bluemeanies wrote:How do the 6550's compare with the KT88's?
You could start a tong war here with a question like that.
I don't think there's any consensus on the power tube front. I personally prefer the original New Jersey-built TS 6550s, but cannot compare them with the British-made KT-88s from that era.
I do have a set of the modern, Russian-built Genalex KT-88s that are very sweet, plus a couple of years' experience with the modern New Sensor/Tung-Sol KT-120s, which IMHO give the best bang for the buck. They're bullet-proof and deliver superb sound, and don't break the bank when replacement time (conservatively 3,000 hours) comes.
Much as I like 'em, I won't be buying any more of the original Tung-Sol 6550s as the price has gotten way out of hand. Jim McShane at http://www.mcshanedesign.net/tubes.htm , my go-to guy for the newly-built Russian tubes, recommends the Genalex "Gold Lion" KT-88s and will get no argument from this quarter, and they cost about the same as KT-120s -- about $200 for a quad with shipping all in.
New old-stock British KT-88s or American 6550s are going for $600 or higher per quad, probably unmatched, and you're taking your chances on the seller... not worth it.
The only new output tubes I disliked were the Winged-C Svetlanas and the General Electric 6550s. They were too tinny-sounding. Some folks swear by them, however.
Give some thought to experimenting with your driver tubes; they can have considerable influence on the sound flavouring, more so than the power tubes. Plenty of old-stock and current production copies out there, and if you don't like what you get you won't be throwing $400 out the window.
Last edited by deepee99 on Sun Jun 07, 2015 9:52 am; edited 1 time in total (Reason for editing : Clarification)