[sdiy] Achieving through-zero flanging using 2 PT2399 echo IC's

[Tom Wiltshire]

JP,

> Using 2 PT2399's echo IC's side by side,
> setting a working delay of around 40msec
> for the first IC and the other
> swept from 35 to 45msec would it be possible
> to achieve a through-zero flanging?

Seems reasonable to me.

> What do you think of the idea?
> The only problem I'd see is aliasing between them.

At the times you're talking about, the clocks will be running at  
17MHz (the static delay) and 15-20MHz (the variable delay).
Obviously there will be a point when they cross when the difference  
between these sweeps through the audio band. However, I'd have  
thought that with the clocks so high, it should be possible to  
eliminate them entirely from the output signal.

There's a question mark over what the actual sampling frequency is. I  
don't suppose the chip samples at the full clock rate, although who  
knows for sure.

Ultimately, I suppose you have to try it and see. Still, it's an  
entirely practical sounding idea, and not too hard to knock up on a  
breadboard.

Do be sure to let us know how you get on. I also have a few PT2399s  
hanging about, and I thought of building an ensemble chorus (like the  
Korg Polysix's) with them, but through zero flanging would be good too.

T.