Vacuum Tube Synthesizer


Lately The Peasant has been building a music synthesizer using vacuum tubes. Although this will be used as a percussion synthesizer, it could just as easily be controlled by a keyboard or a MIDI to CV convertor.

The first module built is a dual VCO. It is based on the VCO circuit from Eric Barbour's Phattytron, and has its own power supplies built right on the chassis.

Top view of VCO chassis


Bottom view of VCO chassis



The next step was to build a power supply for the rest of the synthesizer.

Schematic of the power supply


Sound files of the tube synth.

Using drum sticks with The Peasant's ribbon controller, a basic tube VCA as per Eric Barbour, and a simple diode/capacitor envelope generator, the following sounds were created. Ahhhh, the rich, full sound of tubes!

synw1.wav (412K)

synw2.wav (200K)

synw3.wav (391K)

synw4.wav (496K)

synw5.wav (189K)

synw6.wav (355K)

Here is the schematic of the envelope generator for the tube synth. It consists of a dc input amplifier, Metasonix 2D21 AD generator (Thanks, Eric!), and an ADSR circuit currently under development by The Peasant.

Preliminary schematic of the ADSR


Here is a picture of the prototype under development.

Zap, ouch, BOOM!! +/-150 Volts, anyone?


And some scope shots of the attack/decay section of the ADSR in action.

Analog storage scopes rule!


The next module built is a VCA/mixer/output module. This consists of 3 separate VCAs, one of which is a modified Eric Barbour design using an EF86 tube, and the other two are of the improved balanced design by Rene Schmitz. There is also a basic 3 channel mixer module, which includes an EF86 VCA and the final output driver for the tubesynth.

Front panel view


Bottom component/wiring view


Preliminary schematic


Stay tuned for more updates!