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Trigger probability
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Trigger probability
raccoonboy
How does one achieve this? i.e. Let's say you have triggers every 16th note. This wud be 100% probability. Turning a knob wud decrease probability so that 90% of the time the triggers ping, or perhaps only 10% if you turn further.

Initially I was thinking some kinda sample/hold thing but this wudnt output triggers.

I'm thinking one way is to modulate the amplitude of the triggers with white noise using a VCA.

Then use a negative offset so that some of the triggers are negative. The more offset added the more likely each trigger will be negative, thus the probability of a positive trigger is less. As long as this is then used to trigger a unipolar VCA this should make 100% probability of a trigger every 16th note if there is no offset and as you add more negative offset you have less chance.

Is this correct?

Any other ideas of how to imploment? I may not want to trigger a vca. I assume most things that accept triggers won't react negative triggers? If they do I guess I'll need another message.
windchill
The easiest way to do this is with a comparator. They are very useful things to have. Ladik do a cheap one that I can recommend: http://ladik.ladik.eu/?page_id=1459
Keltie
MI branches with one output left unpatched, no?
raccoonboy
Keltie wrote:
MI branches with one output left unpatched, no?

Are you just assuming I have that module? I'm asking how to create a patch generically not what module to buy. I may not even use euro (I do).

Thanks though
raccoonboy
windchill wrote:
The easiest way to do this is with a comparator. They are very useful things to have. Ladik do a cheap one that I can recommend: http://ladik.ladik.eu/?page_id=1459


I had a feeling a compator might work but it's the only type of CV function I don't completely understand. I know they often have thresholds so I could ditch everything under the threshold. I know they can be used for divide down circuits too. Guess I missed that chapter in Allen Stranges book. I'll have a read thanks.

Ladik also has a probability trigger thing I saw but thought if I use something else it might have more uses.

What else do you personally use a comp for?


edit: Okay looking at the ladik it says it can do the following:
A>B, A<B, A≠B, A=B
So it's like a min/max output type thing, plus more.. interesting.. It's almost like logic in a way but in a more analogue kinda way.. What other types of comparisons can you do? Why does this seem so different from a divider? hmm. need to do some more reading
cornutt
A crude method is to run some white noise through an attenuator, and then patch that into the gate input of an ADSR. Set A and D to their minimums, and the sustain level to 0. How well this works will depend a lot on what level the gate input of the ADSR regards as the "on" level.
mookmoof
Comparator with a manual threshold setting and a S&H with noise input. For example, trigger the S&H with 16th notes giving you 16 random voltages. Send those to comparator. Comparator at lowest setting will pass 100%, giving you 16 triggers, while the highest setting will give you 0. Comparator threshold level will set probability in between. Note, the probability 90% will pass does not mean exactly 90% will pass.
raccoonboy
mookmoof wrote:
Comparator with a manual threshold setting and a S&H with noise input. For example, trigger the S&H with 16th notes giving you 16 random voltages. Send those to comparator. Comparator at lowest setting will pass 100%, giving you 16 triggers, while the highest setting will give you 0. Comparator threshold level will set probability in between. Note, the probability 90% will pass does not mean exactly 90% will pass.


Thanks. This makes sense.. but what is the comparator threshold doing in this case? is it a filter? or is it comparing against a DC voltage of some level and sending out if it's higher?

I'm guessing if I used e.g. this:
Ladik J-120 as suggested earlier. If I put a DC offset into input B for example, then changing the offset value will be the equivalent of threshold? As everything below this would be disregarded at output A.
mookmoof
Yes the comparator compares incoming voltage to threshold voltage and its output goes high when the incoming is higher than the threshold.
And you are correct, a vca triggered by an envelope between the random voltages and the comparator would be required to generate triggers instead of steady voltages
mookmoof
The most basic or typical comparator goes high when the voltage exceeds the threshold. I use the circuit abbey tripfire which outputs gates and triggers and has delay options too. The Ladik may be what I've heard referred to as a "window" comparator. Looks interesting
mookmoof
All that said, +1 on Branches. It's does exactly what you want in 6hp, and is also a flip flop module with 2 channels and other perks. Definitely worth a look
Gizmo
Further to RBoy's original ideas--
- An Envelope Follower with gate output can function as a comparator when strict precision is not an issue (i.e. random input produces rectangular-shaped random output)
- An oscillator square/pulse wave, at audio or low frequency, modulated by noise, used with VCA to gate the trigger pulse train - advantage is well-behaved output

raccoonboy wrote:
I'm asking how to create a patch generically not what module to buy. I may not even use euro...
FWIW It's rare and refreshing to have a post in this MODULAR SYNTH GENERAL DISCUSSION forum that is on-topic and purposely not format-specific. applause
raccoonboy
Thanks for all the input folks. I'm going for comparators etc rather than a dedicated probability module. I like to use the most fundamental voltage control functions I can find rather than a more specific unit, it gives me more options for my limited rackspace and is also more fun.
Yes Powder
The Bastl Little Nerd has this.
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