RO OpATube 2-Channel Preamp PUBLIC

Richter Original "OpATube" 2-Channel Preamp for Guitar

Richter Original "OpATube" 2-channel preamp for electric guitar. Channel 1 uses op-amps chosen for clean operation at all controls settings while Channel 2 uses a pentode designed for a +12VDC supply-voltage on plate AND heater. The channels can be enabled separately, and both have optional shunt-diode fuzz. [At least one channel must be enabled or signal stops.] Controls Include: Input Level, Ch 1 (Op-Amp) enable switch, OA Gain, OA Tone (Bass, Mid-Center, Treble), OA Level, Fuzz 1 enable switch, Fuzz 1 symmetry switches, Fuzz 1 Depth, Ch 2 (Tube) enable switch, Fuzz 2 enable switch, Tube Phase switch, Tube Tone, Tube Level, and master Blend. Frequency Range extends 20 Hz to 16 kHz with both channels ON. Maximum Gains: Ch 1 = 20 dBV @ 500 Hz, Ch2 = 20 dBV @ 1 kHz. Note: Ch 2 can potentially drown out Ch 1 with all controls at the same setting. This circuit gives the guitarist the choice of solid-state or tube sounds, or both. Solid-state in Ch 1 involves a higher slew-rate, for highlighting pick attack, note definition, and clean signal, while the tube in Ch 2 emphasizes even-order harmonics when overdriven, and gives more mellow tone. When enabled simultaneously, both aspects can be mixed by the Blend control, according to user preference. Power-supply not shown. Example Supply: Regulated +12VDC, 420 mA, 5W, XP Power VFL05US120-US-JA, available at https://www.digikey.com . The tube is available from The Tube Store. https://www.thetubestore.com . The IC is available from most electronics supply houses (DigiKey, Mouser, etc.). Note: Channel 1 verified by CircuiLab. Channel 2 is untested. No simulation available. Breadboard test entire circuit before committing to a soldered build. House in grounded metal enclosure to prevent EMF interference. Rackmounting the project is recommended, with vibration damping on the mounts. And use a pad on the tube to help mitigate vibrational noise.