The new tubes are GT6L6-R2. Groove tubes selected SED winged=C=. They are quite similar to the Mesa 6L6GC STR420 with the exception that the internal orientation is inverted on the STR420's. I thought the 7581 (30W versions) were great before they went flat, the GT6L6-R2 are much better. Nice rich harmonics, great saturation, more bass response than the 7581, more mids, just better tubes in all respects. The next best tone I have discoverd was an integral quad of 6L6GCSTR440 in center and 6L6GCTR420 on the outer positions. (only spares I had available that were not in use). I have found that I needed to drop the bass a bit, not too much but enough to keep the wall onrnaments on the wall. I have also rediscovered that the effects loop alters the tone so I am no longer using it. I can vibrate the house in all modes, that reminds me to remove the casters from the cabinet. The SED's are Awsome ! Groove Tube rating is a 4 on all tubes. As before, I requested tubes for the MARKV from Doug.
The high frequencies are not as harsh as they were. I had a few EH tubes left over when I retubed the Mark IV. All tubes are EH12ax7 and final drive is a quad of Svetlana (new sensor) tubes. Tung Sols are also manufactured by New Sensor. I have been very pleased with the Svetlana 6L6GC in the Mark IV so I thought the Tung Sol 7581 may be a good choice. Hopefully the SED' last a bit longer. I hope they last as long as the original Mesa 6L6GC STR420's I had in my Mark IV (while they were in the IV that is. After 13 years of use in the IV, they did not last very long in the V. I have some NOS STR420's on hand since I bought them as spares when I purchased the MKIV, also a pair of the Original STR440's that were in the outer most sockets that remain undamaged after redplating the inner two. Still unclear on the redplate problem, it has not happend since I rebuilt the 412 cab. More than likely a bad tube.
The high frequencies are not as harsh as they were. I had a few EH tubes left over when I retubed the Mark IV. All tubes are EH12ax7 and final drive is a quad of Svetlana (new sensor) tubes. Tung Sols are also manufactured by New Sensor. I have been very pleased with the Svetlana 6L6GC in the Mark IV so I thought the Tung Sol 7581 may be a good choice. Hopefully the SED' last a bit longer. I hope they last as long as the original Mesa 6L6GC STR420's I had in my Mark IV (while they were in the IV that is. After 13 years of use in the IV, they did not last very long in the V. I have some NOS STR420's on hand since I bought them as spares when I purchased the MKIV, also a pair of the Original STR440's that were in the outer most sockets that remain undamaged after redplating the inner two. Still unclear on the redplate problem, it has not happend since I rebuilt the 412 cab. More than likely a bad tube.