Tubulation: High-Gain Distortion PUBLIC

"Tubulation". A High-Gain Distortion Circuit for Electric Guitar.

"Tubulation". A high-gain distortion circuit for electric guitar. Uses two dual op-amp ICs and one dual MOSFET device to produce distortion similar to that of a 12AX7A dual-triode tube. Controls Include: Input Gain, Input Bass, Input Mid, Input Treble, Input Volume, Distortion 1 Drive, Distortion 2 Drive, Distortion 2 Gain, Distortion Tone, Distortion Attenuation, and Output Gain. The input signal is boosted by a JFET-input op-amp and sent to a Fender-style tone-stack and to the Driver Stage of the distortion circuitry. Distortion 1 is from a matched pair of depletion-mode MOSFETs (aka D-MOSFETs) whose output is boosted by an op-amp gain stage whose input can be overdriven to produce Distortion 2. The direct signal and distortion signals are summed in the Output Stage, and only the direct signal goes through the tone-stack. Range above 0 dBV is from 25 Hz to > 20 kHz. Thus, circuit is suitable for 6/7/8-string guitar or 4/5/6-string bass. Maximum gain = +33.5 dBV @ 4 kHz with all controls at 50%, or +51 dBV from 1 kHz to > 20 kHz with all but the tone and attenuation controls at 100%. Thus, this is a high-gain design with emphasis on mids and highs. The batteries can be replaced by a regulated single-polarity +12VDC power-supply providing >= 60 mA of total current. Not recommended for stomp-box applications; rack-mounting suggested. The Distortion Section is designed to accept a 12AU7A dual-triode preamp-tube as a direct substitute for IC3, with instructions given at the bottom of the diagram. The lower section was inspired by Craig Anderton's "Real Tube Distortion" circuit (from Guitar Player mag., Oct. 1981), and which used a 12AU7 tube instead of the MOSFETs. This circuit, however, was designed to accept either type of device, with the circuit shown as-is tentatively verified by CircuitLab's Frequency Domain Simulation. However, while verified, the design must be considered experimental regardless of whether IC3 or a 12AU7A tube is used. Breadboard test before committing to a soldered build. And house completed project in a grounded metal enclosure.