@brumtech if I understood it correctly, an article on Uncle Kevvy’s website says 12AU7 and other low-power tubes should last roughly 10,000 hours. Going by this, I think your 1,500-hour tubes still have a long way to go. 
@drarifakhtar, I’m using a pair of Emotiva XPA-1 Gen 2 monoblock amplifiers. They connect to the BHK preamp via Audioquest Red River balanced XLR cables.
When I first heard the crackling/static noise, I used the remote to put the BHK on standby, which triggered both amps to shut off. Then I unplugged and replugged the XLR connectors on both amps and on the preamp several times in the hope that wiping the contacts clean would get rid of the noise I was hearing. Sadly, it didn’t. I will try James’s suggestion of swapping the left and right tubes.
1 Like
OK the reason I was asking was because your situation is very similar to how the fault in my BHK300 Power amp started.
Before jumping to the conclusion that input boards are the problem or the inevitable next step, swap the tubes side to side and if the nose follows it’s the tube. Tubes can have an early demise for many reason. I’ve had a bad experience with a pair of expensive Valvo NOS. Popping and cracking were the clues to impending failure and the noise changed over a period of half and hour. I pulled them ASAP. There are many 12AU7, 6/7dJ8 tubes available.
2 Likes
I had something very similar happen and it was one tube.
Be sure that the red light inside the preamp is out before you stick your fingers in there.
And if either tube has a milky white color inside, the tube is finished.
2 Likes
@Leonard I agree. I wasn’t planning on swapping them out so soon, but I’m glad I had a new pair ready to go. I guess I was just unlucky? I’m interested to see how long this pair lasts.
2 Likes
Thanks for the tip! I always wait for the red light to go out before opening the top cover.
By the way @jamesh, did you receive my reply to your message?
I sure did. Thanks for getting the info to me. Did you see my last email sent last Thursday?
1 Like
