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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: Help with diode biasing. posted by wheezer on September 13, 2014 at 13:36:22:
Just finished, all worked out fine, right on the expected voltage, 3.9V. Kind of a hassle doing two strings of 5 diodes, two sensing resistors (to measure current through tube) and 4 test points, but well worth it. Line stage sounds better now, even more detail yet smoother.
Don't know if it was the difference between battery bias and diode bias, or whether it was changing the parafeed topology from the conventional (parafeed cap between plate and transformer and grounding the other side of the primary) to directly wiring the plate to one side of the primary, and using the parafeed cap between the other side of the primary and returning to the top of the cathode.
Maybe it was both things working together, never know for sure, as I did two things at one time. I know better, but the underside of the tube socket is hard to get to the way I built the thing, and didn't want to take it apart twice. Very pleased with the sound, just the ticket if you need an active line stage, about 10dB of gain, about 80 ohms output impedance. Maybe one day I can save up for those AVCs, then I'll put it in a pretty chassis and call it a done deal.
twystd
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- RE: Help with diode biasing. - twystd 20:51:45 09/13/14 (0)
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