I did a few tube swaps in my Mark III

[psychodave]

Tonight I was messing around with my Mark III blue stripe simul-class and decided I would test different tube configurations. My main set of tubes is a quad of Sylvania 6L6's. These tubes are great sounding. They are tight yet have a lot of punch...like a good 6L6 should sound. My second favorite tube configuration is the Sylvania 6L6 along with Siemens EL-34's. The Siemens cut out some of the bottom end, but add throat and dynamics to the tone. The Siemens also make the tone brighter...yet darker. It is hard to put words to the exact tone...the brightness is more of a upper mid range thing. I also tinkered with the Sylvania 6L6's and a pair of GE 6CA7 big bottles. The 6CA7's were similar to the quad of 6L6's but they added a dimension that the Siemens didn't have. The 6CA7's also have this tasty "grind" to them. They were looser in the bottom end vs the EL34 and quad of 6L6's. Final conclusion... there is versatility with tubes, but I prefer the big sound of all 6L6's. To fully disclose my tubes, my preamp tubes are as follows: V1 and V2 old Yugoslavian 12AX7's (look like smooth plate telefunkens), V3 and V4 are Sovtek 12AX7LPS and V5 is a early 70's Tungsram. 8)