PAiA 9700 MIDI-to-CV unit and Realistic (Moog) MG-1
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Author:  danielwarner [ Tue Sep 14, 2010 9:20 pm ]
Post subject:  PAiA 9700 MIDI-to-CV unit and Realistic (Moog) MG-1

I've completed a midi2cv8 unit, and I want to use it to interface a couple of different MIDI controllers (a keyboard OR a Boss DR-5 drum machine that I have basslines programmed into) with a Realistic MG-1 (similar to the Moog Rogue). I know that the MG-1 expects S-trig and 1V/Oct pitch scaling.

So, right now, using an external MIDI keyboard going through the PAiA D/A converter, I can get the MG-1 to produce notes, but they're only triggered intermittently: sometimes when I press a key on the MIDI controller the MG-1 will trigger immediately, sometimes long after I've been pressing the key, sometimes not at all.

And the pitch scaling is off, but I'd rather tackle the triggering issue first.

I'm confused by the MIDI-to-CV manual, which reads: "Gate signals are often changed into "S" Triggers by using them to turn on a transistor which then pulls the "S" Trigger line to ground. On the midi2cv8 these transistors are already in place, simply connect the appropriate "G" pad to the "S" trigger input. Gate outputs on the "O" pads can be used simultaneously with the "S" trigger outputs."

Does this mean that I should be connecting the "G" pad on the PCB to the TIP of the 3.5mm TRS jack, instead of the RING? I'm confused!

Author:  PAiA-Scott [ Wed Sep 15, 2010 6:50 am ]
Post subject:  Re: PAiA 9700 MIDI-to-CV unit and Realistic (Moog) MG-1

Hello Daniel.

The S-trigger signals are already wired to the ring terminals of the MIDI2CV8 TRS connectors. The 'open' collector (nothing connected to it) of the transistor for the channel in question works to provide an electronic switch action with the connected device to ground. When you use a TRS plug into the desired trigger output of MIDI2CV8 the ground and ring go to the ground and tip of the S-Trigger connector (Switch Trigger or one that a switch closure between the two contacts works to activate the device). By the way, when a mono TS plug is in the stereo TRS connectors the sleeve shorts the ring to ground but this is not a concern since the transistor is working to conduct or 'connect' ground with ground.

Be sure you're in the single voice modes to get a consistent output from the pitch cv and gate-trigger/s-trigger or re-trigger(pulse-trigger)/s-trigger output set going to the MG-1.

Always assert the low-key transpose mode before adjusting the v/oct trim on the MIDI2CV8 (power the MIDI2CV8 while the low-key is pressed on the MIDI Controller--the first message it will receive is this key being released, or the note off for the lowest key and this is a signal to output 0v).

Author:  danielwarner [ Wed Sep 15, 2010 7:45 pm ]
Post subject:  Re: PAiA 9700 MIDI-to-CV unit and Realistic (Moog) MG-1

Scott, thanks for your reply!

I am assuming then, since I am using a mono/TS (1/8" to 1/4") patch cable, that I could insert the 1/8" plug into the midi2cv8's appropriate TRS jack and at the "first click" the tip of the cable would be connected to the ring of the jack, and I'd be properly tapping the S-trig output?

Also... after reading the MG-1 manual I realized that the midi2cv8's CV output is 0-10V and the MG-1 is expecting 0-5V... I'm thinking a simple voltage divider should solve that problem unless there's something I'm not considering.

Author:  PAiA-Scott [ Thu Sep 16, 2010 8:06 am ]
Post subject:  Accessing TRS Ring, Pitch CV range

Hello Daniel.

That might be OK, but the connection wont be so reliable and might result in contact between the plug tip and the socket ring and tip--the o.c. transistor will be working to conduct the cv to ground, a sort of 'dog chasing its tail'.

When the low-key transpose feature is asserted, your pitch cv will start at 0v for the lowest note on the keyboard and go up by a volt per octave from there. For a five octave keyboard, there will be 0-5v.

A divider connected to a linear pitch cv changes the v/oct scaling to less than than this so the notes wouldn't work out. Run to a divider that results in half the voltage, the v/oct would then be 0.5v/oct. On the other hand, Exponential control (v/hz) or the type that doubles/halves going up/down by an octave can be divided (ie a FatMan's CV output to older PAiA 2720 and 4700 series modulars). This into a v/2 divider is OK and would produce one octave lower on the VCO.

Author:  danielwarner [ Tue Sep 21, 2010 8:34 pm ]
Post subject:  Re: PAiA 9700 MIDI-to-CV unit and Realistic (Moog) MG-1

Great, it's working! Thanks Scott!

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