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.

The Pink Face

The Pink Face

Throughout the history of fuzz pedals, fuzz guitarists and psychedelic fuzzy solos, there is no fuzz which has received greater attention than the legendary Fuzz Face. Originally produced by Arbiter Electronics in England and appeared during 1966 the unit was an immediate success. Many of the greatest guitarists in rock history played their best solos and riffs through a Fuzz Face including Hendrix, Gilmour, Blackmore, Harrison, Townsend and many more. Nevertheless, the dependency of the Germanium transistors on temperature resulted in a lack of tone consistency and many players suffered on stage from this effect. To circumvent this issue Dallas Arbiter started issuing Silicon versions of the FF somewhere around 1969 replacing the NKT275 trannies with BC108. Silicon was the new hype at the time and it seemed that by 1970-71 everybody was switching to Silicon faces. Hendrix's Band of Gypsys, Gilmour on all PF albums and tours since 1971 including all of the solos on Meddle and Dark side of the Moon are probably the most documented examples. One of my favorite guitarists Michael Karoli (Can) also used Silicon Fuzz Faces to create his raw and untamed distortion throughout the history of Can, so this was enough to get me going. 

Both designs are pretty close with the Germs being mostly PNP and the Silis being NPN. Comparing the sound of the Germanium units with the Silicon ones it is often said that while the Germs sound raspy, warm and sweet, the Silicons are brighter, edgy and have more gain. Well....from my builds....this statement is....TRUE!

The original 1966 Arbiter Face - Germanium

On my Fuzz quest I really couldn't imagine the journey without understanding the differences between the two FF versions and there was no other way than building the two. After I finished the Germanium Fulltone version I started to drown with info on the Silicon versions: Fulltone, Analog Man, Dunlop, Runoffgroove, GGG you name it. I looked through dozens of schematics and breadboarded some of them. I even looked at the German Schaller Fuzz (FF variant) after reading that Michael Karoli (CAN) used one. Actually, the first fuzz I ever built was the Runoffgroove SiliFace II and I loved it for some months. That was what got me interested in fuzz pedals in the first place, My Fuzz quest started because one fuzz was not enough to get the range of buzz tones I was after.

The 1970 Dallas Arbiter Fuzz Face - Silicon

Due to the fact that the Fuzz Face design is tolerant to part values many versions have been issued over the years and the amount of Fuzz Face versions became quite vast (just like it happened with the Big Muffs or the Tube Screamers). The design is so simple that small part changes resulted in some sonical change. After all the entire unit incorporates 4 resistors, 3 caps, 2 transistors, 2 pots and 1 switch. That's it!

4 resistors, 3 capacitors, 2 transistors, 2 potentiometers

The sound I was aiming for was that of Gilmour playing the Time solo on the album version of the Dark Side. I started out with the GGG early 70's Boutique NPN Fuzz Face after my success with the GGG 60's version. I liked the PRE GAIN knob and the circuit seemed pretty good, but something was missing. I didn't box the circuit and it stayed on the shelf for some time. I built a few other Fuzz pedals and when I thought I understood more about what I wanted I revisited the circuit. This time I modified the circuit based on the Axis Face version by Phillip Bryant modified by Brett Robinson. 

Gilmour's early 70's rig

I did a lot of testing using Hi-Watt amp emulations, tweaked many of the parts in this little circuit, changed trannies and used several guitars. Surprisingly, I ended up using 2N2369 (hfe=70-90) for Q1 and BC109 for Q2 (hfe=200). The BC108C I had (hfe around 400-550) seemed to be too pumped up for my taste. I settled on a 50kA pot for the PRE GAIN and a 100kA for the VOLUME. 220n cap for the input and 30p cap on the bridge for lo-pass filtering. I replaced the CONTOUR pot with a 470R resistor and kept the 22uF Fuzz cap. I kept the reverse polarity protection and cut off the strange feedback diode bridge which didn't seem to affect the sound. Biasing Q2 I got 4.5V with resistance being about 3k3 so that's about 4k3 total Q2 bias. It's funny that this fuzz is currently my most tweaked fuzz circuit to date. Only a few parts but so much experimentation. Other fuzz circuits you get the schematic, the parts, breadboard and maybe test a few transistors, bias them and that's it. Along with the early Tone Benders and the Maestro Fuzz Tone which are more complex it's one of the toughest, considering its architecture.

Luckily, somebody at work who knows I am always on the lookout for metallic enclosures, gave me this great candy box. I couldn't have asked for a better design with those pink pigs on a round enclosure making it suitable for a Fuzz Face and for a Pink Floyd related sound, so I jigsawed it to the right height, called it Pink Face, mixed my glass paint bottles and came up with a magical pinkish tone... Perfect!

The sound is well worth the effort. It's not as warm or sweet as the Germanium version but it does give you the Time solo style. Bright when the FUZZ pot reaches max. The PRE-GAIN gets you that rolled off effect for cool rhythm chords and sparkly clean chops. Using a treble booster in front enables you to get great tones with the FUZZ knob below max. I also tested it with a Wah in front and no buffer was needed. Definitely a must build on my fuzz journey towards a better future.

If you want to learn more about the the topology of the fuzz face there is no better place than R.G. Keen's article: The Technology of the Fuzz Face. It helped me a lot in choosing the right part values and testing transistors both in my Germanium unit and this recent Silicon unit. It is really the Fuzz Face Bible, highly recommended and insightful. 

The schematic I drew up in Chrome Circuit Lab is shown here for reference but feel free to use it, tweak it or twist it. I will update it if I decide to change it. The feedback diode did not really do anything so I left it as in the Fulltone version.

Hope you get to enjoy it! You can also have a blast using Mark's vero layout on Tagboardeffects.blogspot,com

There is a lot of Fuzz Face info all over the web, here are some more recommended pages for extended reading on this matter:

• http://effectslounge.com/blog/more-history-fuzz-dallas-arbiter-fuzz-face
• http://www.custom-sounds.com/Articles/FUZZ-FACE-by-David-Morin, 
• http://fuzzcentral.ssguitar.com/fuzzface.php.
• http://www.analogman.com/fuzzface.htm
• http://www.gilmourish.com/?page_id=73

Tyme for some High Octave Fuzz

Ever since I have been reading and listening to various type fuzz circuits I was always intimidated a bit to build  an octave fuzz, mainly 'cause I don't really care to much for octave pedals. Sure they are interesting pedals to play with and toy around, and some great guitarists have made some great solos using octavers, both up and down, but it's not what I am usually after in my sound. Anyway what I'm trying to say is...boy...was I wrong.

My first attempt at an Octave fuzz pedal was made by tampering with a Jordan BossTone fuzz which had a pot for battery starving effect (a tip from freestompboxes.com). This yielded an Octave Down effect with a lot of buzzing which sounds a bit like the Motorcycle effect done by Brian May. Pretty cool, hu? but I'll post this one later on.

Then I read an interesting story about Hendrix playing the Purple Haze solo through the mysterious Octavia fuzz made by Roger Mayer. It is told that one of these pedals was stolen, and reappeared after Hendrix's death under the Tycobrahe brand. After listening to more tracks allegedly played through this Octavia pedal I realized that this pedal has a lot to do with what I call the Hendrix sound. Although he used the Maestro FuzzTone and various Fuzz Faces quite a bit, he also used a pedal called the Axis Fuzz and the Octavia. Both of these pedals sound fantastic and very versatile so I could n't sit still, of course, knowing that they are both in one medium difficulty circuit.

Wondering the web for circuits I ended up using the GGG circuit which had some new features like negative ground, PREGAIN knob, polarity protection and also featured the Octave On/Off switch, so that it's actually two pedals in one. The first part of the circuit is actually the highly acclaimed Roger Mayer Axis Fuzz and the second part is the Octave-up which used a coil transformer for frequency conversion. Mind you that the later Roger Mayer Octave Fuzz is a different circuit and does not have the transformer for the octave up thing. From what I understand the original pedal did include a transformer for the frequency doubling.

I ordered some parts from SmallBear and Mammoth, breadboarded the sucker and when I saw that it was all good I boxed it and called the pedal the "High Tyme" fuzz and for a very good reason. As soon as I plugged my guitar in I was back in Psychedelic Ladyland. This pedal is so sweet you wanna eat it. The Axis-fuzz circuit is musical, smooth and rich. It actually sounds much better and more defined than your usual Fuzz Face, and more vintage sounding than any BigMuff if you wanna go 60's. You can play around with the INTENSITY knob but it really sounds good anywhere on the clock. Once you engage the Octave everything goes berserk. You can roll off the guitar knob or use the PREGAIN and as you roll it down you can get a cleaner octave which can sound very interesting on the high notes on the neck pickup. What I love even more is the sound of the pedal on Bass. I spent an entire night playing bass using the pedal with a phaser right after it. The sound was so inspiring that I couldn't stop. It can get really nasty and quirky on the higher settings. Btw, for the Octave on/off switch just cut the transformer's primary channel diode from the ground and hook it on a SPST switch. Yes, it's that simple as shown here.

I don't know if this circuit is the exact circuit Hendrix played through but it is definitely out there. It's probably the closest I got so far to really reaching my goal on this quest. Lately I've heard of a band called T2 which released one album "It'll All Work Out In Boomland" in 1970 and boom they split. On the new CD release there is a bonus track called "Questions and Answers". 17 years old guitarist, Keith Cross, plays 3 amazing solos on this track which climb up the fuzzy scale throughout the track. The fuzz he uses has got to be the Octave Fuzz 'cause no other fuzz sounds quite like it. you can listen to it using this link. You won't regret it. If you wanna build it.and you need the schematic...here is the magical recipe for this Psycho potion.