[sdiy] Weird hobby of the week: BBDs

[Scott Stites]

> People should really try the LM1894 'Dynamic Noise Reduction' circuit from
> National. I was happy to see that these are still in production (albeit
only
> in SMD form). It really does a great job of gating the noise and it does
it
> by basically being a low-pass filter with an envelope follower. This is a
> simplification but it's pretty much how it works. It has a gilbert cell as
> its core. Check out the datasheet. I've used them with very good results
for
> reverb/stereo expansion.

I saw some of those somewhere on the net and wondered about them....

> I should point out that these were BBD's with a relatively small number of
> steps: 128 and 1024.
> The noise gets worse and worse as they get bigger, but an MN3006 has a S/N
> ratio of 90 while the MN3007 is 80.
> That's not /that/ bad.

Yep, it's the whole clock/alias thing that'll getcha.

> > For the past several months I've been working on a modified clone of the
> > Boss Dimension C, little brother to the D.  It uses two BBD's running
with
>
> I've been following this very closely actually. Lots of cool ideas in
there.
> I've seen so many really cool ideas online but I think I'll still end up
> making something up on my own. I have to try some things that maybe
haven't
> ever been done. Still this project and the Storm Tide were hugle
educational
> for me. Thanks, dudes.

I need to clean up things a bit - I spotted a fairly bad mistake on one of
the schematics, and I've changed the bypass circuitry a bit (that part was
the most finicky thing I've ever worked on - ah hates debouncing).  The rest
of the add-ons are my first flailing attempts at working with single supply
circuits.  Just finished testing the first set of boards, though, and
everything works very well.  Time for it to go in the rack, except I'm going
out of town the next two weeks =-(.

As for the Stormtide - yummy.  JH is the well from which all SDIY
springs.....

> PSP makes a free VST plug-in that they cool Pianoverb. It's very very
cool.
> It's liek a spring reverb except it mimics how a piano soundboard sounds
> with the dampers off and a sound is played nearby. I used to make
recordings
> with this when I was a kid. (with my bitchin' now deceased Truetone tube
> reel2reel).
> At first I found it of little utility until I messed with the tuning and
> detuning controls. If there's dissonance that you don't want you just
twist
> and it hits a sweet spot. Way cool.

I've heard samples from a list member of a computer generated Dim C -
sounded damn good to my ears.  If I had that kind of talent, BBD's would
probably take a back seat.

> > The MN3011 appeals to me more as a device for chorus/flanging than as
> > reverb.
>
> Now you have /me/ wanting one of those. Even more than an 05. Thanks @=^)

Sorry =0)

> Know of any links for a good bare bones delta modulator? There is one that
I
> think everybody here probably knows:
> http://www.armory.com/~rstevew/Public/SoundSynth/Reverb/ddl.htm

Didn't Batz do something like along the lines of a delta modulator?

You ought to check out Rene Schmitz's delay here, also:

http://www.uni-bonn.de/~uzs159/

Cheers,
Scott