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 »

CEM3340 VCO (Voltage Controlled Oscillator) designs

Posted by & filed under Memorymoog, MKS-80, Moog, OB-Xa, Oberheim, Oscillators, Prophet 5, Prophet T8, Roland, Sequential, SH-101, Synth DIY, Vintage synths.

To celebrate the 2016 return of the CEM3340 chip, I thought I’d do another page in my series looking at how various synths implemented classic synth chips (the others being CEM3320 Filter designs and SSM2044 LP Filter designs). This is especially useful right now, since many people have bought a few CEM3340s or V3340s for their own use and are looking around for circuits to use them in. If that’s your purpose, note that these are all synth voicecard circuits, so they’re… Read more »

SH-101 replacement processor – a feasibility study

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

The Roland SH-101 is a late-era analogue monosynth which uses a microprocessor to perform keyboard scanning and various related functions, much like the Sequential Pro-One. Since the original uP is a 40-pin DIP, it would be possible to replace it with a more modern 40-pin DIP uP, like the PIC 16F777, or with a modern surface-mount processor on a daughter board. This page is a look at the feasibility of this idea. Original Processor pins and functions The datasheet for the… 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 »