The Avalon ST-4 Spare Tube Kit is a package that includes four matched military 6922 tubes. These tubes are suited for the Avalon S747P compressor and the Avalon VT-737SP Mic Preamp.
The main features of the Avalon ST-4 Spare Tube Kit include:
Four matched military 6922 tubes
Tubes suited for Avalalon mono Class A mic preamplifier-compressor-EQ (VT-747SP) and Avalon stereo vacuum tube opto-compressor and program equalizer (VT-737SP)