Of every factory that built the E88CC, Telefunken's is the output collectors rank at the top, and this one carries the proof on its own stem bottom rather than asking you to take a printed label's word for it. About as good a starting point as exists for a line stage or a phono front end.
Tested on the Tesla BM-215A. Both sections tested very strong, reading well above minimum.
E88CC ~ 6922 ~ CCa ~ CV2492 ~ 9622 ~ GL-6307
The ECC88 and 6DJ8 are the same tube in standard commercial grade rather than Special Quality. The 8416 differs in heater rating and is not a substitute.
The E88CC arrived in 1956, designed for computer and cascode work rather than for music. Its frame grid holds the grid to cathode spacing far closer than a conventionally wound grid can manage, which is where the very high transconductance comes from, while the CC suffix marks Special Quality: tighter tolerances, a longer rated life and testing far past anything a consumer valve received. Professional instrument builders took it first, and audio designers followed once they worked out what a high slope low noise triode does in a preamplifier. Telefunken's version has become the benchmark, which is exactly why the type attracts imitation, and why the diamond moulded into the stem bottom between the pins matters: it is a feature of the glass press itself, not something printed on afterwards, and it is the difference between genuine West German manufacture and a Telefunken label applied to somebody else's valve.
Boxed, unused, diamond confirmed and testing very strong. This is the one you stop searching after.
SKU: 74