Yet another BBD question...

[Paul R. Higgins]

I've been building BBD analog delays for years, and I can say that they most 
definitely do not suck (well, except for long delay times, where they really do 
suck).  But for short delays, and modulated delays in particular, they are 
great.  You can get huge sweep ratios out of them; the "Hyperflange" circuit 
designed by Craig Anderton had a 72:1 clock ratio.  I don't think that even 
modern digital effects boxes can give that dramatic a sweep.

There's also something about the sound of a digital chorus box that I don't 
like, especially with a signal full of high-frequency components (e.g. 
synthesizers, distortion guitar).  I have no idea what's going on inside many of
these digital boxes, but I find them strident and harsh-sounding.

BBDs do have their disadvantages, such as limited dynamic range, low S/N ratio, 
etc., which is why most commercial analog delays used companders to attack this 
problem.  This had the additional side effect of making the resonance feedback 
loop more stable. 

Anyway, this is just my $0.02.  I think BBDs are fun to work with, and they 
sound infinitely better than my digital effects boxes for chorus/flange/etc.

Regards,
-PRH


> its Bucket Brigade Device (or delay...). The idea is a long string of analog
> sample and hold circuits. There is a high frequency (dual phase like Q and 
> not
> Q) clock, which causes the charges to be passed to the next stage in
> succession...
> 
> like firemen passing buckets of water to the next guy in line... there is a
> continuous stream of water being delivered to the output, delayed by the time
> it took to pass the buckets through  (oh...) 512 men...
> 
> Now picture that each bucket is filled with a different amount of water
> (corresponding to the input (audio) voltage at the time it was filled. Then 
> at
> the other end the bucket is emptied and the (audio) voltage is recovered...
> 
> Plus some slop, and noise, and limited range (you can't make the buckets too
> empty or nothing comes out, or too full, they overflow and never reach the
> fire...) and there is the noise of the clock bleeding through to be filtered
> out....
> 
> which IMHO makes BBDs SUCK
> 
> opinion for comparison purposes only
> actual mileage may vary...
> 
> H^)   (harry)


_____________________________________________
Paul Higgins
email: higg0008 at tc.umn.edu
University College, University of Minnesota
_____________________________________________