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Found schematic 50W EL34 AB. Needs help...
Found schematic 50W EL34 AB. Needs help...
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Old 15th April 2018, 06:48 PM   #11
artosalo is offline artosalo  Finland
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I have tested different EL34 PP amplifiers with fixed bias and with 6F12P triode pentode front end. With 4k output transformer and 460 V +Ub the available output power is from 55 W (UL) to 72 W (pentode).

Attached the schematic and some test results.
Attached Images
File Type: gif EL34_6F12P_UL.GIF (34.6 KB, 128 views)
Attached Files
File Type: pdf EL34_6F12P.pdf (44.0 KB, 24 views)
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Old 15th April 2018, 10:40 PM   #12
Zekk is offline Zekk  Singapore
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Hi Arto...Can I use your GU-50 power supply for this schematic?
Thanks!

Zekk
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Old 16th April 2018, 05:59 AM   #13
CaterpilarSK is offline CaterpilarSK  Slovakia
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Quote:
Originally Posted by kodabmx View Post
You should be able to get full power with about 1V input.
Great. Thanks. I sent you a direct message. Please check.
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Old 16th April 2018, 06:26 AM   #14
artosalo is offline artosalo  Finland
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Quote:
Originally Posted by Zekk View Post
Hi Arto...Can I use your GU-50 power supply for this schematic?
Thanks!

Zekk
Basically you can, but that PS has regulated screen grid voltage too, that is not necessary required if +Ub is some 450 V and of course not with UL.

I have used this. The 68 V zener in this schematic can be replaced with a small electrolytic capacitor.
Then input voltage variations has the same effect on all voltages and less effect to idle current of output tubes.
Attached Files
File Type: pdf EL34_PP_UL_PS.pdf (30.8 KB, 34 views)

Last edited by artosalo; 16th April 2018 at 06:40 AM.
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