2. amps-preamps
  3. 164010-2116

Tube Novice Encounters First Hiccup

Bought a PrimaLuna Prologue Classic integrated in Feb., 2019 which I ran with the supplied EL34s for a little over a year before switching to Gold Lion KT77s in Spring 2020. Have LOVED this amp thus far...
Several days ago, and approx. 2 weeks after putting a Bluesound Node 2i on input #1, the PrimaLuna made a very faint ‘bump’ noise about 30 seconds after turning the unit on and the bad tube indicator on the front panel lit up red (This is the smaller PL integrated without bad tube indicators adjacent to each tube.). I shut the amp down, unplugged everything, and removed power tubes and the smaller (signal?) tubes, and re-seated them one by one. Problem solved for about 36 hours. This morning, turned PL on and the BTI on the front panel red lighted again, accompanied by the faint ‘bump’ noise about 30 seconds in again. So far, problem solved by reseating KT 77s only.
Unsure if this has any bearing on anything, but the electrical utility co. has been doing a total replacement of power lines in our area which has directly coincided with everything on our wifi grid basically going ape-s**t for the last couple of weeks along with numerous provider-related internet outages of short duration. Immediately prior to the PL indicating a bad tube this morning, I had installed cat 6 Ethernet cable from router to Node 2i...

I haven’t been able to discern any changes in sound quality during any of this, nor have I seen anything out of the ordinary with the PL’s tubes from a visual-appearance standpoint...no smell of smoke, etc, etc...

Do any of you with more tube amp experience than I have any thoughts as to what may be going on here? Thanks in advance.
lg1

Showing 1 response by yogiboy

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yogiboy
5,791 posts
 
 FYI: Power amp tubes last a lot longer than the 720 hours life that you estimate on those tubes.

Power tubes like EL34’s and KT88’s are good for about 2500 hours or more. But may go longer in an amplifier with a conservative design. Small signal tubes with numbers like 12AX7, 12AU7, and 6922, and rectifier tubes like 5AR4 may go 10,000 hours. So you get years and years of enjoyment. Using a tube tester may or may not tell you if you need a replacement. The best approach is to buy a new set of tubes, and install them. If they don’t sound a lot better, put in the old ones and suck every bit of life out of them.
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