PT2399 - Echo/Delay chip
Tuesday, February 15th, 2011I tried a few experiments with the PT2399 chip over Thanksgiving weekend.
Its an echo chip thats pretty dirt cheap. You can get them at Futurlec for under two bucks. In fact, here is a place in eurozone that has them for 50 cents (plus…ahem…shipping). There have been plenty of work done on the chip, and for lo-fi applications…its pretty ideal.
The low down summary is this: its really low noise for small delays. Anything more that 400ms and it starts to sound pretty noisy. Workable…but noisy. Here is a kit that uses two chips for a total of 800ms delay. Very reasonable in my opinion.
Being that there has been so much work done on the chip, I opted to try a fairly bastardized version of an echo circuit first.
Doing a little digging on the internet, I first found this schematic for a “sewer pipes ringverb“. Low part count and pretty decent sound. Pretty neat. It was inspired from another circuit called the Noise Ensemble. Seemed like a good place to start. I ultimately built this circuit.
It delivered. Delay and noise. If you take a look at the circuit, note the LED feeding into pin 6. Pin 6 is the VCO. The LED is driven from the LPF on the input. IT kinda is like a peak detector. A hard chord will get past the forward voltage (my best opinion at least) and push some juice into the VCO. The clock changes and you get a pitch shift. Kinda neat.
not super clean though.
