Random Walk LFO wave = awesome

Discussion and support for MOTU's Volta software.

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doctorvague
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Random Walk LFO wave = awesome

Post by doctorvague » Thu Dec 10, 2009 9:04 am

Reading this thread: LFO thread I was reminded about the Random Walk LFO wave (it's the last one in the pull-down menu), which I had never tried.

Here's some info, audio and a scope movie I posted in that thread FYI:

I sent a 1/4 note random walk to MS-20 HPF cutoff
and a whole-note random walk to the LPF cutoff
1 step seq>osc pitch (using 1V/Oct and the MS-20 FREQ input)
3 patch cords total, no knob twists

random walk scope movie
The vertical divisions only represent 1V. The quicker the musical division the larger the voltage swing seem to be.

here's a quick audio clip:
random walk MS-20

I am re-posting this info here simply because I think it is such a useful feature, no one should miss it. At very slow speeds it sounds like human-knob-twisting to me. It's different enough from something like a slewed S&H to be a distinct tool in the box.

I'm hoping Stretta will see this and reply:
When you select Random Walk as an LFO wave the sync, symmetry and phase controls don't seem to do anything. Am I correct on this or possibly missing some subtlety? Could these controls (esp symmetry) be made to affect this, like 'more angular/jagged wave edges' or more voltage swing? I'm not minding the low voltage swing (2V p-p at slow settings with a 24I/O) but it would be cool to have some software control over this since there is more voltage than that available at the interface.

Wetterberg pointed out this:Random Walk Wiki
Which begs the curiosity question if Volta is using that math, or just using the name. Is the fact the faster waves have more voltage swing a function of the math used, or just a software anomaly?

I will continue to experiment with these waves since I like them so much. I'll report anything else I find and perhaps others can chime in. I highly recommend experimenting with these, especially for subtle evolving shifts at the slower speeds, or whatever!

Cheers
Phil

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stretta
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Re: Random Walk LFO wave = awesome

Post by stretta » Thu Dec 10, 2009 4:07 pm

doctorvague wrote:Reading this thread: LFO thread When you select Random Walk as an LFO wave the sync, symmetry and phase controls don't seem to do anything. Am I correct on this or possibly missing some subtlety? Could these controls (esp symmetry) be made to affect this, like 'more angular/jagged wave edges' or more voltage swing? I'm not minding the low voltage swing (2V p-p at slow settings with a 24I/O) but it would be cool to have some software control over this since there is more voltage than that available at the interface.
Random walk is aperiodic, so there is no sync, symmetry or phase to control. Could there potentially be more controls added to random walk, I suppose. The diminished voltage output range is interesting, though.

I'm glad you enjoy the random walk LFO. This was a feature we sort of got for 'free' as the LFOs were largely lifted out of MX4.

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Post by 1nput0utput » Thu Dec 10, 2009 4:43 pm

If the random walk LFO is a simple two-dimensional random walk and the algorithm being used to determine the LFO amplitude is the same regardless of LFO rate, then you will probably notice greater deviation from zero when the LFO rate is high because the algorithm is choosing new random values faster.

For example, imagine that the algorithm usually chooses a value greater than 5 once in every hundred choices. When the LFO rate is low, it takes a long time to make one hundred choices and it will be longer before you see a value higher than 5. When the LFO rate is high, one hundred choices go by much faster so you're more likely to see values higher than 5 in a given period of time.

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Post by doctorvague » Thu Dec 10, 2009 6:40 pm

1nput0utput wrote:If the random walk LFO is a simple two-dimensional random walk and the algorithm being used to determine the LFO amplitude is the same regardless of LFO rate, then you will probably notice greater deviation from zero when the LFO rate is high because the algorithm is choosing new random values faster.

For example, imagine that the algorithm usually chooses a value greater than 5 once in every hundred choices. When the LFO rate is low, it takes a long time to make one hundred choices and it will be longer before you see a value higher than 5. When the LFO rate is high, one hundred choices go by much faster so you're more likely to see values higher than 5 in a given period of time.
That makes sense, even to my math-challenged brain. Thanks! :tu:

@Stretta - thanks for the reply. It's more than usable as-, complaints here, just more a curiosity question and wanted to make sure I wasn't missing something. Glad you guys threw this in, I'm really going to be using these a bunch, I'm sure. Also really enjoying generating a bunch a different rhythmic triggers and sending to the modular and then selecting them there. I'm finding more uses for Volta every day, but not necessarily what I expected. It's getting pretty fun, especially with the MS-20 connected now.

Cheers
Phil

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doctorvague
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Post by doctorvague » Sat Dec 12, 2009 10:10 am

1nput0utput wrote:If the random walk LFO is a simple two-dimensional random walk and the algorithm being used to determine the LFO amplitude is the same regardless of LFO rate, then you will probably notice greater deviation from zero when the LFO rate is high because the algorithm is choosing new random values faster.

For example, imagine that the algorithm usually chooses a value greater than 5 once in every hundred choices. When the LFO rate is low, it takes a long time to make one hundred choices and it will be longer before you see a value higher than 5. When the LFO rate is high, one hundred choices go by much faster so you're more likely to see values higher than 5 in a given period of time.
That makes sense, even to my math-challenged brain. Thanks! :tu:

@Stretta - thanks for the reply. It's more than usable as-is, no complaints here, just more a curiosity question and wanted to make sure I wasn't missing something. Glad you guys threw this in, I'm really going to be using these a bunch, I'm sure. Also really enjoying generating a bunch of different rhythmic triggers and sending to the modular and then selecting them there. I'm finding more uses for Volta every day, but not necessarily what I expected. It's getting pretty fun, especially with the MS-20 connected now.

Cheers
Phil

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