Low Voltage Organ Overdrive with 12AT7 (ECC81)

It was 2010 I guess, I have been using my JCM800 preamp for distorting my KORG CX-3 compact organ (famous Hammond C3 clone, Manfred Mann plays it, too). But the sound was not as crispy as I intended it to be.

Then one day I stumbled across this project :


The Peppershredder by D. Munzinger is a guitar distortion with two 12AT7 (ECC81) tubes that operates with an anode voltage of only 12V. Astonished by the possibility of such a thing I started playing with a Brimar 6060 tube that I had laying around (very close to a 12AT7). Heating as well as anode voltage was supplied by an old AT computer power supply.

Within half an hour I had a “one tube circuit” before me that could amplify (or at least buffer) the audio signal from my KORG CX-3 organ. And It got better: This crude tube preamp was easily overdriven by cranking up the volume knob on the organ.

I was amazed how good it sounded while it consists of yet so few parts. The rest of the evening/night I spent building the overdrive into a nice enclosure.

Find the schematics here: 12at7_overdrive.pdf

(there is a little blah blah in german along the schematic, nothing too important)

It is basically the first stage of the LoV Peppershredder with small modifications.

Here’s a little vid of the overdrive in action (sorry for the bad video quality though):

5 responses to “Low Voltage Organ Overdrive with 12AT7 (ECC81)

  1. Oh my god.
    That ia fantastic!
    I just found this and I’m floored…
    I have no electronix skills whatsoever…..
    Any chance in hell you’d build one for me? Happy to pay!!
    I play hammond but no leslie, and my boss emulator is the worst on OD…
    Seriously, would you could you for a fellow player dying with fake OD?
    Keith sturgeon

  2. Hi, nice project. I was actually looking to add an overdrive to my Hammond X5, would you be able to help me with the design?

  3. How did the tube overdrive pedal compare to the original overdrive on the CX3? I’ve never worked with tubes before so I will get my supplies first. were there any changes or updates to the schematics? Also, can the 12AT7 be substituted with the 12AU7 tubes? thanks

    • The original overdrive in the CX3 sounds very dry and lifeless. And more fuzzy than crunchy. Very “transistory”. The schematics have not changed since then. An 12AU7 probably works, too, but expect less gain and hence less distortion. But the organ should provide enough output to also drive the 12AU7 into distortion.

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