FilterFX – 12dB/oct LP/BP/HP LFO filter with 8 waveshapes

Posted by & filed under Stompbox stuff, Wah, Autowah, and Filters.

The FilterFX project uses the Druid STOMPLFO to control a 12dB/oct state variable filter. A state variable filter (SVF) is chosen because this filter design offers highpass, bandpass, and lowpass outputs which gives us the greatest range of different effects. The LFO offers eight waveforms, including two random waveforms (one does those crazy sample-and-hold effects). Furthermore, the PCB provides for addition of an expression pedal to allow the filter to be used like a wah pedal (but don’t expect a… Read more »

Designing the Hard Bargain distortion pedal

Posted by & filed under Distortion, Overdrive, and Fuzz, Projects, Stompbox stuff.

For this post, I’d like to take you through the process of designing a pedal, from initial idea to completed PCB and pedal. Everyone has their own way of doing this, so I thought it might be interesting for people to see the way that I work on something like this. Pedal (or Synth) design is a combination of engineering decisions and aesthetic choices, and engineering in the service of those aesthetic choices. That’s what makes it so fascinating to… Read more »

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 »

One-shot Event Generator

Posted by & filed under Envelope Generators, LFOs, Projects, Stompbox stuff, Synth DIY.

Here’s something slightly different! Is it an LFO? Is it an envelope generator? Well, it’s a bit of both. It produces a one-off event like an envelope generator, but it has a selection of waves more like an LFO. It works by producing a single “ping” when triggered. A ping is like a mini-envelope. The rate and waveshape of that ping are variable (from 55 msecs to 2.5 seconds, and eight different shapes), and the single ping can be augmented… Read more »

TAPLFO 3C – Squashing the bug

Posted by & filed under LFOs, Projects, Stompbox stuff.

We’ve recently discovered a bug in the recently-released TAPLFO 3 code (how embarrassing!). The problem only affects the tap tempo feature of the TAPLFO3. Other chips like the VCLFO or STOMPLFO aren’t affected. We’ve fixed the code, and while we were working on it, we also improved the switch debouncing routine to be more tolerant of bouncy switches. We’re offering anyone who has an affected chip (a TAPLFO 3) a free replacement with the TAPLFO 3C. Please get in touch and send us your… Read more »

Electric Druid chips: The Next Generation

Posted by & filed under Envelope Generators, LFOs, Projects, Stompbox stuff, Synth DIY.

In the last six months, we’ve been very busy here in the Druid workshop, developing and testing new versions of our PIC-based chips. This work is now complete, so I’d like to introduce the new chips. Why bother? What was wrong with the old ones? Ok, there wasn’t anything much wrong with the old ones, but things have moved on since 2008 when most of them were originally developed – ten years ago already! Most importantly, Microchip have released a… 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 »

Boss MT-2 Metal Zone pedal analysis

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

The Boss MT-2 Metal Zone distortion pedal is one of the most complex drive pedals there is, and has probably the most sophisticated (and least understood!) tone control circuit on any mass-market pedal. It’s also quite a divisive beast, with some loving it, and others hating it. It’s a great pedal for modifications – easily available, cheap, and rugged. This article is a technical analysis of the different stages in the pedal, finding out what each part does to the tone…. 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 »