Discussion of AC mains isolation transformers

[asdf1000]

Thanks for the diagram, that helps immensely.

 

The only leakage loop you should have left is DAC to power amp which goes through the power conditioner. BUT the digital stuff also goes through the power conditioner.

 

Contrary to all "it makes sense to me" thoughts on the subject the way cut down on leakage loop noise with the DAC and pre/power amps is to have the tightest coupling you can get in the AC domain. Since a leakage loop goes through the AC main the higher the impedance in the mains side the higher the noise voltage generated between the boxes. I know the power conditioner is trying to suppress noise on the mains, but the methods frequently used actually increase the impedance between outlets thus increasing the noise from leakage loops.

 

So to test this hypothesis, try taking the power conditioner out of the system and just use a very simple power strip, no filters, nothing fancy, just outlets connected by wires. This will give a very low impedance between the AC to each power supply, which should cut down on the noise generated by leakage loops. Everything you now have connected to the power conditioner should go into the simple power strip, including all the digital stuff.

 

In combination with the LPS-1 and other leakage loop breaking devices doing this can really make a big difference. I did this in my system (replaced a $1k power conditioner with a $35 power strip and Topaz isolation transformer) and it made a significant improvement is SQ.

 

Thanks,

 

John S.

 

I'm learning so much about system noise on this forum. Makes me want to sell my flashy $1000 power conditioner for a cheap strip and a good isolation transformer.

 

 

John, what’s the role and benefit of an isolation transformer, in an audio context?

 

 

Am I right, that this plugs into your wall and you plug a powerstrip into the isolation transformer? Apologies for the silly question. This is a new world for me.

 

 

In Australia we have 240V power supply (or 230V) at the wall. If choosing an isolation transformer, do I would want something like a 2000watt transformer (minimum), delivering an 8amp current? Power boards are rated at 10amp max current here in Australia.

 

 

I'm looking to get my system optimised before LPS-1 arrives in November - I’ve just made my order :-)

 

But other than just the LPS-1, I'm looking to improve the system generally.

 

 

Many thanks in advance

[asdf1000]

I'm learning so much about system noise on this forum. Makes me want to sell my flashy $1000 power conditioner for a cheap strip and a good isolation transformer.

 

 

John, what’s the role and benefit of an isolation transformer, in an audio context?

 

 

Am I right, that this plugs into your wall and you plug a powerstrip into the isolation transformer? Apologies for the silly question. This is a new world for me.

 

 

In Australia we have 240V power supply (or 230V) at the wall. If choosing an isolation transformer, do I would want something like a 2000watt transformer (minimum), delivering an 8amp current? Power boards are rated at 10amp max current here in Australia.

 

 

I'm looking to get my system optimised before LPS-1 arrives in November - I’ve just made my order :-)

 

But other than just the LPS-1, I'm looking to improve the system generally.

 

 

Many thanks in advance

 

Something like this 2000 watt medical iso transformer even discusses leakage currents and already has 6 outlets which is sufficient for my system:

 

Medical Isolation Transformer IEC 601 and UL 544 Standard for Medical Instruments Australia

[asdf1000]

The medical transformers may not have very low capacitance between windings, their leakage current is usually speced between winding and ground NOT winding to winding.

 

The leakage current I have been talking about is winding to winding, not winding to ground. So just because something is "medical" it may not be doing much good for the leakage currents I'm talking about. The MAY be very good, they may not.

 

John S.

 

Thanks John

 

In terms of earthing, if an iso transformer stated the following, would you avoid it for audio applications: "Earthing is NOT carried to Outlet Socket, Hence Isolated and Floating."

 

Would you prefer to see Earthing IS carried to the outlet?

 

 

 

[asdf1000]

Run away from that transformer.

 

Run away from which?

 

Earthing is NOT carried to the outlet socket?

 

Or earthing IS carried to the outlet?

 

And may I kindly ask why? :-)

 

Many thanks in advance.

[asdf1000]

I would avoid that transformer for plugging in anything.

 

The incoming safety earth that comes from the wall must <-- (by many rules on this planet, maybe Russia/China is exception) be connected to the outgoing circuit of the isolation transformer, straight passthrough, no filtering of any kind. This is a safety requirement.

 

These days, the output of the Isolation transformer must be protected by a RCD/GFCI, since the neutral connection to ground/earth is lost when the isolation transformer is used. If there is an imbalance on the output between line and neutral, the upstream RCD/GFCI can't see the problem.

 

I'm surprised by Tortech that the earth is not connected. I bet that 3rd pin is connected to earth.

 

Hi mate, the one I linked above does have earthing to the outlet, here again: Medical Isolation Transformer IEC 601 and UL 544 Standard for Medical Instruments Australia

 

Tortech confirmed to me that the medical version has earthing to the outlet,

 

whereas the standard (which you linked) does say "Earthing is NOT carried to Outlet Socket, Hence Isolated and Floating"

 

But like you say, perhaps it's not written clearly

[asdf1000]

There you go, if you are testing something, then in some cases the AC needs no reference to earth, but not audio equipment.

Ah righto, so in this case the only option is the medical version - you'd avoid the standard version?

 

Theyre supposed to be well built, some others have said over on StereoNet.

 

 

 

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[asdf1000]

The medical transformers may not have very low capacitance between windings, their leakage current is usually speced between winding and ground NOT winding to winding.

 

The leakage current I have been talking about is winding to winding, not winding to ground. So just because something is "medical" it may not be doing much good for the leakage currents I'm talking about. The MAY be very good, they may not.

 

John S.

 

Hi John, this iso transformer linked below stipulates: "Double insulated windings ensure a galvanic physical separationbetween input and output as well as holding theleakage current below the stipulated maximumvalue."

 

http://www.noratel.com/fileadmin/content/products/medical/imed/IMEDe.pdf

 

Assuming they mean galvanic isolation between input and output windings, then is this galvanic isolation more in line with leakage currents you discuss for audio applications?

 

Thanks again

[asdf1000]

If you are going to Tortech, get one of these. The one sore point is that they don't mention the output balance regulation, which is important. They use NTC thermistors for soft power, a power company's auto-recloser will make mince meat of them.

 

Thanks for that, I was going to contact Toratech about that.

 

I asked Noratel about the inter-winding capacitance for their 2kVA medical class iso transformer and they replied 1500 pF.

 

Seems like a Topaz (or Elgar?) is the way to go - there aren't many ultra low coupling capacitance iso transformers that I can find on Google.

[asdf1000]

The isolation transformer I'm using is a Topaz model, it is a very special transformer. It has extremely low inter-winding capacitance (.005pf according to the manufacturer). Most transformers have two mechanisms that transfer AC from one side to the other: magnetic and capacitive. The magnetic part is low frequency (it is what the 50/60Hz mains signal uses) and the capacitive is high frequency. The combination means that a "normal" transformer lets a lot of high frequency crud through.

 

With its extremely low capacitiance the Topaz doesn't pass the high frequency crud on the AV main, just the base line frequency and a couple harmonics. Thus it is a very effective noise filter.

 

In addition it is a very good surge suppressor as well. Most of the energy in high power surges is contained in high frequency components, which get suppressed by the low capacitance, thus it is quite an effective surge suppressor without needing any other special circuits to achieve this.

 

This isolation transformer keeps noise and surges from the rest of your house and neighborhood out of your audio system and fully preserves your safety ground.

 

Yes you are correct about the application, the Topaz plugs into the wall, the power strip plugs into it.

 

My recommendation is to use a simple power strip with NO filtering or surge suppression, the Topaz does it much better than what will come in almost any power strip. I plug EVERYTHING into thepower strip. This dramatically cuts down on the impedance between boxes, significantly lowering noise generated by leakage loops.

 

Some people will say "but then the noise injected back into the AC mains can go right into other boxes". Yes it can. BUT recent experiments have been pointing to the leakage loops being a significantly greater detriment to ultimate good sound than the injected noise. Of course different systems are different and this may not be true in all systems, but it is looking like this is a good place to start for many systems.

 

John S.

 

Hi John, a few people on other forums have commented that their Topaz hums, but an Elgar (also with a coupling capacitance of 0.005pF) doesn't. This humming that they speak of, does it contribute to electrical noise at all to music playback or is it purely just a faint audible hum that doesn't affect the sound quality at all?

 

Thanks again

[asdf1000]

Yes my Topaz hums a little, it is an acoustic Hum (the output is 60Hz AC which of course is the ultimate hum!). I built a box around it with some pillows for now. It does get a little warm so you have to be careful with thermal management.

 

Without the box I can hear it when I am standing near it, from the listening position I can just barely hear it with no music playing at 3AM when the house is very quiet. The refrigerator running a couple rooms away is much louder.

 

John S.

 

Thanks heaps. PS: you should be in bed at 3am John not listening to the Topaz ! :-)

 

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[asdf1000]

Just teach it to hum with the tunes!

(or put it in another room)

Hilarious! I'll see if separate room is possible, otherwise a box around it but I'll keep a close eye on temperature.

 

 

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[asdf1000]

Yes my Topaz hums a little, it is an acoustic Hum (the output is 60Hz AC which of course is the ultimate hum!). I built a box around it with some pillows for now. It does get a little warm so you have to be careful with thermal management.

 

Without the box I can hear it when I am standing near it, from the listening position I can just barely hear it with no music playing at 3AM when the house is very quiet. The refrigerator running a couple rooms away is much louder.

 

John S.

 

Hi John, I found an Elgar 2.5kVA iso trans that's a few hundred dollars cheaper than the ones on eBay that are willing to ship to Australia. And I've found a local electrician (who also designed his own smaller iso trannies) who's happy to make it suitable for Australian operation (an IEC inlet and Australian 3-pin outlet) and check the safety etc.

 

The specified coupling capacitance is even lower than your Topaz at 0.0005 pF !!

 

Check out the manual here, where they discuss the use of Faraday shielding and other things: http://www.programmablepower.com/products/Discontinued/Downloads/HIT%20Series%20-%20High%20Isolation%20Transformers.pdf

 

What are you thoughts? Are there any areas where your Topaz would be better or overall are they much the same, i.e. both very very good for audio applications?

[asdf1000]

A few quick words on what is happening with the transformers I have been talking about and how to setup a system using them.

 

It starts with the leakage loops I have been talking about recently. Remember these are loops that go through the AC mains, power supplies, DC output of power supplies, interconnects (audio and digital) to other power supplies and back through the AC mains. Note this has nothing to do with the "third pin" safety ground. I've gone over this in detail in other posts.

 

You can get rid of the noise generated by these loops in two ways, block the loop somewhere in the loop (The LPS-1 does this for certain paths), OR decrease the impedance along the loop, if the impedance is lower the NOISE generated by the CURRENT will be less.

 

This post is all about the AC side of this.

 

To decrease the impedance on the AC you need to have the lowest possible amount of wire, filters, anything else between the outlets you plug your AC cords into. This specifically means NO filters in the power strips, they dramatically increase the leakage currents between boxes plugged into such a strip.

 

Ideally you should have ONE power strip with EVERYTHING in your audio system plugged into that one strip. By everything I mean everything that has an AC plug that is connected into your audio system somehow. This includes power amps, computers etc.

 

Note this is the ideal situation, try and achieve this if you possibly can. For example if you are in a 120V area and you have two 700 watt power amps you can't do that, so some other arrangement will have to be made.

 

BTW the power strip for this does not have to be very expensive. I am currently using a $35 Tripp Lite power strip, no nothing inside, circuit breaker, switch, outlets and wires. Just this alone replacing my $1000 audiophile power filtering strip made a huge improvement in sound.

 

So now you have gotten rid of those expensive filtering power strips, doesn't that leave your system exposed to all the crud on the AC line from your other deices in your house and your neighbors as well? That is where the isolation transformer comes in.

 

These transformers with the very low interwinding capacitance are VERY effective noise filters AND surge suppressors without increasing leakage currents. MANY MANY of the filtering systems in your audiophile power strips DO filter out the noise, BUT they add large amounts of leakage currents into the system. These isolation transformers block the noise without adding leakage currents.

 

So the system as a whole is the isolation transformer feeding a very simple, very low impedance power strip with everything plugged into that power strip. This gets rid of external AC mains noise, deals with surges and provides a very low impedance AC mains path that significantly cuts down on the noise from the leakage loops.

 

Note it does not decrease the actual leakage loops, they are still there, it just decreases the NOISE generated by these loops, and THAT is what really matters.

 

So devices like the LPS-1 will BREAK loops from the digital side of things, which are usually the worst ones in a system, the above AC mains topology will decrease the noise generated by the leakage loops in the rest of the system, DACs, preamps, poweramps etc.

 

John S.

Thanks for sharing John. Always nice to see simple but effective noise reducing solutions that doesn't break the bank at all. I'm constantly learning from your posts. Having purchased a microRendu and now an LPS-1, your time spent sharing your experience and knowledge around here is not wasted, I promise you that! :-) I think many other customers of the products you've worked on would agree

 

 

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[asdf1000]

John, regarding an isolation transformer, something like this? https://www.amazon.com/Tripp-Lite-Isolation-Transformer-Outlet/dp/B00006HPFH

 

If not, would you recommend something?

Thanks,

Jim

 

I'm definitely not answering on behalf of John here (not at all qualified to) but I've been emailing all the worlds major iso transformer manufacturers (even medical class) and none can come close to the <<< 1pF coupling capacitance.

 

But feel free to ask around and share if you can find a current production unit like this. It would have to be an expensive custom design and customer order I would think. I THINK that's why John mentioned the Topaz is a bit of a special beast.

[asdf1000]

From the Eaton 100-Suppress Tech Sheet -

 

"Audible noise: Less than 50 dBA measured at 3 feet from the noise suppressor".

Hmm, my listening noise floor is ~35dBA. //& no next room possible, so box & pillows coming up!

 

Hey mate, are you planning on getting a Topaz too or the Eaton? I hadn't see any Eaton's available in Oz but could be wrong.

 

I've got my Elgar on the way as well as my LPS-1 next month. Can't wait!

[asdf1000]

Well, I was going to ring Eaton Australia & see if they stocked or could get one here - no idea of cost. Their website is hopelessly opaque / all over the place! But iso transformer is on product lists at 240V.

 

I already went to Eaton Aus and asked the question. They said no, it's a US only product, not sold here. Eaton US said yes but to ask Eaton Australia. Round and round we went.

 

So are you going to get a Topaz then? The shipping is as much as the units themselves.

[asdf1000]

An isolation transformer has the capability to markedly reduce mains related issues, but knowing whether your particular location will get a further worthwhile improvement for the additional cost is not predictable, at least for typical suburban areas .Large apartment complexes with lifts etc., or in an industrial area may be a different matter though.

 

It would be great if you were able to first try an isolation transformer before forking out the money.

Neither is it normally advisable to use an isolation transformer with higher powered amplifiers than perhaps 100W per channel.

 

 

I currently have a pair of 1600W subwoofers and a 350W per channel integrated amp (amp's power consumption up to 1100W max) , all plugged into a PS Audio Dectet power board/ power conditioner.

 

If it's not been a problem with this powerboard, could my setup have a problem with an iso transformer (which has a 10A circuit breaker installed of course)? If so, how so? Appreciate the advice

 

Cheers

[asdf1000]

Are your 1,600W Subwoofers powered from a different outlet ?

Perhaps John Swenson or Alex C are better equipped to give you a definitive answer WRT the required size of isolation transformers, although I don't believe you can automatically transfer the USA experience to our own 240V (nominal) 50HZ supply.

The highest powered amplifier I have ever used was a DIY 240W/Ch. amplifier, and it could momentarily dim a nearby table lamp when starting up.

 

My GoldenEar Triton Ones, each with inbult 1600W subs, and my integrated amp are all currently plugged into the same PS audio Dectet powerboard, on the same one outlet. So I have 1600W x 2 + 700W x 1 plugged into the powerboard (in excess of 2400W) and have never had an issue, so I'm guessing my power consumption has to be less than the 2400W limit of the power board.

 

I think 2.5kVA equals 2kW ? So a 2.5kVA iso transformer could potentially not provide enough juice for my setup. Depending on the amp's drawn I'm guessing?

 

Thanks again in advance

 

PS: i really WISH I was consuming enough power to dim the lighting on start up :-)

[asdf1000]

I presume that your 1600W subs are Class D and perhaps SMPS powered as well ?

If so, I am wondering whether your integrated amplifier would perform better if powered via an Isolation transformer .

Perhaps John or Alex C who have vastly more experience in this area could chime in ?

 

Alex

Yep the subs are Class D and so is the integrated amp.

 

I don't know much about their built in power supplies though.

 

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[asdf1000]

Can an iso trans be plugged into a powerboard to power a single device, like my integrated amp (with it's built in DAC)? I know John said it's best to having everything plugged into the powerboard with the powerboard plugged into the iso trans and iso trans into the wall.

 

I couldn't find a 3kVA ++ iso trans (240V) though so went for a 2.5kVA. Which will support up to 8 amps? I THINK I should be ok but don't have the exact power consumption figures for my system and my usage.

 

But if I can use it for my Amp/Dac that would be good but it would need to be plugged into a powerboard

 

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[asdf1000]

Hi John and Alex

 

Would these Topaz iso transformers have a power factor of 1? Or nearer to 0.8?

 

Trying to workout if 2.5kVA is close enough to 2500W or closer to 2000W

[asdf1000]

Hi all, does anyone know what the power factor for an iso transformer like the Topaz would be? Can we assume 2.5kVA equals 2.5kW ? Or does 2.5kVA equal 2.0kW for an iso transformer.

 

Many thanks in advance

 

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[asdf1000]

Very interesting question. I tested mine out and found the PF varied with load current. At low currents the PF was around 5. By the time it got to 10% of rating is was about 8.5. I didn't try higher than that. Somewhere I have a couple 200W halogen lights I could use to load the thing a little more and see what it does.

 

John S.

Thanks John ! I thought power factors ranged from -1 to +1 ? I am no expert, just relying on my limited googling abilities.

 

So I thought kW = kVA x Power Factor

 

 

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[asdf1000]

Sorry, that was supposed to be 0.5 and 0.85.

 

John S.

Thanks again John. So for these Topaz units and other similar, it might be a good idea to use kW = kVA x 0.5 (PF) x 0.8 (safety factor) when sizing an iso transformer. After measuring actual system consumption as per Dave's post above.

 

 

 

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[asdf1000]

Em2016

 

I don't wish to come across as a wet blanket, but your limiting factor may turn out to be your Integrated amplifier using Class D output stages with it's internal DAC. It would be exceedingly hard for a manufacturer to design an internal DAC using the existing power supplies that won't be affected to some degree by the Class D processing, RF/EMI radiation and PSU interaction , in comparison with a high quality external DAC using a completely separate power supply.

I am not saying it's impossible, but it would take a lot of hard work, as it would be a hostile environment .

Alex

Alex - on the contrary I appreciate any comments. I really enjoy and appreciate all the discussion here. I hear what you're saying - the all in one (pre, power and DAC) comes with comprises, sometimes significant.

 

I'm actually going down the path of separates (pre, power and DAC) though in the near future though for the reasons you mentioned. Or just adding a separate DAC and keeping the integrated.

 

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