RO 12V 1-Tube Guitar Preamp PUBLIC

Richter Original 1-Tube 12-Volt Guitar Preamp

Richter Original 1-tube 12-volt experimental guitar-preamp circuit. Controls Include: Input Level, Fuzz enable switch, Fuzz symmetry switches, Fuzz Depth, Bass, Treble, Drive, and Volume. Circuit is based on the output section of a Garnet H-Zog distortion unit but uses a single 12AL8 triode + tetrode space-charge preamp tube with an added shunt-type Schottky-diode clipping-array (for fuzz), a passive 2-band Baxandall tone control, and an output transformer designed to replace that of a Fender Champ, included to get the sound of an output transformer. Experimental circuitry. Untested design. No simulation. Frequency response and overall gain must be verified during breadboard testing. Calculated Frequency Range 20 Hz to 16 kHz with all controls 50%. Calculated Overall Gain Vo/Vi = 6.6 with all controls 50%. The advantage of using is a 12V space-charge tube is the relatively safety of a +12V supply-voltage on the plates AND heater (originally from a car battery), as opposed to the dangerous high-voltage typical with standard vacuum-tubes. Note: The triode section and tetrode section are said to sound like a 12AX7 twin triode operated at high-voltage, though the 12AL8 is at low-voltage. Expect the project to sound like the preamp in a boutique single-ended guitar-amp. The tube is available at The Tube Store. https://www.thetubestore.com . The transformer is available at DigiKey. https://www.digikey.com . An 8-ohm 10-watt resistor is at Parts Express (part # 004-8). https://www.parts-express.com . A ready-made off-the-shelf 12-volt power-supply is available at the AdaFruit website. The 12V DC 1000mA (1A) Regulated Switching Power Adapter, Product ID: 798. https://www.adafruit.com . Rackmount implementation is recommended, with vibration damping on the mounts. And use a pad on the tube to help mitigate vibrational noise.