RM Experimental 12V-Princeton Preamp PUBLIC

Richter Modified 12V Princeton-Style Preamp for Guitar

Richter Modified experimental 12V Princeton-style preamp for guitar. Based on Fender 5D6 Princeton guitar amplifier, for use as a guitar preamp. Modifications include different tubes, circuit changes, and use of a +12V DC power-supply. Controls Include: Drive, Tone, Feedback, and Volume. Uses one dual triode and one pentode, both designed to be operated using a +12VDC supply-voltage on plates AND heaters. No output transformer. No speaker. Overall Gain +20 dBV (Vo/Vi = 10). Frequency Range 31 Hz to 16 kHz. Perfect for 6/7-string guitar. Power-supply not shown. Requires a regulated single-polarity DC supply providing +12V @ >= 500 mA. Experimental circuitry. Untested design. No simulation. House project in a grounded metal enclosure. Example Power-Supply: 12V DC 1000 mA Regulated Switching Power Adapter, Product ID: 798. $8.95 each. https://www.adafruit.com . Notes On The 12U7: The 12U7 tube is a space-charge type of twin-triode tube designed to work and sound like a 12AU7, but using a +12V supply-voltage on heaters AND plates. It is not a "starved" 12AU7, but was engineered to sound like a 12AU7 operated at high-voltage, and offers the same gain (mu = 20). Notes On The 12AC6: The 12AC6 is a space-charge pentode also designed to work off a +12V supply-voltage. Its sound is reported to have a warm and smooth character. No harshness. Slightly rounded tone, with natural mids, low noise, good clarity; not soft or mushy, and adds no coloration (is transparent). More linear and harder to overdrive than high-voltage tubes, and with little/no compression. Cannot be compared to a specific high-voltage tube but does offer pleasing, clean, neutral tone. It's ideal for amplifying the sound of overdriven 12U7 triodes without alteration.