Moog Music Forum

I was reading the last topic (great topic, by the way! I learned alot) about using the CP251 or port-a-pot to scale the MF102s Carrier Wave Oscillator and was wondering if anyone has tried to use the CP251 to re-scale an MS20 CV input or output???

I don't have a 251 yet, but I would think this is possible through the use of the offset knob. I was hoping someone might have tried(or could try ) putting it into practice.

I was able to correctly scale the 102 Ring Mod Osc. with just a volume pedal (probably 50k or 100k pot inside) but did not find this to work on the MS20. The voltage probably needs more than attentuation, right? It needs to be offset?

anyone have suggestions or testimony?

one more thing: Is there an inverter on the CP251 that can change S-trig to V-trig?

eric coleridge wrote:I was able to correctly scale the 102 Ring Mod Osc. with just a volume pedal (probably 50k or 100k pot inside) but did not find this to work on the MS20. The voltage probably needs more than attentuation, right? It needs to be offset?

the ms20 uses two forms of voltage control - the keyboard voltage is hz/V rather than V/oct as on the moog gear.
moog:
oct1=1v, oct2=2v, oct3=3v, oct4=4v, etc.
korg:
oct1=1v, oct2=2v, oct3=4v, oct4=8v, etc.

the modulation inputs on the korg, however, are V/oct like moog. you have to scale them down to 1v/oct...just like the 102!

eric coleridge wrote: one more thing: Is there an inverter on the CP251 that can change S-trig to V-trig?

not as such. to do it right you need to make the little circuit that i think is up at the doepfer site. i've never tried this on the 251, you might be able to pull it off using the mixer's inverted out and careful adjustment of the bias voltage and output level...?

x

newname wrote: to do it right you need to make the little circuit that i think is up at the doepfer site.
x

I can do voltage-trig to S-trig (there is also a circuit in the Micro Moog manual and on the synthesizers.com FAQ page: probably all the same one) as this doesn't require any external power; but in order to convert an S-trig to a V-trig you need a battery or some power source to provide the voltage; I'm thinking this will be an unwieldy and cumbersome cable/convertor; so it would be cool if the CP251 would take care of this task (and others at the same time). So, if anyone else has used the CP251 for this task, or could try it, I'd love to know...

newname wrote: the ms20 uses two forms of voltage control - the keyboard voltage is hz/V rather than V/oct as on the moog gear.
moog:
oct1=1v, oct2=2v, oct3=3v, oct4=4v, etc.
korg:
oct1=1v, oct2=2v, oct3=4v, oct4=8v, etc.

the modulation inputs on the korg, however, are V/oct like moog. you have to scale them down to 1v/oct...just like the 102!
x

Yeah, the Osc modulation inputs are volt per octave; I don't know if you have an MS, but this is not an ideal way to control the MS20-- it requires quite a bit of manipulation of the osc tuning and oscillator modulation, not to mention the attenuation required to the signal itself (on my MS, anyway). So, although this is often given as a solution to the Hertz scale problem, I have'nt found it practical.

If anyone else with an MS or other Hertz scale synth and a CP251 could try this experiment with the offset it would be great...
Or if anyone else cares to venture a guess...

I should just buy it, right?

You could always use the ESP section of the MS-20 to generate a trigger from audio instead of converting the trigger signal.

I happen to own an MS-02 which does both linear to exponential conversion as well as trigger conversion. Not exactly a common unit, but a must for any MS-owner who wants to easily interface with other brands.