2. amps-preamps
  3. 142475-506

tube noise - 2 questions

Q1: Three months ago, I installed two matching NOS 6DJ8’s in my preamp. Sounded great up until a week ago. Barely audible tube rush on startup - and then totally quiet. Three months later, one started making crackling noises. Only intermittently.  It will crackle for a few minutes - then all is well again for days. But, this repeats every so often. Does this intermittent problem mean that tube is soon to be history?

Q2: With a different preamp, a NOS 12AU7 had crackling & popping noises from the get-go. The noise never went away - even after 100 hours of burn-in. I tried the same tube in my DAC, zero noise - ever. Why might that be?
steakster

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,566 posts
 
@steakster

You can count on it coming back again... Its giving you plenty of warning that you need to find another tube.
atmasphere's avatar
atmasphere
11,566 posts
 
Q1: the tube has an intermittant problem. Giving it a good whack on the side might shut it up for a while. Eventually that will get old- just change it out.
Q2: This depends on the gain of the circuit. In a DAC, the gain is relatively low, but if you use that same tube in the front end of a phono section it might be quite noisy. If its not a problem further upstream or in the DAC, that's probably where it should stay.
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