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KT88 vs 6550 tubes

I recently got a quad of EAT kt88 tubes for my Mcintosh MC275. Those are supposedly revered as one of the best. However, less than 10 hours one of them had a spark of fireworks in it and shorted the fuse. I heard KT88s are in general not as reliable as 6550. Is this true? 

I thought also that KT88 and 6550 are interchangeable in the MC275 without any additional bias adjustment. The original 6550 tubes in it has been working for a long time without issue.
angelgz2
angelgz2 OP
42 posts
 
@dentdog 

there are quite a few Tung Sol NOS black plates on eBay. Are they not the same? I mean there’s no way to fake those things based on what I’ve read. 
angelgz2 OP
42 posts
 
@dentdog actually there are also some original British Mullard KT88s. I’m not sure whether they are safe to buy because of my previous problem with the KT88s 
jburidan
803 posts
 
http://www.jacmusic.com/KT88/kt88.htm

Lots of info at jacmusic.
dentdog's avatar
dentdog
469 posts
 
My experience is that the vintage NOS tubes are considerably more reliable.
As for Ebay while I have bought successfully there, when it comes to high dollar output tubes I am hesitant. 
I wil say that the tubes you use in these amps can make a big difference.
Input and driver tubes can influence things greatly. Siemens-Halske 12AT7s are quite nice. RCA 12AX7s seem to round things out. Good bass. Andy at Vintage Tubes provided my AX7s. 

angelgz2 OP
42 posts
 
@dentdog thats true. I didn’t like the EAT tubes at all as they sounded muddy and lacked bass, despite being priced at $450 each. Popped my RCA 6550s and unit came back to life lol. I’ll see if I can track down a quad of black plates 
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