VooDoo Lab OD

oldrocker · September 22, 2006, 12:16:06 PM

I just built this pedal and I really like it. I had the schem laying around since I started building but never felt compelled to try it. I'm glad I did. With the gain set high this thing really screams. I have so many different distortion effects and everytime I think I've heard them all I find another one I feel I can't live without. I read about Mark M.'s Voodoo plus so I'm interested in checking that one out too.

aron · September 22, 2006, 12:18:24 PM

One of my favorites from long ago.

Nashtir · September 22, 2006, 01:15:52 PM

where did you find the project?

oldrocker · September 22, 2006, 01:24:41 PM

Here's where it is although I'm not sure how I got there.
http://www.geocities.com/CollegePark/Library/1355/voodoolabOD.gif

petemoore · September 22, 2006, 01:38:03 PM

Interesting how the clipping diodes connect to 1/2v.
Looks like that'd put even a bit of feedback to the input via the 470k?

JHS · September 22, 2006, 02:52:35 PM

The VL OD is IMHO one of the better ODs. Very good as a volume boost, really dynamic and and it sounds like a mix between an OD and a distortion w great overtones. I changed the volume pot to 250k for a bit more treble ring. Too bad that is was discontinued long ago.

I wire most hard clip dioded to VREF since I analysed it, in tecnical terms it's nearer to a FB-loop-clipper than to a shunt-to-ground clipper.

JHS

Nashtir · September 22, 2006, 03:54:40 PM

thanks for posting the scheme..has anyone of you got a pcb or layout of this pedal? I'm so curious about this pedal!!

Gilles C · September 22, 2006, 04:02:43 PM

Sure...

Gilles

puretube · September 22, 2006, 04:48:58 PM

pete: I`d say that C1 (100µF) shunts all possible feedbacksignal to nirvana...

btw: diodes directly from opamp-output to "Vref",
isn`t that the same effect as from opamp via (large) capacitor to ground?

or does for-/backward biasing of the diodes come into the game??

WGTP · September 22, 2006, 06:03:32 PM

Epiphamy I guess when you have really small resistors off the feedback loop like the RAT, diodes in the loop would be pretty close to ground. Thanks.

JHS · September 22, 2006, 06:08:31 PM

R5 (47k) seems to be a bit to high, 4,7k is a much better value (if it's smaller the circuit will oscillate).
R11 is 250 Ohm R on some units, 150 Ohm will produce a more woofier bass.

If the diodes are connected to pin 1 the sound will be muddy w/o R7 (smaller values of R 7 soften the sound but kill string to string definition at higher gain. Silva Mica caps for the 220n and the 1n will give a clearer sound with more headroom. Ceramic caps will kill a lot of the good treble response. The electrolytic should be plain foil audio types, with cheap rough foil types the bass will be undefine an a lot muddier.

The OCD is very similar, but the tone control has wrong values. One way to fix it is to change the volume pot to 500k, the other to change the tone pot to 10k and the tone cap to 10n (a common mod for the OCD done by some well known pedal modders).
This tone control (a simple treble cut) is in parallel with the volume pot and can be used for the VL OD too.

BTW: On the OCD R7 is switchable.

JHS

PaulC · September 22, 2006, 07:15:11 PM

I believe the reason you'd tie the diodes to the divider instead of ground is because you want the same DC potential on both sides of the diodes. This circuit doesn't have a decoupling cap on the output of the first opamp, so the tops of the diodes are seeing 4.5vdc. You'd want the other side of the diodes to see that same potential. I believe the other pedals that have diodes to ground have decoupling caps off the outputs of the opamps. but it's just a theory...

PaulC

oldrocker · September 22, 2006, 09:25:39 PM

Quote from: Nashtir on September 22, 2006, 03:54:40 PM
thanks for posting the scheme..has anyone of you got a pcb or layout of this pedal? I'm so curious about this pedal!!

Yeah, if you haven't built this one yet I highly recommend it. I avoided building this for a long time and I got bored and had the parts available so I soldered it together. I was blown away when I kicked the gain up. I definatly have to box this one up. It's an easy build too. It worked the first time and fired right up.

vanessa · September 22, 2006, 10:45:41 PM

Has anyone compared it up against the DOD OD250 (original or clone)?

oldrocker · September 23, 2006, 12:13:56 AM

Vanessa that's a hard one. I really like my 250 and is one of my most used distortions. I haven't had a chance to really try out the Voodoo in many situations but I can tell you this. This pedal kicks a@%. At a high gain setting it has a stronger overdrive than the 250. I'm not sure if I would use the Voodoo in the same context as the 250. For some heavier stuff I'd go with the Voodoo and for lighter stuff I'd go with the 250. One thing is for sure the Voodoo gets nice and loud with volume and gain knobs kicked up all the way.

KerryF · September 23, 2006, 12:15:54 AM

Anyone have any soundclips for this thing? It looks like it would be a great builld!

Gilles C · September 23, 2006, 12:30:19 AM

http://sounds.ampage.org/files/voodoo.mp3

What I read about it is that it is a one sound pedal, but that the only sound it does, it does it well. Thick, smooth, etc...

http://reviews.harmony-central.com/reviews/Effects/product/Voodoo+Lab/Overdrive/10/1

Gilles

Nashtir · September 23, 2006, 07:32:30 AM

Quote from: JHS on September 22, 2006, 06:08:31 PM
R5 (47k) seems to be a bit to high, 4,7k is a much better value (if it's smaller the circuit will oscillate).
R11 is 250 Ohm R on some units, 150 Ohm will produce a more woofier bass.

If the diodes are connected to pin 1 the sound will be muddy w/o R7 (smaller values of R 7 soften the sound but kill string to string definition at higher gain. Silva Mica caps for the 220n and the 1n will give a clearer sound with more headroom. Ceramic caps will kill a lot of the good treble response. The electrolytic should be plain foil audio types, with cheap rough foil types the bass will be undefine an a lot muddier.

The OCD is very similar, but the tone control has wrong values. One way to fix it is to change the volume pot to 500k, the other to change the tone pot to 10k and the tone cap to 10n (a common mod for the OCD done by some well known pedal modders).
This tone control (a simple treble cut) is in parallel with the volume pot and can be used for the VL OD too.

BTW: On the OCD R7 is switchable.

JHS

Do you meand that you could make an OCD out of this one? Which changes sould be done?

Gilles C · September 23, 2006, 08:43:18 AM

Interesting mods...

I still have the VL Overdrive circuit laying in a box somewhere. I should try it again someday.

I read a bit about the OCD, and most people seem to talk about its mid scoop sound. I heard a soundclip of it, and I also find that it lacks mids for my taste. So maybe a mix of the VL Overdrive and of the OCD could make a better effect.

So things to try would be:

R5 = 4.7K
R11 = 150-250R (will try 220R)
R7 = smaller? make switchable
C4,5,7 = Silver Mica for clearer sound
Volume control = 500K
Tone control = 10K pot + 10nF (is'nt 10K it a bit low? 100K?)

JHS · September 23, 2006, 12:26:56 PM

Sorry, a small mistake, on the OCD R11 is switchable not R7.

For a 100k pot for volume the tone pot should 10k and 10-33n, for a 500k pot for volume the tone pot should 100k and 33-100n.
If the tone control on the OCD (100k/100n w 100k for volume) is set to zero the tone is very dull and for me nearly useless.

On the OCD I added a 10k in series with the tone pot to prevent that the cap is completely shunt to ground when the pot is set to zero.
IMHO this make the tone control more useful.

If I would add a tone control to the VL OD (it alter the sound a bit) I would make it switchable to have the option to take it out from the circuit.

JHS

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VooDoo Lab OD