Monday, 20 February 2012

Voodoo Labs Overdrive

Voodoo Lab's info:

This vintage overdrive circuit, originally built in the early '70s, delivers singing sustain on leads and crisp, tight bass on chords. Turn the gain down to provide tons of clean boost for overdriving vintage tube and non-master volume amps. Medium gain settings add tube-like harmonics for fatness and warmth. Higher gain settings produce rich crunch tones. Cleans up nicely when you back down the guitar volume.


18 comments:

  1. Mate you can verify this one... A real nice medium gainer :)

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    1. Nice one, thanks for that Vince.

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  2. Just finished this tonight. Passes signal fine, however it's a really clean signal even with both pots all the way up. Tried different pots just to eliminate that, but still pretty much the same. There seems to be no overdrive at all. Most likely something I've done. I triple checked the vero and it seems good to me. Any ideas?
    Awesome site btw

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    1. If you can take a close up front and back pic and post links, I'll see if anything stands out.

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  3. I went thru again for the hundredth time and found that the 150k resistor looks very similar to a 750k resistor. Swapped it out and got some gain finally. Then decided to socket the resistor to play with smaller values which took it into fuzz territory at about the 10k mark. It seems to be quite muffled on the neck pickup on my tele. It's bright on the bridge. Any ideas on a treble mod. Thanks again for all your hard work mate. Greetings from OZ

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    1. Well you could try something simple like reducing the 2u2 output cap, but you could experiment with the 47K from pin 6 and the 2u2 which follows it to ground. Reduce those and see what you think of the results.

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  4. This comment has been removed by the author.

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  5. Has anyone tried different diodes in this one? 1n4001, the like?

    I could always just socket the diodes...

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    1. Socket them and play with different diodes. Try asymmetric clipping too.

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  6. You can add tone control by adding a chained pot and cap parallel to the pins 6 and 7 on the IC. I used 500k lin pot. Cap should be something like 10 or 100 times greater than this 220p cap on the schematic. Thy a few, find what suits you.

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  7. I modded this one to (sort of) Cornish SS2 specs, and I'm really impressed. This is a super fat overdrive, but it manages to stay articulate throughout the gain range. This one will definitely get boxed, because it complements my Barbershop clone beautifully.

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  8. I only get little overdrive when gain pot is maxed and even then it´s quite clean. I think I had it working before it got boxed when I tested it quickly. I don´t know if I did something wrong with the wiring or what could cause that?

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    1. Lots of things could cause it, possible a short somewhere if it's only happened since you boxed it. The best way to see is measure the IC pin voltages to see if that points to a problem somewhere. If the voltages are ok then it may just be a bad connection somewhere.

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  9. Voltages are:

    4.5 --- 9
    5.3 --- 4.5
    2.1 --- 4.5
    0 --- 4.4

    Yes, I think it worked before boxing it, but can´t be 100% sure bacause I built it quite a while ago.

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    1. Your voltages look ok. Pin 2 may be a little high but not so much that it looks like it could be the source of the problem. So that leaves connections and/or shorts which is going to mean checking it over, knifing the gaps and reflowing solder so you know you have a good connection. And of course double check that the values you used are as per the layout (or within 10% anyway)

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    2. Ok, thanks. Will do that and I think I will also unscrew the pots to make sure I used the right ones.

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  10. Hhmm. Everything is checked and seems that theres no building errors... It works just like it should except that there is only very little gain, needs to be maxed before you can hear it doing anything. Already tested a couple of TL072's. What about the diodes, if one of them was burned?

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    1. If there is no build problem then it points to a faulty component because we know the layout is good. I'd suggest building an audio probe so you can see exactly where the signal is dropping, and that will tell you exactly where the problem arises.

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