Pour être sûr ouvre-le mais je pense qu'il n'y a qu'une lampe.Voici ce que dit le manuel :
"A WORD ABOUT VALVES
n Valves need to reach a certain operating temperature. They need a few seconds
after the power has been switched on to warm up before they will work.
n Valves are sensitive to shock. Once you have switched the amplifier off, give it a
few minutes to cool down before transporting it.
n The sound characteristics of valves will also tend to change with time.
Occasionally, they will need replacing. The ECC 83 valve used in the BASSBASE is
one of the most commonly used, and the most affordable. Generally speaking, a
change of valves is only necessary every few years.
Before opening the amplifier casing, ALWAYS remove the mains plug!"