How to salvage a lousy OD pedal for $10 or less...

11 Gauge · June 20th, 2008, 06:01 PM

Well boys and girls - I finally got around to dropping a pair of mosfets (as a clipping pair) in a garden variety OD pedal today, and have come to the conclusion that they are indeed the best devices to use for clipping in your typical OD circuit. No hype or spin. They are the real deal, IMO.

I really didn't want to believe the hype, and didn't want to shill out the bucks for a full blown Blackstone Mosfet pedal, either.

I can't believe that changing just 2 components (took 20 minutes) made a very average OD as smooth as polished marble. But now it makes complete sense - your typical TS clone (opamp based OD) gets almost all of the clipping from the diodes - the opamp simply isn't run hard enough to clip itself (substantially). Since the switching in the mosfets is 100% field effect, the overdrive is sensationally round. They have the same threshold as 1N400X rectos (roughly), but add a completely different texture. All of my 1N400X's will be going in the trash...

I prefaced by stating $10 or less - the mosfets will only run you about 4 bucks, max. The add'l 6 clams will be for tweaking the overall output of the pedal. Just a handful of resistors, but worth it to rebalance things. Also, the mosfets seem to allow for more lower frequencies to squeeze through, so some cap values will probably have to be cut, as well.

The most amazing thing is that the tone control almost becomes unnecessary. I completely removed it from the host pedal. It's almost impossible to get a harsh or muddy tone out of it, even with the drive dropped to almost zero.

One caveat - pedals like the Rat absolutely clip the rails of the opamp. No doubt about it. The mosfets could very well sound like doo doo in a Rat or similar pedal. Then again, it could be flawed logic. This could be the perfect thing to salvage the harsh rail clipping in a Distortion +, with it's cheapo 741 opamp.

If you've got an OD or three kicking around that just sounds like a turd, inject a couple of mosfets into it in place of the 1N148's, or whatever other little nasties might be in there.

June 20th, 2008, 06:01 PM	#1 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,015 10 Photos	How to salvage a lousy OD pedal for $10 or less... Well boys and girls - I finally got around to dropping a pair of mosfets (as a clipping pair) in a garden variety OD pedal today, and have come to the conclusion that they are indeed the best devices to use for clipping in your typical OD circuit. No hype or spin. They are the real deal, IMO. I really didn't want to believe the hype, and didn't want to shill out the bucks for a full blown Blackstone Mosfet pedal, either. I can't believe that changing just 2 components (took 20 minutes) made a very average OD as smooth as polished marble. But now it makes complete sense - your typical TS clone (opamp based OD) gets almost all of the clipping from the diodes - the opamp simply isn't run hard enough to clip itself (substantially). Since the switching in the mosfets is 100% field effect, the overdrive is sensationally round. They have the same threshold as 1N400X rectos (roughly), but add a completely different texture. All of my 1N400X's will be going in the trash... I prefaced by stating $10 or less - the mosfets will only run you about 4 bucks, max. The add'l 6 clams will be for tweaking the overall output of the pedal. Just a handful of resistors, but worth it to rebalance things. Also, the mosfets seem to allow for more lower frequencies to squeeze through, so some cap values will probably have to be cut, as well. The most amazing thing is that the tone control almost becomes unnecessary. I completely removed it from the host pedal. It's almost impossible to get a harsh or muddy tone out of it, even with the drive dropped to almost zero. One caveat - pedals like the Rat absolutely clip the rails of the opamp. No doubt about it. The mosfets could very well sound like doo doo in a Rat or similar pedal. Then again, it could be flawed logic. This could be the perfect thing to salvage the harsh rail clipping in a Distortion +, with it's cheapo 741 opamp. If you've got an OD or three kicking around that just sounds like a turd, inject a couple of mosfets into it in place of the 1N148's, or whatever other little nasties might be in there. __________________