DIY Effects: EHX Freeze with Effects Loop and Expression Pedal

There aren’t many pedals out there that an astute DIY enthusiast can’t build. However, if there’s one company that keeps pushing the envelope away from the same tired, easy to build overdrives and fuzzes it’s Electro Harmonix. Case in point, their Freeze pedal—a sound retainer effect—is next to impossible to piece together on my own. Thankfully Laura was kind enough to buy me one for my birthday and even kinder enough to give it to me a month and a half early!

After a quick test so she could see how happy I was, it was off to the drill press to add some holes into my new gift. In the end, as the above video describes (with a first attempt at annotations too!), I changed the stock stomp switch, went with an expression pedal jack to optionally control the effect level my foot, and added an effects loop. The latter allows me to run just the ‘frozen’ signal through things like a tremolo or phaser and not affect my guitar signal at all.

I couldn’t really find any guidelines on how to do any of this online (the usual suggestion of disconnecting the wiper of the level pot and inserting the effects loop there didn’t work), so I ended up tracing the circuit with an audio probe. All told, I took the ‘send’ signal from R3 and returned it to the wiper of the level pot (there could be an easier way, but I’m no guru—just a lunatic with a soldering iron).

That said, if you’re looking to do this to your own Freeze just be aware that it’s all SMD components and I almost lost R3 a few times (it’s about the size a hangnail). But you know what they say, “He who dares…” blah blah blah.

We used this newly modified bad boy at a show on the weekend and it worked really well. A friend later remarked that he what sounded like an organ playing under my guitar, which is exactly what I was hoping for!

EHX Freeze w/ModsEHX Freeze w/Mods

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17 comments on “DIY Effects: EHX Freeze with Effects Loop and Expression Pedal
  1. Aaron says:

    Nice Pedal….naturally I probably should have heard it in use live at your show rather than watching it on youtube!

  2. Florian says:

    Hi Paul ! Thank you for sharing all this work. It´s been a while I’ve been looking for a way to add an expression pedal to my ehx freeze effect. I’d like to use your system, unfortunately I’m quite novice in electrical stuffs… Is it possible for you to post a wiring diagram or to give us some tips? I don’t want to do irreversible mistakes on my freeze…
    Smart idea to replace this noisy stomp switch !

    • Paul says:

      Thanks for checking it out! If you’re a novice I’d be careful, as there is a lot of room for permanent damage in adding the expression pedal (just getting the circuit out of the enclosure is pretty difficult—I almost destroyed the toggle switch and read about others who did). The mod itself is fairly simple, but you have to disconnect the level pot completely and wire it to a switching jack which is also wired to the expression pedal output (the switching jack works so that when the expression pedal is unplugged the regular pot works normally, but when it’s plugged in the pot doesn’t work, just the pedal).

      I’m still messing with mine a bit, as the sweep of the expression pedal isn’t perfect. It’s definitely more of an experiment than a precise mod.

  3. Florian says:

    Thanks a lot ! With your help and some research I’m now able to do the mod on mine.
    Kind regards,
    Florian

  4. Kay Hyde says:

    Thanks for sharing this DIY effects pedal. I am not actually the one who do this stuffs, it’s my brother. Hes trying this out and I think you video did helped him a lot!

  5. Julian says:

    I’d like to see a picture of the other side of the board to see where you wired it. Or would it be possible to make a 100% wet(send only) output without taking the board out?

    Thanks for the video you made a great pedal awesome.

    • Paul says:

      Funnily enough, the way the effects loop jack is wired allows it to also function as a wet output if you just take the ‘return’ signal and plug it into an amp.

      No need to see the other side of the board, as everything is done up top (and the board is very, very hard to get out without breaking the toggle switch attached to it (mine barely made it and there may have been some crazy glue involved). All I did was take the send signal from one side of R3, then loop the return signal back in at the wiper (lug 2) of the mix pot.

      Mine still needs a bit of finessing, mostly with the expression pedal jack though.

      • julian says:

        Thanks for your reply. I’m looking at your photo now and I can’t quite make it out. Which colour cables are we talking about in your photo? The pink one looks like it attaches to U5 I cant see anything attached to the R3. Any chance you could post close ups?

        Also is it possible to remove the fast/slow switch and hardwire it in latch mode, our switch is broken.

  6. Adiel Ricci says:

    Thank you very much for the ideas, Paul!

    One question: is it possible to mod this pedal without removing the board, so as not to risk losing the switch?

    Best regards from Brazil!

  7. Chad says:

    Hi, Paul. I hope you have a few moments to help me out. I purchased a Freeze because of your video ;)

    From your picture it looks like the send comes off of R3 (did you remove R3 completely from the circuit?), goes through a 5.6nF cap, to the pink wire, to the ring (middle) of your send/return. The signal returns on the tip of the same jack and goes through the grey wire back to the ‘top’ contact of the Effect Level pot (near R28).

    The expression pedal has a yellow (tantalum?) cap from the tip to the brown lead, on to the wiper of the Effect Level pot. The sleeve of the same jack goes through the white wire to the bottom of the Effect Level pot. I can’t make out the wiring to the normally closed side of the expression jack.

    Questions:
    1) Is R3 still in your circuit, or did you remove that resistor completely?
    2) Is the original Effect Level pot still soldered in it’s original place?
    3) Does your send/return signal return to the ‘top’ lug (grey) or the ‘middle’ wiper lug (brown)?

    Thanks a ton. I did what I thought you said in the article. Right now the effected signal does not send/return properly. It’s still there, but it doesn’t go through the vibe pedal, back into the Freeze like yours does. Thanks-CHAD

    • Paul says:

      Hey Chad,

      I don’t have the pedal in front of me to open up, but I did not remove R3, just soldered the connection to one side of it (carefully, as those SMD resistors are easy to lose and hard to work with).

      As for the rest, it’s important at this point to separate the 2 mods (effect loop & expression pedal). I did unsolder the level pot, but only so I could insert connections to the expression pedal jack. If you don’t care about that mod then you don’t necessarily have to remove the pot. The expression pedal mod is still under construction, as I’ve found it lowers the overall level slightly…

      Ignore the specifics about the capacitors, they, like this entire mod, where added on a whim based on what I had at the time and what seemed to sound good. To my ears it worked better to have a coupling capacitor to bridge the mods, but that might not be necessary for the effect loop.

      My mods are VERY imprecise and I’m far from an expert, so please don’t think they are the only or even the best way of achieving this. I simply used an audio probe to find decent send/receive points in the circuit and soldering connections there. In that regard, I can’t recall without the pedal in front of me where the return signal connected to. I would simply play a loop (or any kind of independent sound that doesn’t require you to strum the guitar while doing this) and experiment with where the return sounds best (for me it was definitely either the wiper or outer lug of the pot, but without the open pedal in front of me I can’t be sure).

      Sorry if that’s all a bit vague, but I’m no expert and just got a bit lucky.

      Paul

    • Paul says:

      I just found another thread where I talked about this with other pedal geeks, so it might be worth a read:

      http://freestompboxes.org/viewtopic.php?f=1&t=9967&hilit=freeze&start=20

      • Chad says:

        Thanks for the clarification and link. I’ve read that one and every other one I can find – even before posting here. I build and modify pedals, so I’m used to being careful, but somehow I’m wading through this one fairly slow – there is voltage on the Level pot (http://www.diystompboxes.com/smfforum/index.php?topic=101235.0). I’ll keep on keeping on. I’m used to analog circuits and all the fancy chips start to glaze my eyes over. Thanks again! -CHAD

  8. Ian says:

    That it exactly what this pedal needs as well as a way of changing the decay in latch mode… I am trying to do this outside the box with signal chains (but without much luck so far)

  9. Matt R says:

    All I needed was a 100% wet feed and I was able to get that signal off the left (ground) and right (hot) legs of the Effect Level pot. I could have done this without removing the board and risking the microswitch but luckily everything came out and went back in without damage.

  10. Alfonso says:

    Very Interesting! That toggle switch is the cheapiest thing in the world. Once it broke alone and I sent the pedal for support under warranty. They replaced it with a new one which seems even cheapier and after a year it stopped enabling the latched mode!!!!! I would like to change it myself (with a friend’s help) with a better one,could anybody give me a hint on what specs and which brand? Thank you. Alf.

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