Investigations into what a BBD Chorus unit *really* does

Posted by & filed under BBDs+Delays, Chorus, Flanger, Stompbox stuff, Synth DIY.

I’ve been curious about Chorus for a while, since I’ve been working on and off with chorus design myself. There were a few things I didn’t understand, like what the relationshp is between the modulation LFO’s waveshape and the frequency modulation of signals going through the chorus. You’d think that if you use a sinewave to modulate the BBD clock, you’d get a sinewave modulation of frequency, right? Wrong! So what do you get? At this point, I realised that… Read more »

Useful design equations for the PT2399

Posted by & filed under Stompbox stuff.

The PT2399 datasheet gives some data showing the relationship between the resistor on pin 6, the clock frequency, and the delay time. Unfortunately, it doesn’t offer any design equations relating these three variables. So, can we derive some? Yes, we can! They’re all included here. First, a quick summary of what I’ve learned, if you want to cut to the chase: Delay msecs = (11.46 * Resistance KΩ) + 29.70 Delay msecs = (683.21 / Clock Freq MHz) + 0.08… Read more »