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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: Drd monkey or direct coupled posted by hennfarm on April 24, 2016 at 16:55:14:
The problem with the 6DJ8 as a driver is that they do not like to be run at high voltages - so you need a moderately high gain (mu) for the output triode. The max plate voltage spec is 130v, and there are widespread reports of difficulties if the voltage exceeds 90v.
The thing about power tube operating points is that the plate-to-cathode voltage, the plate current, and the load impedance are connected to each other. I post this every couple years, but it's still not widely known :^) ---:
My target is usually RL = RB - 2.38*rp
where RL is the load impedance, RB is the "beam resistance," i.e. Vp-k/Ip, and rp is the plate resistance at the chosen operating point. Vp-k is the plate to cathode voltage, and Ip is the plate current. You can squeeze out a little more power by reducing the RL, at the price of slightly increased distortion and decreased damping factor. You can usually go as low as 70% of the calculated RL without severe penalties.
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Follow Ups
- RE: Drd monkey or direct coupled - Paul Joppa 19:44:13 04/24/16 (3)
- RE: Drd monkey or direct coupled - Boli46 00:23:25 04/25/16 (2)
- RE: Drd monkey or direct coupled - Paul Joppa 10:07:23 04/25/16 (1)
- RE: Drd monkey or direct coupled - Boli46 23:54:08 04/26/16 (0)
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