Replacement EL34 Mullard valves for Leben CS300X

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