Stompbox Converter

 Had a couple questions about stompbox use with line level, so I drew up this. This allows you to drop the line level signal down to instrument level, send it out to whichever stompboxes you want to use, then back and amplified back up to line level. Schematic and discussion here. Made two versions, one that could be run off typical +9v pedal power, and another for bi-polar 12v supply used in Eurorack synths, so you can build it either in pedal form or Eurorack module form.

Square Wave Oscillator

Came across this Instructable the other day and thought it would be a good addition to the library. Would be a good first step into the synth world and apparently plays nice with guitar pedals. Already built it myself and it works great, and fits nicely in a 1590G.

 

Parasit Studio 8-Bitar

For Fuzz Friday, here's a really cool design from Parasit Studio:

The 8-Bitar is a minimalistic octave down pedal with a 8-bit sound (glitchy and gated square wave fuzz). It's small enough to fit inside a 1590A without any special parts.

The design goal with this pedal was to achieve the core octave tone from the Arcadiator, but with as few components as possible. I'm happy with the result since it only uses one chip (a CD4069).

Usual caveats apply for getting the best tracking - humbuckers, neck pickup and tone rolled off.

Death by Audio Robot

For Fuzz Friday, here's another wild and wacky one from DBA:

The Robot is a low fidelity 8 bit pitch transposer with absolutely no feelings what-so-ever. It is completely synthetic and transforms any input into a spuree of resynthesized robot jargon.

Originals need a dedicated power supply as the HT8950 chip runs off 2.4-4 volts and the power section of the original will not play nice daisy chained with other pedals. To make it a little more user friendly, I've altered the power supply to use a 3.3v regulator (LM1117V33C or similar, though watch the pinout). Here's my modified schematic:

Note: I've also included 4 extra pads on the PCB layout in case anyone wanted to do the mod lvlark describes here.

Korg MS-20 Filter

Switching it up this week and doing a Filter Friday. This one could be used for both synth and guitar/bass. It's a cool filter effect based around the LM13600/13700.

Galactic Fissure

I thought I'd close out Synth week with a fuzz designed specifically for synths. (Fuzz Friday waits for no man!) This one is pretty straight forward and I don't have much to say about it. Schematic can be found here. I added a pull down resistor to the input in case some one builds it for guitar, as well as polarity protection and power filtering.

Devil's Triangle Drone

Here's a synth circuit from Paul in the Lab (schematic and sound samples can be found over there). I've laid it out for board mounted pots with the board vertically in the enclosure. See the drilling template in the library for a visual. Here's what Paul had to say about it:

This is a project based largely on the put up or shut up mentality, for quite some time I've been getting annoyed at seeing youtube videos of people pissing about with these "synths" which are basically boxes of 555 timers with a million knobs that make stupid noises that you couldn't ever actually use in music so I thought I would make my own little synth that would get repeatable sounds and be useful in music and what better type of synth? a droner type - basically cause I love bagpipes - I like drones.

Anyway the circuit itself is quite a simple one basically because I only designed it during the week, all it is really is 3 triangle wave generators configured to operate in the audio range going into a mixer op-amp configuration with the odd filter here and there to soften the waveforms
I've used LM358 op-amps cause they are the cheapest, I'm not too sure if others would work in the same way though they probably will.

Why call it the devils triangle - well it has 3 oscillators one of which can oscillate a slightly high pitch range (for melody) it also sounds demonic so the name fit.

If you want to implement on/off switches for each oscillator, replace these jumpers with on/off switches.

Four Step Atari Punk Console

I thought I'd mix things up a little this week and post some synth circuits people might be interested in. To start things out, here's a modified version of the classic Atari Punk Console. This has a few additional potentiometers for more control and a more versatile version of this popular synth.

In the layout below note that VR stands for variable resistor as the schematic I laid this out from didn't have names for each control (there are 6, labeled A through F).

Pardon all the jumpers, 555s are uncooperative for single sided layouts. Haha

EarthQuaker Devices Bit Commander

The Bit Commander is an synth/octave effect that's all analog. It creates square wave synth tones across 4 octaves (2 up, 2 down) and it's capable of creating a wide range of sounds. The octave down effect is generated from the ICs, while the octave up comes from the 4024 and transformer (kind of like an Octavia). From EQD:

Like all analog octave effects, there are some basic rules to follow that will get you the most enjoyment from your Bit Commander. Use the neck pickup and play single notes. The best tracking occurs from the 7th fret up on all the strings. Below the 7th will still track but there will be occasional glitches and stutters. The lower the note, the harder it is for the Bit Commander to register. The use of Bass and lower registers on keyboards will yield unexpected, sometimes pleasing, sometimes disgusting results. These are not mistakes or flaws, it is the nature of analog octaves.