Mains isolation - would this work?

[woodturner-fran]

This is probably the wrong place to post this, so mods feel free if it fits better somewhere else.

I was at a hifi show last weekend. Most of the rooms had some kind of mains filtering etc, but one guy had some big transformers. They were what we call site transformers and they step the voltage down from 240V to 110V which is what tools on a building site are meant to be by regulation here.

So the guy has 2 of these wired back to back, ie the 110V out of one connected to the 110 out of the other and then using the transformed 240 out for powering his amps etc. (240mains>>110V out>>110Vin>>240V out)

These were each 5KVA rated. The guy reckoned they did all that a £2k isotech mains unit did.

What do you guys think? Worth pursuing?

Fran

[bob_v5]

That really depends what the £2k device you speak of is suposed to do. I cant see that the contraption with the isolation transformers does much of anything. Decent mains filtering should be included inside any piece of equipment.

[woodturner-fran]

yep, I'm hearing ya. I suppose if there was DC on the mains it would be gone, but other than that?


Fran

[gareth]

Originally posted by woodturner-fran
This is probably the wrong place to post this, so mods feel free if it fits better somewhere else.

I was at a hifi show last weekend. Most of the rooms had some kind of mains filtering etc, but one guy had some big transformers. They were what we call site transformers and they step the voltage down from 240V to 110V which is what tools on a building site are meant to be by regulation here.

So the guy has 2 of these wired back to back, ie the 110V out of one connected to the 110 out of the other and then using the transformed 240 out for powering his amps etc. (240mains>>110V out>>110Vin>>240V out)

These were each 5KVA rated. The guy reckoned they did all that a �2k isotech mains unit did.

What do you guys think? Worth pursuing?

Fran

Personally, two quite large bright yellow transformers sitting in the living room with my equipment and generating large magnetic fields..! It's up to you. Not to mention power factor.

If you look in Farnell's they offer iec inlet filters which you can retrofit to pretty much anything. They are made by Schaffner, come invarious types and ratings and will probably offer similar results. More importantly they filter each device as is needed. Have a look and if you are a little unsure then let me know.

Gareth

[woodturner-fran]

yep, I'm not disagreeing with you!

I have one of 2 of those inlet filters. Although I have seen discussion here saying that they have a bad effect sonically.


So the consensus so far is that there is no benefit.

Interesting.


Fran

[bob_v5]

"I suppose if there was DC on the mains it would be gone, but other than that?"
I'm sure that the mains transfo in the amp would also get rid of any DC on the mains. Unless my electronics teacher is lying to me, transformers simply do not pass dc.
I agree with Gareth, buy the filters he talked about, and spend whats left on something more exciting.

edit-- I typed my reply too slow!

[poynton]

Originally posted by woodturner-fran
..........

I was at a hifi show last weekend. .........

Would that have been with JKENY ????????

Startling Claim


Andy

[EC8010]

Originally posted by bob_v5
Decent mains filtering should be included inside any piece of equipment.

Yes, it should, but it isn't. There are arguments for using a big isolating transformer before audio kit; the most persuasive one is that the isolating transformer will block any DC.

[AndrewT]

Hi,
I'm led to believe that the DC in the mains signal is not pure DC nor is it an offset in the zero volt line towards one or other of the voltages.
I believe that the DC, that affects toroids particularly, is the unsymmetrical waveform that creates a net unbalance between the +ve and -ve halves of the distorted mains supply waveform.
The EI transformers that are being suggested will in themselves be fairly resistant to the saturation from the net DC, but are quite good at passing the distorted waveform on to the next stage of the audio equipment.
That's a round about way of saying that a pair of back to back transformers does not block DC.

Look for the balanced mains threads and websites.
The back to back transformers being discussed in there are being used as part of a filter system to remove much of the interference and some of the waveform distortion. These transformers can also be used to create a balanced supply to the audio equipment, the advantage being that leakage from the mains transformer in the audio equipment is balanced and gives a cancellation in the currents flowing to ground. Those that promote this type of filtering claim significant audio advantage.
I think it's Rane or Jensen that have a paper showing the tech side of this ground current cancellation.

[Steven]

See also: http://www.diyaudio.com/forums/showt...88#post1417488

Steven