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Old 4th October 2006, 01:08 PM   #1
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Default I was thinking

Hello

I was thinking. I know the ECL86 where the triode (C) are used as driver for the pentode (L).

Has there ever been made a tube with 2 triode inside, a small triode (driver) and a big triode (output)?

I can't remember I newer had seen a tube like that.
Has anyone seen one?


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Benny
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Old 4th October 2006, 01:26 PM   #2
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Commonly used for TV (vertical osc. / output) use in the US:

Octal: 6EM7, 6EA7, 6GL7, 6DN7
Min 9 Pin: 6DR7, 6FD7, 6EW7, 6DE7, 6CY7
Novar: 6GF7
12 pin: 6FM7

These have a medium to high mu triode (20-70) and a 6-10W output triode.
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Old 4th October 2006, 01:28 PM   #3
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About 20 years ago, I built a small amp using pp 6GF7. Worked very nicely, gave 5 solid watts. This is a good approach for something small and simple.

edit: To be clear, most of these tubes are not designed for linearity, so distortion performance will not be state-of-the-art. But for many applications, it's Good Enough.
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Old 4th October 2006, 05:48 PM   #4
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Quote:
edit: To be clear, most of these tubes are not designed for linearity, so distortion performance will not be state-of-the-art. But for many applications, it's Good Enough.
Actually the vertical amplifier section of a TV needs to be very linear or things won't look right. The tube type TV sets usually had a "vertical linearity" control mounted on the rear panel. This adjusted the amount of cathode degeneration (feedback) in the output stage. You adjusted it to make round things look round. If you are old enough to remember an old TV where people were fat at the bottom, and all stretched out at the top, that was the linearity going away. It was usually caused by a weak tube, or a dying cathode bypass cap.

The tubes that were mentioned tend to make pretty good audio amps. I can get 2 watts from a 6EM7 or 6DN7 in SE mode. The famous Bottlehead SEX amplifier used the 6DN7. It gained a reputation as a decent low priced SE amplifier kit a few years ago.
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Old 4th October 2006, 07:46 PM   #5
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Don't know about the others, but both sections of the 6EM7/6EA7 are about as linear as you can hope for. The combination makes for a VERY good sounding SE amp in a single bottle.

The fact that they are cheap as dirt is just a bonus.

-- Dave
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Old 4th October 2006, 07:53 PM   #6
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Quote:
Originally posted by tubelab.com


Actually the vertical amplifier section of a TV needs to be very linear or things won't look right. The tube type TV sets usually had a "vertical linearity" control mounted on the rear panel. This adjusted the amount of cathode degeneration (feedback) in the output stage. You adjusted it to make round things look round. If you are old enough to remember an old TV where people were fat at the bottom, and all stretched out at the top, that was the linearity going away. It was usually caused by a weak tube, or a dying cathode bypass cap.

The tubes that were mentioned tend to make pretty good audio amps. I can get 2 watts from a 6EM7 or 6DN7 in SE mode. The famous Bottlehead SEX amplifier used the 6DN7. It gained a reputation as a decent low priced SE amplifier kit a few years ago.
One more example is 6P15P (Svetlana sells it as SV83), it was designed for a TV vertical output as more linear than EL84 penthode. It sounds excellent.
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