Kick mic to CV for analog triggery

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syrupcore
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Kick mic to CV for analog triggery

Post by syrupcore » Thu Oct 30, 2014 3:58 pm

I'd like to put a mic or trigger or something inside of our drummer's kick drum and have that trigger the arpeggiator on my sh-101. The SH-101 wants (I'm pretty sure) a squarewave clock pulse of +5v.

I was thinking of stuffing a hot mic (boundary perhaps) in the kick and hooking it up to something with a headphone out and then plugging that into the sh-101. Thought I'd ask here first before I blow something up! Will it even work or do I need some specialty box?

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Post by kslight » Thu Oct 30, 2014 9:28 pm

I am pretty sure you could just use the current kick mic as a trigger...perhaps just gate it but I don't see any reason this would cause damage..it'll either work or it won't.

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Post by Jim Williams » Fri Oct 31, 2014 8:44 am

A comparitor chip like a LM311 could be set up as a trigger pulse. Set the levels with a resistor divider and it will pop out 5 volt pulses if you use something to attenuate the level at 5 volts.

Or if in a fix, grab a fuzz box, set it so the kick drum squares up the output waveform and set the volume pot to get a 5 volt clipped waveform to trigger.
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Post by syrupcore » Fri Oct 31, 2014 6:27 pm

Thanks both. Good idea about the gate.

When I see stuff like "+5v" the fact that I'm not a recording 'engineer' really shines! I'm guessing there's a correlation between signal amplitude and voltage but it's a bit of a black hole for me. I just know, anecdotally, that sometimes folks try to hook up CV stuff and it doesn't work because of voltage problems.

Plus, I bought the 101 in 1986?it was my first synth! As I get older I seem to get a ever more precious about it hence the somewhat atypical ask-before-try.

Jim, the distortion pedal idea is what I was thinking by using something with a headphone amp?overdrive the input to get it square up and then use the headphone level to set it. I have an old boss mulit-effect pedal with a distortion and a gate. Think I'll give that a shot instead.

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Post by The Scum » Sun Nov 02, 2014 11:07 pm

Good schematics are available here:

http://www.synthfool.com/docs/Roland/SH ... Manual.pdf

Clock input comes onto the main board at point 101, Quadrant A7 on page 9. It looks like the external clock in runs thru a 100K to the base of a transistor. So moderately protected against external evils.

The fuzzbox idea might be a bit too brute force, and might cause double-triggering. The fuzz box would turn each kik hit into a series of pulses. Since it's an x0x, I'm not sure how long a pulse has to last for it to register with the CPU to trigger. I seem to recall that other x0x machines needed clocks of longer than 2 msec to register. Try it and see.

If it's a double triggering mess, a peak detector + comparator circuit would be a more complete solution, such as this one:

http://www.freeinfosociety.com/electron ... 720-11.gif

There are even more thorough solutions, using pairs of one-shots to more precisely define the pulse width, and set up a hold-off window, so it won't retrigger too soon after the initial trigger. Probably overkill, but worth mentioning...good drum brains use a scheme like that.
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Post by syrupcore » Mon Nov 03, 2014 10:51 pm

Wow, thank you very much for that.

We were supposed to try it this past weekend but life in our 40s got in the way. Will report back when the kids go to college.

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