audio driven 4017 clock??

[club_spouse]

I've been wondering about a few different ways of clocking a sequencer like a "baby 10" based on the popular 4017 chip.

I've built ones that use a 555 as a clock, but I was thinking about using the individual out of a drum machine to run the clock, the way you would trigger a juno or jx-3p to step thorough an arpeggio at more irregular (and interesting) intervals. 

the signal from a drum machine is too weak to shift the clock so it will have to be amped or used to run a transistor switch to get closer to 5 volts.  So should I just try to amp a rim shot with an opamp a bunch?? Or try to use something like a 2n2222?  Im afraid of trannys...

help me out if you can.

[BrassTeacher]

What's the maximum voltage the drum machine can put out at full volume? For instance, a lot of CD players can pump out 2V (AC) at full volume.

I would use an opamp, depending on how much voltage the drum machine kicks out, to raise the voltage to around 5V or slightly more. Since we are talking about AC signals here, if the voltage in is 2V peak-to-peak, which is really +1V to -1V, so the opamp's gain would need to be set at 5 to get 5V peak-to-peak. I would then follow this with a comparator, with a pot wired as a voltage divider on the input so that you can adjust just how much of a "kick" it takes to trigger the 4017.

As soon as I'm not so tired brain-wise, I'll try to draw up a little diagram on how to rig the comparator if you can't find a circuit online someplace.

DT

[expanoncolin]

As BrassTeacher said, amplifying the signal (probably with adjustable gain!) and sending it through a comparator is the way to go - but I would also highly recommend putting it through a simple envelope follower first.  This will ensure that the signal doesn't flip-flop at audio rates, but rather when a drum kick actually happens.  An envelope follower can be as easy as sending the signal through a full wave rectifier, then low-pass filtering.

-Colin

[club_spouse]

thanks for the help.  I will try to figure out and test some of these solutions with a quad op amp and let you know how it goes.

I've been working on the http://www.musicfromouterspace.com/analogsynth/signaltogate.html audio input/gate module seperately, but parts of that circuit (the rectifier and amplifier) look like they could be modified to fit this problem. 

[expanoncolin]

Indeed, the output of those two diodes should be a nice full-wave rectified signal.

-Colin