Hi,
I've just spent some time noodling with a retro guitar delay pedal that use a simple PT2399 echo chip with an adjustable clock. The way the sound responds to live manipulation of the clock rate is really interesting to me, and I think is part of what they're talking about when they describe it as a 'analog delay' (although the PT2399 is as digital as anything.)
Anyway, this got me to thinking about the ways I could interface my teensy with various analog signal sources and sinks, and I got to wondering if it's possible to slew the clock frequency of the teensy and the audio board via a potentiometer or an external control voltage ... or even internally via software.
To be clear, I'm not talking about adjusting the input or output sample rate by messing with the timers, and I'm not talking about adjusting the prescalers. I'm talking about adjusting the main clock frequency that drives all the other clocks on the chip, from the maximum of 96mhz down to a minimum of 0. So basically, replacing the crystal oscillator with some kind of adjustable equivalent. That would allow me, right off the bat, to do the same kinds of knob-twiddling echo effects that these pedals do, but I can think of a host of other interesting possibilities.
I've read that some chips can deal with this and others can't. ADC performance might be affected, I don't know how much. DAC performance would have to be decent for this to be worth trying. Has anybody tried this? How would you go about it?
Thanks for any advice,
-mykle-
I've just spent some time noodling with a retro guitar delay pedal that use a simple PT2399 echo chip with an adjustable clock. The way the sound responds to live manipulation of the clock rate is really interesting to me, and I think is part of what they're talking about when they describe it as a 'analog delay' (although the PT2399 is as digital as anything.)
Anyway, this got me to thinking about the ways I could interface my teensy with various analog signal sources and sinks, and I got to wondering if it's possible to slew the clock frequency of the teensy and the audio board via a potentiometer or an external control voltage ... or even internally via software.
To be clear, I'm not talking about adjusting the input or output sample rate by messing with the timers, and I'm not talking about adjusting the prescalers. I'm talking about adjusting the main clock frequency that drives all the other clocks on the chip, from the maximum of 96mhz down to a minimum of 0. So basically, replacing the crystal oscillator with some kind of adjustable equivalent. That would allow me, right off the bat, to do the same kinds of knob-twiddling echo effects that these pedals do, but I can think of a host of other interesting possibilities.
I've read that some chips can deal with this and others can't. ADC performance might be affected, I don't know how much. DAC performance would have to be decent for this to be worth trying. Has anybody tried this? How would you go about it?
Thanks for any advice,
-mykle-