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 »

Analog Renaissance? The rebirth of the impossible chips

Posted by & filed under Synth DIY.

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 »

Multimode filters, Part 1: Reconfigurable filters

Posted by & filed under Elka, Filters, OB-8, OB-Xa, Oberheim, Synth DIY, Synthex.

What is a “Multimode filter” anyway? It’s a filter which can provide more than one response. So it might offer a choice of 2-pole or 4-pole lowpass responses, or it might be switchable between lowpass and highpass, or it might have lowpass, bandpass, and highpass outputs. There are basically three techniques for building multimode filters, which I’d like to look at in the three parts of this series. How do we build a multimode filter? The three techniques can be summarised… Read more »

A study of Sub-Oscillators (and Oscillator Waveshaping)

Posted by & filed under Korg, Oscillators, Polysix, Roland, SH-101, Synth DIY, Vintage synths.

This article is a look at sub-oscillators, a common tactic for fattening up the bottom end, particularly  in synths with only one oscillator, or only one oscillator per voice. Classic examples include the Roland Juno 106 and SH101, and the Korg Polysix. More recently, sub-oscs turn up on a lot of modern analog synths since they’re cheap to do and can add more punch and depth. The Arturia MiniBrute, Moog SubPhatty and most of the DSI synths include them. My… 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 »

Adventures in Top Octave Generation

Posted by & filed under Oscillators, Synth DIY, Vintage synths.

Can we make a modern reproduction of the classic top octave generator / top octave synthesiser chips of the 1970s, as used in classic string synths and combo organs? What would be involved? Can we improve on the originals in any way? This page is a summary of what I learned by doing it. A little background In the late 1970’s, many synth manufacturers were thinking about producing polyphonic instruments. One musical area where that was already done was in… Read more »

Timbral Evolution: Harmonic analysis of classic synth sounds

Posted by & filed under Phase Distortion, Synth DIY, Vintage synths.

This post is a place to gather my thoughts about one of the most important parts of synthesizer design: the timbral evolution of sounds. It also presents the results of my analyses of some classic synth sounds. There have been many methods developed over the years to achieve timbral evolution. The voltage-controlled filter is the first and most obvious. Pulse width modulation and oscillator synchronization are two more from the analogue era. Other later approaches include wavetables, vector synthesis, FM, phase… Read more »