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Old 8th Jun 2007, 11:10 am   #1
Radio_Dave
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Default Basic amplifier design

Hi,

I'm thinking about making a single ended, stereo, valve amplifier from scrap radios.

I know the laminations of the mains and output transformers should be at right angles, but my amp will have 2 output and 2 mains transformers. How do I orientate this lot? Is there anything I should know about spacing of these parts?

Thanks
David
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Old 8th Jun 2007, 11:36 am   #2
Paul Stenning
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Default Re: Basic amplifier design

I would try the two output transformers the same way round and the two mains transformers also the same way round as each other but at right angles to the output transformers. Sorry, that wasn't very clear.....
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Old 8th Jun 2007, 11:39 am   #3
Aub
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Default Re: Basic amplifier design

Dave,

I think they should go at right angles to each other shouldnt they? To minimise induction. Obviously, with 4 transformers in a confined space, this will be more of a challenge. As long as you keep the mains trannies away from the output ones, i would think you'll be ok. I recently built a single ended stereo amp using a couple of ECL86's. This used a single, torroidal, mains transformer and the two output trannies. I had a slight problem with induced hum into the input of one channel, but i cured it with a small piece of aluminium for a shield.

Good luck!

Best regards
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Old 8th Jun 2007, 11:54 am   #4
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Default Re: Basic amplifier design

If I placed each set of OP and mains transformers at the outer ends of, say, a 20" wide chassis would the distance, between them, be enough to not cause problems?

David
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Old 8th Jun 2007, 1:22 pm   #5
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Default Re: Basic amplifier design

Hi Dave,
I would think that each set of transformers being 20 inches appart would be more than adequate to prevent each set interfering with the other. Within each set though, you should have the mains transformer and the output transformer at right angles to each other, which i think was part of Paul's answer earlier.

It's important to keep the input circuitry away from the transformers.

Regards

Aub
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Old 9th Jun 2007, 8:57 am   #6
Mike Phelan
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Default Re: Basic amplifier design

Ferrograph power supplies allowed the mains transformer to be rotated for minimum hum.
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