Problem with Moog MP-201 and vintage Oberheim SEM

[Timmay!!]

Hi,

I have a vintage Oberheim SEM that I have been using my Voyager Old School to control via the Voyager's CV outs. Works great (except for no pitch bend capabilities) and scaling is fine.

I hooked up a Midi Controller (Emu XBoard61) thru the MP-201 using patch 34 to try and control the SEM via the CV 1 and 2 outs. The tuning is now WAY off (by a 5th higher) compared to the Voyager's CV and the lowest pitch the Midi keyboard will produce is to the C below middle C. Any further bass notes below that sound the same pitch.

Any idea what gives? From what I remember, I've got the MP-201 CV set to Unipolar, as the SEM doesn't do negative CV.

Thanks,
Tim

[EMwhite]

Hi,

I have a vintage Oberheim SEM that I have been using my Voyager Old School to control via the Voyager's CV outs. Works great (except for no pitch bend capabilities) and scaling is fine.

I hooked up a Midi Controller (Emu XBoard61) thru the MP-201 using patch 34 to try and control the SEM via the CV 1 and 2 outs. The tuning is now WAY off (by a 5th higher) compared to the Voyager's CV and the lowest pitch the Midi keyboard will produce is to the C below middle C. Any further bass notes below that sound the same pitch.

Any idea what gives? From what I remember, I've got the MP-201 CV set to Unipolar, as the SEM doesn't do negative CV.

Thanks,
Tim

A few things.

First, the Old School will NOT merge Pitch bend into it's CV out jack (either the jack on the back of the VOS or the Pitch CV on the VX-351 assuming you have one). If you do have one, the only opportunity that you have to grab pitch bend is to take it from the VX-351 and with an adder circuit, combine it with the pitch CV voltage.

I no longer have the MP-201, but the time I had it I really appreciated all of the functions that were crammed in there; not only was it the best expression pedal from a feel perspective, but the LFOs, envelope, programmable midi footswitch, clock source, Midi->CV etc. It's amazing.

I recall that there was a base voltage somewhere in there but it's been 2 years since I sold mine so I could be off; one thing to try is to measure the lowest key output on the VOS and the lowest note you can generate from your Midi keyboard. It may go without saying, but you ought to be able to shift the octave of your Midi keyboard down by a few octaves in order to bring it lower, but you may have done this already. Some keyboards also have transpose (the M-Audio Axiom does) so you may have the opportunity to kick it down another 12 or 24 steps.

After you've exhausted these tests and setups, you can always tune the coarse knob on the SEM to be in range with where you want to be. If you don't stumble across a setting that will do what you want, you might want to reach out to Amos and be sure that you have the latest firmware. The answer is there somewhere.

EDIT: Check this...

MIDI TO CV

The MIDI TO CV Channel Mode takes MIDI Notes as input, and puts out a Pitch Control Voltage which is adjustable between 0.667 Volts per octave and 1.333 Volts per octave. The default is 1.0 Volts per octave; this is set by the CV SCALE parameter.

One certain MIDI note will always produce a CV output of zero Volts; this is called the Root Note and is set by the user, using the ROOT NOTE=0V parameter. All other Pitch CV output is calculated relative to this Root Note.

If the MP-201 CV Scale is set to UNIPOLAR (all CV outputs are restricted to the range 0V to +5V), then the Root Note is the lowest note that will play; all MIDI notes below this will also cause the CV output to be zero Volts.

If the MP-201 CV Scale is set to BIPOLAR (output voltage range -5V to +5V), then the Root Note sits in the middle of the Pitch CV range, and MIDI notes below the Root Note will cause a negative voltage output, down to -5V minimum.

The default Root Note is MIDI Note 48, or C3. You can transpose by semitones the pitch of the CV output relative to the MIDI notes you play, just by changing the Root Note.

[Vsyevolod]

MIDI TO CV

The MIDI TO CV Channel Mode takes MIDI Notes as input, and puts out a Pitch Control Voltage which is adjustable between 0.667 Volts per octave and 1.333 Volts per octave. The default is 1.0 Volts per octave; this is set by the CV SCALE parameter.

One certain MIDI note will always produce a CV output of zero Volts; this is called the Root Note and is set by the user, using the ROOT NOTE=0V parameter. All other Pitch CV output is calculated relative to this Root Note.

If the MP-201 CV Scale is set to UNIPOLAR (all CV outputs are restricted to the range 0V to +5V), then the Root Note is the lowest note that will play; all MIDI notes below this will also cause the CV output to be zero Volts.

If the MP-201 CV Scale is set to BIPOLAR (output voltage range -5V to +5V), then the Root Note sits in the middle of the Pitch CV range, and MIDI notes below the Root Note will cause a negative voltage output, down to -5V minimum.

The default Root Note is MIDI Note 48, or C3. You can transpose by semitones the pitch of the CV output relative to the MIDI notes you play, just by changing the Root Note.

I did not find this info in the MP-201 manual. Where is it from? Or is it there and I just missed it?

Thanks for putting this up.

Stephen




.

[EMwhite]

Here: http://www.moogmusic.com/sites/default/ ... dendum.pdf