Mu-Tron Tremu-Tron

The Mu-Tron Tremu-Tron is an optical tremolo effect which can be used as a "clean boost", built by Musitronics Mu-Tron and made in the USA¹. It uses the maker's patented opto-mod technology, which Mu-Tron says provides classic, hi-fidelity attenuation without extra noise artifacts¹. The design goal is specific: to give non-tremolo tube and solid state amplifiers the same rich tremolo found in vintage Fender and Vox amplifiers¹.

The pedal is built around an optical circuit with high headroom and a dual rail power supply, and it uses the gain drive preamp from the vintage Mu-Tron III envelope filter². Mu-Tron says that by utilizing an 18 volt dual-rail internal power supply, the Tremu-Tron provides a crisp, clean signal and high headroom¹. The product pages also describe the pedal as 9V DC powered in a rugged Mu-Tron enclosure, so the two power descriptions sit side by side in the maker's own material³.

Optical tremolo with a clean boost

Optical tremolo works by using a light-dependent element to vary the signal's level, and the Tremu-Tron applies Mu-Tron's opto-mod approach to that job. Mu-Tron says the result is classic, hi-fidelity attenuation without extra noise artifacts¹. The intent is to bring vintage Fender and Vox amplifier tremolo to amps that never had it, whether tube or solid state¹.

The boost side is part of the same circuit. Mu-Tron says the Tremu-Tron may be used as a boost to push the tubes on traditionally clean amps such as Fender blackface types, or to "beef-up" the front end of sterile solid-state type amplifiers or mixing consoles¹. That makes it a boost pedal with a tremolo built in, rather than two separate boxes.

On placement, the maker is direct:

That puts it in the conventional modulation slot, after your overdrive or distortion pedals and ahead of reverb.

The controls

The Tremu-Tron has four controls, described by the maker on its product page¹:

The Shape control is the one that sets the character of the pulse: at the sine end the tremolo is smooth and rounded, and at the square end it becomes a harder on-off chop. Blend lets a player keep some of the dry signal in the mix, and Level sets the overall output, which is where the clean boost lives. Pedal of the Day's review highlighted the "wave form and speed controls to tailor tremolo characteristics" and the "level and blend controls for perfect tremolo mix"⁶.

The Mu-Drive preamp from the Mu-Tron III

The Tremu-Tron features the famous Mu-Drive preamp from the original Mu-Tron III envelope filter¹. The Mu-Tron III was Musitronics' landmark envelope-controlled filter, and by 1979/'80 the original Mu-Tron was history, as Vintage Guitar magazine put it⁷. Its preamp, however, lives on in the Tremu-Tron, where it provides the gain drive that feeds the optical tremolo circuit².

The Mu-Tron III's own control set included a Peak control for the volume of the cutoff frequency⁸, and the preamp's behavior with a guitar's volume knob was part of that pedal's character. Commenters on a DIY layout of the Mu-Tron III circuit noted that "guitar volume is part of the effect" and that the down sweep gave "cool phaser like sounds controlled with picking velocity"⁹. Those observations are about the envelope filter itself, but they point to why the preamp section was worth carrying forward into a new pedal.

What reviewers said

Published coverage of the Tremu-Tron itself is limited, but Pedal of the Day reviewed it on 26 January 2022 and was positive⁶:

The same review repeated the maker's description of the pedal as designed to give non-tremolo tube and solid state amplifiers the rich tremolo of vintage Fender and Vox amps, and noted its use of the patented opto-mod technology⁶.

Versions and buying

Mu-Tron sells the Tremu-Tron at a list price of $189.00⁵. There is also an A Stock version, which the maker describes as a way to "save a few dollars with very minor cosmetic case blemishes": the same optical tremolo and clean boost circuit, with slight cosmetic marks on the case⁴. Both versions are made in the USA and carry the same dimensions and 9V DC power description⁴.

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