[sdiy] Possible BBD replacement!

[Ryan Williams]

this does work. I've tried it on the breadboard with a simple current 
sink on the PT2399. but the limiting resistor is a good idea because 
once the current pull is too high the chip will cut out. and the voltage 
at that pin jumps from 2.5 to 5V. I destroyed one once after leaving it 
on like that for some minutes. but the shortest delay I was getting 
before this failure wasn't short enough for me to keep messing with it. 
I liked the pt2395 a little better with it's larger ram and that it can 
use an external clock. some have suggested that it may be possible to 
shorten the delay on the 2395 since it's ram IC is external, but I 
wasn't able to get that working. next week once I've checked the 
schematics over I'll post the circuit and some sound samples.

Ryan

karl dalen wrote:
> Have you realiced that the Holtek/Princeton
> HT8970/PT2399 (same IC) might be a current
> sink output on its VCO frequency pin! pin 6.
> 
> I suggest you try connect your NPN expo to this pin (trough a 680ohm
> currentlimmeting resistor, just for safe) and hopfully get your self
> a voltage controlled digital delay, wich if the datashet are correct
> give you better performance then the avarage BBD.
> 
> Ii might then be possible to shrink the delay time a tiny bit more,
> maybe its possible to get into the milli sec region!
> 
> If this is right we can start talking karplus-strong and real audio
> FM modulation modules here at diy list. :-)