This is a very unusual filter. It consists of three separate bandpass filters with resonance control, each having a built-in LFOs for filter frequency modulation. A similar concept had been used in the Korg PS 3100. Details can be found at Doepfer’s Homepage:

http://www.doepfer.de/a127.htm

I’ve put the usual three A-110 VCOs (sawtooth wave) into the A-127 filter, then each of the three individual outputs into an A-138m Matrix mixer. Here I assign the first and second filter to a first VCA (panned left) and the second and third filter to a second VCA (panned right).

The filters were controlled by their internal LFOs at first, later I plug in outputs of an A-143-9 VC Quadrature LFO for audio frequency filter modulation.

http://www.andreaskrebs.de/assets/media/A-127.mp3

Andreas

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 A-124 Wasp filter quite interesting. It once was a budget filter design (in this respect – not technically – comparable to the Korg MS 20 filter maybe?) which led to some strange distortions and other stuff. Technical details can be found at Doepfer’s homepage:

http://www.doepfer.de/a124.htm

As usual, we go into the filter with three A-110 VCOs (sawtooth waveforms, one VCO is tuned down 1 oct). Input level is cranked up to maximum. The VCOs are controlled by an A-155 sequencer, the filter is modulated by an ADSR envelope and a slow sine wave LFO. We start with no resonance. Since not everything is CV-controllable at the A-124, I manually blend from lowpass to highpass. Then (via A-134-1 Pan) from LP/HP output to bandpass output of the A-124. 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-124.mp3

Andreas

The A-137-2 Wave Multiplier II is a very nice module which can do very subtle as well as quite extreme things. Here’s an example with an A-111 (triangle wave) and four independent LFOs (triangle waves from an A-143-3):

http://www.andreaskrebs.de/assets/media/A-137-2.mp3

It begins with slight modulation of a single quite slow LFO, then the other LFOs were added. Increasing CV levels and LFO frequencies. Then I switch all LFOs to high speed, with maximum modulation depths in the A-137-II.

Technical deatails can be found at Doepfer’s homepage:

http://www.doepfer.de/a1372.htm

Andreas

Here’s a little sond example of the A-106-6. Since this very versatile filter has 16 different modes (with 8 separate outputs), we can feed it into the inputs of an A-155 sequencer and use the sequencer to switch between the modes. Input are three A-110 VCOs (sawtooth, one VCO is 1 oct below), filter cutoff frequency is modulated by (a) a slow LFO and (b) a fast A-140 envelope. Finally, the Resonance („Q“ called here) is modulated by another A-155. The two sequencers are synced, but have different number of steps / trigger divisors in use.

We start with the right filter group (3A/1L, 2N/1L, 4B, 3H/1L, 2H/1L, 2B, 4L, 2L) and after 1’00“ the left filter group (3A, 2N, 2H/1L, 3H, 2H, 1H, 3L, 1L) is used. Technical details about the filter may be found at Doepfer’s homepage:

http://www.doepfer.de/a1066.htm

Here we go:

http://www.andreaskrebs.de/assets/media/A-106-6.mp3

Another example with similar setup (this time we modulate resonance via Sample & Hold), but now with distorted input: 1 min. normal input right filter group, 1 min normal input left filter group, 1 min distorted input right filter group, 1 min distorted input left filter group:

http://www.andreaskrebs.de/assets/media/A-106-6b.mp3

Andreas