Seeking Info From Long Term KT88Z Treasure Owners

[robinmtns]

Hello All--

I have decided to buy a replacement set of KT88s for my MC275 MkVI. Top of the list for tubes to check out are the Shuguang KT88-Z Treasure tubes. I found it persuasive that both Ron C and nsgarch have owned the KT88-Zs and have spoken well of them, as have others. Seems first experiences with the KT88-Z happened in 2010 when a number of folks were going gaga over them. So I'm thinking by now, y'all must have a lot of learnings you can share with me!

Looking for any help you can give me with any of the questions below:

• First, what is the current, 2018 Aficionado McIntosh consensus opinion on the KT88-Z? Is it still considered in the top tier, esp for the MC275? Or have other KT88s (such as the Psvane) eclipsed it?
  
• Have the years revealed any concerns about reliability? I remember Neil Garch saying he had trouble with 2 of the tubes among the first he ordered and they had to be sent back. Is that a recurring problem?
  
• What's the experience with longevity? Are we talking the 2000 hours often cited as the norm for power tubes? Or as this is a premium tube, are they acting more like a NOS premium 'long life' tube?
  
• I saw one post that indicated that the MC275 bias should be reset for using high Gm tubes, and that there is a possibility (I suppose if the bias is not reset) for them to take out output tube plate resistors in the MC275. Is this accurate? I remember Neil noting that his AC line draw was higher with the Shuguangs. Any history or potential for these tubes to damage my amp?
  
• Finally I recall Neil recommended a vendor in Hong Kong as the preferred source for the Kt88-Z. Is that still correct? Has the vendor proven to be a great guy? And is he still selling the same quality tube he was selling back in 2010?

I appreciate any help you can offer. Thanks!

[Masterlu]

Unfortunately, this won’t help you but I do have a locker full of new matched Shuguang KT88-Z’s

I was waiting for one of my Gold Lion’s to fail, and then was going to switch them out. 2,100 hours later, my Gold Lions are still going strong.

[robinmtns]

Well, maybe it does help. I guess I can take it from that that you dont feel the Shuguang has been proven inferior over time or badly eclipsed by another KT88. Afterall, you still have 'em---havent sold 'em off. I guess that says something!

[Masterlu]

Yup, they are Premium Tubes for sure.

[W9TR]

Because the amps that Ron C and ngarch used are older models, you'll need to get feedback from people who have the MC 275 VI. There are some significant circuit topology differences between the MC 275VI and the older amplifiers, not the least of which is higher plate voltage and a different input circuit topology.
Tom

[robinmtns]

W9TR --

Thanks for the caution. You're right. Its really surprising how many think the Mk VI is almost identical to the earlier reissues, and of course its not. I was hoping for more response here so I might get feedback that links to the MK Vi specifically.

In the absence of that all I could do is go back to the web again to try to find any references to Shuguang or Psvane KT88s and the Mk VI. I've been able to find three positive reviews about Psvane KT88 TII tubes delivering good sonic results and working without problems in the Mk VI.

On the other hand can still only find the one reference (I mention in my first post) of use of the Shuguang KT88-Z Treasures in a Mk VI and it seems to implicate the Shuguangs in uneven tube heating, possibly overstressing the output trannies and possibly causing a blown plate reisistor!

Also I dont see any posts stating that a Psvane had reliability problems or caused a problem in an amp it was used in. Notable because its not hard to find those problems reported with any of the other new production KT88's.

Still wish I had a bit more to go on. But given what I do know, it seems it would be irrsponsible not to go with the Psvanes. When I get them in my amp and after a bit of break in, I will report back on what I find.

[W9TR]

I'll be interested in your findings for sure. What I've found with more recent McIntosh tube gear, specifically the C1100 and MC 2301, is that the sonics are much less sensitive to tube types and variation. Since I have three MC 2301's for a total of 24 KT-88's, I use the GL reissues in those amps.

But I also have an MC 275V in another system and I could spring for higher end tubes when the time comes. I also have several sets of "Winged-C" KT-88's that are waiting to roll in so it may be awhile.

Tom

[robinmtns]

Tom --

I did get the Psvane KT88s in and am posting my impressions now in a new thread.

--Rob