CP-251 attenuators..

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noddyspuncture
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Joined: Wed Sep 16, 2009 7:57 pm

CP-251 attenuators..

Post by noddyspuncture » Sun Sep 21, 2014 4:00 pm

Hi guys,

CP-251 attenuators... one on mine seems to have a small voltage coming from the output with nothing patched into the input.

The pot makes no difference - just like it shouldn't - but when the output is plugged into my Moog 901a controller - the pitch changes slightly, by nearly a semi-tone.

The other attenuator is fine... does anyone know if there is an internal calibration I need to perform or is it more than likely just 'faulty'...?

Cheers,
Tom

Croyote
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Re: CP-251 attenuators..

Post by Croyote » Sun Sep 21, 2014 11:52 pm

This post belongs in the "Controllers" forum.

Beyond that . . .don't know what to tell you. Contact Tech Support.

kwtsh
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Joined: Fri Jun 13, 2014 5:23 am

Re: CP-251 attenuators..

Post by kwtsh » Mon Sep 22, 2014 1:43 am

Hi

Considering the CP-251 is actually a Moogerfooger and processor it would appear either sub forum is appropriate. Just checked mine, zero.zero volts on both attenuators outlets, nothing in the inputs.

How much voltage are you seeing? What's the scenario where you need to do this, is it a battle to keep two devices in tune with each other?

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noddyspuncture
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Re: CP-251 attenuators..

Post by noddyspuncture » Tue Sep 23, 2014 5:36 am

kwtsh wrote:Hi
How much voltage are you seeing? What's the scenario where you need to do this, is it a battle to keep two devices in tune with each other?
I would like to use the attenuators on the CP-251 to sweep the pitch of two oscillators on my Moog Modular, one up and the other down, to hit a predetermined interval

The patch would 'stay' in when playing live. This would be set up for ELP's 'Toccata' - but when I found that one attenuator affected the tuning, just sitting there, not supposedly doing anything, I wasn't comfortable with it. I called Moog here in the UK - not too helpful.

I thought of sellng it and getting another unit to see if it was any better... then I had the 'Modular idea' of introducing an 'offset' of an equal amount... -36mV. Yes, that right... -36mV sends the 901 oscillators maybe a quarter tone flat..!

So yesterday I built this circuit: http://bbs.dapj.com/2014_02_01_archive.html
It's the 4th image down... so I can set this for +36mV and strap it across the output socket of the faulty attenuator - which basically cancels out that voltage.

All sorted now... :D
Cheers,
Tom

JnGd
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Re: CP-251 attenuators..

Post by JnGd » Tue Sep 23, 2014 9:35 am

Hi,

I have noticed the same when both attenuators output are patched (one after the other) in the Voyager's pitch input at the back.
I will discuss that with technician here in Canada as soon as they give me news for the MF-104MSD issue I have presently. Thank you
for posting that CP-251 particularity may I say so.

salutations !

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