While playing the guitar many times there is a problem that unwanted noise can appear. Hence the need for a guitar noise gate. It happened specifically to a high-gain circuit is very sensitive to the surrounding radio signal.
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.