Moog Music Forum

i think the S&H trigger input is acting funny, but i'm not sure.

test 1:

* MF101 envelope out to the trig of the 251's S&H
* S&H out 1 to cutoff of the 101

results: nothing! the cutoff filter doesn't move.

if i remove the S&H trigger input, the S&H resumes input from the square wave of the 251 and outputs as usual (i get the bubbly changing filter sound)

control: i know the env out of the 251 is functioning correctly. i hooked it up to the freq input of the 102 and it functions as expected (the pitch of the carrier decays with the falling envelope)

test 2:

* LFO out from the 102 to the trig in of the 251's S&H
* S&H out 1 the cutoff in of the 101

results: the cutoff doesn't move.

control: i know the LFO out is working correctly, if i connect the LFO out of the 102 to the cutoff jack of the 101, the cutoff filter is correctly oscillated by the wave and frequency of the 102's LFO.

this seems to indicate that the S&H input is not functioning. i've tried this test with many patch cables and other obvious things. is my 251 broken or am i doing something wrong?

i should add that it's been like this since i first received it (new) a few months ago, but it just occured to me that i thought it should work differently.

What you're trying should work. Try running the CP-251's LFO Square out to the trigger in. It's already normalled this way, but this should test the trig in jack itself. If this still doesn't trigger the S&H, then the problem is probably with the jack.

routing the square wave to the trig in seems to work properly.

routing the sawtooth wave to the trig in also works, but sounds the same as the square wave.

as soon as i unplug that same cable and connect it to the LFO of the 102, the S&H output is stagnant. (and yes, the rate is up on the 102's oscillator)

weird!

the S&H input does appear to work though - i can plug a cable in and then touch the end of the cable to complete the circuit and advace the S&H forward a step each time i touch it.

why am i not able to control it from an external oscillator?

The only thing I could think of is that the output from the MF-102 isn't high enough to trigger the S&H. I thought the trigger only took, 1V, but if it's actually 5V like most other triggers, this could be the reason.

To test this, try running the LFO out from the MF-102 into the CP's mixer, and the mixer out to the S&H trigger in. With the mixer out at maximum, adjust the offset past 12 o'clock, which should raise the voltage higher than what the MF is putting out. If this doesn't work, I give up!

that did the trick - routing the 102's LFO into the mixer and boosting the offset into positive territory produced a strong enough signal to trigger the S&H

thanks!