Minitaur and cv control

[stansbury]

I have just gotten the Minitaur, and the sound(s) are just awesome. A fantastic synth.

I have experimented with the cv control inputs with cv coming from either an EP, CP-251 or an EHX 8 step program. Only the filter part gives result, enabling autosweeps and the like as expected. But there is very little response to amplitude, and pitch cv gives either nothing or a high pitch sound (above the oscillators' range).

The last is particularly disappointing as I had hoped to do some sequencing with the 8 step (which works like a dream on a MF-101 set to selfoscillation where filter cutoff then is pitch control. I can make nice step sequences with that setup. But the minitaur gives just nothing or a high bleep. Does one really have to do a lot of computer calibration for this to work? (Ultimately I can of course trigger sequences from my DAW via midi, but I like the idea of controlling the pitch with CV.)

Any comments most welcome!

[dct]

It seems this issue is coming up every few months in this board. It is a pity moog didn't explain it in full depth and details in the manual.
See some background in the discussion of viewtopic.php?f=11&t=12645. And the logical explanation and conclusion at the end:

1 V/Hertz linear control instead of typical 1 V/octave exponential control!
You need a table (converter) to reflect the incoming voltage into an oscillator pitch. But anyway: Using this linear control you have only a few octaves available, before you fry your cirquitry with too high voltages (outside -15 and +15 V), because the frequency needs doubling the voltage for each octave.

I hope the following table explains the problem of the CV control properly:

Code: Select all

-11 V = C1 32 Hz = 64'
add 1 V
-10 V = C2 65 Hz = 32'
add 2 V
-8 V = C3 131 Hz = 16'
add 4 V
-4 V = C4 262 Hz = 8'
add 8 V
+4 V = C5 523 Hz = 4'
adding 16 V
+20 V would be already too high!

The only official source I found is the official Minitaur manual mentioning the highest possible frequency (The highest pitch produced by Minitaur’s Oscillators is C5 (523.25 Hz) or MIDI note value 72). This confirms the assumption of the highest note and the problem with CV using exponential octave controls. And this explains why you don't have problems via MIDI control, because there is a translation function (table) in the circuitry, which maps the MIDI input notes to correct voltage. On the other hand the Pitch CV input is confirmed for 0...+5 V. There seems to be also a CV mapping from 1V/oct format to internal Hz/v It is not explained further...
Neither the lowest possible note is explained, using transpose functions. Because internal -11.5 V = C0 (around 15 Hz) is electrically still feasible and with good subwoofer perceptible. Does someone know more?