Ray Wilson authored this content while he was actively running MFOS as the founder and resident genius.
We retain the content because it reflects a valuable point of view representing that time and place.

Article by Ray Wilson
This is an advanced project and I do not recommend it to beginning electronics or synth-diy enthusiasts. If you have successfully built a project on the level of a Sound Lab Mini-Synth I would estimate that you have the necessary skills to successfully complete this project. It is assumed that you will know how to provide a bipolar power supply for the project that delivers +/-12 volts with capacity to deliver at least 200 to 300 mA. The circuit draws between 90 and 100 mA but the 200% to 300% current capacity padding is always a good idea.
The MFOS Adjustable 1.5A Bipolar Power Supply PCB (LM317/LM337) would be a good choice to power both the Sound Lab ULTIMATE and the ULTIMATE EXPANDER but the power supply is left to the discretion of the builder.

Prototype board support page: ULTIMATE EXPANDER PROTOTYPE PCB

The MFOS Sound Lab ULTIMATE EXPANDER in combination with an MFOS Sound Lab ULTIMATE is a completely full featured modular synthesizer. Although specifically designed to be a companion to the Sound Lab ULTIMATE the ULTIMATE EXPANDER has the features to stand on its own as a super "Swiss Army Knife" module. The MFOS Sound Lab ULTIMATE EXPANDER includes:

  • A State Variable Voltage Controlled Filter (doubles as a 1V/oct sine wave oscillator over several octaves)
  • A Voltage Controlled Amplifier (expo response)
  • An ADSR Envelope Generator
  • A Four Channel Active Mixer
  • A One-In Three-Out Voltage Distributor
  • A CV Inverter
  • An Analog Multiplier (Ring Modulator)
  • An External Signal Buffer
  • An Envelope Follower
  • Two Passive Voltage Attenuators
  • A Headphone Amplifier
  • Signal Routing and Buffering for The Sound Lab ULTIMATE
  • Patch Panel Design
  • Professionally machined panels and PC Boards available from MFOS
The samples below demonstrate the incredible sounds and range capable when the Sound Lab ULTIMATE is combined with the Sound Lab ULTIMATE EXPANDER. For a keyboard controller I used my Korg N1 with the Frostwave Quad MIDI-CV Plus. I found some free MIDI files on the web with the various parts as different tracks and recorded each track separately to achieve the polyphony you hear in the sound samples below. A touch of reverb has been added to the samples.

Expander prototype during evaluation at MFOS labs.

J.S. Bach Fugue I
J.S. Bach Fugue II (listen for the EXPANDER's filter as a sine oscillator)
Cascading Thoughts (R. J. Wilson)
Short Claude Debussy Sample (listen for the EXPANDER's filter as a sine oscillator)
Guitar X Sine Wave Modulated With Env Flwr
Guitar through LP EF gating ADSR modulating filter
Guitar through BP EF modulating filter
Microphone X Sine Wave
Microphone X Sine Wave Modulated With Env Flwr
Organ Through SV-VCF LP modulated by two LFOs
The Sound Lab ULTIMATE in conjunction with the Sound Lab ULTIMATE EXPANDER can rival many of the vintage synths you may have drooled over as a kid. MFOS committed to having the expander available for sale by summer's end of 2009 and we delivered. The Sound Lab ULTIMATE EXPANDER is the latest tool from MFOS to help keep your Imagination, Ingenuity and Creativity solidly turned up to 11.