[sdiy] BBD Chips

[Harry Bissell Jr]

Yeah so it was a black and white llama then ???? ;^P

You could do the through zero with BBDs.... the
problem will be you want to keep the fixed delay
short.... and vary the other delay.  So a long BBD has
to be clocked at a very high rate.... or you would
possibly need unequal length BBDs that would have
different attenuation and noise levels.

I did the through zero trick with two DeltaLab
"Effectrons" and it works great. You will never need
a delay longer than 16ms.... with probably a 4ms delay
being ideal.  This might be the point you remembered
???

H^) harry


--- Scott Stites <scottnoanh at peoplepc.com> wrote:
> Thanks guys!  (Mental Note:  Never post before
> morning coffee).  Filter before
> mix.  Sigh.
> 
> But on first glance of Roman's idea for through-zero
> flanging something twanged
> in my brain about it being problematic when
> implementing with BBD's.  It seems to
> be from some previous discussion on this list or
> maybe it was off-line.  Or
> perhaps I dreamed it - Harry Bissell on a green
> llama saying "#%s#ssshhhThou
> zshalt not tHroew w sszero with bBd..D..Sd..zzst"
> (bolt upright in bed).  Nah,
> that wasn't it.  I don't dream in color =0).
> 
> Somewhere on the net I picked up the doc
> "flanger.pdf" that is a copy of a 1984
> ETI article detailing the construction of a
> chorus/flanger unit using the
> MN3207/MN3102.  I borrowed the part for the
> transistor current sink from that for
> the flanging (it's got a linear sink also for the
> chorus part).  
> 
> Cheers,
> Scott
> 
> 
> On Tue, 22 Jul 2003 18:57:30 +0200, "Jaroslaw
> Ziembicki" wrote:
> 
> > 
> > ----- Original Message -----
> > From: "Scott Stites" <scottnoanh at peoplepc.com>
> > To: <synth-diy at dropmix.xs4all.nl>
> > Sent: Tuesday, July 22, 2003 5:51 PM
> > Subject: Re: Re: [sdiy] BBD Chips
> > > But wait - don't ensemble choruses by nature
> have the BBD clocks
> > 'crossing'
> > > themselves in the frequency domain?  Now I'm
> confused.....
> > 
> > Yes, the clocks are independent, but there's no
> danger that any new
> > frequencies in the
> > audio range would arise.
> > It's due to a fact that the output signals of all
> BBD's are mixed together
> > in a *linear*
> > summing circuit. That means, no additional
> sums/differences of output
> > frequencies can
> > arise. The signal after mixing is a sum of
> "useful" low frequencies, and
> > high frequencies
> > which result from the sampling. After low-pass
> filtering, only the "good"
> > low frequencies
> > will be left at the output.
> > Of course the input signal or signals must be well
> low-pass filtered before
> > passing in the
> > BBD (or BBDs) in order to cut off any frequency
> that is above the half of
> > the BBD
> > clock frequency. It's the well-known Shannon
> theorem - also called the
> > Kotielnikov
> > theorem in some countries ;o)
> > 
> 
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