Do a search in the Tube Forum in Audio Asylum - you will find a lot of comments about the Mullard re-issues, the SED's, and some comparisions of the two.
9 responses Add your response
I have read and heard many non-flattering things about the Mullard reissues. I had a pair of Electro Harmonix EL34's and another pair of 6CA7's. They were both OK, but not ideal. I pondered the SED's, but wound up buying a quad set of JJ/Tesla E34L's (they are quite inxpensive and supposedly had a more extended top end than the SED's, which I have heard roll off a bit).
Bottom line; I'm quite happy with them. Now if your system tends to be bright, then maybe the SED's will work better for you in helping to tame that (I haven't heard them though). I think the SED winged C's and the JJ/Tesla's are probably the best in production EL34's out there right now, by popular consensus.
Bob, I tend to agree with your comments regarding the sonic's of the SED's and the Tesla's, both the JJ's and the pre-JJ's. The E34L also has a bit more energy and requires a bit more bias. I find the E34L's to be very sparkly (maybe a bit more than the Tesla EL34's). The SED's are IMHO more linear, certainly not bright/sparkly.
But the one thing that I have found undesirable in actual use of the JJ's or earlier Teslas - the tubes are not as reliable as the SED's. I've had several major failures with the Tesla's and I've had none with the SED's. I've been using them both for over 10 years.
Its probably only important for those with amps that don't deal well with shorted power tubes (which can take out resistors etc when they fail).