Cwejman VCO-2RM Dual Oscillator Review + Demo (Youtube Video)

Cwejman modules have gained the status of the holy grail of modular synthesis over the past few years. Recently I was offered to buy a VCO-2RM second hand for an OK price so jumped the opportunity and got my hands on it. I had tried some Cwejman modules before (including the VCO-2RM) at Schneiders in Berlin and was always intrigued by their classy and beautiful sound. I had read lots of good things about Cwejman stuff on the internet as well. Some critical voices tend to nitpick about the Cwejman sound being too sterile or clinical. I can understand what this criticism is about, as Cwejman really sounds very "precise" but I never saw this as a problem. If you want warm/fuzzy/overdriven sound you can still mangle your audio signal with distortion or waveshapers or whatever is available (and that's a lot!).

Briefly going through the VCO-2RM's features, it is a dual VCO with a wide frequency range (there is also an LFO mode available for both oscillators), 3 FM inputs for each oscillator (exponential FM only!), PWM, sync and a ring modulator. Since the ring modulator is  DC-coupled it can be used with CV signals, making it a VCA. Yes, you can use the VCO-2RM's ring modulator as a full-fledged audio VCA! I tried it, it works. Each VCO has 7 selectable waveforms available (everything from sine to pulse including some odd mixed waveforms). Each VCO can only output one waveform at a time. 

Cwejman VCO-2RM Dual Oscillator

So how does it sound? Well, compared to the vintage oscillators I have experience with (Moog, ARP, Octave, Roland etc.) it strikes me as being "on the spot" as opposed to "warm and organic". So, depending on what you are after it might indeed be a touch "too controllable". Obviously the components Cwejman uses for his modules are so well-selected and precise that there is hardly any room for tolerances or random fluctuations. For me the VCO-2RM really shines once you start modulating it. Feed it with CVs from various sources, amplitude-modulate these CVs with VCAs, sequence everything, well... you will see (and hear) that the VCO-2RM really begs to be modulated, and the sonic possibilities opening up are infinite. As you tweak the VCO-2RM's knobs even a tiny bit of change can make a huge difference in timbre. What I love about it is that it covers everything from classical subtractive to experimental sounds. And did I mention the VCO-2RM tracks like a champ? Tune both oscillators to a specific interval and play them across multiple octaves. Voila! Stays in tune.
For my demo video I used both VCOs and the ring modulator sequenced and modulated by Doepfer A-155 sequencer, A-145 LFO, A-143-9 VC Quadrature LFO, A-140 Envelope Generator, A-149-1 Quantized/Stored Random Voltages, A-133 Dual VC Polarizer and A-183-2 offset generator. The mixed output of the VCO-2RM runs through a STG Soundlabs Sea Devils filter and in part through a Synthrotek Echo. Enjoy!

STG Soundlabs Sea Devils Filter Demo

Play MP3 clip: STG_Sea_Devils_Filter_Demo.mp3

During my last visit to Schneidersladen in Berlin I scored a very nice module from the bargain bin: An STG Soundlabs Sea Devils Filter. It is a three pole (18dB slope) diode ladder lowpass filter with signal input, ouput, 3 filter CV inputs (one with attenuator) and resonance CV. While testing this module at Schneiders I was really impressed by its character. It is both fat and vintage sounding as well as really precise in its response to external CV modulation. It reacts gorgeously to sequencer lines, envelopes and LFOs. It does however get quite growly with audio-rate filter CV modulation. Anyway, with low resonance you get a monolithic, huge sounding bottom end. Cranking up the resonance results in wonderfully "plucky" sounds, and as soon as resonance reaches self-oscillation you end up in creamy & bubbly acidic musical territory. This filter has so many sweet spots it's a real pleasure to use. Build quality is excellent. The knobs are large and sturdy and have a firm yet smooth action. I can say I am really happy I got this module.

STG Soundlabs Sea Devils Filter

For this demo I took my trusted MFB Kraftzwerg's 3 VCOs, tuned them two octaves apart and pitch-modulated them with MFB Megazwerg's 4-step CV sequencer. This sequence is getting some random transposition via Doepfer A-149-1. The 3 VCOs were then fed into the Sea Devils' input. To modulate the Sea Devils' filter cutoff frequency I used a mix of different CV sources: Electro Harmonix 8-Step Sequencer, Doepfer A-140 ADSR Envelope, Doepfer A-171-2 VC Slew Processor plus some manual tweaking. The Sea Devils' output was then fed through the MFB Megazwerg's delay. No other FX or EQ'ing was used.
In the beginning resonance ("response") is set to zero. I gradually turn up the resonance until the filter starts self oscillating at the end of the demo.