[sdiy] Digital Noise, FYI

[Harry Bissell]

hmmm...

When I got my ProphetV, it used the dreaded (and feared) MM5837 noise source.  I tried to make an exact
replacement with analog techniques, but could not get the 0>15V "all or nothing" voltage swing. I suppose
with my superior skills these days, a comparator would have done the trick...

A CD4006 based solution was exactly what the doctor ordered, it did not mess up the factory presets in the least, but
removing the MM5837 did eliminate the (your choice) <ticking time-bomb> <roaring freight train> <chinese water torture>
from the sound...

The digital techniques have their place. I don't really care about 'random'... a repeat every few hours or so doesn't
get too much of my attention :^)

H^) harry



----- Original Message -----
From: karl dalen <dalenkarl at yahoo.se>
To: Synth DIY <synth-diy at dropmix.xs4all.nl>, Matthew Smith <matt at smiffytech.com>
Sent: Wed, 16 Feb 2011 05:31:46 -0500 (EST)
Subject: Re: [sdiy] Digital Noise, FYI

If you replace that CPLD *thing* with an analog one FET based S/H
and one NPN based noise source you end up with a cheaper and 
simpler and better sounding result.

Did i mention Moog Source envelopes?
KD


>Matthew Smith <matt at smiffytech.com>:

> ...
> >> 555 -> CPLD -> 10-bit parallel load DAC
> 
> I actually got that a bit wrong - it's a 12-bit DAC, the
> MX7541, which is just a Mexican version of the AD7541 ;-)
> (Not really, it's the Maxim version. Just my silly joke.)
> 
> > That's an awesome circuit, from an awesome book. 
> It's high on my to-do list
> > as well.
> 
> I'd recommend Lancaster's books to anyone in this field -
> he's a really good teacher, it's just a shame he never
> published more. I have the TTL Cookbook, CMOS Cookbook,
> Active Filter Cookbook.
> 
> To address Dave Manley's question, yes. String of flipflops
> with some XOR gates. (Photo of relevant page mailed to
> Dave.)
> 



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-- 
Harry Bissell & Nora Abdullah 4eva