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 - 12A6, Tetrode, Beam Power
Heater-cathode type beam-power amplifier tube designed for use in the audio-output stage of ac or ac/dc receivers.
Vacuum Tube - 6C9, Dual Tetrode, Sharp Cut-Off
6C9 is a duo tetrode contained in a 10 pin bulb. It is designed for service as a VHF RF amplifier and a VHF autodyne mixer. Except for heater characteristics, type 17C9 is identical.