Sonic Frontiers Power 1 Tube advise

In the Power 1, you can get more midrange bloom with Ei KT90 Type 3. Note we recommend them for the Power 1, but not the Power 2. We have also had a great experience with the Svetlana KT88 in that amp. Smooth and musical. DO NOT use the Tesla KT88. They have been very problematic. Then for even more confusion, there is a Chinese KT88 that looks just like the British classic Gold Lion. They were sold by Gold Dragon for a while, and have been unavailable, though we are supposed to get 100 or so soon. That tube is dependable, and sounds great with the little more extension at the tip top if that is what you want. Valvo never made a 6922. The ones you see being sold everywhere nowadays are older Tesla. We have some Valvo branded 6922 that are the real thing, made in Holland by Philips NV in 1964, but they are very rare.

On the Power 3, you would be better off changing out one pair of tubes in the Line 3 than changing the tubes in the Power 3's. As I mentioned previously, the Valvo ECC88 and E88CC you see at most every site are actually early production Tesla...and were never made by Valvo. Valvo was a German arm of Philips Holland, the same way Philips Holland bought Amperex in 1955. At some point they had Tesla make these ECC88 tubes for them, but remember this was the cold war, so it was not so cool to have "made in Czechoslovakia" on your product, so it was hidden. An experienced tube head can ID them easy. Does not make it good or bad...and in fact in the Pro 3 I hear they sound quite good. I might suggest though leaving your power 3's and doing the preamp tubes. More predictable, and more effective. You can change just two tubes and get a 10-20% bump in performance.