Discussion of AC mains isolation transformers

[asdf1000]

A fuse may protect the equipment from further damage, or perhaps even a fire. (fuses don't normally blow except in major fault conditions) but it only takes 50mA through your body to kill you. You can even get a shock at from a light switch that has absorbed moisture, (I did a couple of years ago, although the shock was mild) with the return path through the floor. In that case, if the leakage was high enough, the RCD that most modern houses have will protect you. The same can happen when using an electric drill on a wall and the bit hits a hidden power cable.

Ah yep. But there was an earlier post from One and a Half that mentioned the home's RCD may not be enough when specifically using an iso transformer though, hence the recommendation for a portable RCD on the iso transformer's outlet (I may have misunderstood the technical explanation about why though).

[sandyk]

Ah yep. But there was an earlier post from One and a Half that mentioned the home's RCD may not be enough when specifically using an iso transformer though, hence the recommendation for a portable RCD on the iso transformer's outlet (I may have misunderstood the technical explanation about why though).

 

Like One and a half, I am also recommending using an RCD with the transformer and not just relying on a fuse. The Jaycar website does not appear to be recommending the use of an RCD in conjunction with fuses, which I doubt was their intention.

[asdf1000]

Like One and a half, I am also recommending using an RCD with the transformer and not just relying on a fuse. The Jaycar website does not appear to be recommending the use of an RCD in conjunction with fuses, which I doubt was their intention.

Noted. The death-by-50mA is enough reason !

[asdf1000]

Like One and a half, I am also recommending using an RCD with the transformer and not just relying on a fuse. The Jaycar website does not appear to be recommending the use of an RCD in conjunction with fuses, which I doubt was their intention.

Something like this plugged directly into the iso transformer, with all your Hi-Fi gear coming off it, should work well right?

 

https://www.bunnings.com.au/arlec-8-outlet-10a-rcd-and-lp44-heavy-duty-power-block_p4420225

 

No surge protection and no filtering between outlets. And the build quality would be good (I think Australian made).

 

Just thinking about the circutry between the outlets in a powerblock like this - is it just wires? No filtering components?

[sockpit]

Sorry, but I must have missed something about these transformers (I got a Topaz last week and it does work!). Is it really necessary to use a ground fault interrupter? I thought the point was to go utterly simple: a transformer that can take a surge plus a dead simple power strip. I'm in US if that makes a difference. Thanks for your patience with someone not electrically informed.

 

 

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[asdf1000]

As promised, here is the reason to install an RCD/GFCI.

Hi all, this is the post and link to read, regarding using an RCD with iso transformer. The technical stuff is a bit over my head but the conclusion and recommendation definitely can't be ignored (regarding safety).

 

 

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[sandyk]

Something like this plugged directly into the iso transformer, with all your Hi-Fi gear coming off it, should work well right?

 

https://www.bunnings.com.au/arlec-8-outlet-10a-rcd-and-lp44-heavy-duty-power-block_p4420225

 

No surge protection and no filtering between outlets. And the build quality would be good (I think Australian made).

 

Just thinking about the circutry between the outlets in a powerblock like this - is it just wires? No filtering components?

 

That should be fine. Devicres like that are often used by tradesmen working outside from mains extension leads.

[sockpit]

So in lay terms: is the problem that these isolation transformers isolate my system from my home circuit breaker box such that if there was a short or malfunction somewhere in my system the circuit breaker couldn't do its job? That doesn't seem quite right since the job of the simple breakers in the box, I thought, were to protect from outside surges. My bathrooms and kitchen have ground fault outlets, no doubt because near water. But my listening room/office doesn't, nor do most rooms in American homes. So what exactly does a Topaz or Elgar do that makes it wise to add a GFCI/RCD? Patience is appreciated.

 

 

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[Middy]

I thought it doesn't trip through the Transformer back to the main board? Is this why?

 

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[One and a half]

I thought it doesn't trip through the Transformer back to the main board? Is this why?

 

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Briefly, yes.

[asdf1000]

That should be fine. Devicres like that are often used by tradesmen working outside from mains extension leads.

I returned the Clipsal plug in type adapter. The RCD on LED indicator is either too faint or doesn't work.

 

The Arlec has access issues to the outlets for my thick shielded power cables so I got this instead: https://www.bunnings.com.au/hpm-10amp-electresafe-power-centre_p4420181

 

No LED indicator, just the traditional safety switch type indicator which flips up and down for on and off - a much clearer indication.

 

I just have the basic power board just plugged into one of the portable RCD's 4 outlets and all my gear in that power strip.

 

Really enjoying the improvement in sound of my system with this iso trans and it's nice to know the safety side is improved too (thanks One and a Half).

 

 

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[sockpit]

John S.: might you comment on the safety of the Topaz isolation transformer with respect to the need to add a GFCI to its output? See the few posts above. I bought one. It has improved SG? I'd don't want to die. Thank you.

 

 

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[Cornan]

John S.: might you comment on the safety of the Topaz isolation transformer with respect to the need to add a GFCI to its output? See the few posts above. I bought one. It has improved SG? I'd don't want to die. Thank you.

 

 

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+1 I am also very interested in a reply from @John Swensson regarding the safety aspect in 120v and 230v countries with a central RCD/GFSI installed. I have recently e-mailed to Airlink support regarding adding a extra portable GFSI between the IT and my DAC. I will post it here as soon as they have replied (ie. no reply yet). I will also check if this issue is somehow different with 120v and 230v mains.

 

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[sockpit]

John S.: might you comment on the safety of the Topaz isolation transformer with respect to the need to add a GFCI to its output? See the few posts above. I bought one. It has improved SG? I'd don't want to die. Thank you.

 

 

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Correction, it should read: "It has improved SQ!" I've listened for a week now , and it's akin to upgrading an LPSU. Am doing this on US 120 v.

 

 

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[One and a half]

So in lay terms: is the problem that these isolation transformers isolate my system from my home circuit breaker box such that if there was a short or malfunction somewhere in my system the circuit breaker couldn't do its job? That doesn't seem quite right since the job of the simple breakers in the box, I thought, were to protect from outside surges. My bathrooms and kitchen have ground fault outlets, no doubt because near water. But my listening room/office doesn't, nor do most rooms in American homes. So what exactly does a Topaz or Elgar do that makes it wise to add a GFCI/RCD? Patience is appreciated.

 

Protection system in lay terms is not simple to explain, well not for me anyway. I try.

 

The breakers in your box protect against thermal overloads and direct short circuits from Hot to Neutral and Hot to ground.

Bathrooms and kitchens in the US (I've seen in hotels too BTW) do have a GFCI and rightly so, and so should the rest of the house. Speedskater may confirm, I believe new installs for homes would fit a GFCI for all receptacles in the house. Their use is mandatory in AU and I bet in EU. Reason why, is the GFCI protects people and also against a smouldering event.

 

An isolation transformer's secondary side is "isolated" from the house, the neutral is not tied to the ground any more.

If a short circuit occurred on the secondary side of the isolation transformer, there is often not enough current to blow the fuse, due to the transformer's impedance. It cannot supply the necessary over-current to blow the fuse, and you need two of them BTW since each leg on the secondary side is above ground, so are considered live. So the transformer will need to be massively oversized to supply short circuit current, this is not practical.

 

A better approach is to use a GFCI on the output, so that if current (depends how much and which country you are in) doesn't come back to the transformer, the GFCI trips the supply and all is safe. The breaker on the other side of the fence, just supplies the current whatever the transformer wants, it doesn't know about what's happening on the other side. The drawing I posted and referenced here by EM2016 (ty) explains towards this. It also doesn't matter on the type of Isolation transformer, they all do the same function, some are suppressing noise a lot better than others.

[One and a half]

I returned the Clipsal plug in type adapter. The RCD on LED indicator is either too faint or doesn't work.

 

The Arlec has access issues to the outlets for my thick shielded power cables so I got this instead: https://www.bunnings.com.au/hpm-10amp-electresafe-power-centre_p4420181

 

No LED indicator, just the traditional safety switch type indicator which flips up and down for on and off - a much clearer indication.

 

I just have the basic power board just plugged into one of the portable RCD's 4 outlets and all my gear in that power strip.

 

Really enjoying the improvement in sound of my system with this iso trans and it's nice to know the safety side is improved too (thanks One and a Half).

 

 

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Try and avoid the LED or NEON, just adds to the racket we are trying to remove The orange powerboard will do the job, the breaker at the side does all the smart bits, there's only wires inside. Keep it behind the rack for WAF. I did see an inline type with RCD, plug and socket, orange of course.

 

Happy to know of the SQ improvement!

[asdf1000]

Protection system in lay terms is not simple to explain, well not for me anyway. I try.

 

The breakers in your box protect against thermal overloads and direct short circuits from Hot to Neutral and Hot to ground.

Bathrooms and kitchens in the US (I've seen in hotels too BTW) do have a GFCI and rightly so, and so should the rest of the house. Speedskater may confirm, I believe new installs for homes would fit a GFCI for all receptacles in the house. Their use is mandatory in AU and I bet in EU. Reason why, is the GFCI protects people and also against a smouldering event.

 

An isolation transformer's secondary side is "isolated" from the house, the neutral is not tied to the ground any more.

If a short circuit occurred on the secondary side of the isolation transformer, there is often not enough current to blow the fuse, due to the transformer's impedance. It cannot supply the necessary over-current to blow the fuse, and you need two of them BTW since each leg on the secondary side is above ground, so are considered live. So the transformer will need to be massively oversized to supply short circuit current, this is not practical.

 

A better approach is to use a GFCI on the output, so that if current (depends how much and which country you are in) doesn't come back to the transformer, the GFCI trips the supply and all is safe. The breaker on the other side of the fence, just supplies the current whatever the transformer wants, it doesn't know about what's happening on the other side. The drawing I posted and referenced here by EM2016 (ty) explains towards this. It also doesn't matter on the type of Isolation transformer, they all do the same function, some are suppressing noise a lot better than others.

Fantastic explanation for a muppet like me to understand. Appreciated, once again.

 

I'm LOVING my Hi-Fi system at the moment but not more than life itself. Safety first ! [emoji1]

 

 

 

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[asdf1000]

Try and avoid the LED or NEON, just adds to the racket we are trying to remove The orange powerboard will do the job, the breaker at the side does all the smart bits, there's only wires inside. Keep it behind the rack for WAF. I did see an inline type with RCD, plug and socket, orange of course.

 

Happy to know of the SQ improvement!

Yep that inline one is that LED indicator type again. Except I saw Clipsal (Clipsal 956: http://www.clipsal.com/Trade/Products/ProductDetail?CatNo=956) makes an inline with the traditional safety switch that flips up and down for on and off. But this 4 outlet HPM does the same. Nicely sturdy build quality too.

 

Great to know it's just wires between these outlets.

 

Really is sounding fantastic. I hope this thread has helped others as much as it's helped me, thanks to your input and others.

 

 

 

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[asdf1000]

The beast lurking in the background

 

 

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[sockpit]

+1 I am also very interested in a reply from @John Swensson regarding the safety aspect in 120v and 230v countries with a central RCD/GFSI installed. I have recently e-mailed to Airlink support regarding adding a extra portable GFSI between the IT and my DAC. I will post it here as soon as they have replied (ie. no reply yet). I will also check if this issue is somehow different with 120v and 230v mains.

 

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To my knowledge, my house in US just has an old fashioned breaker panel, but no centralized GFCI protection. But I could be wrong given my ignorance.

 

In any case, I'd sign a liability waiver to hear @JohnSwenson, who recommended the Topaz/simple strip solution, tell us whether he uses a GFCI on the output end of his Topazes, and why or why not? Am as curious how dangerous these units might be as I am thankful for learning about them. See above about a dozen or so posts for a sprinkle of concern and discussion of GFCIs/RCDs. Thanks in advance.

 

From a JS-2, mRendu, and soon-to-be LPS-1 owner

[mikicasellas]

Hey John,

 

While i am waiting for the LPS-1 and don't have the adequate power conditioner/Isolation transformer, i have been plugging every item of my system to the Tripplite and from it to the wall to an Oyaide wall outlet and i feel like the sound is more "dirty" at least more anemic . I used to have every gear direct to the wall with Oyaide wall outlets, do you consider that once the Topaz or similar in this equation things will better and noise will go down considerable? or do i need a dedicated PS for my system and the Topaz is only intended for the digital end?

 

Sorry if i am asking about already answered issues, i am a little lost here and just want to be sure that i will be putting my coins in the right place in the right order

 

Thank you

 

Regards

 

Miki

 

The fourth one down in your list is the only one with outlets and a cord so it is probably the one to go with. The picture does not show if there is a plug on the cord, you may have to add one yourself (very easy to do). I assume you are in the US so you use 120V? This one is 120 in 120 out which is what you most likely want for a room in the US.

 

John S.

[jamesg11]

Yep that inline one is that LED indicator type again. Except I saw Clipsal (Clipsal 956: Clipsal - 956 - Extension Lead, 10A, 240V, 30mA, 2m, IP56) makes an inline with the traditional safety switch that flips up and down for on and off. But this 4 outlet HPM does the same. Nicely sturdy build quality too.

 

Great to know it's just wires between these outlets.

 

Really is sounding fantastic. I hope this thread has helped others as much as it's helped me, thanks to your input and others.

Em, so you eventually went for a 4 outlet HPM - which one? Sorry, I lost track!

/& I'm pleased that the Elgar was quiet - my reservation has been fear of adding to the noise floor, seeing I can't locate an iso tran anywhere else other than the listening area.

[asdf1000]

Em, so you eventually went for a 4 outlet HPM - which one? Sorry, I lost track!

/& I'm pleased that the Elgar was quiet - my reservation has been fear of adding to the noise floor, seeing I can't locate an iso tran anywhere else other than the listening area.

Hi mate, the HPM is a cheap charlie board I had lying around. But they're the ones with no surge protection and no filtering, so they'll do the job while I'm still looking for a better built board with Aussie outlets.

 

Even VT4C weren't able to help because they don't have any Aussie outlets. Other option is I buy some outlets and send them to him to wire up and install, if he's happy with that. Might send an email now.

 

The only issue with the HPM board is I can't use my shielded power cable (which I used with my PS Audio Dectet) from the RCD outlet.

[asdf1000]

Em, so you eventually went for a 4 outlet HPM - which one? Sorry, I lost track!

/& I'm pleased that the Elgar was quiet - my reservation has been fear of adding to the noise floor, seeing I can't locate an iso tran anywhere else other than the listening area.

 

Greg Osborne (Osborne Loudspeakers) sells this: Untitled Document

 

8 international outlets, shielded box, no filtering/conditioning circuitry, IEC inlet so I can use my shielded power cable.

That might be the only option I'm left with but I'm in no rush - still looking around.

[JohnSwenson]

Hey John,

 

While i am waiting for the LPS-1 and don't have the adequate power conditioner/Isolation transformer, i have been plugging every item of my system to the Tripplite and from it to the wall to an Oyaide wall outlet and i feel like the sound is more "dirty" at least more anemic . I used to have every gear direct to the wall with Oyaide wall outlets, do you consider that once the Topaz or similar in this equation things will better and noise will go down considerable? or do i need a dedicated PS for my system and the Topaz is only intended for the digital end?

 

Sorry if i am asking about already answered issues, i am a little lost here and just want to be sure that i will be putting my coins in the right place in the right order

 

Thank you

 

Regards

 

Miki

 

Are the Oyaide outlets all right next to each other? if yes then it IS already a very low impedance connection. The tripp Lite is probably notas good as the Oyaide. (but is a lot cheaper!) If you think the Oyaide sound better you have a couple oprions: keep them in the wall, you then get to wire the ISO transformer somehow into the outlets in the wall, OR build your own power strips with your existing Oyaide outlets (those ones from China listed earlier for this will be great for that).

 

If you currently do not have anything between the wall circuits and those Oyaide outlets then adding the Topaz should clean up a lot of noise on the line.

 

John S.