RO 4-Stage Tube + Diode Fuzz PUBLIC

RO 4-Stage Tube Preamp With 2-Voice Shunt-Diode Fuzz

Richter Original 4-stage tube preamp circuit with 2-voice shunt-diode fuzz. Uses three 12V space-charge tubes. Controls Include: Input Level, Bass, Mid-Center, Treble, Drive, Fuzz 1 enable switch, Fuzz 1 symmetry switches, Fuzz 1 Depth, Fuzz 2 enable switch, Fuzz 2 symmetry switches, Fuzz 2 Depth, and master Volume. Both specified tube types were designed to work using a single +12VDC supply voltage on plates and heaters (originally a car battery). Note: The 12U7 dual triode (not 12AU7) has no other part number. Do not substitute with any other tube for the 12U7. The 12DZ6 does have substitutes, including 12EK6 and 12EA6. Both tube types are available at The Tube Store. https://www.thetubestore.com . Overall Frequency Range 20 Hz to 16 kHz with all controls at 50%. Suitable for 6/7/8-string guitar or 4/5/6-string bass. Overall Gain = +20 dBV (Vo/Vi = 10). This design should deliver a sound like the preamp of an American-made boutique guitar amplifier that uses two 12AX7 twin-triode tubes in its front-end. The fuzz has two separately enabled shunt-diode fuzz voices; one from standard diodes and one from Schottky diodes. The symmetry switches (SSw) set the harmonic content of the fuzz voices. For tube distortion, the input can be overdriven by a boost or overdrive stomp-box; V1 can overdrive V2, while V3 can overdrive V4, depending on control settings. Power-supply not shown. Example Supply: 12V DC 1000 mA Regulated Switching Power Adapter, Product ID: 798. $8.95. From AdaFruit website. https://www.adafruit.com . Experimental circuitry. Untested design. No simulation available. Build at own risk. Breadboard test before final soldering. House in a grounded metal enclosure. Rackmount implementation is recommended, with vibration-damping on the mountings. And put pads on the tubes to help mitigate vibrational noise.