I am currently using the Calypso. I have done some tube swapping, and have currently settled on the Mullard 10M 12ax7 gold pin and the Amperex 6922 PQ white label. I have found this combination very musical, although I admit to being influenced by all of the 'tube lore' floating around out there. Unfortunatly, these tubes are hard to come by. I was using the Mullard M8137 (for the 12ax7 slot) prior to the 10M, and I must say it was also excellent. Those are easier to come by, and much less expensive. I haven't AB'd them in a while, but I don't believe there is a huge difference. Also, long plate Mullards should be good.
Of course, it is a matter of personal taste, system synergy, and the quality of the actual tubes that will ultimately tell which is best for your system.
John.
Of course, it is a matter of personal taste, system synergy, and the quality of the actual tubes that will ultimately tell which is best for your system.
John.