An LED bargraph audio level display

Posted by & filed under PIC/Programming, Projects.

Replacing the LM3914/LM3915/LM3916 with a PIC Most designs you see for audio level LED bargraph displays use the LM3914/LM3915/LM3916 series chips that are no longer made. However, the chips are simple, so we can replace them with a PIC and build a nice LED bargraph driver on a single chip. So why do you need this thing? You need this if you want to display an audio level and make sure it doesn’t go above some well-defined threshold, usually the level at… 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 that way 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 do!… Read more »

Experiments with variable rate drum sample playback

Posted by & filed under DMX, Linn, LinnDrum, Oberheim, Projects, Synth DIY, Vintage synths.

Or how to get a vintage 1980’s drum machine sound without selling your kidneys! There was a discussion on the SynthDIY mailing list recently about how the early digital drum machines like the LinnDrum or the Oberheim DMX used to change the pitch of drum sounds by simply changing the sample rate. They literally just played the samples back faster or slower, exactly like speeding up or slowing down a tape recording. At the time, this was relatively easy because… 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 »

Adding Vintage Hiss, Crackle, and Pop!

Posted by & filed under Noise, Projects, Synth DIY.

In general, we’re trying to keep noise out of our circuits. Somewhat inspired by this thread on DIYStompboxes, I thought it might be fun to build a circuit that could generate that “vintage background noise” sound so that I could make things sound like they’re being played back off a phonograph cylinder or an ancient 78rpm record or something. It’s been an interesting little challenge and made me look at some different circuit elements and try a few different things. First,… 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 »