More on Fav Designs

[Joe Grisso]

VCOs
====

First, no VCO has a "sound", sterile or otherwise. They may have THD, but a
pulse is a square is a saw. But what they DO have is drift and have
linearity errors.

Now even the CEM3340 will drift some. But not as much as most, because
there is a circuit on the die that generates the +3300ppm voltage. Note
that this must be MULTIPLIED with the input voltage. A resistor divider is
a multiplier (by a coefficient <=.9999). The on-chip multiplier (OK there
goes my trivia question: where did OnChip get their name) has linearity
errors. This is also called a "tracking error": instead of 1V/oct, get .993
in the first octave, .997 in the second, 1.002 in the third, etc.

8< Snip! 8<

I hate to bridge the gap into digital, but you mentioned the AD9825/30/31
from Analog Devices were a good DCO chip to go with as well, how would it
hold up in computer controlled situations, and what have your overall
results for this chip shown?

The 3080/LM13600
==============

Hey, these are OK for poking around. Heck, I bought them in tubes of 100
for years. But they suffer from:

8< Snip! 8<

There is another company that is making VCA's specifically for audio, can't
remember their name, but I have some of their part numbers: 2150, 2155,
2159. Rob Urry (CEO of dbx) said that dbx had a big hand in designing these
VCA's, and also based some of the V2 and V8 VCA designs on these IC's. If
you've heard of these IC's, and have tried them, please let me know.

The 3310 EG
=========

All agree, this is the chip. So concern over the availability. Gene, I GOT
1200!! Now, this is certainly enough for now. So don't be shy using it. I
will design an equivalent from discrete later this year.


Once again, what about using a uP for generating the envelope? Trade offs?


Power Supplies
===========

It's hard to beat a 723/D40xxxx pass transistor. 

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What about switching supplies in analog designs? Too much voltage and
current ripple?