Synching a Vortex?

gstopp at gstopp at
Fri Jan 31 18:59:54 CET 1997

     Rather than Wheatstone bridge you probably mean full-wave bridge... 
     that is the right concept but I do think that a simple peak detector 
     should be tried first. This is one of those times when a gross 
     conversion is all that's needed rather than a precise one.
     Regarding making my own chips - one of the current rages in EE work is 
     the use of FPGA's and EPLD's and other acronym-intensive technologies, 
     in this case creating circuit designs on CAD software and then 
     "burning" it into a big chip. I use the Altera system right now, and I 
     can put about four full pages of standard TTL schematics, probably a 
     hundred chips, onto a single 84-pin PLCC. There are restrictions:
     1. TTL only - no comparators, no analog, no schmidt triggers etc.
     2. LSI and MSI only - no UARTS (yet), no micros, no special purpose
     3. The software is thousands of dollars and you need the burner too
     4. The chips are $50-75 each (fortunately they're eraseable!)
     I use these at work, so I use all this stuff for free. The chips I use 
     for myself are samples we get from distributors to use as practice. 
     It's actually good for me to try different designs (like MIDI stuff) 
     just to keep in practice so I probably wouldn't even get in trouble if 
     my "goofing off" was discovered.
     So these have limited use in electronic audio, but they're great for 
     clocking and driving DAC's for CV stuff. So far I've made a keyboard 
     interface, a Shepard function generator (Honcho's design), and the 
     MIDI-clock converter.
     For the MIDI-clock circuit, I had to make a UART receiver out of shift 
     registers, and then added some pattern identifier circuits to detect 
     MIDI clock, start, stop, and continue bytes. The resulting pulses get 
     fed into some counters and latches so that I have various divisions of 
     the 24ppq clocks as triggers (all the divide-by-two's and 
     divide-by-three's) plus the command outputs. In addition I added a 
     gated clock that runs after a "start" or "continue" and stops after a 
     "stop", plus a gate output that is high when running and low when 
     stopped. Therefore this gizmo could easily drive analog sequencers as 
     well as Roland X0X boxes.
     I can't really steal any of these chips, except for the samples, so I 
     can't really be a supplier of these. Many times you can provide an 
     electronics distributor with the source files and they will burn the 
     chips for you so you can buy pre-programmed chips in quantity, but I 
     haven't checked into this.
     - Gene
     gstopp at

______________________________ Reply Separator _________________________________
Subject: Re: Synching a Vortex?
Author:  "Arnim X. Sauerbier" <arnims at> at ccrelayout
Date:    1/31/97 3:52 AM

>     Converting the audio pulse to a voltage trigger can be done with an 
>     envelope follower plus a comparator. Actually for such a specific 
[writing this down... "Look-up in textbook: envelope follower, 
comparator" ... hah! :-*
Would a wheatstone bridge hooked-up to the line-out of the drum machine 
convert the AC wobbles into DC?   Then some kind of RC circuit to -uh- 
'store' that voltage for a few milliseconds while it triggers a 
transistor short-to-ground?  I was actually thinking of going back to my 
radio-shack "101 electronics projects" kit which featured a 
sound-detector alarm circuit.  Figured it's doing something similar.  
Doubt I can find the book tho.
But seriously, if you build this, let us know how you did it!  If I 
manage to, I'll do the same - thanks!
>     A couple weeks ago I built a MIDI-clock to voltage pulse divider 
>     circuit on a single chip, but that's another story...
Umm, maybe not.  Couldn't that chip be used to provide the voltage 
trigger?   Waitaminute, YOU design and produce your OWN chips?  
Huhuhhuhhhh-uh, cool.

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