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In Reply to: RE: Help on oscillation. posted by akltam on February 09, 2016 at 05:41:33
Is this an amplifier you just recently finished? In other words, not an amplifier that was previously working? In either case, can you post a photo showing the parts layout and wiring underneath at the 6SL7?
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Buy Chinese. Bury freedom.
Edits: 02/09/16Follow Ups:
From the picture, there is a cap which I found not soldered properly. That capacitor was removed.
I then checked the output, the oscillation is still there.
The component are very crowded. I am not sure if you can deduced anything from there.
Alan
I think you may have some layout issues. The crowding around the 6SL7 is just begging for trouble. A straight line layout with smallest signals at one end and largest signals at the other would be much more likely to be stable. I'm also wondering if you need that much gain - can you change a few values and replace the 6SL7 with a 6SN7? Regarding the discussion about grid stoppers, the higher values being suggested shouldn't be necessary. I've built dozens of 6SL7 stages for prototyping various designs, and the only one that ever oscillated had its grid pin within an inch of a third stage anode. Except for that one layout error on my part, 1K carbon comp grid stoppers have always been sufficient.
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Buy Chinese. Bury freedom.
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Yes, the triple KT150 amplifier is the one I have been building recently.I took your advice and use 6BX7 as the driver tube. I appreciate your suggestion very much. Your suggestion has reduced the complexity of my amp. Thanks.
The amp area is very crowded around the 6SL7. I will post some pictures.
Edits: 02/10/16
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