog de strymon esta entrada sobre transformar un pedal de volumen en uno de expresión. En el esquema se aprecia que el pedal [...]

  21. Daniel says:

    Hi Terry!

    Expression Ernie Ball VP JR 25k works with the timeline?

    Thanks!

  22. [...] This is a pretty cool idea: Strymon Tech Corner #3 [...]

  23. Ron says:

    I just tried it with Boss FV-60 and my Hammond XK-1. I got almost the full range (about 30-127 which is plenty for the Hammond) in the pedal Monitor page on the Hammond (nice feature). So I am going to brush up on my basic electronics schematic reading and modify the pedal to use TRS connectors on a single cable. And the nice thing about it is that it’s a stereo pedal- it has a dual pot so I can make it a double CV pedal- just because I can! This will work well enough for rehearsals.

  24. Jeremy says:

    Hi everyone, I´ve been thinking about how to use my old Zoom FP01 expression pedal with my two Strymon pedals.

    So, I´ve bought a Stereo 1/4 inch “Y” splitter adapter to two 1/4 stereo jacks, this:

    http://www.amazon.com/Monoprice-6-35mm-Stereo-Splitter-Adaptor/dp/B0069M5U6C/ref=pd_sim_sbs_e_1

    Then, I connected the stereo plug into the expresion pedal input, and use two stereo (or trs cables) to connect my pedals into the two stereo jacks of the adapter.

    I´m not sure if I may damage my Flint and El Capistan on the long run, but they´re working fine by now, can someone tell me if i´m doing something very stupid or kind of clever?

    Cheers!

  25. rick says:

    @Jeremy, there’s no reason why that would damage your pedals. Glad to hear that works for you! :)

  26. Jeremy says:

    Hi rick, thanks for the reply!

    So if the trick goes for me I hope that someone else read about this and could go try it too.

    Cheers!

  27. Learjeff says:

    I wouldn’t use a Y cable to connect one pedal to two units with expression pedal inputs, unless they’re both Strymon. Here’s why:

    Both units will try to put a constant reference voltage on the ground side of the pot. If they’re not the same voltage (and there is no standard), one unit will be draining current from the other.

    It may appear to work, but you may be overheating components, causing them to fail before their expected lifetime. My guess is if you have this problem, one of the units might not show the full range of MIDI values.

    Even without this problem, you’d probably be introducing a ground loop, which might leak as audible noise into the audio chain.

    The other trick of using a stereo pedal would be far better.

    Given that Rick from Strymon assures us this is OK with those pedals, then they’re apparently isolated to avoid ground loops, and they’d be using the same reference voltage so current drain wouldn’t be a problem. But I wouldn’t do this with arbitrary gear, or two units from different manufacturers (even if one of them is a Strymon).

    Hopefully Rick will correct me if I’m mistaken.

    In any case, thanks for this great tech tip, Terry!

  28. rick says:

    @Learjeff just wanted to jump in here and make a few points. Thanks for the input by the way!

    You said: Both units will try to put a constant reference voltage on the ground side of the pot.

    We actually put out a reference voltage on the ring but there is a 1k Ohm series resistance.

    You said: It may appear to work, but you may be overheating components, causing them to fail before their expected lifetime. My guess is if you have this problem, one of the units might not show the full range of MIDI values.

    This is possible but unlikely given the 1k impedance. It’s there for all things that people might do to abuse the output. It doesn’t protect from all possible scenarios but should handle most.

    You said: Even without this problem, you’d probably be introducing a ground loop, which might leak as audible noise into the audio chain. The other trick of using a stereo pedal would be far better.

    Totally agree with this!

  29. Steffen says:

    Thanks for the tip! Is a TRS cable the same as a regular stereo to two mono Y-cable or is there a difference? I’m using such a cable, which works no matter which of the mono jacks I put into in/out. But I can’t turn off the expression pedal, it’s on even if it’s set to “off” in the parameters. Could that be because of the cable?

  30. rick says:

    @Steffen, a TRS cable stands for Tip, Ring, Sleeve. They are 1/4″ cables that have two black bands around the jack as shown in the pic above. A non Y cable would have that kind of jack on both ends. It’s tough to say what the issue could be without knowing what kind of expression pedal you are using. Email support@strymon.net directly and we can dive in a little deeper and try to help you out! :)

  31. Erik says:

    I know that this is an older thread, but I found that a 250K EB Jr works great with the Timeline but the 25K does not. Anyone know why?

  32. rick says:

    @Erik, how exactly is it not working? How do you have it connected?

  33. Michael says:

    I just purchased a Bigsky and I can’t seem to get this technique to work. I have the 250K EB Jr and when I plug the TRS cable in(as shown above), the reverb still comes through no matter where the pedal is set at.

    I have tested the pedal and cable separately and they both work. Could I be missing something?

  34. Hugo says:

    @Michael – Did you make sure to assign the parameter you would like to control with the expression pedal? Try following the steps in the following link if you have not done so already:

    http://www.strymon.net/support/faqs/how-to-control-delay-time-with-an-expression-pedal/

  35. Hi,

    Do you know if I can use an Ernie Ball VP JR as an expression pedal via the midi port? If I were to make a custom cable?
    Thanks!
    Derek

  36. Hugo says:

    @Derek – The MIDI ports will only accept MIDI messages which the VP Jr. does not have the ability to do. You would need to use a dedicated MIDI controller into the MIDI ports or use the VP Jr as an expression pedal into the EXP jack only following the suggestions from this article.

  37. Scott says:

    I have been thinking about the technique of using the stereo cable with a volume pedal and was wondering if the same set up could be used, but instead of a volume pedal, could I use a channel on a mixer, which in theory would allow the fader to control parameters just as the foot pedal would do? I have an old 4 track recorder that I do not use, if I could use it for this, it would allow easier control via the fader instead of accessing various display screens in my eleven rack and / or my Zoom HD16 recorder. I am dying to try this, but don’t want to risk damage to the Avid or Zoom. Thanks for any help you can give.

  38. Hugo says:

    @Scott – I really don’t think that this setup would work the same, if at all, with your Zoom recorder as that device is much more involved than a Volume pedal with a treadle pot.

  39. Moe Alan says:

    What is the pot value that im supposed to buy from the mini-expression knobs? 100k or 250k? Im running through a bigsky.

  40. Hugo says:

    @Moe Alan – We don’t have the exact spec on his expression knobs, but those look like T1M mini-expression pedals set to 100k-250k Stereo. You should be fine with 100k.

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