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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: Full music TJ 300B mesh Sofia traced plate curve posted by Balle Clorin on September 1, 2014 at 14:57:36:
Let's see, 390V 70mA 90V bias.
WE Specs these:
400V plate, -91V bias, 40mA plate current (gasp!), and a 5K load should make 8.5 watts with the 2nd harmonic 26dB below the fundamental and 3rd harmonic 37dB below fundamental.
400Vp, -89V bias, 50mA IP, 3K load, 11.5W, 21dB 2nd, 31dB 3rd.
400Vp, -89V bias, 50mA IP, 4K load, 9.4W, 25dB 2nd, 38dB 3rd.
400Vp, -87V bias, 60mA IP, 3.5K load, 10.5W, 26dB 2nd, 38dB 3rd.
400Vp, -87V bias, 60mA IP, 5K load, 8.3W, 30dB 2nd, 46dB 3rd. (look familiar?)
These datapoint suggest that your operating point should work very, very well with a 5K load. Who gives a rip about 8W vs. 11W (I don't).
The WE curves are for a "bogey" tube, and WE had a reputation for throwing away tons and tons of 300B's, only keeping the best of the best. We could certainly do that with modern production 300B's, but I would ask why? Do we need this kind of consistency, or is a little variation in plate curves acceptable for a 75% reduction in costs?
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