[sdiy] new project working!!!

[Michael Ruberto]

hey all! the sucker is doing it's thing!!!
what I have is the input circuit for the signal which is your standard 
offset + span deal, the input for the CV which is the same but without span, 
the divider, and the core. the core was a real pain to breadboard - note to 
self, buy SIP resistor packs!
also, setting the offset was a pain without an O-scope. I had to use an 
analog voltmeter and run an LFO into the input at a very slow rate. then I 
watched the LED on the meter that indicates negative voltage and adjusted 
the trimmer till it went out and the full range was positive. then I cranked 
it up to audio range.
now, the bad part. the divider is exactly as shown in the AD633 datasheet 
and seems to be working fine at audio frequencies. however, using subaudible 
LFO wave causes the output to lock up at 15 volts :-(
is this because I am feeding single ended signals? please help me with this.
ok now here is a really dumb one for you. the output of the divider is 
supposed to be -10 * (E/Ex) according to the datasheet. now when I get out 
my scientific calculator this gives me negative results. so is it a problem 
to use only positive signals? what am I not groking here?


oh yeah, I though you might be wondering how it sounds. it sounds great!!! 
it's not quite as dramatic as in the SynthEdit Demo I cooked up, much less 
harsh sounding and suprisingly smoother considering how few bits I have in 
comparison. I haven't even tested to see if all bits are turning on, I just 
adjusted the range by ear ;-)
oh yes, the sound is quite like PWM but with a "beat you with a bat" 
attitude. obviously, the more bits in use the more it sounds like PWM, but 
as the bit count is reduced it gets FATTER and eventually sounds like more 
than one tone. the harmonics get stronger and start fighting with the 
fundamental till it gets a bit like ring modulation. yes I am drooling...
when I add the multiplier things should get more interesting! I'll get some 
samples up when I can.

I haven't even drawn the schematic yet. I am just breadboarding straight 
outa the ole grey noodle so far. I think once I draw the schematic I may 
feel embarrassed ;-)
look for it over the weekend. 
http://www.sunrisecomputersolutions.com/samples/decimator.html

~M

PS: should I be buffering the output of the divider to prevent interaction 
between stages?

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