Balanced Power Supply

BilliumB · Post by **BilliumB** » Thu Sep 18, 2014 12:05 am

Hi Paul.

I'm wondering if you ever put together your EI based balanced transformer supply?

Thanks. Bill

Paul Barker · Post by **Paul Barker** » Thu Sep 18, 2014 2:32 am

No. When I broke my foot life became a fight for survival under the new benefits system. The other home demands on my time and rehabilitation back into my very physical job mean action in this domain unlikely to return for medium term.

BilliumB · Post by **BilliumB** » Thu Sep 18, 2014 8:08 am

Sorry to hear that Paul.

pre65 · Post by **pre65** » Mon Jan 19, 2015 10:54 am

Ali, are you still using the circuit shown on page 1 of this thread ?

Also, can one use multiple isolation transformers wired together ? ie two 1000va units to make a 2000va unit ?

I believe the 3000va one from Russ Abbott uses two 1500va transformers.

Ali Tait · Post by **Ali Tait** » Mon Jan 19, 2015 1:52 pm

Yes, still using it that way. Do yours have a center tap? ( I guess not if they are isolation trannies)

As for using two, yes I think so, if you wire them in parallel. I think in series would halve the VA? In any case, might be worth trying both ways to see what sounds better, as long as you're not asking too much of them.

Also, make sure polarity is correct or they will buck each other (I think)

I'd also use protection on both primary and secondaries, as I did with my balanced power supply.

Ali Tait · Post by **Ali Tait** » Mon Jan 19, 2015 2:02 pm

A further though occurs- be aware that connecting more than one item to the trannie may negate the floating mains safety aspect of these, say if a second piece of equipment had a neutral fault to case.

Copied this from the web cos I'm lazy.

Mains is referenced to earth ground: the same potential that you're standing on, that your workbench is at, that nearly anything you touch (that's not isolated) is at. It develops voltage with respect to those items.

After an isolation transformer, the earth ground reference is gone. If you touch the line side after the transformer, suddenly that becomes the reference for the whole system, and the neutral side (which you're not touching, and which would normally be safe) is a dangerous sinusoid with respect to earth ground. The important thing is that the point you touch is still safe.

However, touching both sides of the transformer simultaneously is just as dangerous as not using the transformer at all.

But, I guess you are looking at sound quality improvements rather than the safety aspect.

So yes, make sure you don't touch both secondaries at once, you'll still get zapped!

pre65 · Post by **pre65** » Wed Jan 28, 2015 10:46 am

I am putting together a plan for my balanced mains unit.

I have a single phase RFI filter (20A) and would like to know if this is best fitted between the mains in and the DC blocker ?

Ali Tait · Post by **Ali Tait** » Wed Jan 28, 2015 3:11 pm

Will you be fitting an NTC Phil?

Inrush may trip your consumer unit if it's a more modern one fitted with breakers.

pre65 · Post by **pre65** » Wed Jan 28, 2015 3:17 pm

Ali Tait wrote:Will you be fitting an NTC Phil?

Inrush may trip your consumer unit if it's a more modern one fitted with breakers.

Yes, I think so. Always a good option with big toroidal transformers.

jack · Post by **jack** » Wed Jan 28, 2015 3:19 pm

Ali Tait wrote:Will you be fitting an NTC Phil?

Inrush may trip your consumer unit if it's a more modern one fitted with breakers.

...or change the MCB to being a C(x5-x10) or D(x10-x20)-rated one to handle the inrush...

pre65 · Post by **pre65** » Wed Mar 04, 2015 1:47 pm

Looking at commercial BMUs (the NVA one as an example) they seem to be no more than an isolation transformer in a fancy box wired up as balanced.

http://www.nvahifi.co.uk/balanced-mains-unit/

Obviously I don't know exactly what is in the box.

Anyway, I was going to do a breadboard lash up of one of my 1000va isolation transformers as balanced and see if I could hear any differences.

The ultimate plan is to use one for the two power amps and another one for the other components.

pre65 · Post by **pre65** » Mon Mar 09, 2015 5:06 pm

The breadboard "lash up" with just a double socket is now finished.

I won't have time to try it till tomorrow (Tuesday) afternoon.

Are there any hi-fi component parts that won't run off a balanced transformer ?

I understand soldering irons don't like balanced mains.

Ali Tait · Post by **Ali Tait** » Mon Mar 09, 2015 8:37 pm

Haven't found anything that wouldn't work, though our new telly made the supply noisy, had to plug it in to normal mains. Telly worked fine though.

Guess it must be an SMPS thing.

jack · Post by **jack** » Mon Mar 09, 2015 9:10 pm

Phil's isolation transformers would make an excellent balanced supply...

pre65 · Post by **pre65** » Mon Mar 09, 2015 9:29 pm

nickds1 wrote:Phil's isolation transformers would make an excellent balanced supply...

That's why I did the bulk buy, I assumed that is what folks were going to use them for.

audio-talk

Balanced Power Supply

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