How to implement "choke" function?

moosapotamus · Joined: May 11, 2007 Posts: 113 Location: New Hampshire USA

For those unfamiliar with the term...
To 'choke' a signal is to cut off or silence that signal, as when hitting an open hihat and then stomping on the pedal to close, silence, or 'choke' the sound. In the modular world, you might have two identical circuits, Ch1 and Ch2, each comprising an Envelope Generator and a VCA. A trigger on Ch1, for example, sends ENV1 to VCA1 enabling Ch1 output. But, when the 'choke' switch is turned on, a trigger to Ch1 also silences the output of Ch2. This is ideal for creating OH and CH type sounds/rhythms. The Befaco Percall incorporates this 'choke' function.
(Okay, I'm done typing choke with quotes Wink

)

The schematic, below, is what I currently have on my breadboard. It is Ian Fritz' AD AR Generator feeding a LM13700 VCA. It's working great. I plan to build two of them into a single module. The schematic only represents a single channel. However, I am also interested in adding a choke switch, such that Ch1 trigger input will choke Ch2 output. But, I don't have a clue and could use some advice. Haven't been too successful searching online, either.

Instead of looking at the envelope generator to produce the choke, I am guessing that the VCA should just be closed, somehow? Perhaps a trigger input to Ch1 produces a low gate (close VCA2) and a trigger to Ch2 causes that same gate to go high (re-open VCA2), again, somehow? I don't know. Right or wrong I have no idea how to do that, anyway. Definitely need some help.

Are there any thoughts or ideas on how to incorporate a choke switch into the schematic posted here? Presume the schematic is showing Ch2 and a remote trigger (to Ch1) would silence the output. If not, any info on how best to implement a choke, even if different ENV or VCA circuits would be required would be much appreciated! Much thanks, in advance!

Fritz ENV VCA.png

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moosapotamus · Joined: May 11, 2007 Posts: 113 Location: New Hampshire USA

In retrospect, perhaps I should have titled this thread - How to add Choke to Ian Fritz' AD AR
Anyway...

Here is a link to the Befaco Percall schematic that they have posted on their website.
https://befaco.org/docs/Percall/Percall_V1_Schematic.pdf

I could be wrong, but it looks like the switch at LINK1, between Envelope 1 and Envelope 2, is one of the two choke switches. The other at LINK2 between Envelopes 3 & 4.

Is anyone able to decipher what is going on with the Choke switch in the Percall? How it works? I looks like there might be some similarities between the Percall and Ian's AD AR, maybe? While the Percall only has Decay control, Ian Fritz' AD AR also has Attack. Is the VCA really not involved with the choke? Could something similar to the Percall's method be adapted to work with a pair of Ian Fritz' AD AR circuits?

Cheers!

richardc64 · Posted: Thu Jul 06, 2023 8:26 am Post subject:

In drumming "Choke" usually refers to ending the sound of a single cymbal, by hand or with the stick. The same action applied to Hi Hats -- including via the foot pedal -- is called a "Stop."

With that bit of pedantry out of the way...

moosapotamus · Joined: May 11, 2007 Posts: 113 Location: New Hampshire USA

richardc64 - Thanks for the reply! And for clearing up the lingo. Cool

I would have replied sooner, but I first wanted to find the time to try the Choke snippet from the Percall (attached below) with the Ian Fritz AD AR envelope generator currently on my breadboard (scheme above). Unfortunately, no joy. I am guessing that IC5D in the Percall could correspond to U1C in my scheme of Ian's AD AR. Tried a couple of different arrangements based on that assumption, none of which seemed to work.

With fixed attack and decay, yeah, the DR-110 does look nice and simple. Especially next to the Percall! I am looking to have both adjustable Attack and Decay. I found Ian's circuit here and it's working great for me. But I thought adding a Choke control between 2 channels would be useful.

Would it be reasonably possible to implement a choke switch between 2 channels of Ian Fritz' AD AR circuit? Or, does that particular envelope generator just not lend itself to such modification?

ChokePercall.PNG

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richardc64 · Posted: Fri Jul 14, 2023 2:22 pm Post subject:

moosapotamus · Joined: May 11, 2007 Posts: 113 Location: New Hampshire USA