sample/hold, mf-102 & lfo help

The Moog Forum Moogerfooger Forum
1

Alright, I got my cp-251 and love the thing obviously. There’s a certain application I’m having trouble with though.

I want to patch an lfo like a triangle or sine instead of the defaulted noise for the s/h. The only mf’s I have right now are the CP and ring mod. So the s/h is affecting the carrier osc’s frequency. I would either want the sine wave from the ring mod’s lfo to patch to the IN, or use an attenuated triangle from the CP as the IN and the ring mod’s square lfo to the trigger.

My problem is, using the LFO from the ring mod defaults to affecting the carrier osc. Is there a way to stop the ring mod’s lfo from affecting the carrier while still effecting the sample/hold?

2

You need to turn down the amount knob on the Ring Mod, and be sure to patch the output of the s&h to the Freq knob.

3

So basically you are wanting the sample and hold to carry the properties of the sine wave? Essentially a random voltage that is also following a sine wave (or other LFO waveform)?

I don’t think that its possible to decouple the LFO from the carrier frequency of the 102 unless you have the amount set to zero. Id have to open my rack and mess with it.

If im following you correctly, what Im thinking that you need to do is to use the Mixer on the cp251.

You want to take the LFO output from the 102 and the sample and hold output from the cp251 and combine them together to crate a complex waveform.

Maybe I misunderstood your question?

Eric

4

EricK you pretty much had it right the first time. I want the s/h to follow a sine or tri wave, to get a staircased type effect.

I think I might also have to use the mixer or attenuator or both. It could be possible to turn the rate and amount to zero, and patch the lfo to the attenuator to control the range and then the mixer for the speed, if possible. I’m just not sure with the lfo parameters at 0 to start with (actually the rate is always on) that there will be anything to work with.

Certainly I’ll try this idea out, but if anyone else has an ideas feel free to share.

5

Here’s two setups for staircase modulation:

Triangle LFO from MF-102 (LFO out) to S&H input
Clocked from CP-251 (internal)
Output to MF-102 Freq

Triangle LFO from CP-251 to S&H input
Clocked from MF-102 (square wave LFO out)
Output to MF-102 Freq

Attenuate S&H output if needed

The triangle LFO should have a slower rate than the squarewave. Turn the amount knob to zero, unless you want a mix of both.

BTW, the LFO out from the 102 has a fixed amount (i.e. not affected by the amount knob).

6

lol you shoudl have just said Staircase lolol.

No thats cool though cause I like trying to figure out things the hard way.

Eric

7

yeah lol I got it, thanks dudes. “staircase” kind of just slipped my mind at first. After my 2nd reply I figured out how to get it, although a bit more complicated, with the 102’s lfo going to the mixer first, but I see now from latigid’s post that it’s not neccesary to do so.

I’m having trouble w/ the triangle modulation though. The trigger doesn’t seem to respond to anything (although with everything patched up, my finger triggers the s/h via the unplugged cord! )

8

What are you trying to trigger from? The CP-251 S&H trigger is normalled to the LFO clock, so if you patch a cord in there, it will be disconnected, and will wait for a clock signal.

The trigger voltage is +1V. I think the LFOs go to 2.5V so they should work as triggers.

9

EDIT: I got the triangle modulation to work, had to patch the square lfo from the 102 into the mixer and out the “-” output.
I’m not sure why the LFO from the RM won’t just trigger on its own though.

10

Yah at least I was right…not really specific but I was right.


My head grows ever larger.


Eric