Best I understand, and I am new to this, is that in the family of 6DJ8 tubes which are used in the AH preamp, the 6922 and 7308 designations were premimum versions of the 6DJ8 rated as 10,000 hours with 6922 the premium industrial version and 7308 the guareenteed low noise version. European designations for these same tubes are the 6DJ8=ECC88, the 6922=E88CC, and the 7308=E188CC. According to Joes Tube Lore:
The Siemens E88CC is characterized by warm, lively, palable and real quality to individual performers, not recommended if your system is already bright. The ECC88 is similar with a slightly forward balance, the E188CC is preferred by him to the cca as slightly warmer, more vibrant and wetter, and is his favorite Siemens, though he prefers Amperex. He describes Siemens cca's (Victor's favorite)as pricey, slightly more dimensional, transparent, and focused compared to these others but lacking a bit of bass punch and slightly dry in comparison. And best I understand the early sixties version of all these tubes tend to be better than late sixties and newer. These early version ofetn come in yellow/blue boxes and have all gray plates. Later version may be in orange/blue boxes. A full guarenteed quad of early cc'a is currently selling on ebay for about $1,600 which puts them out of my league if I want to stay married, which I do:). Hope this helps. Anyone agree or disagree with the descriptions or terminology?
