Pretty much every synthesizer has a lowpass filter, but far fewer include a highpass filter. Today I’d like to take a quick look at a few that do. I’m leaving aside synths that have more sophisticated multimode filters that can be set up as highpass, and just looking at the few that included a simple […]
I’ve often seen it said online that the LM13700 is just two CA3080’s in one package. Even by one of the co-designers! While it’s almost true, it’s not exactly right, and the little differences are sometimes important, so I thought we could take a look at what the differences are. Luckily we have schematic diagrams for […]
The Jupiter 4 was Roland’s first polysynth in 1979. Given that the Prophet 5 had been released the previous year, Roland were definitely playing catch-up, and the design looks notably less “modern” than Sequential’s game-changing instrument. Nonetheless, the Jupiter 4 is well thought of and sounds great, with a character of its own. It’s the […]
We’ve recently started stocking Alfa’s clone of the famous old Roland IR3109 filter chip. This is the chip that was inside a ton of Roland synths, including the SH-101, Jupiter 6 and Jupiter 8, Juno 6/60 and even the Juno 106, although in that case it was hidden in a potted module! I thought it’d […]
Let’s continue our deep dive into analogue drums with a look at something even earlier – the Korg KR-55. This is a preset drum machine from 1979. It uses a Read-Only Memory (ROM) to store patterns, but it has no processor, unlike the Boss Dr. Rhythm we looked at. Consequently the digital side of this […]
I was exchanging a few emails with a customer recently, and they suggested designing a chip that allowed you to define an LFO shape with a set of controls – obviously sliders would be perfect for something like this, like a Graphic EQ for LFOs! The idea was that you’d have some waveform sliders, plus […]
I’d like to share a couple of things I’ve had kicking around on my desk for a long while. They also show a couple of ways to use vactrols. One is a simple optical tremolo, presented below, and the other is a modulated delay effect. StompLFO Optical Tremolo One very simple way to produce a […]
Last time we looked at reconfigurable filters, filters that include switches to rearrange parts of the circuit during normal use. However, that’s not the only way to produce different responses from a single filter circuit. This time, we’ll look at another approach: pole mixing. “Pole mixing”? It sounds like stirring a cake with a broom handle… […]
The LM13700 is a bonafide classic synth chip, plus it’s cheap and *still* available decades after it was originally introduced. Ok, it’s no longer the state of the art, and its noise and distortion figures are pretty poor, but that’s actually a part of its charm. It’s definitely got that “vintage sound”. So let’s have […]
The TR-909 uses a hardware implementation of an LFSR as its noise generator. We’ve dealt with LFSR noise generators in a few other articles, but we’ve only looked at firmware implementations, so it might be fun to see how the same thing is done in hardware. The circuit is composed of three parts; the shift register […]
