300 hour followup -- Shuguang Treasure Series KT88-Z
I have a friend Mark, in Austin, TX, with amazing hearing. And he has an amazing "audio memory" too. He's familiar with my system first hand, but still, he didn't even know I'd ordered new tubes, much less installed them, much less they'd only been burning for about 25 hours! I had no sooner picked up the phone one night, and Mark says, "What record is that?" I say, "It's the radio, why?" He says, "Wow, your system sounds really good!" -- over my crappy Panasonic cordless phone, apparently . . . . .
OK, well I had some issues with a couple tubes in that first quad I received, and the factory insisted I return the whole quad -- who am I to argue? -- it's not like I don't have tubes. When a hand-selected (by my dealer, at the factory) quad arrived 2 months later, they were equivalent (after 300 hours burn-in) in all test values to EAT's specs and to (really new) NOS British Gold Lions as well. We're talking transconductance values of 12,000 micromhos. By comparison my gently used quad of ANOS (almost new old stock ;--) Gold Lions read 10,500 +/-- micromhos.
When I did re-install the replacement set about 3+ weeks ago, I didn't say anything to anyone. One reason was by then, I'd come to realize Shuguang was quite serious about the 300 hour burn-in time (intitially, I thought it outrageous, but not now) and I just wanted to give them the benefit of the doubt, and not do any evaluating or testing until after that period. One night my Mark calls up and, I swear, the first thing out of his mouth is, "Oh, you got the new tubes"!? Now had he said something like " . . and the soundstage is better too!" I would have known he was pissing on my leg But no, he has great hearing, and you can pretty much believe anything he says about sonics! 'Course, he's 24 years my junior!!
Now about these tubes: first a disclaimer. I have only used the Treasure Series KT88-Z's, and only in my MC275. I have no idea how they would sound in other amps, or how other tubes in this series would perform. However, Shuguang has a long history with the KT88 tube (they also have a long history with some of the other tubes in this series.) Internally, the KT88-Z is physically different than any other KT88 I've seen. The plates are a bit shorter, black, and have the biggest, oval-shaped alignment holes I've ever seen -- three on each side of the plate. There are no side getters -- the carbon coating would prevent that; instead, there are two huge halo top getters. They also draw more power. My MC275 Mk IV draws about 195W at normal listening levels with most KT88's. With the KT88-Z's, it draws about 240W. Nevertheless, these tubes run extremely cool, but again, that's in a Mac.
I used to think NOS Gold Lion KT88's (and all the other NOS Genalex power tubes as well) had a special shimmer and sparkle that no other KT88's had (with the exception of the very expensive EAT's.) So I was pretty surprised when after about 80 hours, I had to admit that the Shuggies sounded better than my originals GL's. How? The best way to describe it I think, is the "size" of the presentation. They have the other attributes of NOS GL's (and EAT's?), plus an enormous soundstage, and a substance, or gravitas, to every sonic detail regardless of frequency. Now I know those sound like pretty wild claims, but (at last) I'm not the only one who thinks so, and consider this: Mark spotted the difference in ten seconds flat, on the telephone!! (He can hear things on the telephone I can't even hear in the flesh!)
These tubes are available in North America from a number of dealers: the TubeStore and GrantFidelity, both in Canada. GF is running a special on AgoN for $450, and TubeStore is about $525/quad incl. shipping, I think. In the US, Woo Audio in NY, and Pacific Valve in Chicago. GrantFidelity claims they "add value" by thoroughly testing all their Treasure Series tubes for various parameters that the factory does not. I
might have bought that, except that Shuguang tests their 'non-Treasure' tubes for multiple parameters, so why not these? Simple: they can't! No manufacturer could spend the 280 (extra) hours these carbon-coated tubes require before any testing would be meaningful; and BTW, they
do test all these different parameters at the factory, but only qualitatively. And I can tell you from my own experience with these TS tubes, most numbers will change over the 300 hour period. So unless GrantFidelity is actually burning in the tubes
they sell for 300hours, their claims are without merit, IMO.
The Chinese seller I have worked with is already providing reliable service to the people I refer. (He does not sell on eBay.) His English, his prices, and his product are excellent: he charges $357 for a matched quad of Premium A KT88-Z's, which includes international PayPal fee and 3-day insured DHL airfreight. Hard to beat -- especially if you need eight or more tubes!! I spent a considerable amount of time with Clark so that he now understands the care and feeding of the neurotic O/C North American audiophile You can email him from his website www.goodcomponent.com and tell him I referred you, which will identify you as a bonafide nutcase! Make sure you specify you want Premium Grade--A tubes, a matched quad (you will get two
matching matched pairs), and most important, that you want tubes with no less than 47mA plate current. 60mA is the max., mine are 57mA. You may have to wait for a new production run if you want the highest values, but anything over 50mA is terrific, so don't obsess over it!
Neil
N.B. -- I previously posted this report on the McIntosh forum at AudioAficionado; where you will also find some comments by my friend John (jprest) regarding his experiences comparing the Treasure Series KT88-Z's versus NOS Tung Sol solid blackplate 6550's. At first, he thought he liked the vintage 6550's a little better. Now he's not sure