Guitar pedal, OP-1 and Digitakt

I dug an old guitar effect pedal out of the closet today. It’s a Rat distortion by Proco. Seems to be in good shape. I bought it new about 10+ years ago. Never took it out of the house or stomped it. It wasn’t stored with a battery.

Got a new 9v and tried it with Digitakt, then OP-1, then both together.

With all at max volume I could only barely hear anything.

Are pedals like this usually compatible with synths and other (not guitar) electronic gear?

Guitar pedals are designed for high impedance signals like electric guitar but in my experience, It should be fine w/ other line level (or headphone level in the case of the OP-1)
The Rat gets crazy loud so I’m not sure what’s going on. Can you explain your signal path? What are you plugging it the output of the Rat into?

I had an OP-1 once and had this issue. I recall that the solution was specifically a hosa stereo mini jack to mono quarter inch cable.

I have a hosa stereo to mono splitter. Can’t recall which way. I need to look at the set up again to describe it though. I’ll update with details in the morning.

You can try that and it may work, but to clarify, the solution for me was a cable that summed both channels coming out of the op-1 to a mono jack.

I used my OP-1 with guitar pedals all the time when I had mine. Used a simple mini-jack to jack cable from OP-1 to the pedalboard, stereo in both ends. I would guess there’s somethings up with your pedal?

What cables are you using ? You just need mono cables, basically.

It does sound as if you get phase cancellation ,which would explain the very low output.

Most guitar pedals handle line level without problems (some fuzz are picky with impedance but a RAT should be fine, they’ve been used on synths in probably hundreds of records).

Stereo/TRS on the pedal end doesn’t work with some pedals, I think due to the way the auto switching when you plug in the cable works - some work, but some pedals I have used require a mono/TS cable, and the Rat is only in mono anyway, so I’d try a 3.5mm TS to 1/4" TS cable and see if that works, presuming that isn’t what @oldbuildingandloan already tried.

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Ah, yeah, my bad. When I come to think about it I think I maybe mostly used a cable that had stereo mini-jack to a split jack L/R on the other end. I often used the OP-1 with Strymon pedals which has stereo I/O.

Originally, I was running it trough several splitters. t’s better without the splitters. It’s definitely more audible and the pedal appears to be working.

I have several 1/4 to 3.5 stereo adapters plugged into: each jack on the Digitakt and the IN jack on the Rat. A 3.5 stereo cable connects either OP-1 or Digitakt to the Rat. My headphones have a 1/4 jack plugged into the OUT jack on the Rat. (I don’t have any mono 3.5 cables yet; they should be here tomorrow)

I’m trying the following now…

  • OP-1 to Rat - Only getting Left out to headphones. Knobs on the Rat need to be almost wide open to get sound. Anything before the last 10% of the Rat’s vol knob is inaudible. It quickly goes up in volume though, and at max, it’s louder than it is straight from the OP-1, or if the Rat is switched off. With vol max, and Distortion and Filter on the Rat turned off; no sound. I don’t remember if that’s how the Rat should work… Distortion off and Filter and Vol at max, only get a quiet buzz.

  • Digitakt (headphones out) to Rat - Same results as with the OP-1.

  • Digitakt L/R Out to Rat - no sound; doesn’t work. The red light on the Rat isn’t even on. I have a splitter with 3.5 L/R mono male jacks (red white) to stereo 3.5 female. The L/R sides are connected to Digitakt L/R Out. 3.5 stereo cable connects the female side of the splitter to the Rat.

I think the left channel problem is happening in the Rat. I can connect Digitakt Right Out to Rat and still only hear in left ear.

That might be it. I don’t have cables or adapters to try that now though. Will have to order the adapter.

Oh, I didn’t realize you were trying to listen with headphones. You need to be using a headphone amp, mixer, or some kind of powered speaker/amp. You’ll never get a normal result trying to plug headphones directly into a pedal, even if you have line/headphone signals going in…pedal outputs aren’t designed to drive headphones.

You’d likely be well-served by getting a small mixer (something like this or similar) with an aux send. Plug your OP-1 and Digitakt into the mixer inputs, aux send to the Rat, output from Rat into aux return channel, then listen via the mixer’s headphone output.


Ah. I ordered a Bastl Dude mixer last week. It should be here tomorrow. I’ll let you know if that resolves everything.

mmm. the Behringer costs less than the Dude and does a lot more. It’s not as pretty though. And desktop real estate is dear. This’ll be my first mixer and wanted to go with something small and simple.

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This is 100% your problem.
You can’t run headphones off of a guitar pedal. Instead plug the Rat into an amp, audio interface, mixer, etc … then monitor the output from there.