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KT 150 failure

I bought a set of 150’s early this year for my Primaluna Dialogue Premium.  I’ve always run Gold Lion KT 66’s with no problems. Last week, during silence between songs, I heard this soft fluttering sound thru the woofer.  Cornwall’s.  The slightest tapping of the floor in front of the speaker produced the sound.  I went to the amp which is @6 feet away, and all looked fine- no red tube fail lights.  But the lightest touch to the far left tube really made the woofer flutter.  No red plate, static or popping.  After cool down and restart, tube is quiet until it warms up, then same situation.  Pulled them all and replaced with KT66’s.  All good now.  But I have a geeky question.  What happened with that tube?  In Dynaco Days, I had more dramatic failures.  It’s a fail, but what failed?  Thanks in advance for satisfying my curiosity.  

george53
vinylvalet
891 posts
 

One of my amps uses KT150s. Terrible reliability; three of the four have failed in the first 250 hours. One for vacuum loss, the other two flashes, loud pops and dead. One of those took out the fuse. Fortunately no speaker damage.

I spoke to the amp manufacturer and he confirmed that others were having the same problem. Very good sounding in a well designed amp but terrible quality, the worst I’ve seen in new production output tubes.

jjss49's avatar
Ag insider logo xs@2x
jjss49
6,612 posts
 

@vinylvalet 

what you say is hardly surprising, given what is happening in that part of the world where these tubes are made

oddiofyl's avatar
oddiofyl
3,718 posts
 

Fortunately it wasn't something catastrophic.   I would definitely pull that tube before something bad happens.  I have had fairly good luck with other GL tube types but I did have a KT 66 red plate and a KT77 lose vacuum.   

I recently have been paying the match and low noise fee on new tube purchases , so far so good .   I have a tester but I feel more comfortable if they are matched on something like an Amplitrex or similar .

curiousjim's avatar
curiousjim
4,538 posts
 

Monophonic noise is the Bane of tubes. What does Upscale say??

jerryg123's avatar
jerryg123
3,429 posts
 

I have had great performance from my KT150’s and 170’s all purchased prior to the issues in Russia. Be mindful that all these Russian Tube Factories are US owned. How old are these 150’s? Meaning when did you buy them?

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