MINI MU

OPTICAL AUTOWAH

COMING SOON

SCHEMATIC (PDF)

This pedal is discontinued. Please check our dealers or our Reverb store for any remaining stock.

The MINI MU is derived from the classic Mutron III envelope filter (aka autowah), and has all the same great fat and funky filter sweeps inside a much smaller box. A few extras have been added, namely an active clean gain stage and an "in between" position on the range switch. With the included charge pump, the MINI MU runs on +/-9V like the original without needing a special power supply or two batteries.

Click the different parts of the pedal to learn more.

Demos

How It Works

Features

Tech Specs

Story

Older

Versions

MINI MU BLOCK DIAGRAM

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FEATURES & CONSTRUCTION

TrueSoft  Bypass

Low Noise Op Amp

Extended Headroom

DualMode Switching

We combine durable true bypass relay switching with an effect-side FET switch for pure and smooth switching.

A modern, high-speed op amp was chosen for its low-noise and high-fidelity properties.

A simple voltage inverter circuit was used to effectively turn 9V into 18V. No need for special power supplies.

DualMode Switching can convert the footswitch into momentary operation.

To use, wait 5 seconds, then press the sequence tap+tap+hold until LED flashes.

USA Made PCBs

Our circuit boards are made in the USA by Advanced Circuits (large PCB runs) or OSH Park (small PCB runs).

All Analog Circuitry

The Mini Mu uses analog optocouplers that were selected for their faster response times - for a more funky filter reponse.

All VFE Pedals are built by hand in Puyallup, WA and include:

 

- Rugged diecast aluminum enclosures

- DualMode standard or momentary switching operation

- Industrial-grade Carling switches & Neutrik audio jacks

- Alpha pots soldered directly to PCB

- 5% WIMA film capacitors & 1% metal film resistors

- Ultra-pure, eutectic silver solder

- 1 year warranty on parts & labor

DIMENSIONS:

Enclosure dimensions: 2.37"W x 4.37"L x 1.16"H  (60 x 111 x 29mm)

With knobs & jacks: 2.6"W x 4.4"L x 2.1"H  (66 x 111 x 53mm)

 

POWER:

Standard 2.1mm, negative-tip 9V to 15V power supply or 9V battery.

 

INPUT IMPEDANCE:

1M-ohm

 

CURRENT DRAW:

~25ma continous

+30ma surge for 4ms during on/off switching

BY THE NUMBERS:

31 RESISTORS

21 CAPACITORS
1 INDUCTOR

2 TRANSISTORS

7 DIODES

3 OP AMPS

3 INTEGRATED CIRCUITS
5 POTENTIOMETERS
5 SWITCHES

3 JACKS
2 CIRCUIT BOARDS

2 OPTOCOUPLERS

HOW THE MINI MU CAME TO BE

THE STORY

I started tweaking with the Mini Mu after continual requests for an autowah, most frequently one based on the original Mutron III pedal. The original design was a straight-up clone with a volume control added. Countless tweaks followed, all of which were attempts to smooth out the filter's response, add headroom, and increase versatiliy - each tweak came from either user responses or my own personal testing.

 

The Mini Mu is great at adding quack & funk to your tone. However, don't look here if you want slow filter sweeps. The Mini Mu utilizes optocouplers with a faster reaction time, which was key aspect of the custom units used in the original circuit.

-- Peter Rutter, founder of VFE Pedals --

Here is the list of versions of the Mini Mu circuit:

 

#1 - The first revision was a clone of the Mutron III autowah circuit. The circuit was miniaturized and a passive attenuator circuit was added at the end to adjust the output volume.

 

#2 The second revision tweaked with the filters for a more natural response, and added a post-filter gain stage to both re-invert the signal and add boost (both common complaints about the Mutron III).

 

#3 - While the external control layout never changed, over time we made minor, but steady improvements to the noise specs, clean headroom, and feel of the filter sweep.

 

Here is what is new in the current version:

- More natural sweep & gain range balance

- Smooth treble response, partically when adding feedback

- Lower overall range, better for bass guitar

- Dual-Mode switching