[sdiy] BBD Chips

[Scott Stites]

I think the problem comes with by-products of the two clocks mixing - the sum and
difference frequencies wind up in the audio band.

I've thought about combining two different types of delay to see if that problem
could be defeated, though I've never got around to doing it.  The PT2399 digital
delay chip clock operates in a different range of frequencies than a BBD, but
chip itself lacks the minimum time delay to make flanging feasible.  However, if
you delayed the signal with the PT2399, and then put enough of a delay in the BBD
to sweep back and forth past that point, I wonder if the clock aspect of the
noise problem would be eliminated?  

Cheers,
Scott



On Tue, 22 Jul 2003 17:03:06 +0100, Roman wrote:

> 
> I know at least one person who'd hate me for saying this, but...
> What if we use 2 BBDs and 2 clocks. When one frequency rises, second drops. When
> frequencies are equal, there's no delay between BBD outputs, so flanging can
> begin at zero delay, or go back and forth into positive and negative delay. As
> long as there's no original signal added, and everything passes thru BBDs,
> there's no minimum time limit.
> Only twice the noise...
> 
> Roman
> 
> ---- WiadomoϾ Oryginalna ----
> Od: Scott Stites <scottnoanh at peoplepc.com>
> Do: synth-diy at dropmix.xs4all.nl
> Data: Tue, 22 Jul 2003 06:39:20 -0700 (PDT)
> Temat: Re: [sdiy] BBD Chips
> 
> >I've gotten very good results both for chorus and flanging using the MN3207. 
The
> <br />
> >spec sheet gives a 200 kHz max clock rate for a minimum delay time of 2.56 ms,
> <br />
> >which is in the heart of flanging territory.  Seems I've overclocked the chip
too
> <br />
> >for even better results with no problem, but I'm at work now and can't remember
> <br />
> >the particulars.  Looking at various manufacturer schematics for flangers,
> <br />
> >choruses and ensemble choruses, it seems they routinely overclocked BBD's. 
Maybe
> <br />
> >Harry mesmerised the manufacturers and overclocking *really* destroys them
=0). 
> <br />
> >
> <br />
> >The MN3102 clock is definitely worth the few extra bucks.  It rather
> <br />
> >uncomplicates things, and the waveshaping in it helps to ensure you don't have
> <br />
> >any clock overlap.  Using that, the addition of a couple of transistors makes a
> <br />
> >nice logrithmic current sink for flanging.
> <br />
> >
> <br />
> >Cheers,
> <br />
> >Scott
> <br />
> >
> <br />
> >________________________________________________
> <br />
> >PeoplePC:  It's for people. And it's just smart. 
> <br />
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> <br />
> >

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