Moog Music Forum

ive been mucking around with the CP and i was wondering if it is at all possible to to clock division on the lfo. im trying to send a steady square wave to the filter and a half speed square to the osc but all in sync. example; for every single pulse (up OR down) sent to the osc the filter would recieve two pulses (up AND down) any thoughts???? or am i going to have to go into full on modular territory to do this with analog gear?
thanks

Rectify one of them and you will get 2 positive (or negative depending on diode orientation) leading edges for every one of the original signal. (You can modify a patch cord to do this.)

thanks, I'm not super tech savvy but I might be able to pull this off. How do I modify the patch cable for this?

Unsolder the leads and put a recifier between the wire and plug. You can use a chip full wave recifier or 4 diodes. Or you can put it in a small experimenters box with jacks for your patch cords.

Another way to do it would be with a 555 timer / flip flop circuit.

willi wrote:Another way to do it would be with a 555 timer / flip flop circuit.

Ok, I have no clue what that is lol. I was originally looking for patching opinions, rectifiers im fairly familiar with and could probably (fingers crossed) manager once I get some time to really start playing with that kinda stuff more.

Thanks for the help, I had feeling this was going to require a bit of work

Well, looking at the datasheet for the 555 shows it only requires a positive power supply. So I think it might be tricky to use that IC for a waveform that includes negative voltages. Why would you want to do this? Well, as I understand it, the cable/diode trick shown above would be used with a positive voltage square wave (which includes both rising and falling voltage phase), and would work fine for something just looking for a clock signal (the rising and falling portion of the waveform is what triggers this in many IC's or circuits). But what if you had an LFO that can produce a square wave that went from -5v to +5v? This would produce a different result than a similar LFO that only went from 0v to +5v, if you were to feed it to something like an oscillator. So if you wanted to divide a LFO that included negative voltage range, you would need to use a different method than the cable/diode trick or the 555 circuit. Perhaps someone else can identify an IC similar to a 555 that is capable of negative voltages.

In other words, using full wave rectification should give 2 pulses per clock cycle, but will limit the voltage to a positive (or negative, depending on diode orientation) range ending at 0v. I think another solution is needed if it is desired to have the full range include positive and negative voltages.

Yeah I was thinking using a second square wave lfo to "turn off" the first lfo. Something like sending square wave patched to a mult, one channel going to an oscillator one going to a mixer to boost/expand (or would the signal need to be inverted?) the range of the square wave, then the third channel would go to a filter or amp then to a second oscillator. The second channel from the mixer would modulate the third channels amp/filter to turn off every other step. So the result would be eg; first oscillator modulated up and down an octave at 16th notes and the second oscillator modulated up and down an octave at 8th notes.

Is my thinking correct? Or is there another piece of the puzzle that I'm missing?

You could use your square wave osc as the clock for a binary counter ic to obtain multiple octave divisions. A 4 bit counter would produce 16th, 8th, 1/4, and 1/2 notes if driven by a 16th note clock.

Ah ok, yeah I did some experimenting and didn't quite get the results I expected. I did get close using two square waves but it was impossible to keep them in sync.

ColorForm2113 wrote:Ah ok, yeah I did some experimenting and didn't quite get the results I expected. I did get close using two square waves but it was impossible to keep them in sync.

The counter ic will give you sync'd square waves. You could also use an oscillator with a sync function, such as a freqbox,for your second lfo.

jeepo wrote:

ColorForm2113 wrote:Ah ok, yeah I did some experimenting and didn't quite get the results I expected. I did get close using two square waves but it was impossible to keep them in sync.

The counter ic will give you sync'd square waves. You could also use an oscillator with a sync function, such as a freqbox,for your second lfo.

the freqbox can into lfo range? or just when its sync'd to an lfo via audio in? dont have a freqbox yet but i wish i did, have you tried syncing lfo to the freq osc before?

ColorForm2113 wrote:

jeepo wrote:

ColorForm2113 wrote:Ah ok, yeah I did some experimenting and didn't quite get the results I expected. I did get close using two square waves but it was impossible to keep them in sync.

The counter ic will give you sync'd square waves. You could also use an oscillator with a sync function, such as a freqbox,for your second lfo.

the freqbox can into lfo range? or just when its sync'd to an lfo via audio in? dont have a freqbox yet but i wish i did, have you tried syncing lfo to the freq osc before?

Without a cv input to the freqbox the osc goes down to very low audio/fast lfo range. I've read on this forum that by using a negative cv one can push the frequency much lower. I have not tried using the freqbox as an lfo because I don't have a negative cv source, but I will try to wire something up to test it then report back with the details and maybe even an audio recording.

thats VERY exciting! im just dreaming of what would happen with that while modulating the wave form

I tested the freqbox as an lfo with sync using a negative CV. The square wave lfo from my ring mod was plugged to the audio in of the freqbox. The carrier out from the ring mod is plugged into it's own audio input. The demo starts with a constant tone from the ringmod, then the amount of the lfo is turned up, then the freqbox's osc is plugged into the freq input of the mf-102 and I adjust its frequency. At about 1 min I turn on the sync and continue to adjust knobs. At about 3 min I begin to periodically unplug the freqbox's osc, and briefly disable sync before re-enabling sync and adjusting the env. amount. In my opinion the freqbox makes a great lfo.

Here's a link to the recording http://soundcloud.com/questionmark_and_ ... n-lfo-test