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Author Topic: Sawtooth LFO phase wrong  (Read 1280 times)

darkflow

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Sawtooth LFO phase wrong
« on: January 12, 2014, 04:12:50 am »
Hi, I've been messing about with the LFO's and found that when using the Reverse Sawtooth shape, the lfo starts prematurely, before the peak. It should start dead on at the peak... this incorrect behavior causes stabs to sound out of sync. I have the lfo set to reset on key trigger.

See the image:

The top wave is how it should behave. The middle wave is how it actually behaves. Hopefully this can be fixed in a firmware update  :-\
soundcloud.com/timcapelle

Bruno@arturia

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Re: Sawtooth LFO phase wrong
« Reply #1 on: January 13, 2014, 09:50:21 am »
thanks for the feedback.
Indeed it's out of phase.

thanks
Bruno
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Bacon

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Re: Sawtooth LFO phase wrong
« Reply #2 on: January 13, 2014, 09:52:32 am »
Is it possible to fix this in a firmware update? This behavior is very annoying.

Bruno@arturia

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Re: Sawtooth LFO phase wrong
« Reply #3 on: January 14, 2014, 09:48:14 am »
it's in the bug list, and fixable in Firmware
Bruno
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JnC

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Re: Sawtooth LFO phase wrong
« Reply #4 on: January 17, 2014, 04:24:04 am »
On the topic of the LFO, one problem I have with it is when it modulates pitch.

On a traditional synth, LFO to pitch will retain the root note and play higher pitches based on how much amount you give it. The voltage is added to the root note voltage. Thus if you are playing with other instruments, you can stay in key and use the LFO to trill. The vibrato on the MiniBrute works like this.

On the MicroBrute, LFO to pitch is not DC added, but AC. Or perhaps multiplied? Anyways if you play a root note, and invoke the LFO the pitch played is below and above the root note. Adding amount makes the width further apart. The problem with this is, if you are playing with others, it makes you sound out of key because you lose the root.

Could the option to have the LFO be positive only, negative only, or both positive and negative (as it is now) be added to the software configuration?

Thanks

3phase

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Re: Sawtooth LFO phase wrong
« Reply #5 on: January 25, 2014, 05:25:22 pm »
it's in the bug list, and fixable in Firmware

could you pleas make it an option than? I personally think that it is also a feature when you modulate the filter on a sequence because it emphasises th offbeat region than which is more groovy than an emphasis on the main counting times.. I personally think that there cant be too much options as personal preferences as people have different musical ideas and workflows.

Since this thread shows that the lfo is digital one also could provide other wavefroms as modulator or a sample and hold style stepped random

3phase

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Re: Sawtooth LFO phase wrong
« Reply #6 on: January 25, 2014, 05:35:19 pm »
Or to formulate it as demand..

when Seq is selected as the LFO sync source the saw should be phase shifted as it is now, or all patches involving the saw and seq sync will alter theire soud drastical.

Any "bug" fix should allow older patches to be dialed in again.

I wonder wether the processor has enough ram to allow multiple preference cards the user  could select with a program change. Already the options available change the behavior and sound output of the instrument significantly. And there is definitely room for some more options as this thread shows.

One persons bug is the other persons feature. Giving options relieves you from the duty to judge.


darkflow

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Re: Sawtooth LFO phase wrong
« Reply #7 on: January 26, 2014, 07:21:32 pm »
Or to formulate it as demand..

when Seq is selected as the LFO sync source the saw should be phase shifted as it is now, or all patches involving the saw and seq sync will alter theire soud drastical.

Any "bug" fix should allow older patches to be dialed in again.

I wonder wether the processor has enough ram to allow multiple preference cards the user  could select with a program change. Already the options available change the behavior and sound output of the instrument significantly. And there is definitely room for some more options as this thread shows.

One persons bug is the other persons feature. Giving options relieves you from the duty to judge.

...it's a bug. the phase does not reflect what is shown for the wave. If you want the phase to start on the offbeat, why don't you just start the note on the offbeat. It a lot more logical than starting the note on-beat to get an off-beat sound. It should be, you want it off-beat, hit it on an off-beat. You want it on-beat, hit it on-beat.

Having the phase in sync with the seq tempo is the most important part here. Wont get it right unless you hit the note off-beat before the note you want phase to start at, which is not intuitive.

 Ideally we would have an LFO phase knob and all of us could have our way, but that is not the case.
soundcloud.com/timcapelle

3phase

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Re: Sawtooth LFO phase wrong
« Reply #8 on: January 27, 2014, 04:34:02 am »
has nothing to with the behavior i like on the brute.. that is the relation between lfo phase and sequencer position when you let the lfo run sequencer sync mode.

There the position of the saw gives a very animated fx which would get lost when it triggers on a different position..

Since this is a nicer FX than just doubling the envelope on note triggers, this should be preserved and not destroyed by a hasty "bug" fix.. 

Since we deal with a software LFO it should be possible to take the seq sync mode into account for the phase position of the waveforms.. Otherwise Arturia wil get more complains on changing the old behaviour than they get from people that see it as buggy.

And is it a bug? According to ableton its only a bug when it crashes the program..every other flaw is called feature.

Anyway..i suggest that the Mod files an add on to the bug report that points to the situation where the actual behaviour leads to nice results. 

Maybe a solution would be to have more syncpoints in the Seq sync mode..  the  normal speed divisons plus some extra positions with the shifted phase..

This way you would have your exact phase..the sequencer users keep theire nice filter warble..plus a handfull extra phase positions on sine and sqare wave that give additional rhytmical patter s on the modulation of a sequence. so a win win win situation instead one where fixing one mans bug is killing another ones feature.

« Last Edit: January 29, 2014, 02:48:41 am by 3phase »

darkflow

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Re: Sawtooth LFO phase wrong
« Reply #9 on: January 27, 2014, 05:42:11 am »
Actually, I noticed some more incorrect behavior today.

First of all, the incorrect phase of the reverse sawtooth wave only occurs when lfo sync is set to free. When sync is set to seq, phase is correct. in fact it is the only one that is correct when sync is set to seq.

Square and triangle lfo forms do not have the correct phase when sync is set to seq. the square form starts at the low point rather that the high point and triangle starts on the decline between the peak and the valley. these both have the correct phase when sync is set to free, however. So, opposite of the reverse sawtooth form behavior.

Hope to see a fix soon, Thanks Arturia!
soundcloud.com/timcapelle

Bacon

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Re: Sawtooth LFO phase wrong
« Reply #10 on: January 27, 2014, 08:12:47 am »
On a traditional synth, LFO to pitch will retain the root note and play higher pitches based on how much amount you give it. The voltage is added to the root note voltage. Thus if you are playing with other instruments, you can stay in key and use the LFO to trill. The vibrato on the MiniBrute works like this.
I agree that this would be a desirable option to have.

However, I'd like to know which traditional synths you have used that have an LFO that works like this. I've played, programmed, and owned many synths over the last three decades and all of them have had the bipolar LFO as standard, while very few even offered the option of setting the LFO to provide positive-only or negative-only modulation.

JnC

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Re: Sawtooth LFO phase wrong
« Reply #11 on: January 28, 2014, 06:33:09 am »
On a traditional synth, LFO to pitch will retain the root note and play higher pitches based on how much amount you give it. The voltage is added to the root note voltage. Thus if you are playing with other instruments, you can stay in key and use the LFO to trill. The vibrato on the MiniBrute works like this.
I agree that this would be a desirable option to have.

However, I'd like to know which traditional synths you have used that have an LFO that works like this. I've played, programmed, and owned many synths over the last three decades and all of them have had the bipolar LFO as standard, while very few even offered the option of setting the LFO to provide positive-only or negative-only modulation.

Well that explains it. The dumbed down LFO phenomenon started to occur about 3 decades ago. Fortunately, I've been playing synths for 4 decades. :)  :)   (I kid, I kid, but sadly yes I'm getting that old.)

I just did a quick audition. That was 2 hours ago. These things are addictive. :)

Ok, except where noted, I'm using a square wave on the LFO to trill the oscillator. Positive only preserves the root pitch, and the LFO plays an interval higher than root. If the LFO acts bipolar, the root disappears.

Start off around mid seventies.

Octave The Cat LFO to pitch works as I described (positive only).

Jump 5 years.

The Realistic MG-1 LFO to pitch works positive only. I suspect its cousins the Rouge & Liberation work the same way. Maybe someone with a MiniMoog can chime in.

Fast forward about 5 years.

Juno 60 and SH-101 both have bipolar LFO when routed to pitch. The Juno only has a triangle as the LFO wave. The SH-101 is more versatile in waves and faster.

Sequential Circuits SixTrak is positive only. LFO speeds have been compromised at this point.

Casio CZ series digital poly synths work positive only, but the LFO has been renamed vibrato, as it can't be routed elsewhere than oscillator pitch. Other than 4 waves, not much going for it as it's also slow.

Go to one of the last poly synths with analog filters, the Ensoniq ESQ1 & SQ80 circa late 80's, can offset the LFO pitch positive or negative, but the LFO is likely in software at this point. Speeds also have slowed down.

After that, I suspect that bipolar LFOs to pitch became more common, but so did digital synths. Seems like with the advent of digital synths without a VCO/DCO and/or analog filters, the role of the LFO as a necessary tool for sound mangling fell by the wayside.
« Last Edit: January 28, 2014, 06:53:44 am by JnC »

Bacon

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Re: Sawtooth LFO phase wrong
« Reply #12 on: January 28, 2014, 10:26:15 am »
I wasn't aware of that . Of course, my experience is with synths made from the mid 80s onward that I either owned or have used extensively:
Korg Poly 800, Akai AX60 (I still have this a pure VCO/VCF synth but with only a bipolar LFO)
Roland Alpha Juno 1
Korg 707 (FM synth)
Yamaha SY85 (ROMpler).
As far as I remember, all of them behave like the Microbrute.

I have more limited experience with a few of other synths:
Roland Juno 106 (it's probably been 25 years since I played one, but I'm fairly sure it had a bipolar-only LFO)
Ensoniq ESQ-1 (as you note, highly configurable, like all Ensoniq synths and samplers).
E-MU Proteus MPS (I can't recall how the LFO worked on this one).

I've also owned Ensoniq's EPS 16+ and ASR-10 samplers, which are really synths that samples and use sampled sounds as the basic sound sources for their synth engines. Both of these have the same LFO capabilities as the ESQ-10/SQ-80.

It is certainly strange that synths in the 80s tended to lose the more flexible LFOs of their ancestors. Probably a way to cut costs. Coming to think of it, a positive-going LFO actually makes for more natural vibrato for some sounds vibrato on string instruments can only go up from the root. I guess it's a different matter with wind instruments (and the human voice).

3phase

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Re: Sawtooth LFO phase wrong
« Reply #13 on: January 29, 2014, 02:55:58 am »
on lfo that only goes up can be achieved with a diode at the patch amtrix.. however half of the waveform will be cutted

 

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