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Power Amp Tubes Blowing - what's wrong?

Hi Folks:
A couple of days ago one of the tubes on my power amp flared up and blew. Then yesterday, another one (from the other power amp) looked like it was going to flare up too, but I turned it off in time. I'm at a loss as to what's happening, and how I can prevent the loss of the tubes. I've a pair of KR Audio 6000 modified power amps - each uses a pair of KR Audio 300BXLS tubes. Output is about 22wpc. I've been enjoying the amps for a couple of years, and I'm at least the second owner. Another symptom is that I've noticed the odd crackle now and again as I'm watching movies - not sure if it's related to the tube issues. i'm using no power conditioner at this time - one of the amps is plugged into a PS Audio Juice Bar, the other directly into the wall on the otehr side of the room. Power cords are FIM Gold.

Any ideas on what is amis and how I can eliminate the problem? These tubes are very expensive - a new pair is about $530, and I may even need two new pairs now if the other one goes out. Do I need a power conditioner? Is there something else amis?

Thanks in advance!
128x128outlier
outlier's avatar
outlier OP
381 posts
 
Guys:
Thanks for the advice and input - all good stuff. Hopefully the problem is isolated to tubes that are on their last legs. In which case my new quad should get me up and running again with no other issues to worry about. it looks like I'll need to have the amps manually biased when I get the tubes, in which case I'll get the technition to evaluate the voltage too - good tip that one (the high voltage issue is likely one that killed a tube in my CRT projector a few months back ;-) Damn, these hobbies can get expensive - a labor of love I guess.
sayjul's avatar
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sayjul
27 posts
 

Hi Outlier,

In your case I think is time to buy new tube's, since your are the second owner and you been enjoying the amps for a couple of years now using 89db speakers which I think you be run out the tube's life quicker than a 92db speakers. Also Alfred at KR Audio products is a very nice guy to deal with and is a really helpful guy too.

I'm not a PRO but you should keep your amp's in the same wall outlet if possible, that way you get the same result. Later

Bernie
outlier's avatar
outlier OP
381 posts
 
HI Bernie - yes, I got a matched quad of KR842vhd tubes. I'm still waiting on my new speakers though (Acuhorn Biancore 155 horns). They're 99db, so if anything I may have too much power with these amps, but it should be a pretty good match (the Acuhorns are voiced with KR amps).
sayjul's avatar
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sayjul
27 posts
 

Hi Outlier,

Very nice! the Acuhorn Biancore 155 should be a GREAT match for your KR amps and BIG improvement. Good Luck and please Keep us updated on your new set up. Later.

Bernie
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