RO Experimental 12V Real-Tube Preamp PUBLIC

Richter Original Experimental 12V Real-Tube Preamp

Richter Original experimental 12V real-tube guitar preamp circuit. Controls Include: Bass, Mid-Center, Treble, Drive, Fuzz, Output Tone, Intensity, Feedback, and Volume. Employs one 12U7 dual triode (not a 12AU7) space-charge tube and two 12AF6 space-charge pentodes. Both tube types were designed to use a +12VDC supply-voltage for heaters AND plates voltages. They are available online at The Tube Store. https://www.thetubestore.com . Note that this circuit is not intended to provide much gain but just tube-type fuzz/distortion. Overall Gain +20 dBV (Vo/Vi = 10). Frequency Range 27 Hz to 16 kHz. Suitable for 6/7/8-striing guitar or 4/5/6-string bass. Recommend rack-mount implementation, with vibration-damping mountings. And use pads for the tubes to reduce vibration noise. Experimental circuitry. Untested design. No simulation. Breadboard test before final soldering. Power-supply not shown. Requires a regulated single-polarity DC supply providing +12VDC @ >= 500. House project in a grounded metal enclosure. No guarantee is implied. Build at your own risk. Example Power-Supply: 12V DC 1000 mA Regulated Switching Power Adapter, Product ID: 798. $8.95 each. From the AdaFruit website. https://www.adafruit.com . Notes On The !2U7: The 12U7 is a space-charge type of twin-triode preamp-tube designed to work and sound like a 12AU7, but using a +12V supply-voltage on the heaters AND plates. It is not a "starved" 12AU7, but a totally different tube engineered to sound like a 12AU7 operated from a high-voltage supply, and provides the same gain (mu = 20), despite the lower supply voltage. Notes On The 12AF6: The 12AF6 is a space-charge pentode, also operated from a +12V supply, but sounds different than standard tubes, such as a 12AX7 at high-voltage. Not as warm, with less smoothness on the lows, and less headroom. Tight and controlled rather than lush. However, it provides bright mids, crisp upper-mids, and edgy highs. It is thus more "snappy" (i.e., has faster responsiveness) than normal tubes, and produces a pleasing soft-clipping tone when overdriven, emphasizing even-order harmonics, for a sweet type of distortion.