tomic601 is correct. the MC240 is pretty easy on tubes. not sure what speakers you are using but try both 8 and 4 ohm taps. usually one will sound a bit better. Also try some KT66s in the 240.
not sure if your 240 is original or not, but greatest improvement you can make is to add a film cap to the 100uf electrolytic cap in the feedback circuit.
Takes longer to remove the bottom cover than it does to solder in the cap, one for each channel.
not sure if your 240 is original or not, but greatest improvement you can make is to add a film cap to the 100uf electrolytic cap in the feedback circuit.
Takes longer to remove the bottom cover than it does to solder in the cap, one for each channel.