By the way Rec, it seems as per your post you are using Mullard ECC88's in V6 and V7. The ECC88 is the European designation for the 6DJ8. The ECC88 is not a 6DJ8 equivalent, but exactly the same tube as the 6DJ8. So, you are violating your own rule by using a 6DJ8 in V6 and V7. The E88CC (European designation), is the same as the 6922. Both the 6DJ8 (ECC88) and the 6922 (E88CC) fall into the same 6DJ8 "family" of tubes of which there are several others, including the 7308 (E188CC), the cca (This is the European designation. I don't think there is a U.S. designation.), the E288CC (European) and the 7922, etc. These "equivalents", while not exactly the same as either the 6DJ8 or 6922, are considered to be "premium versions" of the 6922. Generally they are considered to be safe to substitute for a 6DJ8/6922, but there are exceptions with certain equipment and certain circuits. The warnings of Superclamp and others notwithstanding, all of these tubes will produce a different sound in the CAT. The Telefunken cca at V6 and V7 produces the best sound I have ever heard from the CAT Ultimate. However, I am sticking with Telefunken 6922's (E88CC) in V6 and V7 until I get this V6 and V7 thing fully understood and resolved. Can anyone speak in detail about what the CAT can and cannot accept in V6 and V7 and why, reconciling this information with the extremely brief and unrevealing information in the CAT manual?