using cp-251 with macbeth m3x

[cliffman]

Hi there,
I've recently bought a cp-251 to control my M3X. My main needs where adding a proper portamento to the M3X, which I was intending to do with the lag processor, ad to use the S&H to control the filter cutoff.
I did the latter with no problem, but when it comes to portamento there's a lot of weirdeness happening.
My idea was to connnect M3X cv out to lag processor in, then from the lag processor out to the attenuator and finally back to the M3X.
Rise and fall seems to work backwards, and the synth struggles to stay in tune.
Can the s-trig configuration of the other cv in and out of the M3X be responsable for this?
thanks
David

The trigger or s-trigger should be independent of the pitch CV, not part of the problem. You should not need the attenuator, the cp-251 attenuator is also an inverter, so that may be part of your tuning/reversal issues. If there is a looping issue, you should be able to test for it by running the M3x CV out back into the CV in with no device in between. Should work.

[scimmiamk]

thanks cliffman

[rokkinrikk]

Portamental,


You are wrong, and you are right...

In all of my modular experience (just barely enough to call myself a specialist), a 'Lag Processor' is the PRIMARY METHOD of achieving portamento AKA glide AKA Slew Limiting.

http://www.synthesizers.com/q105.html

So on that note, you are undeniably wrong...

BUT! (Don't kill the messanger yet!)

The Moog CP-251 'Lag Processor' has a serious shortcoming, and to date, Moog has not corrected this shortcoming or offered any kind of repair. To elaborate:

The CP-251 will function fine as a 'Glide' if you are NOT running through any sort of 'Multiple' (i.e if you only go direct to a VCO)

http://www.synthesizers.com/q124.html

As soon as I ran my pitch CV through the CP-251, then to a Multiple, the Pitch would not track correctly with Octaves (IE C4 - C5 was not scaled properly and sounded out of tune). My guess is that the electric current draw from addl' VCO modules in the chain affect the V\Oct output from the 'Lag processor'. This issue has been confirmed from many users on the synthesizers.com forum. If an 'old school' style modular synth like a dotcom system has issues with this, I'm guessing most modulars that run on the standard 1V\Oct platform will suffer the same...

So is a Lag\Slew how you create portamento? YES!!
Will the CP-251 Lag work as a Portamento? Not really, no...dammit!

Mark that as another strike against my friends at Moog Music (Slim Phatty .97 V\Oct, WHAT WERE YOU THINKING???????)

Erik

[Portamental]

Portamental,

You are wrong, and you are right...

Well, maybe not for the reasons you assume.

I was wrong first in assuming the Lag processor was using the lfo as time constant. But since I have learned it's not, things have changed. However, achieving a glide in tune is not possible for me for one very good reason : I don't have a modular. I can take a CV out from the Voyager Old School, but when I feed it back to pitch CV in, the voltage adds up to the bus voltage and this voltage changes with every note played. So it is out of the question for me.

Now , as for you, you are right and wrong too. If you use a modular, you can use a CV out to sent to the CP-251 mult, and the capabilities of the CP-251 to boost voltage a bit to make it in tune, so you WILL be able to achieve a portamento in tune with your modular.

[unfiltered37]

BTW, one cool trick with portamento, at least on the model D, if you haven't messed with it already, is turning glide all the way up, doing long slides, and changing the octaves of the oscillators with a fast delay and lots of feedback. Crazy simultaneous up/down/sideways effect.