Musitronics Mu-Tron III



  • Mode (LP/BP/LP)
    Selects the type of filter: Lowpass, Bandpass, Highpass.
  • Peak
    Controls volume of the cutoff frequency.
  • Gain
    adjusts the filter's sensitivity to the signal of your instrument.
  • Range (Low/High)
    Selects the frequency range covered by the filter envelope.
  • (Down/Up)
    Selects the direction of the filter sweep: down- or upwards.
  • Power (Off/On)
    Switches the power on or off :)


Before the pedal went into production in 1972, it was called "Auto-Wah". The "Mu-Tron" name came about when one of the four founders of Musitronics suggested it as a good contraction of the company's name. The "III" was a favorite number of Mike Beigel, the company's Engineering V.P. There never was a Mu-Tron I or Mu-Tron II.

This is the original envelope filter, developed by Mike Beigel in 1972 and brought to attention by Stevie Wonder's endorsement.

The cardboard design mock-up was constructed at Creative Designs International (CDI) in New York, and was styled by the late Herb Ross, a prominent industrial designer.

Famous Users?

uhm... almost every artist making funky music has one, uses one or wants one :)

Bootsy Collins admits: "Without that Mu-Tron, there ain't no Bootsy".

For a lot of envelope filter users this is still the best one ever made.

Mike Beigel about the Mu-Tron III pedals made by ARP

By the time ARP was making Mu-Tron IIIs, I was already out in my own (Beigel Sound Lab) consulting and product design business again, and i never paid much attention to the ARP Mu-Tron products. They are the Mu-Tron III products WITH the AC line cords, and labeled as produced by Mu-Tron INC., not Musitronics Corp. which made them from 1972 to 1978.

Last night (January 17, 2014) while working with my colleague Richard Lingenberg on some new product design work, we got to talking about the ARP (Mu-Tron INC) units, and I got a BIG and DISAPPOINTING surprise. I had always figured that they were competent enough to make the product the way I had originally designed it, but that was WRONG.

Apparently they changed the inside POWER SUPPLY VOLTAGE but in doing so, they apparently DID NOT UNDERSTAND to change some component values that were designed for the ORIGINAL power supply voltage.

To make this brief, Richard (who gets all my Mu-Tron Vintage repair work and his own repair work from other sources) has fixed up and calibrated a lot of these ARP units. What Richard noticed about (ALL?) the ARP units coming in for repair, was that the FREQUENCY SWEEP was WAY TOO HIGH and also that the DOWN DRIVE never really worked to drive the filter down "all the way" as it was supposed to. Both of these symptoms had to do with changing the power supply voltage but not compensating for the change by changing ALSO some very critical component values.

So Richard (who knows what a Musitronics Mu-Tron III unit SHOULD sound like), changed the offending parts values and recalibrated the SWEEP range and DOWN DRIVE to what they were designed to be.

I never knew about this before, and am sharing it now.

If you have an ARP Mu-Tron III and don't like the way it sounds or works, now you know why. If you want it to be fixed (even though it's not officially "broken") and recalibrated, please send me a note at <info at mu-tron dot ORG> (NOT .com), and I will forward the information to Richard, who will contact you and give you a quotation on fixing the parts values and re-calibrating it to the frequency sweep range of the original factory Musitronics Mu-Tron Calibration.

(But if you are perfectly happy with your ARP-Mu-Tron unit, then by all means USE IT AS IS. Richard also noticed enough variation in the calibration of the ARP units that it's just possible ttyat YOUR vintage ARP-MuTron III unit is accidentally calibrated "just fine".)

There weren't all that many ARP units made, but I thought it appropriate to inform the owners of these vintage (and AUTHORIZED by Musitronics Corp) i.e. LEGITIMATE reissues, that there might be issues with the units that (I) didn't know till last night.


myFXDB user reviews

1 review, average score of 10 / 10

2017-06-1510/10  ......

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  • Gain
    Variable from 0.1 to 40, when driven from low impedance source.
  • Input Impedance
    1 Megohm at lowest setting of GAIN control, variable to 3.3K ohms at maximum gain setting.
  • Output Impedance
    600 ohms
  • Minimum Input signal for full Mu-Tron Effect
    1.5mV from 600 ohm source.
  • Maximum Undistorted Output Signal
    3.6 volts RMS
  • Power Supply
    +/- 9 Volts from 2 NEDA 1604 batteries or Musitronics Model PS-1 Battery Eliminator



Where to find one?

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