It’s been around ten years since I developed the original Druid NOISE 1B chip to produce good quality white noise. Finally it gets an update, and the new NOISE2 chip can produce pink noise as well as white noise, so there’s no need for external “pinking” filters. Here’s what it sounds like, white noise and pink noise: Here’s the spectrums for the two outputs. Note the scales on these two graphs are different, so you can’t compare one to the… Read more »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
We live in interesting times. For many years, people have been wondering if it would be possible to reproduce the old CEM (Curtis Electro Music) and SSM (Solid State Music) chip designs from the late 1970’s and early 80’s. We’ve always been told that there wasn’t enough interest to make such a thing commercially viable, or that the start-up costs of setting up a design ran into millions or hundreds of thousands of dollars that you’d be highly unlikely to… Read more »
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