[sdiy] Aztec Revisited

[mike ruberto]

Tested up to 4000 hz so far with no problems at all. Couldn't stand to
go any higher as my ears are bleeding now.
Interestingly the Slope control can actually control the number of
octaves from the multiplier regardless of bit depth thanks to the big
DC offset it adds to the output.

I am observing new behaviors I can't quite explain now that
I removed the previous output leveling circuit. Instead of feeding the
LM3914s output pull-up resistors with a dynamic voltage I tied it to
the reference supply rail. Now as I vary the bit depth it goes from 1
bit up to 20 and then starts to decrease again and ends at 6 bits for
maximum depth voltage. I think there is some interaction going here
with the way the slope control varies the LM3914's output current. The
good news is that it sounds interesting. I'll need to study this a
bit. It could be that I'm overdriving the 3914.

Also the multiplier pulse output is a bit on the indecisive end.
Certain conditions lead to some very dramatic toggling. Fun to watch
on the scope and even more interesting to hear. While I'm sure I could
stableize this I'm not sure I want to. Compared to the samples of
Ian's 5Pulser this circuit is much less subtle and clean about
introducing a new octave. Yes it's something like PWM but with a bad
attitude.

This is fun, I wish I had more time so this project didn't start
collecting dust.

M. A. Ruberto