Vacuum Tube Preamp
Note: Click on images to enlarge VACUUM TUBE PREAMP The kit came with an unpopulated printed circuit board and a bag of parts - but no documentation. Fortunately, I was able to find a schematic online, as well as a few articles about the circuit. The PCB was good quality and was easy to solder the parts to. Power comes from a 12 VAC 1000 mA power adapter, bought separately. Assembly in-progress, showing PCB component markings PCB bottom Side view Schematic Diagram courtesy of: https://www.circuitlab.com/circuit/9vnehk/fever-6j1-tube-pre-amp-circuit/ Operation The preamp worked the first time I turned it on. The filaments glowed orange within seconds. (The blue lights are from LEDs that serve no purpose other than to look cool for dramatic effect.) I applied a sine wave to the inputs and observed an amplified sine wave on the outputs. The output signal was 180 degrees out of phase with the input signal. It was clean and its level remained remarkably constant throughout the a...