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Old 13th February 2014, 10:08 AM   #1
Tesla88 is offline Tesla88  Italy
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Default A tube for SE with 1k-1k5 load

Hi guys, i'm working on a low cost amplifier using a putput transformer with 1k or 1.5k primary 100mA rated and i'm wondering what tube for the output stage and B+ value ?

The goal is 8W but 5W is enough...i would avoid GNFB

What about using EL34 triode connected ?

EL86 maybe ? i've seen this tube driving low load at low B+ without problems

6080 can drive 1K easily but need a lot of drive voltage at grid.

thank you all
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Old 13th February 2014, 10:39 AM   #2
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For EL34 triode connected you need 3k or 5k OPT, unless you use parallel single ended, than you should halve those values
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Old 13th February 2014, 10:54 AM   #3
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PL 504 with cathode feedback
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Old 13th February 2014, 11:14 AM   #4
osscar is online now osscar  Latvia
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maybe 6c33c (in your avatar ) at low current - 100mA will be fine.
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Old 13th February 2014, 11:17 AM   #5
euro21 is offline euro21  Hungary
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2A3 PSE?
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Old 13th February 2014, 11:29 AM   #6
davorin is offline davorin  Croatia
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F2a or F2a11 triode connecteed need OPT with Ra=1,5kOhma will give You output power Pout=5,5W.
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File Type: pdf F2a11-3.pdf (375.9 KB, 61 views)
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Old 13th February 2014, 12:51 PM   #7
Tesla88 is offline Tesla88  Italy
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Quote:
For EL34 triode connected you need 3k or 5k OPT
Thank you, i've tried

Quote:
maybe 6c33c
Isn't a bit overkill ? and expensive at least here

Quote:
PL 504 with cathode feedback
Cathode feedback, intresting i can give it a try having a bunch of them...maybe screen drive?

About 2A3 and F2a , i don't have any ...

I have some 6P13S , 6P31S , EL36 , GU32 (832) , GU29 (829)

Thanks
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Old 14th February 2014, 12:33 AM   #8
Junm is offline Junm  Philippines
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How about GU-29 in parallel? (Both sections in parallel)
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Old 14th February 2014, 03:47 AM   #9
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hello ,

it is curve exploited for PL 504

so good for approximalty 200 or 250 V= , OPT = 3.0 K , power out at 8 ohms = 7 W ~

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Old 14th February 2014, 06:42 AM   #10
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Very suitable and cheep decision is 6S19P /Russian/ in parallel. +U for tubes is not high, about 220-230 v after rectifier. They are on Ebay. I have a schematic.
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Last edited by azazello; 14th February 2014 at 06:46 AM.
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