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Old 18th November 2010, 12:02 PM   #21
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I was about to mention the EL156 in pentode, but see someone beat me to it.

I built an Shuguang EL156 ULSE amp with 450V on the plate, but never measured the output. It is an easy tube to drive - I used an EF86 in pentode. Plenty of power to run a pair of UREI 813A speakers.
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Old 18th November 2010, 04:34 PM   #22
45 is offline 45  Italy
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I don't think EL156 with input step-up transformer will work well unless one has a beefy and mighty source. It's not a real solution, it's just shifting the problem from the driver to the source and usually it's just asking for more troubles......
It's that step-up the main problem.

Last edited by 45; 18th November 2010 at 04:50 PM.
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Old 19th November 2010, 09:36 AM   #23
mik190 is offline mik190  Russian Federation
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Originally Posted by coldcathode View Post
So that is an 833A with 2300 Volts on the plate?

Yes, I like this concept - only 1 element, but 2300V - is extremely high. At the moment I try to find something less energetic. But all other single tube variants are around 2W output.
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Old 19th November 2010, 06:03 PM   #24
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What's about this (sadly almost extinct) tube: EL503(EL530)

Plate resistance 7.5K
Transconductance 23 mA/V (!)
Plate dissipation 27W is a little small, but is 20W SE is an absolute necessity for you?
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Old 2nd April 2012, 05:54 AM   #25
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Nearly 20 years ago John Atwater (of one-electron fame) had an SE shoot-out at his home in San Jose. The max power for most of the entries was on the order of 3W...But for the finale I set up my '13 Cubed' SE amplifier. 813's running into custom Doc Hoyer OPT's; 1300V on the plates and 2x SIXTY FIVE WATTS (130 watts total). Of course to spite the narrow minded group; the amplifier was all pentode; drive tubes were EF86's running 6AU5 cathode followers. The amps blew everything into the weeds with their premium OPT's and great circuit design. Later, Svetlana came out with the SV572 triodes. These beauties were good for well over 20 watts; the higher mu ones could easily do over 25 watts. Again, Doc Hoyer came up woth the output iron. I built several of these and sold them to fellow audiophiles.
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Old 2nd April 2012, 10:05 AM   #26
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A Schadeoed EL156 with a depletion mosfet at the input ala MJK would probably do it with acceptable fidelity.

Last edited by revintage; 2nd April 2012 at 10:16 AM.
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Old 2nd April 2012, 02:09 PM   #27
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I surprised no one mention the 805, more rugged than the 211/845 tubes as the 805 plate=125W, and gain is 50 with the same 900V from 211(gain=12) and 845(gain=6), all this for the same sale price.
Howeber these 3 tubes need a driver.
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Old 2nd April 2012, 02:23 PM   #28
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Originally Posted by mik190 View Post
Here is the single tube single stage 45W amplifier.

I read that some people build it in Russian forums.

Some people in Japane did similar as well as I heard.

I would like to repeat it at less powerfull tubes but did not find the scheme.
WOW, this GM70 amp had a triple secondary output transformer!!... Very impresive, I wonder how it sound??

Any chance did you know the price of this GM70 Integrated?? ("МикроГМка")
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Old 2nd April 2012, 05:15 PM   #29
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Does 10 of 4P1L in parallel count?
Output transformer will be peace of cake, and no lethal voltage required.

Also, B+ easy to stabilize.
The Devil is not so terrible as his math model is!
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Old 2nd April 2012, 05:34 PM   #30
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YL1260/1350 EL3010 crazy steepness

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