Thursday, May 23, 2013

A Nu Tone clone for the old Mu-Tron III


The Mu-Tron III clone - NU-TONE III
For a very long time I have been interested, mainly, in pedals which gave me sweet fuzz and overdrive crunchy sounds. This is because I use them. It seems pointless to build too many pedals if you don't use them. I did build the wonderful ROG (Runoffgroove) Tri-Vibe and loved it, I did buy reverb and delay pedals and I use them all the time. However, I am always ready to dive into a new sonic adventure if given the proper incentive. Well this time I was approached by a guy who runs a gig-rehearsal room-bar kinda place and he saw our band's pedal arsenal and asked me to build him a pedal which is called Mu-tron III by Musitronics.

Stevie and the Original 1972 Mu-Tron III
This pedal is the sound of funky 70s bass, clavinet, guitar and more. After Stevie Wonder hooked it up to his clavinet and had it do the auto-wah thing for his wah-clavinet everybody from Bootsy Collins on bass to Jerry Garcia on his guitar were wahkin' off their instruments on stage and on albums. It is actually an envelope controlled filter which was made to produce synth sounds from regular instruments. It's quite a unique piece of gear running on 18V and having opto-isolators as the coupling mechanism for the envelope generators. It was built in 1972 by a spin-off company of Guild Guitars who wanted to make a synth for guitars and ended up as Musitronics and built some nice synth-like pedals for a large range of instruments including this crazy auto-wah pedal called the Mu-Tron III. In the 90's Electro-Harmonix used the original circuit to issue their more updated Q-Tron family. 

When I researched it I was super thrilled by the challenge and told him I would make him one. I didn't have a clue where to begin but after a few hours which became days I understood what this legendary pedal was all about and I found the schematics, layouts, manuals and most important a ready-to-solder PCB from JD Sleep at GeneralGuitarGadgets which I love so much.

The next issue was locating all the parts with 2 key components which I didn't find, the opto-isolators. There were a few options how to go that path and I chose to listen to Steve Daniels at SmallBear who recommended the H11F3 Photocouplers which were supposed to be similar to the Original Hamamatsu ones. Other options seemed less appealing to me and sure didn't want to go into building my own couplers with a LED and an LDR hooked up together.

From reading about the circuit design it was also obvious that tuning the unit's frequency response with a single resistor would make the unit less versatile and I decided to add a 10k pot instead. This pot gave me an extra frequency sweep control which made the filter pedal even more versatile and playing with it was like a manual frequency knob on an analog synth filter. Great Fun, check out this audio clip below:


Anyway, while building this incredible pedal as an order to a friend who plays bass, I knew I had to have another one for myself. So...I built a second one.


The GGG PCB all populated and ready for wiring up
Experimenting with the unit prior to the artwork

Planning the Artwork
The finished Mu-tron clone unit - Nu-Tone III
Once again, with a fuzz or an overdrive you could get the Prodigy's Voodoo People synth loop or a lot of really crazy riffs with a hard Electro-Rock feel. Fuzz after the pedal sounds good but it is really best to place it before the pedal that makes the envelope filter shine through.

If you get the PCB you can do it without to much trouble. It would be braver to go at it without a ready-to-solder PCB. Also don't pass on the 9-18V charge pump option, it's a must. One think I am not to certain of was the bypass switch which is accomplished using a FET instead of a normal true bypass configuration. It works, nevertheless.

There are so many settings with this baby and so many options that it blows me away. Subtle or hard, LP, HP, UP and DOWN, it's really the Endless Enigma (if you know what I mean...ELP...), I just wish I would play more music that demands this kind of sound. I usually use it nowadays on bass more but for a Clavinet or a Rhodes style electric piano it would be a killer.

GGG have all the necessary technical info right here. It's off the beaten fuzz track but certainly a worthwhile addition to your fuzz tone arsenal of eccentricities.


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