Difference between Siemens CCa & 7308

The top end of the CCa is more refined, and the CCa's image is larger. It's not a big difference from the 7308 (E188CC), but it's a difference that most people would discern, IMO. Whether the cost/benefit ratio of the CCa is worthwhile is something for each individual to decide.

The price of CCa tubes is only going to rise (along with other tubes). IMO, buying a pair to hear, and reselling if you don't like them, is a zero sum game.

10-02-07: Audiofeil
I'd opine that in most systems a good 6922 or 7308 will suffice. To fully appreciate the nuances of Cca, the other system components must be a very high level.

True. System resolution is key. Unfortunately, unless we've gone through some system iterations and heard resolution improve or decline, many of us don't know where our system's resolution lies on the scale.

I do agree that most people would be quite happy with a good Siemens E88CC or even a good Siemens ECC88. Amperex, too.

The only Siemens CCa to own is the grey riser version from the late 50s through mid 60s. Period. Big air, big soundstage, deep and tight bass, and wide image.

Otherwise, one might as well buy Siemens E188CC (7308) or E88CC (6922), which are excellent in their own right, and less expensive than CCa versions with shiny risers or thin getter supports.