At first glance, the A-124 WASP and the A-106-5 SEM Filters almost look like siblings (well, probably like Danny DeVito and arnold Schwarzenegger in „Twins“…) Although quite similar in functionality, they are very different beasts soundwise. The A-106-5 is based on the filter of the Oberheim SEM. It has a very smooth and pleasant sound, quite „retro“ (and can be used nearly everywhere). Technical Details on the Doepfer Homepage:
http://www.doepfer.de/a1065.htm
We go into the filter with three A-110 VCOs (sawtooth waveforms, one VCO is tuned down 1 oct). Medium input level. The VCOs are controlled by an A-155 sequencer, the filter is modulated by an ADSR envelope and a very slow sine wave LFO. We start with no resonance. I manually blend from lowpass to highpass. Then (via A-134-1 Pan) from LP/HP output to bandpass output of the A-106-5. Now I start to increase filter resonance up to maximum value. Back to LP/HP output, here I blend from HP to LP again and finally reduce the resonance to zero – that’s where we started. Here we go:
http://www.andreaskrebs.de/assets/media/A-106-5.mp3
Andreas
The SEM filter does not no self oscillate „as is“, but it will produce nice bassdrum sounds if you crank up resonance (nothing to hear) AND modulate filter frequency with a fast envelope: http://www.andreaskrebs.de/assets/media/A-106-5bd.mp3
I start with an A-106-5 through an A-132-3 VCA. The VCA is set to maximum gain (i.e. constant amplification). When I increase the filter resonance, some noise will become more audible (made much louder here than it is in reality!), but no self-oscillation. Then I add filter frequency modulation by an A-140 and we can hear some nice things. Finally, the VCA is changed from constant amplification to being modulated by the same A-140.
This doesn’t work with an A-124 (Wasp), which will remain (nearly) silent even when modulated.
Andreas