As for 6550 tubes, I like NOS Tung-Sol grey plates, no-hole and 3-hole. I can't say I hear a difference between them. I also like old stock black plate TS 6550s, but I sold my quad a few years ago. Now, I can't afford to have one again!
I've been liking the new Shuguang Treasury KT88s quite a lot. They produce the best string sound on orchestral music I've yet heard from new issue power tubes. I got them from Grant Fidelity in Canada and have been using them in my deHavilland KE50A monoblocks (Class A, 40W) for a couple of months now. Before that, I used old stock TS 6550s. Before that, I had the new issue Genalex KT88s in the amps.
I also have Shuguang KT88-SC tubes in a VAC Phi-200 amp that sounds terrific--very linear--and I have not rolled output tubes in it yet.
The old stock TS 6550s have more extension, both top and bottom, than any of these other tubes. But the Shuguang Treasury KT88s have a luscious midrange and have extension "near enough" to the TS 6550s that I've switched to them as my main power tube in my reference amps. The Genalex KT88s are all right--probably better sounding overall than the SED Winged "C" KT88s--but they're not as reliable or tough as the SED tubes, which are very tough. I used the Genalex and SED tubes both in an Air Tight ATM-2 amp that pounded the hell out of them on start up and I had several failures with Genalex and none with SED. The Shuguang KT88-SC tubes sound fine in the VAC Phi-200 amp--very linear, very extended at top and bottom, tight bass. But I heard that VAC was going to start using Shuguang Treasury tubes in their amps soon, starting with the 6SN7 Psvane and maybe the KT88 Treasury tubes later.
I convinced Kara Chaffee at deHavilland she ought to give her customers the option of Shuguang Treasury KT88s in her amps. As an upgrade over the standard Genalex KT88s she usually ships them with.
The short of it--I LIKE the sound of the Shuguang Treasury KT88s, but I don't yet know how reliable they are, as I've only used them about two months. No drift of bias, though, and no runaway tubes so far. But the deHavilland KE50A amps aren't hard on output tubes. I still think old stock TS 6500 greyplates are "better," but why spend more and burn those out fast when the new Shuguang Treasury tubes have almost the same extension and a better midrange?
I'm also trying Shuguang Psvane 12AX7 and 12AT7 signal tubes in a couple of applications.
My Gold Lion KT88s arrived a few days ago. For over a year, I was listening to the ARC VS115 amp on stock SED 6550 tubes. Prior to that amp, I had an ARC VS110 that had EH 6550s but within a month I changed them into SED KT88s, which lasted for many years till the change to the VS115 last year.
I have been reluctant to play any of my vocals for the past year on this 115/6550 amp. Reason is there is simply no emotion on the singers, and there is virtually no life in their voices. But, when I play acoustic instrumentals like Windham Hill, and classical music, the amp sounded fantastic and way better than my old VS110/KT88 amp. I was torn between getting the KT120s or the KT88s but after so much self debate, I chose to go the path of KT88 and chose Gold Lion. Upon installation, I warmed it up a little and then played Eva Cassidy's Songbird album because I recall that playing it through the 6550s, there is an edge that bothers me and sibilants were too pronounced and her voice is totally lacking in warmth and lushness. After a few minutes of playing this LP with the GL 88s in place, immediately I felt my audio life was going to be better, because my main genre has evolved into female vocals over the past few years. Her voice sounds warmer, lush, and full of emotion when she sings. I am very happy to get this back. I also played Enoch Light's Provocative Percussion on Command Records just to find out if instruments are clear and boy, was it clear and crisp, with good transient attacks, not tubby at all. Of course the tubes are still only a few hours old and more things can change, and I'm very eager to hear what improvements can still show up.
Phil-I’m glad you like the GL KT-88 tubes in your ARC VS115. I can tell you the VS115 sounds great with the KT-120 tubes and they were rock stable during their time here. When I had the Jadis Defy 7 MKII amp, I retubed it with the GL KT-88s with the owner of Jadis giving his blessing and saying they were very nice sounding tubes. I just couldn’t keep tubes functional in the Jadis. They did sound great when they were working though.
I used these KT88 in 3 amplifiers: Audio aero prestige , one PP classe A 50 watts, audiopax mono 88 a SET 30 watts, and audiopax maggiore one SET with 100watts ( in this I used only GL and EAT tubes) :
JJ tesla-good, but not special
Shuguang 88 - I did not like it
EH kt 88 - the wrost tube
Shuguang treasure - it was not beter than GL, we tested against GL and EAT, both better that ST
GL- better than all above, more transparent and reliable, had no problems in recent years.
EAT-best of all, the first 50 hours I thought I'd go back to using the GL, without highs and without sound balance, but after 50 hours they became very balanced with all frequency , are very expensive, should cost less.
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