CATALINBREAD / Knight School Synth DIY Kit

The Knight School Synth DIY Kit is a kit for building your own compact guitar synth pedal. Assembly is easy, requiring only a soldering iron, solder, wire cutters, a hex wrench, and a screwdriver.

This pedal is a DIY history of Catalinbread. Before college, I learned how to make breadboards and read schematics and created many of the circuits posted online on breadboards.
Then I discovered a new DIY website. One of the world's leading DIY sites is Beavis Audio. One of the projects posted there was called “Heterodyne Peyote Space Explorer.
I learned about the CD40106 chip from this project and spent a lot of time tuning that device while taking the EE class.

When I combined the CD40106 chip with the boost circuit I was developing at the time, it produced some strange noises. However, improvements could be made to make it cooler. When we incorporated the boost circuit, the operation improved. I didn't know why, but I thought it was cool, so I made one for a friend. Then I found Tim Escobedo's Circuit Snippets web page. I compared his circuit analysis with mine and made a new “discovery”.

The Knight School Synth DIY Kit is my most ambitious project. It is a guitar synth pedal completed by using Tim Escobedo's method of pre-gain generation.
The pedal converts the guitar signal into square waves and modifies the pulse width using a CD40106. There is an LFO to modify the pulse width and a Depth control to modify the shaping.
This effect emulates the monophonic synthesizers of yesteryear.

■ Controls
RATE: Adjusts the variable pulse width speed of the LFO from low speed to ray gun.

LFO TOGGLE: Turns the LFO ON/OFF; RATE and DEPTH do not function when OFF.

VOLUME: Adjusts the volume.

DEPTH: Adjusts the depth of the LFO. Lowering the value makes the effect softer, and maximizing the value makes the effect more dramatic.

PULSE: Modify the pulse width of the squarewaved guitar signal. It can be thought of as the flavor and character of a synthesizer. From high pitched sounds to thicker, deeper tones, you can adjust the tone by listening to the sound like a “half-stopped wah”.

Power Supply
Knight School Synth operates on a 9V DC power supply (minus center) with a minimum of 0.5mA.

DIY KIT
The kit board shows which components are to be placed where.
The resistors included in the kit are as follows.
1K: Brown/Black/Red/Gold
10K: Brown/Black/Orange/Gold
33K: Orange/Red/Red/Gold
47K: Yellow/Black/Orange/Gold

■MOD
The following are some of the less common modifications that can be made at your own risk.

Change the LFO speed
The 4u7 electrolytic capacitor controls the range of the RATE knob. Increasing the value shifts the range down and decreasing the value shifts it up.

Bass Mode
As with many guitar pedals, increasing the output capacitor increases the range of the device. This circuit uses a 100n capacitor, and a larger value will slightly enhance the low end.