Chico Fuzz
I recently was given a dead handmade fuzz (no schematics or any info whatsoever) for repairs. I drew its schematic and found it quite interesting and unusual...
Posts by Year
2021
Adding Libraries to OrCad Capture
Do you have some .lib and model files and can’t make them work in an OrCad simulation? I sure had this problem before, and before going crazy on stack exchan...
Wien Bridge Oscillator
A variable Wien Bridge Oscillator, including an output stage. I built this one beacuse I needed a decent(ish) sinusoidal generator for testing. Distortion is...
Voltage Controlled Amplifier
A single 9V supply voltage controlled amplifier based on a discrete OTA topology. Input amplitude must be adequately small as not to saturate the OTA. The vo...
Balancers
Here are a couple of circuits I’ve designed to convert an unbalanced signal into a balanced one.
Tremolo
Simple tremolo circuit using LDR’s. Besides amplitude modulation, there’s an one pole low pass filter modulation in tandem. LFO is a relaxation oscillator, w...
Ring Modulator
A transformerless diode ring modulator. The summing and subtracting of the carrier and modulation signal are done using opamps, with a differential amplifier...
Phaser
This is my first try at a phaser, and I have to say that I’m very pleased with the result. I started this project by delineating some design guidelines:
Ladder VCF
This is my go at the classic transistor ladder VCF. The twist here is using a single 9V supply and trying to keep it as simple as possible. The response is l...
Envelope Filter
My take on the classic Mutron envelope filter using a single supply (the Mutron uses dual +9/-9V). The envelope follower is quite different, but it’s easier ...
Booster/Buffer
This one was one of my first designs, and arised out of a necessity to have a preamp and a booster to facilitate my experimentations. With this nifty little ...
One Transistor Booster
My goal here was to design a very simple booster using only one transistor. No tone shaping is intended, though different cap values could be chosen for some...
Log Pots For All!
Audio circuits often use logarithmic and anti-log/reverse log potentiometers. Frequency and volume controls come to mind. Those kinds of tapers (especially t...