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Berning ZH-270 Tube Swap

My zh-270's 12av7s(5965)were burnt out. I purchased 2 nos rca 12av7 and 4 rca 12at7 to replace the burnt and stock tubes. To my surprise, when I used the 6 new rca tubes, the sound was very bright, lean, and the bass was very weak, even weaker than my tv's small speakers. I used them for about 30 hours without seeing meaningful improvements. Then I put back the 4 stock Jan Phillip 12at7s, the 270 sounds better, but still too bright, less bass, and causing listenning fatigue. On the whole, in the two situations, the 270 sounded not as good and as natural as using the stock tubes.
Anybody has similiar situations before? Anybody has the experience of using the EI 12at7.

Any ideas, suggestions, and recommendations.

My gear is VPI TNT6_HR with 12.5 Arm, Transfiguration Temper W Cartridge, Manley Steelhead Phono Pre, Berning ZH-270 Amp, Merlin VSM-MXe Speaker, Stereovox SEI600 II and Cardas Golden Reference IC, Cardas Golden Reference Speaker Cable, PS Audio Power Plant Premier, etc.
hzhu1920

Showing 1 response by hzhu1920

hzhu1920 OP
6 posts
 
I changed back to the RCA 12at7s and let them run. After 50 hours running for RCA 12av7 and 12at7, the sound became obviously better than taht of the stock tubes. So the reason is even tubes need enough time to be broke in not as the seller told me that good NOS tubes would sound excellent at once when you plug them in.
Thank Oneprof and Slowland to gave me suggestions.
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