Digitech PDS-1550 Programmable Distortion pedal analysis

Posted by & filed under BBDs+Delays, Distortion, Overdrive, and Fuzz, Stompbox stuff.

The Digitech DOD PDS-1550 was a member of the 1980’s Digitech “Dual pedal” range. It’s a pretty weird thing, and that’s partly why I’d like to take a closer look at it here. During my analysis of this pedal, I’ve discovered its dirty secret. Let’s get one thing out of the way early on though – despite being called a “programmable distortion”, it’s not programmable in any sense we’d understand today. “Tweakable” is more like it. You can open up… Read more »

Flangelicious – A super-dooper flanger (Now in 2 versions!)

Posted by & filed under BBDs+Delays, Flanger, Projects, Stompbox stuff.

Flangers are generally regarded as one of the most complicated pedals to build. A typical design has tons of chips and lots of circuit elements. Flangelicious isn’t like that. By using a microprocessor to generate an LFO-modulated clock signal directly, we can get rid of a lot of the non-signal path stuff and add features whilst we’re about it. This gives us a much cleaner, simpler design for a flanger with a genuine fully-analog signal path. In fact, it can all be done with… Read more »

DIY 4 Second Digital Delay

Posted by & filed under BBDs+Delays, Projects, Stompbox stuff.

Recently I’ve been working on a four second digital delay with tap tempo and delay trails. There are lots of digital delay projects already, but the vast majority of them are based on the PT2399, which limits both the length of the delay and the sound quality.   A quick summary of the features: 0 → 4 Seconds of digital delay 12 bit/32KHz input, 16 bit/32KHz output Delay trails (tails) on/off Clickless effect in/out bypass switching Momentary/latching feature on bypass… Read more »

Noise Reduction with Companders

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

What’s a “compander”? It’s a simple way to make your circuit quieter! So how does it work? Let’s say we’ve got a fairly noisy effect, like a BBD. The basic idea is that you make quiet signals louder before you put them through the effect, and then you make them quiet again after the effect, and thereby make the noise quieter too. And that’s the clever bit! “Compander” is a compound of “Compressor” and “Expander”, since those are the two… Read more »

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 »