A MATHS attenuverter scales and inverts a channel's contribution, nulling at 12:00

Each MATHS channel has an attenuverter setting the amplitude and polarity of that channel’s contribution to its Variable Output and to the SUM/OR bus. It combines an attenuator (scale toward zero) with an inverter (flip polarity): one side of the knob passes the signal upright, the other side inverts it, and near centre (12:00) the contribution is nulled. Channels 2 and 3 have no function-generator circuitry — they are attenuverters used as bi-polar DC offset sources: with nothing patched they output a static DC voltage set by the knob (CH.2 spans ±10 V, CH.3 spans ±5 V), and with a signal patched they scale/invert it. CH.3’s narrower range gives finer resolution, which is an advantage for precise tuning (e.g. small pitch offsets). DC offset is a fundamental utility — it opens VCAs, biases pitch CV for transposition, shifts sequencer outputs, and resets clocking modules — so these channels are primary tools, not mere trimmers. A common mistake is leaving an unused CH.2/CH.3 attenuverter off-centre, which injects unwanted DC into the SUM bus; the fix is to set unused channels to 12:00 (or insert a dummy patch cable into their Signal Input).

Examples

CH.3 → a VCO’s 1V/oct input: dial a static offset to transpose the sequence by an octave (narrow range aids fine tuning). CH.2 → VCA CV: hold a static gate to keep a note open. Patch a signal to CH.2, turn its attenuverter full CCW to take an inverted copy (voltage mirror) from the SUM output. Set an unused CH.3 to 12:00 so it adds nothing to the bus.

Assessment

What two operations does an attenuverter combine, and what does the 12:00 position do? Explain why CH.3’s ±5 V range (vs CH.2’s ±10 V) helps pitch tuning, give two non-pitch uses of a DC offset, and explain why unused CH.2/CH.3 attenuverters should be left at 12:00 when using the SUM output.