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Old 15th March 2006, 01:04 PM   #1
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Default Need help for DIY EL34PP tube amp

Need help for EL34 PP project Post #11
Some more questions about my EL34 project:
I need some help for my EL34 PP project.

From the scheme in page 19 of

http://www.lundahl.se/pdfs/claus_by...ifier_30wpp.pdf

1. What value of volume control VR should I use?
2. I got some 1u 630v MKP cap in hand, can I use it in the phase splitter (replace the 0.47u under the Ecc83, any bad effect?)
3. What type of 47K VR (carbon, wire wound, conductive plastic, etc. and what rating) should I use between the two 150K resistor beside the Ecc83?
4. What type of 22K VR (carbon, wire wound, conductive plastic, etc. and what rating) should I use in the bias supply for EL34s?

Could anyone tell me what value of resistor should be used on the plate (instead of 150k + 47k VR)and cathode (instead of 82K) if I replace the Ecc83 with the 12AT7 then?

Thanks for your help
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Old 15th March 2006, 01:10 PM   #2
lndm is offline lndm  Australia
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Check your link
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Old 15th March 2006, 01:24 PM   #3
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Sorry the scheme should be in here

http://www.lundahl.se/pdfs/claus_byr...fier_30wpp.pdf
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Old 15th March 2006, 09:27 PM   #4
lndm is offline lndm  Australia
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To answer your questions in order,

1. preferrably 250k or less. Less if your source can handle it.

2. use them

3. This VR is a partial plate resistor and carries DC. Rate for 1/2W for good measure.

4. Not really in the signal path. Very little dissipation. Use a reliable quality VR.

Hope this helps.
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Old 16th March 2006, 01:39 PM   #5
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Thank you very much for your suggestion, Indm.

"This VR is a partial plate resistor and carries DC. Rate for 1/2W for good measure."

Should it be a wire wound or carbon type VR ?
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Old 16th March 2006, 10:01 PM   #6
lndm is offline lndm  Australia
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I've had problems with each. You dont want pots carrying DC and failing (like getting dirty). There are quality brands out there though.

If it were me, I'd find the correct resistances for each side and hardwire actual resistors there. Even if you don't do this balancing at all, you won't cause any damage.
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