Vintage Synth Repair

----- Original Message -----

From: freeloverdk

To: vintagesynthrepair@yahoogroups.com

Sent: Monday, October 31, 2005 2:32 PM

Subject: [vintagesynthrepair] Arp Odyssey CV/GATE

>Hey All.

>Here I am again. As I said on previous posts, I just bought this Arp Odyssey Whiteface. It
>has a CV/GATE build in as well, but I cannot get it to work. I have the Roland MPU-101
>interface (that I already use for my SH-101 - which is working like a charm).

Yes it does, I use it for my Minimoog...

>The Arp has these specs CV in+out, Gate in+out, Trigger in+out.

>My SH-101 do not have the "Trigger" option.

>;And the MPU-101 does not have a "triggerout" -

The MPU-101 has a trigger out but it´s called "GATE" !!!!

>What does this do? Is it necessary to get it working?

It is necessary !

The CV-out of the MPU-101 carries the "PITCH" ( p.ex. what key you have pressed in which octave range ) and the "trigger" or "gate" -out carries a "pulse"-wave which opens/closes the synths VCA and triggers the filters envelope.

In the case a synth has a separate envelope generator for the VCA too, this envelope is been triggered also and the envelope opens and closes the VCA by its "shape" as also the filter cutoff frequency is modulated by the filters envelope generator ( filter contour ).

The trigger ( gate ) wave of the MPU-101 is a 5V positive pulse or square wave.

If you hit a key on a midi keyboard, the note number represented by midi is converted to a voltage representing the related pitch at the MPUs CV-OUT.

The moment you hit this key ( midi note on ) is converted by the MPU to a rising 5V voltage ( gate open ) and if you release the key this voltage falls down to zero volts which is ( gate closed ) midi note off or Midi note off=vel 0 .

The time between depressing and release of any key the gate voltage remains 5V+ and that is the hold time of the gate ( as long a key is held down ).

It´s been a long time ago I´ve played a ARP Odyssey white face in the end of the 70th and there was no Midi at all.

So I can´t remember exactly what kind of additional inputs the synth has on the back.

In any case you should connect the CV-out of the MPU w/ the CV-in of the synth...( if it accepts 1V per oct.)

the Gate-out of the MPU w/ the trigger in of the synth ( if it accepts 5V positive trigger/gate )...

If you have more inputs for the ARP, maybe CV for Filter cutoff, Frequency modulation inputs for the oscillators, CV inputs for the VCA, you can use these in several ways w/ the MPU-101.

The "dynamics" out of the MPU can control the filters cutoff or / and ( Y-cable or multiplier ) the VCA to make the synth ;velocity sensitive for colour and loudness.

With the separate Bend ( Pitchbender ), Modulation ( Vibrato ), AT ( After touch ) and VOL ( volume control ) outs of the MPU you are able to control different more to be modulated modules of your synth.

These controllers are related to your midikeyboard but the resulting control voltages ( CVs ) can run to anywhere into you synth if enough inputs are available.

>As far as I read online - several people are using the MPU-101 with the Arp Odyssey, but
>apparently I can't. I just hope the CV/GATE in my Arp isn't dead.

You never used the gate / trigger the right way it seems, - so it couldn´t work anyway until now... :-)

>Can anyone of you cleaver ppl help me?

Check it out the way above and try to find out first which voltage-signals your ARP accepts.

Sometimes a mod helps !

>Thanks,
>Michael.

PeWe