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Bitrex Bitrex is offline
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Default What is the most powerful audio output tube?

On 12/08/2016 11:59 AM, John Larkin wrote:
On Thu, 8 Dec 2016 10:39:35 -0500, bitrex
wrote:

On 12/08/2016 10:19 AM, wrote:
What is the most powerful audio output tube, as far as RMS wattage
output?

I have gotten some powerful sound from four 6L6 tubes in push-pull
parallel. but I want more. I know it's possible to use eight 6L6 tubes,
which I believe is called " push-pull parallel - parallel", but I'm
looking into other possible tubes.

At one time, I thought the 807 tube was more powerful than the 6L6, but
after careful research, it's almost identical, but with a different
envelope (plate on the top cap).

I'm looking to get a full 500W RMS (or more) output (per channel), from
all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
RMS (per channel).


The output tranny required for 500 watts RMS is going to be a huge piece
of ****-off iron that will probably set you back the better part of a
grand, at least.

500 watts RMS from four tubes will require you to step up way beyond
6L6es and 807s, I think. You're probably going to want to look at
something like RF power triodes or tetrodes, 813s or the GU-13 if you're
okay with going ex-Soviet.

I am not a pro tube guy though so that's just my guess.


The transformer is the problem, especially if you go with a giant
transmitting tube that runs at high plate voltages.


Yeah, not to mention the "instant death" ~1.5kV supply and cap bank that
would be required to feed such a beast.

There have been transformerless audio power amps, using that beast
low-mu triode tube, the one Tek used in their B+ regulators.


I think that's the 6080/6AS7. I saw a 50 watt OTL amp that used
something like 8 or 12 of 'em in push pull parallel to hit that.

I can't even imagine what you'd have to throw at that topology to get 500.

Why not use mosfets? Toobs are silly.


An OTL headphone amp using say a single 6N7 power triode for each
channel and something like a 12AU7 used as a diff-pair gain stage would
be a nice weekend project for maybe half a watt per channel - way more
than required.

You can drive MOSFETs or tubes of the same polarity stacked totem-pole
from a tube diff pair, but the driver design has to be a little clever
to equalize output impedance and gain between the stages:

http://www.tubecad.com/2010/12/29/Low-Voltage%20OTL.png

I'd question my sanity if I started thinking about a 500 RMS watt
all-tube amp though. Well, this guy actually did do something rather crazy:

http://www.chambonino.com/construct/const9.html

Output transformer looks like it weighs about as much as I do.