Moog Music Forum

I just had a question about the CP 251, I was wondering if there was any difference between the old model, with the red nuts around the jacks and the new one with the the black nuts around the jacks. I'm curious because I'm thinking about buying an "old" one second hand for pretty cheap, but curious if it's worth my money. Thanks.

If im not mistaken, on the onld units, the red paint on the jacks kept chipping off or something. Of corse the Red Jacks indicate that they will power an expression pedal. The current ones all have black rings but white lines around the ones that will power the pedals.

The Newer CP's might be better because the attenuators are reversible....meaning that they go from -10 to 10 (i think that I got the numbers right). Anyway, 12:00 is zero so you can actually lessen or increase the signal level whereas on the original CP 251 you could only boost the signals.

Hope this helps...it would probably be a great unit anyway so its worth a shot....unless you feel lke youll be needing reversible attenuators.

EricK

EricK wrote:If im not mistaken, on the onld units, the red paint on the jacks kept chipping off or something. Of corse the Red Jacks indicate that they will power an expression pedal. The current ones all have black rings but white lines around the ones that will power the pedals.

The Newer CP's might be better because the attenuators are reversible....meaning that they go from -10 to 10 (i think that I got the numbers right). Anyway, 12:00 is zero so you can actually lessen or increase the signal level whereas on the original CP 251 you could only boost the signals.

Hope this helps...it would probably be a great unit anyway so its worth a shot....unless you feel lke youll be needing reversible attenuators.

EricK

A few points of clarification:

On older units, red jack nuts were used to indicate those connectors that supplied power for expression pedals. There was never any red paint on the panel. Newer units eliminate the red jack nuts by using a white ring (part of the panel silk-screening) around those connectors that supply power.

I can think of several advantages with this change:

1. Assembly time is reduced and made more efficient since all jacks use the same nuts.
2. Eliminating red nuts simplifies cost (only one stock of nuts needs to be purchased instead of two).
3. Color-blind users may have had difficulty discerning the the jacks. The change may make it easier for them.

Concerning the attenuators: I'm sure you are referring to 'active' attentuators, which provide standard attenuation as well as inverted signal attenuation. AFAIK, these designs do not provide 'boost' (gain), only attenuation. Active attenuators are featured on the VX-352 RME CV Expander. I'm unaware that Moog includes them on new CP-251's (it's certainly possible, but I can't tell from the web site, and the CP-251 manual still speaks of passive attenuators).

Moog's active attenuators use the 12 o'clock position for maximum attenuation of the input (i.e. 'zero'). Rotating the knob CW decreases the attenuation, which allows more of the signal to pass through. Rotating the knob CCW also decreases the attenuation, but now the signal is inverted (i.e. negative), and it goes more negative as you rotate the knob CCW.

In addition to the active attenuators on the VX-352, there are 'OFFSET' controls that allow you to add up to +/- 5V to the attenuator signal. This is a feature I wish the CP-251 offered, as it would mean not having to tie up the Mixer just for that.

so if you used the negative attenuation on the ENV OUT of the LowPass filter it would cause the envelope to go down instead of rise, right?

I have the older "red" cp-251, and it works nice*.

GregAE is right, the attenuators don´t boost, they only attenuate. I wish they were the
active type with negative - 0 - positive outputs.. but according to the diagram of the "white" cp-251 the attenuators go from "0" (9 o´clock) to "10" (5 o´clock) and the downloadable manual still shows the picture of the "red" one, so AFAIK nothing new on the new cp-251.

*the noise out hums a little.. I actually had my first cp-251 replaced, because the hum was louder than the noise.. the unit I have now hums, but much less...

ColorForm2113 wrote:so if you used the negative attenuation on the ENV OUT of the LowPass filter it would cause the envelope to go down instead of rise, right?

Yep! Cool possibilities, eh?

Hey,
Im just glad that there was that clarification so I wouldn't be under the wrong impressions lol.

THanks Greg.

Eric

thats exciting! that was the one thing i wish the MF101 had was to beable to switch the env direction like on the mutron and Qtron. now if i could get the new Cp, a freqbox and a sequencer i would be set for long awhile

ColorForm2113 wrote:thats exciting! that was the one thing i wish the MF101 had was to beable to switch the env direction like on the mutron and Qtron. now if i could get the new Cp, a freqbox and a sequencer i would be set for long awhile

I thought from the post above that we determined there has been no change in the attenuators on the new 251? From every picture and every piece of literature I can find, they still appear to be the passive type.

No matter though. You can still invert the signal in the mixer. It has + and - outputs. So...you can do the effects you are after with either the new or old 251.

On my CP-251, the attenuators on the right side of the panel (not the ones that are part of the mixer) go from -5 to +5. I haven't actually tried inverting with them (always used the mixer for that), but the numbers lead me to believe that you could...

pff..great now ill have to get BOTH so i can compare the two side by side....either way id probably end up with 2 somewhere down the line

vier-personen wrote:according to the diagram of the "white" cp-251 the attenuators go from "0" (9 o´clock) to "10" (5 o´clock) and the downloadable manual still shows the picture of the "red" one, so AFAIK nothing new on the new cp-251.

I just got my 251 and the attenuators go from -5 to +5. Just like narrowcaster said above.
So the picture on the website (which has white painted rings, but looks like it still has the 0 to +10 markings) needs to be updated.

soundxplorer wrote: I just got my 251 and the attenuators go from -5 to +5. Just like narrowcaster said above.
So the picture on the website (which has white painted rings, but looks like it still has the 0 to +10 markings) needs to be updated.

Excellent! Being able to invert a signal through the Attenuators (without tying up the Mixer) is a very handy thing indeed!

You know, I've been wanting a second CP-251 anyway...

Update! - The CP-251 now comes with active attenuators that additionally allow you to invert and attenuate the control voltages.

So I understand that the new CP-251 has active attenuators that let you invert the incoming signal.
They now also mention it on this page:
http://www.moogmusic.com/moogerfooger/? ... duct_id=12

"Update! - The CP-251 now comes with active attenuators that additionally allow you to invert and attenuate the control voltages"

My question is - where do I buy the new model? do you know where I can get the new module shipped worldwide? I usually shop on ebay but I can't seem to see from the sale-description if the seller is selling the newer CP-251.

By the way - can I expect this inverter to work the same way as I currently use the mixer minus (-) output to invert my synth (korg ms-10) envelope out??

Many Thanks.