Sonic LAB: Pittsburgh Modular Microvolt 3900 Desktop Semi Modular Synth

US A mix of features from both East and West      18/06/18
    MP4 20:15 mins    

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A new desktop synth from Pittsburgh Modular,  who are ramping up the new products schedule. The Microvolt 3900 is described by them as “a love letter to the analogue mono synth”.

Not entirely sure what it means, but it sounds good. I think on reflection it's a collection of features and functions that make a subtractive synth what it is - or something.

Microvolt uses classic subtractive elements - VCO, VCF, ADSR, LFO and adds some more West Coast style features such as complex wavefolding, function generator and Low Pass Gate on the VCA.

There’s a quite a lot packed into the small case (think 0-Coast size) and as a result small faders (with blue LEDs) and small nylon knobs are used - a bit like Volcas.

It does give the unit a less solid feel, I guess the whole thing would have been bigger if they’d used larger faders and knobs.

Anyhow, back to the synth - it's a desktop semi-modular analog synth - no Eurorack mounting options here, with 39 patch points, a single oscillator (based on the Double Helix Core, and with some complex wavefolding.

Waveforms: Sine (+ harmonic sine), Saw, Square (with PWM), Fold with shape control  + Noise. Each with a dedicated level control. There’s also an external input with 30dB of extra gain for some added drive.

Each has its own output on the patch bay,  and they do sound nice, plenty of heft and buzz as one would hope for from a Pittsburgh Oscillator.

Next up is the binary filter - which is a fixed low pass resonant filter based on Pittsburgh’s classic 2-pole State Variable Filter,  but with an extended resonance button (another of the tasty blue backlit ones they use) resonance at the highest level just starts to self oscillate, hitting the resonance mode button boosts that and inverts the value, now moving the fader down increases the self oscillation until its pretty out of control.

The filter has a nice character with modulation pre-routed from the function generator which can be used as a Rise Fall Envelope with modulate-able rise and fall levels, which can generate some really whippy envelope type sounds, but also by switching cycle on for some audio rate modulation or slower LFO action. The filter will track the keyboard while fully self oscillating, though it's almost impossible to dial in a Volt/Octave scaling to make it usable to play notes.

Back to the VCA which is normalled from to the ADSR envelope for usual usage, but additionally there’s a LPG mode - Low Pass Gate with variable decay - sadly this can not be modulated - shame as fast snappy sequences while tweaking this parameter sound great. Additionally, there’s a Pluck mode - faster percussive LPG stuff. The VCA has a second input with a mix control - routing one wave via the VCF and another directly in, using only the LPG mode gets some additional flexible routing. It's here that you find yourself craving a second VCO - that would have been great, but space and cost would have come into play.

Back to modulation and the LFO / Random  gives you a fairly wide range for the LFO speed (switchable between high and low modes) with Ramp Up/Triangle/ Ramp Down or Pulse Width via the wave knob, the Random or Chaos generator has variable speed based on the master clock and with a middle range offering more random-ness. A Mix of the Random/LFO is normalled to the VCO FM mod, Pulse Width and Folder Timbre - with knob control of the blend between the two modulation signals.

Sadly, the FM depth appears to be linear meaning smaller amounts of modulation are hard to dial in, just the smallest amount can be too much.

Drive at the output stage there’s an additional drive circuit which can add a lot of extra character to the final sound, the range of it seems nicely set - just a little can really beef up the signal, and full on is not totally out of control, but still can create some excellent distortion.

Arpeggiator - on board with multiple modes and taken from the master clock (tap tempo) , useful for some stuff, especially when patching the random gate output into the Function Generator for some great random accents via the VCF.

Power and Stuff
Microvolt requires a 15v power supply (included) and comes with six patch chords.

Also supplied is a MIDI in DIN socket to 1/8th jack as Microvolt has a built-in MIDI CV. Tracking and tuning of which are pretty good over 5 or 6 octaves. I had to re-calibrate mine as it was not a production model, but once I had it was all good.

Overall, I like the sound, it has some great qualities to it, I do miss a second VCO two of them would sound awesome, but the unique collection of features when combined with another modular sound source will yield some lovely results.

The Pittsburgh Modular Microvolt 3900 arriving in stores now priced at $630 / £540. It's not the cheapest of synths, but it does sound good and offer an useful set of features.

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