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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
Syncing and Resetting Poly LFOs
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TEMAS



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PostPosted: Tue Apr 20, 2010 4:37 pm    Post subject: Syncing and Resetting Poly LFOs Reply with quote  Mark this post and the followings unread

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

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PostPosted: Tue Apr 20, 2010 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

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.
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TEMAS



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PostPosted: Wed Apr 21, 2010 1:28 am    Post subject: Reply with quote  Mark this post and the followings unread

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?
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PostPosted: Wed Apr 21, 2010 1:59 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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TEMAS



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PostPosted: Wed Apr 21, 2010 2:24 am    Post subject: Reply with quote  Mark this post and the followings unread

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
 Description:

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 Filename:  3 Voice LFO trigger Test.pch2
 Filesize:  1.86 KB
 Downloaded:  510 Time(s)


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PostPosted: Wed Apr 21, 2010 5:15 am    Post subject: Reply with quote  Mark this post and the followings unread

TEMAS wrote:
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?


Hmm .. maybe ... how about using a couple of edge delay modules set to different times? Those can be triggered from the keyboard or for noodle operation just use a constant module set to some positive value (on patch startup that will cause a transition from zero). This would be repeatable and each voice would have a different phase.

For a noodle you could also use the multiplexer to send different frequency modulation values to each LFO, so they can run at slightly different speeds.

Anyway, just some ideas.

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PostPosted: Wed Apr 21, 2010 5:26 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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TEMAS



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PostPosted: Wed Apr 21, 2010 5:56 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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PostPosted: Wed Apr 21, 2010 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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PostPosted: Wed Apr 21, 2010 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

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.
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PostPosted: Wed Apr 21, 2010 8:43 am    Post subject: Reply with quote  Mark this post and the followings unread

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.
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PostPosted: Wed Apr 21, 2010 9:04 am    Post subject: Reply with quote  Mark this post and the followings unread

TEMAS wrote:
The method I have used to trigger the voices without a keyboard is similar to those you have suggested


With one important difference, all inputs of the multiplexer have the same signal, so all three instances of the LFO will see the same signal.

Quote:
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.


Yes, as the Gate pulse is only present in one of the voices.

Quote:
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.


Yes as such a pulse is present in all the voices, the "one important difference" I meantioned before is exactly the thing you are running into here.

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PostPosted: Wed Apr 21, 2010 9:06 am    Post subject: Reply with quote  Mark this post and the followings unread

iPassenger wrote:
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.


Exactly!

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PostPosted: Wed Apr 21, 2010 10:11 am    Post subject: Reply with quote  Mark this post and the followings unread

The three different methods mentioned above attached:


3 Methods.pch2
 Description:

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 Filename:  3 Methods.pch2
 Filesize:  2.5 KB
 Downloaded:  526 Time(s)


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PostPosted: Wed Apr 21, 2010 10:28 am    Post subject: Reply with quote  Mark this post and the followings unread

iPassenger wrote:
The three different methods mentioned above attached:

But, with my method you DO NOT have to reset the LFO, but you DO have to set the LFO mode to mono to avoid the problem described in the OP.

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PostPosted: Wed Apr 21, 2010 10:38 am    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
iPassenger wrote:
The three different methods mentioned above attached:

But, with my method you DO NOT have to reset the LFO, but you DO have to set the LFO mode to mono to avoid the problem described in the OP.


Nice one, I wouldn't have imagined a mono lfo to work that way but it does as you say.

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PostPosted: Wed Apr 21, 2010 12:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

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.

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PostPosted: Wed Apr 21, 2010 12:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

TEMAS wrote:
[...] 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.


Indeed, it can be mind boggling at times too Laughing but fun!

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PostPosted: Thu Apr 22, 2010 3:32 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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PostPosted: Thu Apr 22, 2010 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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PostPosted: Thu Apr 22, 2010 9:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:

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


I'm willing to bet my expansion card that it's because it's much easier to program that way...

Yeah, that's a useful bit of information indeed.

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PostPosted: Thu Apr 22, 2010 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Laughing
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PostPosted: Sat Apr 24, 2010 1:04 am    Post subject: Reply with quote  Mark this post and the followings unread

iPassenger wrote:
...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

As you now can see, the LFO mono/poly switch can be a bit confusing and misleading if you don’t know how it actually works. Setting the LFO in a polyphonic patch to mono mode does not change all the LFOs of a polyphonic patch to a single LFO, it only synchronizes the initial waveform phase of the separate LFOs, which then basically gives the same effect as a single LFO waveform output.

The tests that I have done lead me to think that when the LFO is set to mono, the LFO waveform will start from phase zero any time the patch is reset (on patch load or because of a patch change in the Editor). This is all that is normally needed to keep LFOs across polyphonic voices in synch (in phase), and in effect, acting like a single LFO. But, if the LFO starts in the poly mode, or is switched from mono to poly mode, the LFO waveform will start at a random phase. This is probably intentional… and for the most part desirable, but can be considered a problem in that the LFOs in a polyphonic patch will not always generate a consistent phase output relationship between polyphonic voices, as is described and complained about in the original post. But, the way my method works, you have complete control of the polyphonic phase of the LFO outputs across the voices by setting the LFOs to mono mode (to synch them to an initial phase start) and then using the Status Voice Number output to generate a unique but consistent control value for the phase modulation input of the LFOs in each polyphonic voice…
alcofribas wrote:
Quote:

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


I'm willing to bet my expansion card that it's because it's much easier to program that way...

Just an easy programming compromise? I don’t think so. Smile Just synchronizing the phase of the LFOs in mono mode across the polyphonic voices is all that is necessary to get the same result as a single (mono) LFO, but still allows you to use the phase and rate modulation inputs of the LFOs along with the unique Status Voice Number output to generate a different (but not random) LFO output for each voice. The simple (but wrong) way to program the LFO mono switch mode would be to use the LFO output of voice 1 for all voices and ignore the LFO output of the additional voices, but then that would not allow the feature of unique control the phase and rate of the LFOs between voices. I think that the Clavia software programmers did a pretty good job regarding how they implemented the mono/poly function of the LFOs.

BTW, you can keep your expansion card anyway, I don't need it Wink Laughing

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PostPosted: Sat Apr 24, 2010 2:26 am    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
The simple (but wrong) way to program the LFO mono switch mode would be to use the LFO output of voice 1 for all voices and ignore the LFO output of the additional voices[..]


And not simple either .. it would break the voicing model where different voices can be on different DSPs.

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PostPosted: Sat Apr 24, 2010 4:19 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Cool Laughing

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