This is the Gold Pin Option Retube Kit for the Mesa Strategy 400 Power Amp. The preamp section uses four Matched and Balanced Gold Pin ECC83S's for a very smooth and rich tone. The default power tubes are a matched octet of the JJ Electronic 6L6GC’s and a matched quad of the JJ E34L's. With the Customize option you can configure this kit to use an octet of the JJ 5881's and a matched quad of the JJ EL34’s, EL34II's, E34L's, KT77’s, the big bottle 6CA7’s or even a quad of the JJ KT88’s. These can all be run in the EL34 sockets (the four sockets closest to the back of the amp) with no bias mod necessary!
These amps are fixed bias with no adjustment. The 290 is a Simuclass amp and can run a quad of 6L6GC's along with a quad of EL34's, E34L's, KT77's and 6CA7's. Please see the addition views which explain where to run the tubes depending on which version you have.