NOS KT 88s or GE 6550s

KT120s continue to rack up the cred...I stuck a set of them in a newer Jolida 502p that wasn't designed for them (I did check with Jolida and they insisted the extra heater burden was non issue) and stood back in case the amp was gonna explode...it hasn't and it's been many months. I'd like to try a set of GL kt88s (I like the way they look...lame but true) but somehow I can't justify pulling the 120s since they sound so good. Your results may vary of course, but I still have never heard of anybody's amp transformer melting from the extra juice demand of 120s...I think it's a myth, but what the hell do I know?

Well, it make take a few years before damage happens. This of course depends how over built the heater winding of the transformer is. Obviously 4 KT-120's would be less of a burden than 8 etc.

Just as points of reference regarding heater current draw:

GE 6550A: 1.6A
Genalex KT88 (1974 vintage): 1.6A
Ei KT90: 1.6A
SED =C= 6550C and KT88: 1.65A
Tung-Sol KT120: 1.8A
Original Tung-Sol 6550: 1.8A

conrad-johnson has given its blessing to using the KT120 from at least the Premier 11A onward for its amplifier product line.

Whether there is any damage down the road is doubtful IMO, but only time will tell. I do know that many c-j owners are using the KT120 with no reported difficulties so far. Personally, I prefer the Tung-Sol reissue 6550 to the KT120, but that's a matter of taste.

I've also used the GE 6550A and it's an excellent sounding tube, and few match it, again IMO. Whether you think it's worth the extra cost is unfortunately something only you can ultimately decide.

I've been told that the transformer would get into trouble sooner than later if the KT120s were incompatible somehow...but my informal research results remain: Happy KT120 users in the thousands, reported transformer deaths 0. It will be a sad day when all these overworked transformers give it up. I do like the Tung Sol 6550s that came with my amp and I swap 'em in when I'm bored or have a need to burn my fingers, and I also have a set of Sovtek KT88s that sound fine but lack the groovy gold lettering of the Gold Lions, so there's that. I understand the gold lettering makes them sound 13% better than otherwise.

Pradeep, I haven't heard the NOS JAN 6550A...were these GE's as well and just Joint Army/Navy or ?? I do own a matched quad set of GE 6550's that are like new, and once my SED 6550 C's give up the ghost will replace them with the GE's. You have to be VERY careful that the GE's you will be receiving will still be good. I have heard several horror stories about supposed NOS GE's going up in smoke. I had this happen on my amp when I first acquired it, however, I knew that the tubes were very old and it was a matter of time before ..poof. Happened almost immediately after I acquired the amp...luckily no other damage except to the tube itself.