This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Wednesday, August 17, 2016

Wampler Cranked AC

Another amp emulation overdrive from Wampler that's supposed to sound like (you guessed it) a cranked Vox. This one has been discontinued, but was very popular. It's very similar to the Plexi-Drive, but doubles the transistors and there are a few component changes. I've added trimmers to help bias the J201s.


  1. What's the purpose of doubling the transistors?

    1. I would assume the reason was for the tone. Not really sure otherwise.

    2. This one has much more gain than Wampler plexi drive.. ...just like VOX AC30 compared to a Marshall. Both sounds great.

  2. It assumes that each pair of transistors should be matched?

  3. I had a 1st gen CrankedAC, when it was an etched circuit board, not machine-fabbed.
    A couple of points:
    1) Mine had a 2.2uF elec cap in parallel with the 1K resistor at the Q1/Q2 pair
    2) Mine didn't have the power filtering this one does; just the 47uF cap

    Everything else looks pretty much the same.

    I cloned my original one recently, with a few of mods:
    1) Used all 2N5457s - a little more open/less gain than J201s, which I find to be more compressed/higher gain
    2) Pulled the two .0022uF caps in the filter at the end - gives more chime/treble, makes the tone control more useful
    3) Used a 250K pot for gain - the stock config with J201s and a 500K gain pot was a bit much - the 250K allows me to dial in the low-med gain tones I wanted.

    Tried the Vox Afterburner (CoolTube series), Runoffgroove Britannia & English Channel, Menatone TBIAC, Boss Combo Drive, Catalinbread Galileo clone (admittedly a good circuit) and Tech21 DoubleDrive. The CrankedAC is the only one that uppermid/treble chime I was looking for, with a good range of usable overdrive.

  4. Sir, this one is verified, sir!
    I use the exact components listed above.
    Awesome as usual!

  5. What is the bias voltage in the original circuit?, do we need to assume Vd 4.5V like Plexi Drive does?

    thank you

    1. Yeah, set the trimmers to 4.5v to start then adjust as needed.