Saturday 24 November 2012

Fonitronik mh11 ADC Pattern Sequencer

Hands-on preview of Fonitronik's novel 8-step CV & Gate sequencer.

The mh11 offers a new take on the basic sequencer concept. An analogue to digital converter generates 256 patterns. The notes and direction stay the same, but the sequence of steps that actually get played is under manual or voltage control.

For more on the concept, see Matthias' own description and video. Here's a demo of the effect of CV-ing the pattern on notes played & (0:34) gate length and (0:57) the mh11 as graphic VCO.

(edit: Bandcamp's MP3 conversion has mangled the graphic VCO example. Download the WAV.)

To understand what's happening, feed the mh11 a clock and set all step switches to the up/ on position. All steps play. Then 'mute' certain steps by setting the switch to the off position. The ADC is used to automate this muting - it generates an 8-bit string of on & off values which is AND gated with the incoming clock. To test this, stop the sequencer, set all switches down to the ADC position and turn the manual PCV pot until all lights of the pattern LED-bar are lit. Restart the sequencer and turn the pattern knob. Any incoming CV is summed with the manual offset to generate a new string of on & off values.

Programming the mh11 is easiest with another sequencer or S&H (running at a clock division) or a S&H-synchronized manual CV from Pressure Points. This is because the ADC 're-computes' the pattern with every change. You can use an LFO, but depending on the speed, things can get glitchy. At audio-rates, as per the graphic VCO example, this is not a problem. The 4MS PEG makes a good partner for the mh11 as its swings can be synced.

In use, I found a few minor issues: if fed more than 8V, the ADC can lock up. Remove the external CV and twist the offset pot to reset it. I felt this offset should be inverted so that one can start with all steps on and then progressively mute them with a +ve CV. The output CV droops slightly when passively multed, so you may want to buffer it. Finally, the ADC controls both the CV and gate signals. Muting a trigger or tying a gate also mutes the CV. So, you can't send the CV to two VCOs and have one follow the pattern and the other the master clock. I asked Matthias whether this could be changed, but quickly realized it would require a second, parallel ADC.

The build quality is solid, the layout generous and the LEDs give good visual feedback of the ADC's current pattern. A microprocessor-based sequencer might offer more options, but I do get a kick out of imaginative designs like the mh11. Thanks to Matthias for the loan of the module and for keeping it analogue!

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