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Little OTL / Class " A "
Little OTL / Class " A "
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Old 12th November 2014, 11:42 AM   #1
jean michel is offline jean michel  France
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Default Little OTL / Class " A "

hello ,

i test the build to OTL / Class A to EL 504 ( up EL 502 or 6P45s ) .

the power in build is small , +/- 600 mW to 8 Ohms .

i joint the schéma and pictures to build to test .

and sound for the test 2 EL 502 for 1 Way ( 1 triode ECC 83 )

Test Prototype OTL - Music Freddie Mercury - Vidéo Dailymotion

nice sound for very small build ( and big consumer energy ) ...

tk , good day for all
Attached Images
File Type: jpg OTL_Asymtric_EL 504.jpg (173.7 KB, 709 views)
File Type: jpg Alim OTL_Asymtric_EL 504 - 170 V=.jpg (186.8 KB, 690 views)
File Type: jpg OTL - 160 V=.JPG (251.3 KB, 663 views)
File Type: jpg PICT6565.JPG (225.0 KB, 644 views)
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Old 12th November 2014, 12:31 PM   #2
Bigun is offline Bigun  Canada
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Little OTL / Class " A "
Looks fun!
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Old 12th November 2014, 03:05 PM   #3
TheGimp is offline TheGimp  United States
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I think you need some form of negative bias for the grid (G1). As drawn the only bias for the tubes will be due to the 25R resistance of the choke L1.

With 170V B+ to bias the tubes at 70% dissipation, you need about -24V of bias.

Without this the tubes will run very hot (red plate) and suffer short life.

Be aware that the output on the top of the inductor can go negative if the amp is driven hard enough, resulting in reverse bias on the output capacitor(C2).
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Old 12th November 2014, 04:54 PM   #4
jean michel is offline jean michel  France
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Hello TheGimp ,

the L1 is up to 56 Ohms approximatly and the power is 160 V= +/- 5V=

the all's tubes ( EL 504 or EL 502 and maximum EL 509 / 6P45S ) is adjoint small résistor to equal ( +/- 1 Ohms ) to série at inductance to 56 Ohms .

the test in prototype to 2 EL 502 use 1 Hour is good , not red plate

tk for help
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Old 27th November 2014, 03:26 AM   #5
jean michel is offline jean michel  France
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hello , i continous test to me prototype build ...

i tested the stéréo to 1 EL 519 for 2 Ways and 1 drive ECC82

+/- 500 mW to 160 V= and +/- 200 mA to 1 way ( the résistor for bias is 89 Ohms )

good day for all
Attached Images
File Type: jpg OTL 2 X EL 519 and 1 ECC 82.JPG (256.0 KB, 423 views)
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Old 14th July 2016, 07:21 AM   #6
Tyimo is offline Tyimo  Hungary
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Hi!

Is there any news, progress?

Greets:
Tyimo
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Old 14th July 2016, 07:36 AM   #7
jean michel is offline jean michel  France
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hello ,

not , i only std-by the build for progress build SE to OPT ( 7 K / 5 K / 3.5 K and 2.5 K ) , possible build later to PP class A for ECL 805 ( adapt the EL 86 ... ) .

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Old 14th July 2016, 01:54 PM   #8
Fuling is offline Fuling  Sweden
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Nice! I did exactly the same thing with 4x PL504 per channel ten years ago, burned almost 300W to get 2x 0,75W out
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Old 14th July 2016, 02:38 PM   #9
Tyimo is offline Tyimo  Hungary
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Quote:
burned almost 300W to get 2x 0,75W out
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Old 24th July 2016, 07:21 PM   #10
soundbrigade is online now soundbrigade  Sweden
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Quote:
Originally Posted by Fuling View Post
Nice! I did exactly the same thing with 4x PL504 per channel ten years ago, burned almost 300W to get 2x 0,75W out
Det kunde man räkna från dig ....

But this kinds of experiments are refreshing, do (and het workibg) and watch other do.
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