Mesa did state the IIC+ reissue was suitable for EL34 in the Class A sockets. Even Mike West stated it is best to use the older NOS EL34 tubes. This is more of a quality issue regarding current production EL34 tubes not holding up under certain conditions. STR450, STR442, STR416 would be suitable. The STR447 or others may be questionable. Bottom line, Mesa/Gibson decided not to include any mention of the EL34 as alternative use in the Class A sockets as this could be an issue as most NOS tubes with Mesa branding (yeah it has to have the Mesa logo printed on them to be acceptable to meet warranty requirements) may lend to issues as the STR447 or the STR446 may not do well in the reissue. Whatever the case may be. I do not have the reissue yet. Still waiting and waiting, and well not sure it will come this year. Perhaps by April, I may see it. That did get upgraded to March then to February. If everyone drops off the list I may see it sooner. This has nothing to do with supporting the heater current. This is not 1960. I doubt they skimped on the windings to support the heaters. Perhaps KT88 or 6550 tubes may pose some issues. It is more of the bias voltage at the control grid of the class A sockets. Is it low enough to support EL34 effectively or is it too high (in magnitude) that ends up with cold tubes?
If you want that 6CA7 effect with 6L6 tubes, just leave the STR445 in the Class A sockets and change what you place in the Class AB sockets. The STR445 do have some 6CA7 characteristic sound to them. Actually, I am curious to find out how the reissue will sound with the stash of Mesa tubes I have. NOS STR415, NOS STR454, NOS STR440 (they became NOS when the company closed shop due to fire), current STR441, STR443, STR448. Since it is Simul-Class, you do not have to run the same tubes in the amp. Blending STR415 in Class AB with the STR445 in Class A may be interesting. I actually like the blend of the STR448 with the STR445 in the Mark VII but that runs full pentode at 90W. the triode/pentode thing may be different with the EL34 in the Class A. At this point, I no longer care. Mark III DRG sort of lost its flavor with all 6L6GC tubes. The EL34 were ok but not as nice as the 6CA7 STR416 tubes. I am sure some remember the 90's when you could not find any Mesa power tubes. Nothing but Groove Tubes or Sovtek tubes of unknown origins back then. At least in PA/NJ the tube availability was rather scarce in most shops that carried Mesa amps.
