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Old 26th September 2008, 11:56 AM   #11
SY is offline SY  United States
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Quote:
Since power triodes are sooo expensive, why not use miniture 9 pin tubes?
Only the fashionable ones are expensive. Quality miniature tubes are also expensive. You can have 10W per tube of triode dissipation for less than $5 per if you choose something made for tv.
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Old 26th September 2008, 02:27 PM   #12
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Quote:
Originally posted by kenpeter
Darius,

What happens to Triodlington if grid ever conducts A2?

I don't know and I am not interested in A2, sorry.

Kind regards
Darius
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Old 26th September 2008, 04:33 PM   #13
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Wasn't meant to imply that A2 would ever be an intentional
long term operating condition. With a Triodlington there is
plenty more than enough class A power already.

Though I guess with me you can't make any assumptions
Probably in the top 10 most likely to try something weird.

I was only looking to see if an accidental hard A2 transient
might make it latch or otherwise go bananas? In your specific
case, it certainly seems it would not.

The parts you selected look very hard to kill. Its still difficult
to believe something so simple needs no extra compensation.
The deeper I research to find the flaw, there just isn't any.
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Old 27th September 2008, 08:04 PM   #14
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A tube like 6N6P can take 4W and I have seen aplications for both SE and PP-amps. I also have a schematic for a SE-amp using parallelled ECC88. I find the idea thrilling but still, there are tubes that do the work without the need to connect them in parallell.




I am building a 6N6P-PP amp (4W).
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Old 5th December 2015, 10:00 PM   #15
Sheldon is offline Sheldon  United States
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Dormant thread, but I'm intrigued by the idea of using a small dht (as in 3A5) as sort of a spud pp headphone amp. The triodlington would give a nice high impedance load line. How to find low Hfe bjt's? I assume that they would need to be closely matched or can the sides be balanced by changing the load resistor?

Sheldon
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Old 6th December 2015, 11:02 AM   #16
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Quote:
Originally Posted by Captn Dave View Post

Why not? These are good tubes with low distortion characteristics. .
They have just about the highest intrinsic distortion of any of the small preamp tubes.

Cheers

Ian
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Old 6th December 2015, 06:34 PM   #17
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Better use 6sn7 if you want a ~20 gain double triode imho, 82's not great performance. I bought a stack of the Russian variant, I think they are 6h8 when Russia first opened up with the same idea. I think a better tube would be the 6e5p, one of the most linear tubes, tough and with a low enough plate impedance that your opt could be cheap and good :-)
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Old 6th December 2015, 10:18 PM   #18
rongon is offline rongon  United States
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If paralleling multiple tubes is a good idea, and if a relatively high mu is a good thing in an output tube, and if a low ra is a good idea in an output tube, then you'd think a good candidate would be triode-wired 6e5P, or parallel up some 6N6P or 5687.

6N6P was apparently designed for use as a small push-pull output stage. It stands to reason that it would be even better paralleled. How about two PPPP (four 6N6P triode sections in parallel, per side, push-pull)?

Figure on a B+ of about 200V.

Each triode's Ia could be 17mA (3.4W dissipation per plate), so 68mA for four sections in parallel (not unreasonable).

Mu would be around 15x.

ra would be around 3k/4 or about 750 ohms (pretty good). It could use a 3k p-p impedance primary. 5k p-p for better damping.

It would only need about 7V peak at the grids for full output. Easy to drive, but all those grids in parallel will build up some Miller C. Maybe drive it with an LTP made of a 6N6P running at 17mA per triode. The low(ish) voltages lend themselves to an all DC-coupled design.

So there ya go, 10 6N6P's for about 6W per channel output.

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Old 7th December 2015, 01:40 AM   #19
piano3 is offline piano3  United Kingdom
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Many 6n6p per channel would also be a good candidate for that lovely idea on Steve Bench's website for using inverted triodes; I wonder if anyone has actually tried it.
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Old 7th December 2015, 02:27 AM   #20
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Modern production Push Pull ECC99 dual triode good for 10W per channel. 2 ECC99 for 20W per channel.

Push Pull 6EM7 would be an attractive option too.

Cheers,
Ian
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