[sdiy] Quiet/noisy grounds on Music Easel envelope generator

[Magnus Danielson]

Aaron Lanterman skrev:
> Howdy folks,
> 
> I'm working on getting the envelope generator for the Music Easel into 
> Eagle for PCB goodness (yup, I plan to make this and other related PCBs 
> available if and when I get them done and debugged):
> 
> http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_3_200.jpg 
> 
> 
> There's three digital chips in that circuit: A MC14001, an MC14025, and 
> a MC14016 quad bilateral switch. There's a bunch of analog stuff, 
> including some op amps and a LM3900 norton amp.
> 
> Like most Buchla designs, this schematic employs a "noisy ground" and a 
> "quiet ground."
> 
> I'm guessing that I should power the three digital chips with +15 V and 
> "noisy ground," and I should power the LM3900 with +15 V and "quiet 
> ground." But, there's no specific mention of any of this on the data sheet.
> 
> Anyone see anything wrong with my plan?

That you haven't executed it. It sound design.

> (The MC14016 is a "digital" chip, but it is passing analog signals, 
> which lead me to wondering...)

You don't want the inverters within the 4016 to disturb the analog side, 
but you don't want to let the other digital circuits polute too much 
either. I assume you use decoupling caps which can swallow the impulses. 
fairly efficiently. Recall that the slew-rate of the impulses is what 
eats you. Some of them have repetions rates of the oscillators, so the 
frequency of impulses is audio-frequency.

Cheers,
Magnus