EL 34 tubes

agree w others here who have mentioned new production russian ’reissue’ gold lion kt77 and mullard/tungsol el34’s are the best of the lot

as with most tubes, they need some burn in time to settle into their true sound character

Langrex has some Winged C Svetlana tubes that are sold as quad matched pair and sound good. I ran these in my Air Tight amps with great success. I would also second the Gold Lion KT77. Jeff Day at a positive feedback likes the Sophia EL34s in his Leben but they are pricey.

Word is that the 6L6 might be interesting too, assuming you have a CS600.

JJ EL34's are a good recommendation. And they are not made in Russia!

@jasonbourne52

i have had poor luck w JJ EL34’s in the past in both sound quality (harsh treble and mids) as well poor reliability ... but others seem to have better experiences more recently

KT77 will give you a uniform top to bottom sonic presentation. They are very transparent. I found to be to be light in the mid and upper bass. 7581A is in the 6L6 family and has a beefier bass sound and is tonally more dense. Have fun!