It is a low voltage tube preamplifier, specifically guitar preamp. Uses 12AX7 or ECC83 tube. No complicated circuit. The circuit is similar to the famous old guitar amplifiers bright channel. Low voltage operation, does not require a separate anode and output transformer.
Low voltage tube preamp.
Low voltage tube preamplifier test
His voice does not want to write much, rather, here is a test video:
Nice clean and natural voice, with little deep voice and great dynamics, but I missthe power. The power supply to the DC to DC converter has been previouslydescribed in the circuit. BUT you must change because they are noisy, highvolume noticeable.