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Optimal Operating Point for E280F Driver for 300B Single End Amplifier

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To drive a 300B, you'll need a driver that can provide 200 Vpp of swing, cleanly. Whether the E280F is a good candidate for this, I don't know. But I'm sure if you look at the datasheet, you should be able to figure out whether this tube can provide that much swing.

Driving a 300B is no simple task. I've only found a few tubes that are up for the task - JCC99, 6N6P, 12BH7A, and ECC88. But I haven't looked at every tube known to man and in my circuit, I needed a tube that had high gm and reasonable mu (20~30), which imposed some restrictions on the tube selection as well.

~Tom
 
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Far better? IMHO it's thing of taste.

In my 300 SE (E280F/D3a, 2V green LED bias, 11mA DN2540 cascode CCS, 220nF CuTF coupler, FET source follower -powerdrive to A2- to 300B, 5K:8 OPT) I tried some tubes.

D3a (Siemens, Valvo, Telefunken) gives more power (up to 10W), dynamic -rock!-, but E280F (Siemens, Telefunken) more refined (only 7W).


Although I listen mostly classical and jazz music.
 
d3A in triode is nice as well.

~Tom

The problem with D3A is it runs out of cathode bias, it has a lot of gain but since the distortion rises as the grid reaches zero adding a preamp won't help a D3a-300B amp scale. The 6e5p may be better for of the triode wired pentodes.

If you want to stay away from pentodes, I am liking the JCC99, 6N6P, 12BH7A, and ECC88 types. I still think there is something to be said for a good triode vs a pentode wired as triode. One that is hard to find of this same series is the E182CC (a good one has a gain of 24.) All of these have a healthy g-k bias and can benefit from a peamp or source with a high output.
 
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