Your amp has output power tubes which can be hooked up as pentode or triode by flicking a switch. The pentode choice will give you about double the power of the triode hookup. If your speakers need the power you might hear better dynamics in the pentode mode. Sometimes the triode mode will give you a sweeter sound. Since it is easy to switch just try both settings and see which you like better. On amps like this that I have owned I usually like the pentode mode better. The triode mode is usually a design compromise
Alan
Alan