For more than a decade, synthesizer players across the world have benefited from Dave Smith’s musical rejuvenation. Lately the Eurorack community have been included too, as the fruits of Dave’s labour begin to be ported to modular format. Naturally, the series began with the Curtis filter we know from many synths (eg. the Prophet 08 and 12) and this was followed by a ‘character’ module, a toolkit of sonic manglers to warm and dirty your audio. The third outing, DSM03, introduces tuned feedback — an important component in DSI synths ranging from the little desktop Evolver of 2003 up to the recent Pro 2.
The DSM03 consists of a delay line (8Hz to 64kHz), a digital white noise source, a simple envelope and a digital low-pass filter. The filter is a four-pole design that is clear and sharp, its ringing resonance only becoming abrasive towards its maximum where self-oscillation kicks in. Thanks to over-sampling and a 24-bit, 96kHz audio path, it’s an eminently usable filter for the occasions when you aren’t making use of the tuned feedback.
Of course, feedback is primarily what the DSM03 is about, and the presence of a noise source means you can kick the delay into action without even connecting an external signal. All that’s required is a trigger input to fire the envelope which shoots noise into the filter and delay. This provides a quick introduction to the range and quality of the filter and its tonality but, more importantly, as you turn up the feedback amount it introduces the characteristic ringing as the delay feeds back into the filter input.
At the lowest tuning values you can hear the individual delays, but after turning the knob a few degrees that noise burst propels you into resonant territory, hinting at Karplus-Strong synthesis and plucked string effects. For the boldest results I found it important to keep the filter open and resonance low, otherwise — even at maximum feedback — the filter tends to act as a dampener on the whole process.
Naturally, you aren’t limited to triggered noise as input — any audio signal can be added to the mix and treated alongside it. When pitched input is introduced, the module takes on a quite different personality. Primarily this is because the feedback tends to soft-sync to the input frequency. The tuned feedback will track with reasonable accuracy over three to four octaves, but since the filter is in feedback loop too, any adjustment of cutoff frequency and resonance is liable to throw the tuning off. It’s therefore a continuous process of balancing the four main controls to best highlight the ringing resonant effects and make your source gleam like never before.
The DSM03 is surprisingly effective for subtle enhancement, exciter-like effects, flanging and a wealth of formant-like tones that simulate human modulation of a vocal tract or nasal cavity. It becomes positively gnarly at the maximum feedback and with the filter wide open. In such cases, the lowest tunings evoke strange and shifting atmospherics — the perfect accompaniment to a magic mushroom trip, especially if you introduce subtle modulation of the tuning.
As well as the audio input and output, the module offers CV control of filter cutoff and resonance plus the feedback amount and tuning. All are -5 to +5 V except the filter cutoff input, which accepts between -10 and +10 V — a wider range than most modulation sources provide. I had only one brief moment of regret: that there was no voltage control of the decay, as this would have extended the DSM03’s value as a stand-alone percussive voice.
This apparently simple module rewards exploration and careful fine-tuning, but it’s well worth taking the time to find its sweet-spots. It can act as a low-pass filter and even a basic delay, but it really comes alive when its feedback is exploited to produce shimmering metallic tones, dirty flanging, tuned noise or many colours of ringing, roaring feedback.