Basic amplifier design - UK Vintage Radio Repair and Restoration Discussion Forum

Radio_Dave · 8th Jun 2007, 11:10 am

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

Paul Stenning · 8th Jun 2007, 11:36 am

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.....

Aub · 8th Jun 2007, 11:39 am

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

Radio_Dave · 8th Jun 2007, 11:54 am

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

Aub · 8th Jun 2007, 1:22 pm

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

Mike Phelan · 9th Jun 2007, 8:57 am

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

8th Jun 2007, 11:10 am	#1
Radio_Dave Nonode Join Date: Jun 2004 Location: Norwich, Norfolk, UK. Posts: 2,543	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

8th Jun 2007, 11:36 am	#2
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	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..... __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

8th Jun 2007, 11:39 am	#3
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,038	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

8th Jun 2007, 11:54 am	#4
Radio_Dave Nonode Join Date: Jun 2004 Location: Norwich, Norfolk, UK. Posts: 2,543	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

8th Jun 2007, 1:22 pm	#5
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,038	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

9th Jun 2007, 8:57 am	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Basic amplifier design Ferrograph power supplies allowed the mains transformer to be rotated for minimum hum. __________________ Mike.