Replacement EL34 Mullard valves for Leben CS300X

6+ months ago I succumbed to temptation and bought a used CS300X over the internet from a German dealer. The unit was in very good condition and the sound quality has been excellent. Sadly one of the Mullard EL34 output valves has now failed and a second is about to go. I have no idea how to source a replacement quad set - though I suspect scarcity is the least of my problems. Finding genuine NOS at a reasonable price feels like a very tricky business. Does anyone have any guidance?

PS - I have bought a quad set of Golden Dragons to keep me going. I suspect there is some run-in required but it does seem as though some of the original magic has gone.
I would suggest trying a new production quad of the SED brand ....Jim McShane,Tube Depot etc.........I think you will be suprized at how good they are.
AES Antique Electronic supply, in Az. might help you, or point you in the right direction. Not sure.

They do sell the original CED winged C EL34 from Russia... I run them in my mono blocks and enjoy them immensely. I doubt seriously though they possess that SET like sound the orig Mullards possess... My understanding of these newly 're-issued' (remade) Mullards are that they are very diffferent from what they used to be.

Also, I understand NOS EL34 Mullards are quite expensive.

Do report back if you indeed find a source for those tubes... depending on price, I'd like to give them a try myself.

the winged C 34's have a very good midrange BTW... a bit more tubey sounding than some other 34's.

Good luck.
I replaced Xf1 Mullard EL34s in my SET monoblocks (where they're used as driver tubes) with the reissue Genalex/Gold Lion KT77s. Supposedly a drop-in replacement for EL34s, these KT77s have been absolutely amazing. Much clearer than the Mullards, which are supposedly the holy grail of EL34s. I have no idea how they'd sound in your amps but thought it was worth a mention. Dave
Doesn't the CX300 use EL84's?
Genelex/GL KT77s or Tesla EL34L Blue.
Have been through them all and those 2 have been the best for sound and reliablity.
agree with Jwmazur .. the 300X uses el84's
guitar amp thread

the tube store (canada )

tube subing website

vaccumm tube world ??

I'm not endorsing any of the above for purchassing or sourcing tubes from as I've no personal experience with most of them. I figured these links would help inform so some more intelligent choice could be made thereafter.

Only thing I'd also look into is the plate boltage or bias the maker of the amp intended for the tubes... although some are 'drop in exchanges, I'd prefer to know if I'm going to go another way... often minor voltage variances can and are acceptable.

I also agree with the mini remarks on the CED winged C the tube store posts.

if you need EL84... HAPPY GOOGLING!
Apologies everyone. It does appear that these are EL84's. I have no clue(as is even more obvious now!!)whether these tubes are even more challenging to find alternatives for.