Syncing and Resetting Poly LFOs

TEMAS · Posted: Tue Apr 20, 2010 4:37 pm Post subject: Syncing and Resetting Poly LFOs

Using a sinewave LFO in Poly mode to modulate the pitch of an oscillator, with voice mode set to 3, sweeps polyphonically through the pitch 3 times in one cycle, whereas it would make just 1 sweep in Mono mode.

Adding more modules or making alterations to the patch, can cause the LFO's polyphonic sweeps to re-start themselves at completely random places.

The fact that the sweeps aren't triggered in unison is what makes the poly LFO sound interesting, but its annoying that they are triggered randomly because the patch never sounds exactly the same.

Sending a pulse to the reset input of the LFO re-starts all of the polyphonic sweeps at the same place, which actually makes the poly LFO sound like a mono LFO, so this is not the answer.

Is there any way to decide when each of the polyphonic sweeps is triggered, rather than just completely randomly or all in unison?

Hope this makes sense. Thanks

blue hell · Posted: Tue Apr 20, 2010 5:19 pm Post subject:

Yes you could make something for that using the status module from the in/out tab. That one has a Voice No output that you could use to control a 8 -> 1 multiplexer with (with its output connected to the LFO reset) and the inputs of that multiplexer would then act as individual LFO resets for each voice.

TEMAS · Posted: Wed Apr 21, 2010 1:28 am Post subject:

Hi Jan. Thanks. I just tried this and it does work if I use a keyboard to trigger the voices, but is there any way to re-trigger voices without a keyboard, for noodles that don't use a keyboard?

iPassenger · Posted: Wed Apr 21, 2010 1:59 am Post subject:

I would have thought so, how are you triggering the different voices within the noodle?

Are you trying to make sure that each voice when triggered, triggers its own lfo? Or do you just want each voice's lfo to be a defined distance from the others voice lfos? For example, an even spread.

An example patch of what you are trying to do and why it isn't working would help. Smile

TEMAS · Posted: Wed Apr 21, 2010 2:24 am Post subject:

Here's a simple little example of the problem I'm trying to solve.

There are two modes of operation that you can toggle between to trigger the voices of the LFO:

Keys - use the a keyboard.

Switch - Use the momentary switch.

When using the keyboard, the LFO's voices can be triggered individually. But when using the switch, the LFO's voices all trigger in unison.

The only reason I can think of is that the LFO must somehow be hardwired to the keyboard and is triggering the LFO's voices according to the keys that are being played.

3 Voice LFO trigger Test.pch2

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3 Voice LFO trigger Test.pch2

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blue hell · Posted: Wed Apr 21, 2010 5:15 am Post subject:

iPassenger · Posted: Wed Apr 21, 2010 5:26 am Post subject:

Can't look at the patch right now, as I am at work Smile

but I think Jan has the right idea.

Use the status module to send voice number to control an 8-1 muxer.

Have a logic signal (the reset signal) that is wired direct to the first input of the muxer, and via logic delays to the other inputs of the muxer. So that each input to the muxer has different sync/reset delay. The muxer then wants wiring to the lfo reset input.. I think that is what jan is saying and it seems like it should work... in my head at least. Smile

Another (and maybe better) way round, same as before but wire different constant modules to the muxer and wire the muxer to the phase input on the lfo. the constant modules would allow you to offset the phase of each lfo. You would need to send the lfo a single reset signal at patch load too i think to make it consistent. This way may be better as the phase relationship would remain the same across the voices even as you changed the speed of the lfo.

TEMAS · Posted: Wed Apr 21, 2010 5:56 am Post subject:

Thanks guys for your ideas. Have a look at the test patch when you get a chance, which will hopefully explain the problem better. The method I have used to trigger the voices without a keyboard is similar to those you have suggested and I see no reason why it shouldn't work.

The patch has just one LFO and one Oscillator. When the LFO is in Poly mode and the Voice number is set to 3, for example, the LFO is polyphonically looping 3 times during one cycle. Each time a key is hit on the keyboard the phase of next voice of the LFO is reset, so you can choose how out of phase they are. But when not using a keyboard ANY signal sent to the LFO's reset input will reset the phase of ALL the voices at once, hence making all 3 voices completely in phase with each other.

iPassenger · Posted: Wed Apr 21, 2010 6:25 am Post subject:

I'll take a look when I get in but I think the problem is that the reset gate signal your using is the monophonic bit, it is occuring in the same place across the 3 voices. Like it is being triggered by gate signal from a sequencer module or just an on/off switch module or something like that. In which case the lfo is behaving as it should. You need some way of either A) making the gate signal poly, like when triggered from a keyboard or B) forcing the phase of each lfo to be different like in my second example above.

Anyway I'll shut up now as I probably have it all wrong and will realise I haven't a real clue what your problem is as I haven't looked at your patch yet. Smile

varice · Posted: Wed Apr 21, 2010 8:36 am Post subject:

I think that what you want to do is control the phase of the LFO for each voice. To do that, set the LFO mode to mono (to keep the phase relationship between voices consistent) and use the Status Voice Number and a Control Sequencer to set a separate value for each voice into the Phase modulation input of the LFO. For example, if you have a 3 voice patch, you may want to have the phase of each voice LFO at 120 degrees apart. Set the Control Sequencer so that Voice 1 is at 0 degrees, 2 at 120 degrees, 3 at 240 degrees.

iPassenger · Posted: Wed Apr 21, 2010 8:43 am Post subject:

Yeah that should do it too and probably more efficient than my method, but I think the lfo wants to still be in poly mode rather than mono.. not sure though... Just get the status module to send the logic signal to reset the lfo on patch load, so that the phase relationship remains consistent.

blue hell · Posted: Wed Apr 21, 2010 9:04 am Post subject:

blue hell · Posted: Wed Apr 21, 2010 9:06 am Post subject:

iPassenger · Posted: Wed Apr 21, 2010 10:11 am Post subject:

The three different methods mentioned above attached:

3 Methods.pch2

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3 Methods.pch2

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varice · Posted: Wed Apr 21, 2010 10:28 am Post subject:

iPassenger · Posted: Wed Apr 21, 2010 10:38 am Post subject:

TEMAS · Posted: Wed Apr 21, 2010 12:06 pm Post subject:

Thanks. I'll check out all these suggestions as soon as the footy finishes.

I've been making a lot of progress with the G2 of late, but I'm really struggling with voice mode and making oscillators polyphonic for noodles, and there's no mention of this kind of thing in the manual.

blue hell · Posted: Wed Apr 21, 2010 12:20 pm Post subject:

TEMAS · Posted: Thu Apr 22, 2010 3:32 am Post subject:

Ok, so I tried those solutions out and they work great. The Control Sequencer option, in either poly or mono mode (as Varice suggested) is the cheapest and most elegant method. But if I want to modulate the phase positions of the voices then an 8-muxer is more suitable.

I would never have worked that one out by myself. I still don't understand why the Voice No output of the Status Module appears to be sending out a constant control signal value of 0 and when connected to a Control Sequencer module the display light remains at position 1, but positions 2 and 3 are also sending data to the control signal output.

Still a lot more to learn! study

iPassenger · Posted: Thu Apr 22, 2010 6:30 am Post subject:

Nice one, glad you got it working. Smile

The reason it doesn't seem to be doing anything but obviously is, is due to the fact that your only seeing one layer or voice.

I think of anything you build in the poly area as just one layer of your synth, if you have 5 note poly then you have 5 of those laid on top of each other.

When you use the keyboard to trigger the different voices, the keyboard can cause the editor to step through the layers or voices, so the status module appears to update. In reality the status module is not changing but what layer your looking at is.

What I don't understand is why the mono lfo operates more like a poly one if it receives a different phase offset for each voice...that just means to me that it is never really a mono lfo. Question

Cool to know though. Smile

alcofribas · Joined: Oct 03, 2008 Posts: 22 Location: Eastern France

iPassenger · Posted: Thu Apr 22, 2010 10:26 am Post subject:

varice · Posted: Sat Apr 24, 2010 1:04 am Post subject:

blue hell · Posted: Sat Apr 24, 2010 2:26 am Post subject:

varice · Posted: Sat Apr 24, 2010 4:19 am Post subject:

That is right Jan, even the idea of “simply using the output of LFO from voice 1” as a mono LFO for all polyphonic voices may not be practical for multiple DSP programming…

Maybe the best idea is to do the LFO mono mode just like the Clavia programmers did it Shocked