Request: Woody acoustic simulator

Make your guitar sound more like an acoustic. Mark Hammer’s schematic and design documentation can be found here. Apparently there are a few conditions that need to be met for this to sound good (read the info that goes with the schematic).

I’m not a big fan of effects requiring a bi-polar/non-standard power supply so I have attempted to incorporate a charge pump to obtain +9v/-9v in-circuit from a regular +9v power supply. I’m thinking this will work, but I haven’t tried it yet. If you go with the 7660 IC make sure you use one with an “S” post-fix to avoid high frequency noise.


Update (19.02.2013): Now also verified, thanks to Earplane.

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17 thoughts on “Request: Woody acoustic simulator

  1. John,
    Check out the FAQ section on squeeling/oscillation. This is a quite common problem that, unfortunately, can be a bit tricky to solve.

  2. Dear all
    I built this pedal, when I roll the top knob up, I can noticed the high pitch whine, I have tried using both MAX1044 or ICL7660S, but the whine sound still exists. Any other ICs that I can try?
    Many thanks in advance.

  3. I’ve double check the polarity, It’s same as the schematic. I don’t know which part to debug again, it’s better build another one. And I also think the problem is IC3. There was no effect when I replace IC1 and IC2 with the new one. I’m still waiting for online order for ICL7660S. If the replacement of IC3 got no success, I will build another one. Thx

  4. Sounds like something is wrong, I agree. And it used to work? Did you give it the wrong polarity power or something? Your ICs may be dead at this point. If it used to work and you haven’t done any modifications to it, maybe IC3 went bad bridging +9v and ground? You’ll have to do a bit more debugging I think.

  5. Hi Harald, mine is now dead (previously working with low volume). After I dump it for about 4 month, I want to change the R10 like Pablo did. But before replace R10, I try it first, than I just know that it was dead.I check with audio probe and signal only heard before the R1 (seems like it cannot bypass R1), and also the voltage of IC1 pin 4, IC2 pin 11, and IC3 pin 3 are around 8.9V, that should be 0. Do you have any suggestion? Is it IC problem? thx

  6. Hi Again.
    Using R10 a 3,3k it gets more volume. May be the solution to the low volumen of the Woody.
    And the hiss is just the charge pump. I used a noisy ICL7660S, but when the Top pot get too much treble you get the hiss. I’m getting a MAX1044, it must be noisy but in a frecuency you can’t hear….

    See the Mutron III, they used the same charge pump.

  7. Hi Pablo. Had to double check, but both of the schematics I have calls for a 12k. This might very well influence the unity gain issue you’re having though. You could try swapping it for a 3k3 of course.
    As for the hiss/buzz it could be a number of things, but I’m not really knowledgeable enough to give you any good advice, sorry.

  8. Hi Harald.
    I do it and it sounds well. But three questions.
    First, low volume. Even volume in max level it is close to the normal volume, not much.
    Second, there is a huss or buzz all the time, that increase with the Top pot level.
    Third, the original schematic has the R10 as 3,3Klike the R9, and yours is 12K.

    The sound is really good as acoustic, but the buzz is annoying…

  9. It is lower than unity, so when I turn it on, I have to increase amp volume. Is it because I use B100k pot for volume? Because I can not find A100k pot at nearby store. I also try to make log pot base on schematic on, but it’s not working well. I use B500k and base on taper 99% calculation, I add resistor 1k (at lug 1 to 2) and 160k (at lug 2 to 3) and yes the volume is louder, but no sound up to 90% rotation. Am I make a mistake in creating log pot? Thank you and appreciate for your help.

  10. Hi prabuchresno,
    You’re saying it’s low on volume, but is it lower than unity or just unity (I’m guessing this was not designed to add a volume boost)?

  11. Hi Harald, thx its working.
    But the volume is low (even in max level). How can I rise the volume? thx

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