I had an E-mail from someone who went to RMAF and noted an ARC ref 75, tubed with KT150's. I contacted the manufacturer, whom I won't name, but is a well respected US company. He kindly replied saying the KT150's are a straight swap with the same bias setting and no modification required. He also said he thought the sound was a real upgrade. I had already been told by a retailer for ARC, he thought this would be the case, but may not apply to larger amps using more tubes, such as the Reference 150.
When I have some time, I am going to be brave and find some KT150's and give it a go.
When I have some time, I am going to be brave and find some KT150's and give it a go.