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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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It is currently 24 Nov 2017, 04:23

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PostPosted: 06 Nov 2017, 16:36 
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Joined: 23 Feb 2017, 02:02
Posts: 50
I would try a larger input cap maybe 3.3uF, or even a 4.7uF-10uF polar cap on input, sometimes the grid/input of the valve is not negative enough with respwect to cathode and input impedance becomes high.


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PostPosted: 07 Nov 2017, 01:29 
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Joined: 18 Oct 2011, 03:15
Posts: 11
Morning KochiyaYamato, thanks for the tips, i thought there was nothing i coukd do, as it was already below audible range etc. Will pick some for caps and give it a try


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PostPosted: 12 Nov 2017, 17:30 
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Joined: 18 Oct 2011, 03:15
Posts: 11
Changed to a battery, what a difference!!! Ultra quiet!,, didnt hook up the posh cans but no hum at all. Still getting nasty hum with the wallwart, but it is ok when the 50k pot is at 0, so if i use source to adjust vol. its ok. Middle of the pot is worse for hum. Tried a 1000uF cap acroos power supply but dont think it did anything. Also tried additional caps across input to earth and tha just screwed things up, sounded really wierd, lost all treble, from some instructables post.
Building another one now, got some more tubes on order, will use for pre amp into an MF DrT i have. Have one for work, iphone into a pair noise cancelling bose qc15, make them sound almost decent. I have crappy plastic boxes, trying to find a nice wooden job. Going to order a book on valve amps, but i think i should get to know this simple circuit first!,,, i am hooked for sure :-) big shout out and thanks to Rogers Gomez. Would love to do some more low voltage builds, not ready for all that high voltage stuff!,,


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