Audio click to Vortex tap

[gstopp at fibermux.com]

     Hi DIY,
     
     As you may remember last week I contributed to a thread about syncing 
     the tap input on a Vortex to an audio click. I guessed that one could 
     probably use a peak detector into a transistor switch - well 
     surprisingly enough my guess turned out to be useable! At least on the 
     test bench...
     
     OK I haven't actually hooked it up to my Vortex yet but it all looks 
     good on the scope. I used an Alesis HR-16 drum machine as the audio 
     click source, into a non-inverting amplifier with a high gain (2.2K 
     input, 100K feedback) into a diode/cap peak detector (cap = 0.1 uF) 
     with a 180K bleeder resistor) into an op-amp buffer, into the base of 
     a 2N3904 through a 2.2K resistor. The NPN has a grounded emitter and 
     the collector would go to the Vortex tap input cable tip, with the 
     sleeve of the cable grounded.
     
     When a sound arrives at the input, the preamp boosts it to a 
     high-level clipped signal that passes through the diode and dumps a 
     positive voltage on the cap. When the sound goes away, the bleeder 
     resistor discharges the cap. The buffer then provides a copy of this 
     voltage pulse to the transistor, which grounds its collector (and 
     whatever is connected to it) for the duration of the pulse. On the 
     HR-16 you can set the record click to any instrument, and I found that 
     they all worked fine with the exception of the gated sounds (which 
     cause multiple random triggers). This is not surprising. Just stick to 
     a nice short sound and you should be fine. The tap output goes to 
     ground for a couple hundred milliseconds each time a drum hit comes 
     in, which should emulate a foot-tap nicely.
     
     Try it, have fun!
     
     - Gene
     gstopp at fibermux.com