I’m about to set up the ranges on my 921b clones.
This is more complicated than I thought as I’m using an Oakley mididac I built so its particular range is not factory set.
Added to that is the range on my 921a, again not set.
What I need to know is …for a properly set up modular, controlled by midi keyboard and CV convertor and playing note 49. (ie A440 )
What would the settings be on the 921b front panel to obtain correct A440 ?
Its the range switch on front panel I need to know..would it be set to 32 / 16 / 8/ 4 etc (frequency control at 0)
Maybe I’m going about this wrong, or perhaps there’s no definitive setting ?
Your correct…the more I’ve gone into this the more complicated it becomes as there are so many variables involved ie 921a/b …midi CV convertor …midi keyboard octave set …but I just want to make sure the modular is roughly around concert A.
For instance I have a Synth.Com oscillator and to me it seems to be set an octave to high…maybe ? I’m not sure …which is why I posted here.
The lowest note on Moog monophonics are always zero volts. That’s an inherent feature of the keyboard CV circuitry.
The catch is that zero volts does not always conform to the same key.
Some Moogs have F as the lowest key (Rogue, Taurus 2, Minimoog, Prodigy, Micromoog, Multimoog, MG-1, Liberation, Voyager)
Others are C with lowest key (Source, Minitmoog, Satellite, Sonic 6, Taurus 1, Phatty, T3/Minitaur/Sub, modulars).
The Liberation with low F had scale/range controls for the CV output so you could change the lowest key to something other than zero volts.
Then there’s the oddball Polymoog CV out… it was a split controller at Eb/E. I know that the lower split went in the negative volts but I don’t remember where they set zero volts. But the Polymoog manual does have a procedure to adjust trimpots to range/scale the external CV. The b!tch is you can’t use both lower/upper splits at the same time.
Memorymoog has range/scale trimpots on the CV output.
Not only was there a lack of CV/gate standards between manufacturers, there wasn’t a standard between all the products of one manufacturer. That’s why MIDI was developed.
The modular Moog series controllers did vary a bit with what the low end voltage would be. The 952 keyboard is centered on zero volts for middle “C”. So the low “C” would be -2 volts output giving a -2 to +2 volt range. The 950/951 has low “C” at zero volts giving a 0 to +5 volt range. And the 956 linear controller had a switch to select -1 or zero volts for the low end voltage. The 950/951/952 have a range dial so this low voltage could be shifted up or down. Due to the modular nature, these have little in common with a fixed architecture synthesizer like the latter produced Moog units. So having a setting of say zero at the 12 O’clock position on a frequency vernier would mean little when there are so many variables that make up the final frequency setting. Using a Voyager with the VX-351 gave a -1 volt from the low “F” and was easy to offset with the oscillator driver section to give an “F” at the 12 O’clock position on the oscillator frequency vernier. (Although the next oscillator might be a bit to the left/right.)
Rebuilding a 952 controller with -2 volts output at low 'C".
While it would be nice to have a reference of what frequency a modular Moog oscillator is at with a given dial setting. The modular Moog philosophy seems to be that it is more important that all oscillators tune together over a wide range, than it is to have a dial setting of zero equal some frequency. Nowhere in the Moog manuals can I find a reference to a particular dial setting equaling any specific frequency on the modular series oscillators.
This statement is given:
I do have the keyboard tuning procedures outlined in the modular Moog operations manual if that would help. The modular Moog oscillators have built in offsets, so any range can be selected. This is not the case with many other brand modular oscillators like the Dotcom Q106 or Roland 100M where there is a set “zero” on the tuning dial, and no offsets without an extra module to add/subtract this voltage. What voltage equals middle “C” is irrelevant to a modular Moog oscillator and it varies with MIDI to CV converters. Simply dial in the offset and tune the dial to whatever setting you want or need. The calibrations outlined in the service manual address the scale and tuning of oscillators together, while the frequency range they operate at a given voltage is variable. All the calibrations seem to start with the trimmers centered. Any adjustment after that is only for scale and tuning over a wide input CV range.
EDIT: As a reference the 901’s here output a very low frequency with zero volts applied to the CV inputs with no offsets applied. Can barely get an A-440 with 901B set at 2’. This makes sense though and even a Minimoog oscillator with all voltage inputs removed wil be a very low frequency if not sub audio. So guessing the 921’s would be similar and operating at a low frequency without some voltage applied.
My Roland MPU-101 MIDI to CV Convertor manual has A442 in “Mid” transposition at 2.75 V. MIDI note 48 is approximately 1 V. The MPU-101 will transpose up and down one octave. The maximum voltage range shown for MIDI notes 0-127 is -3 V to +7 V.
