2. amps-preamps
  3. 146929-1264

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

Showing 1 response by stevecham

stevecham
3,298 posts
 
Forgive me but, that was unwise. You need to ALWAYS adjust bias in a fixed bias circuit if you change tubes, let alone tube types. 6550 and KT88s are NOT swappable without doing this.

Did the KT88 plates that blew the fuse turn cherry red by any chance before it did?
More to discover