I still use a McIntosh C20 stereo vacuum tube preamp from the late β50s in my office. First Mac pre with a glass faceplate and the last with a vacuum tube rectifier. Itβs still 100% original: tubes, caps, incandescent bulbs. Never needed to clean the potentiometers. Those original Telefunken 12AX7s and 12AU7s are approaching 70 years old! As is the vacuum tube rectifier with its soft start which probably contributes to the continued life of the capacitors. That, and everything in there is run at a very sane B+ rail. It still sounds great though admittedly highly colored in a very tubular way π.
