The first electronic amplification of sound was done with Vacuum Tubes. We have pre-amp, power and rectifier vacuum tubes among other types in New Old Stock from the golden era of American & European manufacturing as well as current production tubes from today.
Vacuum Tube - 6FG6 / EM84, Indicator, Tuning
Indicator tube with amplifying triode for use as tuning indicator or for modulation control
Vacuum Tube - 6DA5 / EM81, Indicator, Electron Ray
Electron-ray tuning indicator