EL34 upgrade

I replaced the original Svetlana EL-34's with a matched quad of Genelex Gold Lion KT-77's ..... my Rogue Audio Cronus sounds better than before.

I second Maxmads' suggestion re the NOS Tesla EL 34s. There is some info on an Audiosociety shootout against a host of tubes in blind tests in which they came out on top. I hopefully can find the file of the shootout and post it.

Mesa Boogie, the guitar amplifier company, has a cache of NOS Siemens EL34 that are offered as matched pairs on their web site store, directly, $150/pr. These are re-labled Mesa STR-450 tubes, after surviving stringent testing on Mesa's proprietary tube tester. They are well worth the price for any EL34 amp, and will improve upon any current production EL34. The supply is fixed and won't last forever, but guitar players are mostly cheapskates about this sort of thing, so these tubes are around for now.

Phil

There's already a highly active pre-tube discussion thread called "12ax7 vs 5751". I think you'll find it a highly active forum for pre-tube advice. Enjoy yourself. Generally many EL34's last for about the same amount of time. Some are significantly less reliable (current production Tesla/JJ seem to have a high failure rate). Most have found that many NOS tubes seem to last much longer (well maintained Mullards seem to last forever). In my guitar playing days, I found that Mullards, RCAs, RFT's, and pre-Sensor Svetlanas all seemed to last longer than JJ, EH, or Sovtek. These are just my findings. I haven't lived with the Treasures long enough to comment on their lifespan.

And yes tubes definitely have a burn in time. Even if you don't believe the sound changes, they definitely take a while before the bias will settle down. I find the better tubes tend to take a little longer to settle down.

Yes output tubes have a break in period. With 6550's is usually 10-30 hrs. Depends on the amp and the tube.