My really dumb tube mistake(s)


8 years ago, I bought a sweet sounding Line Magnetic amp for my office system which a few years ago died and had to go to the repair shop. $500 later it was back working, but then recently I noticed the sound was getting thin, I couldn’t bias the tubes and thought something else was wrong with it, arghh.

Then I noticed one newer tube was able to be biased and decided to replace all 4 KT-88 power tubes.
Presto, the amp sounded great again!

Like the boiled frog, the sound degradation had been so gradual my brain had gradually adjusted. But the new tubes brought it back to life.

So, then I thought, wow, maybe I should try the same thing in my primary system with my Primaluna monoblocks, switch out the Primaluna tubes for some new Gold Lions. Again - wow! What a difference. Like I bought new amps, much richer and fuller sounding.

Tubes wear out, even if they don’t blow out.
Yes, duh, it’s a good idea to replace them every 4 years or so and not wait eight.
cdc2

Showing 1 response by rushfan71

Being fairly new to tubes and dealing with 2 reputable guys in the NOS tube business, I’ve had very good luck thus far until the other day. I got some 1958 Mullard 12AU7 long plates several months back that I put in my Primaluna Dialogue Premium preamp.
The other day I was showing off my turntable to a friend and I was knocking on the maple isolation shelf while it was playing showing how the table doesnt skip a beat.
It seemed like I could hear a door bell off in the distance. After some investigating found it was tube in my preamp one shelf below. As I tapped or even rubbed a finger on the glass it sounded like a ringing door bell. The tube is now crackling weeks later.
That’s my first experience with a tube going bad.
What I paid for a matched Octet of Mullard EL34 XF2’s has my fingers crossed on those.
Although I have seen several posts here and elsewhere about owners of Primaluna amps using current production Gold Lion KT88’s with favorable results. Maybe a second set of power tubes to switch out now and then would be a good idea to keep the hours down on the Mullards.