@krelldreams You mentioned, that in the RM 9, two KT120 or KT150 output tubes could be substituted for four EL34s in each channel. Is there an advantage to using fewer higher output tubes as opposed to using double the number of lower output power tubes, or vice versa? In other words, is the former following a “simpler” path than the latter?
The advantage lies in fewer tubes to fool with, a little less heater draw so the power transformer will run cooler and you get away from the tight matching of 4 tubes. The path is the same. The idle current will be the same. Might have to shift the bias a little. I know the 120s work. We have had several people do it. If I get a chance I will give the 150s a try in an RM-9. Might look cool having 4 x 150s in the front row.