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Can I use a CP-251 to Attenuate my Beatstep CV?

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Can I use a CP-251 to Attenuate my Beatstep CV?

Postby MaxFerency » Fri Dec 29, 2017 2:03 am

So I have a CP-251, Beatstep* (the normal one, not the Pro) and a Minitaur. The CV Gate output of the Beatstep is 8V and the CV out is 1 Volt/octave, from 0V to 7V. My Minitaur has a limit of 5V+ for both Gate and CV. The CP-251 Attenuators, however, have a max input of 8V and the mixer has a max output of 5V. So does that mean can I can run the 8V Beatstep CV output into the CP-251 Attenuator and then through the mixer to step it down for the Minitaur without damaging any of my gear?

Also, does it have to run through the CP-251's mixer to have the max output attenuated to just 5V or can it just go straight from the Attenuator's output? The CP-251 manual doesn't say anything about what the max output of the Attenuator is, just what its max input is (8V).

*Note: I know the Beatstep Pro allows you to scale down the CV and Gate output but the original Beatstep does not allow you to do that even with the Midi Control Center.
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SYSTEM: OSX 10.11.2, Logic X Pro 10.2.0
GEAR: Sub 37, Minitaur, Sano Zon-Rio Accordion, MF Drive, MF Delay, CP-251, Roland KC-300, Roland RD-300
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Re: Can I use a CP-251 to Attenuate my Beatstep CV?

Postby GregAE » Fri Dec 29, 2017 1:46 pm

Yes, you can use the attenuators in the CP-251 CP to reduce Beatstep CV values. The attenuators are linear 50K ohm potentiometers (not 50KW as stated in the User Manual).

Reducing the Gate voltage is as simple as patching into one of the CP-251 attenuators and setting the control to about the 1 o'clock position. That should reduce the 8V Gate signal to approximately 5V. No further processing is needed.

Reducing the CV output is not so straightforward, as attenuating the V/oct signal will change the overall scaling and throw off the tuning. If you have voltmeter, a simple solution might be to measure where the V/oct signal goes above 5V, make a note of the dial position for that value, and then not program any notes above that value. Of course, the Minitaur may simply ignore anything above 5V anyway, so this may not be an issue (the manual simply says "will accept a Control Voltage from 0 to +5V", and the note range is limited to MIDI notes C0 to C5).
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Re: Can I use a CP-251 to Attenuate my Beatstep CV?

Postby MaxFerency » Fri Dec 29, 2017 3:31 pm

Ok, thanks. That makes sense. I guess part of my concern is if it just doesn’t accept CV over 5V or if it is actually damaged immediately or gradually over time by CV over 5V.
Max Ferency | http://maxferency.org | max [at] maxferency [dot] org
SYSTEM: OSX 10.11.2, Logic X Pro 10.2.0
GEAR: Sub 37, Minitaur, Sano Zon-Rio Accordion, MF Drive, MF Delay, CP-251, Roland KC-300, Roland RD-300
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Re: Can I use a CP-251 to Attenuate my Beatstep CV?

Postby Quatschmacher » Sun Apr 01, 2018 5:46 am

I asked a related question in the Minitaur forum: whether ther cv inputs are protected from over voltage.
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