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Wrapping my head around Analog Shift Registers
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Wrapping my head around Analog Shift Registers
witchbutter
So the typical application I see for an ASR is to sort of hold pitches on different outputs to move notes around to different oscillators taken from a quantized input. I get that this is essentially a series of sample & holds.

So what if you wanted to use it to move a series of filter envelopes around to different parameters? Can anyone suggest some patch ideas using ASR for CV that isn't pitch? Am I confusing this with a gate delay?
cptnal
Here's a few I've been messing with. Further details are scattered around these fora...

I'll get the pitch one out the way first. I know you didn't want pitch, but it's not the obvious one where each channel goes to a separate oscillator. Instead of that you mult each channel to a separate mixer, and send the mixed outputs to their destinations. Have a look at Dinko Klobucar's Youtube channel, which is where I kicked it from.

I've used the gates from each channel to fire different envelopes, and the end of cycle from each of these goes into a mixer and back to the ASR's gate input. If you have an ASR with a random setting any envelope can fire any other.

And this one's more hocketing than ASR (Shifty). In track and hold mode, stick your modulation in the ASR's CV in, and send it to up to four destinations. In T&H mode you get periods of stasis alternating with periods of modulation. If you can PWM your gate so much the better.
authorless
Since it is a series of sample and holds, any CV you are using would be static. So no, you couldn't send an envelope to different locations. You would want a sequential switch for that. Or a sequencer and a voltage controlled envelope.

Use it for anything you would use stepped random voltages for. You can turn a single random voltage into as many random voltages as you have outputs.
leonvanbokhorst
witchbutter wrote:
So what if you wanted to use it to move a series of filter envelopes around to different parameters? Can anyone suggest some patch ideas using ASR for CV that isn't pitch?


No ASR, but maybe a CV recorder can distribute delayed envelopes the way you intend it
huffnPuff
Like authorless says, to send moving voltages around you need a switch. Besides the common multiplexers, sequential switches etc, there’s also manual switches, temporary gate-controlled switches and burn the witches.

If we’re speaking Eurorack then have a look at the Olegtron Confusor / Confusor 2 (the latter can be controlled by gates as well as manually).
The fundamental difference between the Confusor (2) and the garden variety sequential switch is that this one sends 4 inputs to 4 outputs concurrently.


pugix
Here's Ken Stone's description of his ASR.

http://www.cgs.synth.net/modules/cgs34_asr.html

It is a series of sample & holds, where the voltage held by the previous one is passed to the next on receipt of a trigger. One application is to patch a pitch CV (say from a keyboard) to the first S&H. The three outputs are routed to three VCOs, tuned to a common base pitch. Each trigger can also control one envelope generator, and one VCA in which all the VCOs are mixed. The result is an arabesque pattern of notes following each other.

I have Ken's ASR. One problem with it is that the input to output transfer function is not precisely unity. There are minor gain and offset differences. This makes it useless to run a quantized CV into it and get the same on the outputs. I have to use three quantizers to get scales to work properly. I don't have any other ASR modules, but I could patch one up.

Patching your own ASR presents a bit of a problem in that if all S&H's are clocked at the same moment, the next in line tries to sample the changing output from the previous one. I've got around this by using a square wave and clock every other S&H with the inverted square wave.
sduck
Dr. Sketch n Etch came up with an updated analog ASR circuit a while back. It's not perfect, but it's a lot better than the CGS one. I built a few of them. I tried to make a video demoing it, hoping that it would explain what it does, but I don't think I did a very good job of talking. I should really write a script for these things...

pugix
sduck wrote:
Dr. Sketch n Etch came up with an updated analog ASR circuit a while back. It's not perfect, but it's a lot better than the CGS one. I built a few of them. I tried to make a video demoing it, hoping that it would explain what it does, but I don't think I did a very good job of talking. I should really write a script for these things...



Nice! thumbs up

Sounds like it can pass a quantized CV through with better accuracy than the CGS.

So, the bypass switch selects between the stage output and the input? And the circulate switch by the input chooses between the input and stage 3 for stage 1? What happens if all the bypasses are on with circulation? Maybe all three hold the last stage 3 value?

There's always a question of droop for pitch CV. How does this do? Normally, if the clock rate is a typical tempo, droop shouldn't be an issue.

Left field question: How does this perform as a signal decimator? Can you feed it a fast clock and process audio at the input? Might be interesting to hear phase differences on the three outputs.
huffnPuff
Analog shift registers are awesome for audio rate signal shredding. For pitch applications I still think digital is the way to go.
The Snazzy Telephone Game is another fun ASR to play with once you come to terms with its limitations.
sduck
pugix wrote:

Nice! thumbs up

Sounds like it can pass a quantized CV through with better accuracy than the CGS.

So, the bypass switch selects between the stage output and the input?


Yes.

pugix wrote:
And the circulate switch by the input chooses between the input and stage 3 for stage 1?


Yes.

pugix wrote:
What happens if all the bypasses are on with circulation? Maybe all three hold the last stage 3 value?


Hmmm. I'll have to try and find out.

pugix wrote:
There's always a question of droop for pitch CV. How does this do? Normally, if the clock rate is a typical tempo, droop shouldn't be an issue.


The droop on this is fairly minimal - if you put it on Loop, it'll start dropping in pitch noticeably, but not too bad. It can be kind of a nice effect actually. Note that this one is a version 1 - he later revised it slightly, and the newer ones actually go up in pitch, although at a slower rate.

pugix wrote:
Left field question: How does this perform as a signal decimator? Can you feed it a fast clock and process audio at the input? Might be interesting to hear phase differences on the three outputs.


I haven't tried that. Yet...
Dcramer
Iz gotz Euro one’s comin’ twisted
sduck
By the way I highly recommend an Ornament & Crime if you're into ASR's - it's a completely digital implementation, very precise. With a lot of cool extra features also.
witchbutter
My o_Cs are always in piqued, lowrents and dialectic ping pong. I've been using Shifty and E102 quad temporal shifter.
Umcorps
There are also (inevitably?) two very useful ones in Disting if you are space challenged.
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