The extra ruggedness of the 6550EH was engineered with the punishing abuse of guitar amps in mind. The nickel steel side rod mica supports ensure that the 6550EH will hold up in even the most punishing environment of high powered bass amps like the Ampeg SVT and combos where the tube is only inches from the speaker and still deliver the sweetest tone of any 6550 or KT88. The 6550EH will greatly improve the performance of any amp.
Great Review by Martin
Replaced the stock valves in an ENGL Savage head with these, noticeably better bass response and higher output, very pleased, and extremely quick delivery once again ! (Posted on 16/08/2012)