You didn’t specify your amp’s manufacturer. If those meters are there, for you to determine bias settings: that typically indicates, you’re able to adjust them. Look for pots labeled, "BIAS" or, "B+", externally, on the amp. Do you have a manual?
DC meter on power amp
My 300B power amp has two DC (mA) meters. I know a VU meter moves along with the music, but this DC meters doesn’t. I realized one has a lower reading caused by the 300B power tube, 0.64 mA and 0.72mA. I switched left and right, and the lower reading follows. I tried another pair of tubes and the readings are matched. Does it mean the lower reading tube needs to be replaced? What is the effect of one reading is lower? I bought them used, and they are tested with no leak and shorts, and they are pretty closed in terms of percentage life left. Would this mismatched in DC reading reflect in a tube tester?
Thank you very much in advance.
Thank you very much in advance.
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It is a custom built Otomon Lab amp. The builder, Ken, said it is “fixed bias”. I request to have two meters just because I think they looks cool. I am actually thinking a VU meter that will move when playing the music, LoL. http://soundgate.net/product/ODg2.highend I feel one channel is louder, then I observed the difference in reading. |
One tube has over 10% more B+ than the other, accounting for the difference in balance. "Fixed Bias" means it's adjustable, by you. It appears: there are pots behind the 300Bs. Just split the mA, between the tubes, if you like it's current presentation. That's a gorgeous piece of equipment (build and looks). |
btw: After you're well acquainted with the amp's presentation, listening to your favorite/most familiar, albums; get one of these and place it atop the power transformer. Let me know your reaction, if you do. I think you'll be surprised and delighted at the improvements it will make. https://elusivedisc.com/vpi-magic-brick/ The old ones are prettier: https://www.hifishark.com/search?q=VPI+Magic+Bricks:
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- 13 posts total