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OK, so I just picked up a used Triwatt and it came loaded with KT66s. I played with it for a while and was not impressed at all. It was brittle and had no guts at all in any channel input. So to satisfy my curiosity I opened it up to see the tubes and check if anything was obviously burnt out (I AM NOT AN AMP TECH). What I found was the power tube switch was set to 6v6. Obv not a good thing. I switched it to KT66 and some life came back to the amp. More bottom and a fuller range of sound were evident. But, it's still not very loud at all. I am now thinking maybe the bias is off? I would love to check myself and save myself the trip and tech fees. I have a multimeter but I have no idea how to do this or how to adjust? Is this crazy? Let me know.

I have my bias set at 35ma when running KT66. My Triwatt is seriously loud. Cranked, I can’t be in the same room with it. Lol There are bias test points on the rear of the amp. The black one Is the ground the two red ones read one tube at a time. There is a trim pot above the black socket that you put a screw driver in to adjust the bias. It’s very important to have that switch set to the KT66 setting. If your tubes start glowing cherry red, they’re red plating and are under biased and are getting too much voltage. The Triwatt is a great sounding amp with KT66 output tubes.

Thanks for the guidance Brodie!
I am on it.

No problem. I hope it helps.

It was a huge help. It's all dialed in now and now the amp, along with all of my pedals, just sound better.

To adjust the bias on your Triwatt amp, I suggest using a multimeter to measure the current flowing through the KT66 power Block Blast tubes, typically at a test point on the chassis or with a bias probe.