Discussion of AC mains isolation transformers

[Forehaven]

Further regarding safety, for medical/hospital equipment, in which electrical leads are attached to people's bodies, these isolation transformers, with low leakage current, are used, in the configuration above.

 

This is *better* than GFCI -- my understanding is that GFCI trips in the 5mA range whereas the leakage current with such high quality transformers may be in the 10s of microA range i.e. roughly 2-3 orders of magnitude less.

 

E.g. : https://shop.plitron.com/specs/600VANA.pdf

 

Hi Jabbr,

 

I have two Oyaide R1 outlets not in use. I have a 10"x10"x 2.5" solid block of Padouk wood. So I'm going to router out some space for the outlets and build a simple 2 outlet power block. Can you, or anyone else, recommend a very high quality Hook Up Wire to wire outlets together?

[jabbr]

Hi Jabbr,

 

I have two Oyaide R1 outlets not in use. I have a 10"x10"x 2.5" solid block of Padouk wood. So I'm going to router out some space for the outlets and build a simple 2 outlet power block. Can you, or anyone else, recommend a very high quality Hook Up Wire to wire outlets together?

 

There are various gauges of mil-spec silver plated copper wire for cheap on eBay that I use. Get 3 colors for black/white green/ground.

 

You can also use 3 braided twisted pairs for AC cords etc.

 

Eg: https://www.ebay.com/itm/142191303287

[Middy]

There are various gauges of mil-spec silver plated copper wire for cheap on eBay that I use. Get 3 colors for black/white green/ground.

 

You can also use 3 braided twisted pairs for AC cords etc.

 

Eg: https://www.ebay.com/itm/142191303287

I got a good twist using a drill and a vice.

Lock the 3 wires in the vice then twist the other 3 bare wires together so they fit in the chuck.

 

You may have to slightly over twist for spring back of the sleeving..... if you can a heat gun or hairdryer just to soften the sleeving a bit to set the twist....

 

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[Middy]

I am actually thinking of scrapping my Isotek Isoplug plan and ask ATL Hi-Fi for a boxed screw terminal DC BLOCKER TRAP FILTER pre my Peaktech....so I can use it with my coming DH-Labs SS AC cable with the longer half of the cable (1,5m) with Schuko plug to the AC input (from wall outlet to DC BLOCKER TRAP FILTER) and the shorter half (0,5m) with IEC plug to the AC output (connected to Peaktech). My IT is dead silent even close up...but still..it could be interesting if it can accomondate 12 AWG wires. Hmmmm?

It looks like there is some latitude on what you can ask for which is rare these days ...

Does the peak tech have a soft start for your kit safety?

 

But I have gone down the Iso plug route last night.... I'll see what it does when it comes......

But I suppose we all have different issues so my noisy 1930 house may benefit......

I may save up and get a separate line for just my audio... Will have to get new power unit....

 

I just need Cornan to move here to try things first..... If he snores less than the wife he's in....

 

Keep smiling

Dave [emoji4]

 

 

 

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[JohnSwenson]

There have been several posts recently in this and other threads where it has been stated that the common mode noise attenuation of an isolation transformer depends on whether the secondary is connected to safety ground or not.

 

This is simply not true. It is easy to test this. Take any transformer (it doesn't have to be an expensive iso transformer, any transformer will do) it can be anything as long as it is a true transformer, not an autoformer. For the test a simple 120V to 12.6 V transformer will do fine. You need a signal generator and a scope, set the generator to either 200 or 240 Hz. If in an area with 60Hz AC line use the 200Hz, if in an area with 50Hz AC line use 240Hz. You want something that is NOT a multiple of the line frequency. You will need a safety ground. Take it off a chassis that is grounded, or the green wire of a power cord etc. We will NOT be using the hot or neutral, just the safety ground.

 

The definition of common mode noise is that it is noise that is the SAME on both wires of the primary of the transformer relative to some other reference point, usually the safety ground. So we will deliberately inject a common mode signal into a transformer and see if we can detect it on the output. So connect the negative of the signal generator to safety ground, and the positive to BOTH primary wires of the transformer. Nothing else connected to the primary wires, DO NOT connect the primary wires to the AC line. You have been warned, I will NOT be responsible for what happens to your signal generator if you do that!!!

 

Now use a scope to measure if you see any of the input signal on the secondary wires. But first we have to figure out what we are testing. Are we testing common mode noise on the output (common mode in to common mode out) or differential (common mode in to differential out). Nobody ever mentions this distinction when talking about the subject. So lets measure both.

 

But second we have to figure out where safety ground comes into this. The problem is that most scopes have their "gnd" of the probes connected to safety ground, which makes it very difficult since we are testing how the system behaves relative to safety ground. So the best way to do this is with an isolating differential probe.

 

Then it is simple, use the differential probe to measure between the two secondary wires, this measure the differential output, then measure between safety ground and one wire of the secondary, then between safety ground and the other. THEN connect the safety ground to one of the secondary wires and repeat the three tests.

 

THIS will test whether common mode attenuation of a transformer has anything to do with how safety ground is connected.

 

John S.

[JohnSwenson]

Duplicate

 

John S.

[flkin]

So we should float the secondary?

 

 

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[asdf1000]

Thoroughly enjoying the John Swenson value meal of gadgets at the moment.

 

Although my wallet won't be happy, I can't wait to see what Swenson and Co. cook up next.

 

My dreams are for an integrated with ultracap power supply but my guess is a DAC is more likely to come first. Just guessing though.

 

That would be cool and potentially more affordable than the existing integrated on the market - an external DAC and matching external power amp, each with in-built (or higher capacity external?) ultracap power supply.

 

Apart from John himself (and Alex C I'm guessing) are there any other "microRendu + LPS-1 + DC-4 + wire only powerstrip + ultra high isolation transformers (<<< 1pf inter-winding capacitance)" users out there?

[bunno77]

Mine is close (different iso) but you already know that [emoji14]

 

-Peach Audio Balanced Isolation Power Supply, Uptone LPS-1, Sonore Microrendu, Geek Pulse S Infinity, McIntosh MA2275, Paradigm 30th Anniversary Tributes, SVS SB13 Ultra

-Cambridge 752BD Oppomod PSU, Halcro MC50, Sonos ZP90 (Cullen Mod), Cyenne Audio CY-3100 DAC , Denon AVR4520, Aaron ATS-5, Aaron CC-250, Epos Epic 5, Cambridge Audio Azur 551R V2

[asdf1000]

Mine is close (different iso) but you already know that [emoji14]

 

-Peach Audio Balanced Isolation Power Supply, Uptone LPS-1, Sonore Microrendu, Geek Pulse S Infinity, McIntosh MA2275, Paradigm 30th Anniversary Tributes, SVS SB13 Ultra

-Cambridge 752BD Oppomod PSU, Halcro MC50, Sonos ZP90 (Cullen Mod), Cyenne Audio CY-3100 DAC , Denon AVR4520, Aaron ATS-5, Aaron CC-250, Epos Epic 5, Cambridge Audio Azur 551R V2

Haha nice one. Hadn't seen you on this forum before. Using Tapatalk on my phone I sometimes forget which forum I'm posting on (between this one, StereoNet and AVS).

 

I bet you're looking forward to getting it all hooked up and singing! Not long to go now right?

 

I tried to ask the Peach Audio iso transformer designer what the inter-winding capacitance is but he never replied :-( Otherwise I probably would have got that too. My Elgar was only USD200 + USD150 shipping + AUD150 to make it suitable for Australia, so worked out to be semi reasonable in the end.

 

I backed away from the medical iso transformers after a few manufacturers replied with their interwinding capacitance specs (Noratel had > 1pf from memory, compared with 0.0005pf for the Elgar I picked up on eBay). Not because I'm any sort of expert but I wanted to follow John's and Alex's recommendations on ultra low interwinding capacitance pretty closely.

 

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[bunno77]

I had been stalking you from the shadows haha.

Yeah I can't wait but won't be until Feb/ March next year when I'm back in the country unfortunately.

Ahh ok. He was easy to find a while back via a phone call...

That's very cheap mate.

Hopefully not long until your Lps arrives

 

-Peach Audio Balanced Isolation Power Supply, Uptone LPS-1, Sonore Microrendu, Geek Pulse S Infinity, McIntosh MA2275, Paradigm 30th Anniversary Tributes, SVS SB13 Ultra

-Cambridge 752BD Oppomod PSU, Halcro MC50, Sonos ZP90 (Cullen Mod), Cyenne Audio CY-3100 DAC , Denon AVR4520, Aaron ATS-5, Aaron CC-250, Epos Epic 5, Cambridge Audio Azur 551R V2

[asdf1000]

For anyone interested, I just rechecked the email with the Noratel medical iso transformer spec. While it has ultra low leakage current between the primary and secondary windings as you'd expect for medical applications, the inter-winding capacitance spec they told me was < 1300pf . So while I did ask John S earlier in this thread about medical iso transformers, this is why I went looking for a Topaz type in the end. That's not to say every medical iso transformer has an interwinding capacitance spec of that figure but rechecking old emails , the figures from medical iso transformer manufacturers were > 100 pf .

 

I don't know if > 100 pf is a bad thing but John and Alex seemed to emphasise going for an ultra low figure so I just went looking for one of these old Topaz type units from the US.

 

Just wanted to share all that, in case that helps others that are shopping around for an iso transformer.

 

Again, I'm no expert. I just followed John's recommendations.

 

 

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[JohnSwenson]

For anyone interested, I just rechecked the email with the Noratel medical iso transformer spec. While it has ultra low leakage current between the primary and secondary windings as you'd expect for medical applications, the inter-winding capacitance spec they told me was < 1300pf . So while I did ask John S earlier in this thread about medical iso transformers, this is why I went looking for a Topaz type in the end. That's not to say every medical iso transformer has an interwinding capacitance spec of that figure but rechecking old emails , the figures from medical iso transformer manufacturers were > 100 pf .

 

I don't know if > 100 pf is a bad thing but John and Alex seemed to emphasise going for an ultra low figure so I just went looking for one of these old Topaz type units from the US.

 

Just wanted to share all that, in case that helps others that are shopping around for an iso transformer.

 

Again, I'm no expert. I just followed John's recommendations.

 

 

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To figure out what aspect of the transformer is important, go back to the reason for using it in the first place. Go back several posts where I talk about what the iso transformer was for in the first place, it was NOT for low leakage, other parts in the system deal with that, it was to provide a means of surge protection and external world noise reduction. The very low inter-winding capacitance of the Topaz etc is what does that. The low cap means that the transformer starts blocking frequencies at about 400Hz, which means it does a very good job of blocking external world noise. Because power surges contain most of their energy in higher frequency components it also is an effective surge suppressor.

 

If you use a transformer with much higher inter-winding capacitance neither of those things is true, so you have negated the whole purpose for using the transformer in the first place.

 

John S.

[Cornan]

To figure out what aspect of the transformer is important, go back to the reason for using it in the first place. Go back several posts where I talk about what the iso transformer was for in the first place, it was NOT for low leakage, other parts in the system deal with that, it was to provide a means of surge protection and external world noise reduction. The very low inter-winding capacitance of the Topaz etc is what does that. The low cap means that the transformer starts blocking frequencies at about 400Hz, which means it does a very good job of blocking external world noise. Because power surges contain most of their energy in higher frequency components it also is an effective surge suppressor.

 

If you use a transformer with much higher inter-winding capacitance neither of those things is true, so you have negated the whole purpose for using the transformer in the first place.

 

John S.

 

Thanks John!

Let's talk about inter-winding capacitance since this is a crucial part of the benefits with ITs. AFAIK a grounded shield between the primary and secondary windings will increase impedance and ensure low inter-winding capacitence. Is'nt that a fact?

 

 

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[asdf1000]

To figure out what aspect of the transformer is important, go back to the reason for using it in the first place. Go back several posts where I talk about what the iso transformer was for in the first place, it was NOT for low leakage, other parts in the system deal with that, it was to provide a means of surge protection and external world noise reduction. The very low inter-winding capacitance of the Topaz etc is what does that. The low cap means that the transformer starts blocking frequencies at about 400Hz, which means it does a very good job of blocking external world noise. Because power surges contain most of their energy in higher frequency components it also is an effective surge suppressor.

 

If you use a transformer with much higher inter-winding capacitance neither of those things is true, so you have negated the whole purpose for using the transformer in the first place.

 

John S.

Thanks John. If anyone didn't fully and clearly understand the reasons for going for the Topaz/Eaton type units (including myself) versus other units , it's now crystal (clear) to us all.

 

 

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[joelha]

My amplifiers are a good distance from my front end and even from each other.

 

I already have a 1Kva Topaz unit on the front end and on day one the results are remarkable.

 

My question is, will I still get the benefit of additional transformers if I put one each on each mono amp, separate from the unit powering the front end?

 

Thanks.

 

Joel

[d_elm]

My amplifiers are a good distance from my front end and even from each other.

 

I already have a 1Kva Topaz unit on the front end and on day one the results are remarkable.

 

My question is, will I still get the benefit of additional transformers if I put one each on each mono amp, separate from the unit powering the front end?

 

Thanks.

 

Joel

 

I suggest you try an amp on a transformer before purchasing one or two more. My amp sounds better without an Elgar 1.0R than with.

 

 

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[joelha]

I suggest you try an amp on a transformer before purchasing one or two more. My amp sounds better without an Elgar 1.0R than with.

 

 

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What an interesting post, d_elm. Thanks for offering your experience.

 

I never would have guessed that the transformer would have reduced the sonic quality of an amp. On the other hand, that's why I'm asking.

 

Switching my transformer to just one amp would be a little tough for a number of reasons, but I appreciate the suggestion.

 

Joel

[One and a half]

What an interesting post, d_elm. Thanks for offering your experience.

 

I never would have guessed that the transformer would have reduced the sonic quality of an amp. On the other hand, that's why I'm asking.

 

Switching my transformer to just one amp would be a little tough for a number of reasons, but I appreciate the suggestion.

 

Joel

 

Au contraire. Left channel can have the transformer, the right channel the existing setup. A mono signal should give you a very different image.

[sig8]

I have been following this thread for a while, and I have bought a 1kVA Topaz isolation transformer. I have read some concerns about fire risks. is there any real fire risk with these transformers,if one does not overload it? I know all electrical gear has some risk, but do these transformers need extra care? If there is any increased risk, I would not want to take it, just not worth it. Please let me know. Thanks.

[d_elm]

I suggest you try an amp on a transformer before purchasing one or two more. My amp sounds better without an Elgar 1.0R than with.

 

 

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I changed the AC plug on the Elgar 1.0R to a Hubbell and retried the amp on the transformer. SQ is better than with the old plug and now I have not determined a difference. I am comfortable with that as now the amp is isolated from the furnace motor and fridge compressor.

 

 

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[JohnSwenson]

I have been following this thread for a while, and I have bought a 1kVA Topaz isolation transformer. I have read some concerns about fire risks. is there any real fire risk with these transformers,if one does not overload it? I know all electrical gear has some risk, but do these transformers need extra care? If there is any increased risk, I would not want to take it, just not worth it. Please let me know. Thanks.

 

No, there is no extra risk of fire with these transformers. The only issue is that they can hum a little bit (I KNOW someone is going to ask if they can hum in tune with the music), IF you put a lot of flammable material around it to block the hum you can block air flow which could cause it to get hot. So don't do that!

 

John S.

[Superdad]

The only issue is that they can hum a little bit (I KNOW someone is going to ask if they can hum in tune with the music),...

 

Not today sparky, but I did find this fun video of some very musical Tesla coils!

 

[Middy]

Hi John, I bought as you probably read a DC offset filter...I only got in case the humming was to loud in the bedroom...

I did find apart from reducing the very slight hum to almost nothing....

To my ears it sounds a lot better out of my Amp DAC...

Is this as the Toroidal trans former is energised equally so the balanced feed cancels out more common mode noise? The x 2 115v rails are more in opposit phase...

Please this is a wild guess from what you and other have mentioned here..

That DC bias/offset does more that vibrate the Transformer? Reducing the filtering aspect...

 

Thanks as always for the help much appreciated. . and Super D..

Cheers

Dave

 

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[joelha]

At the risk of being a pain, I''ll ask again about the value of putting separate isolation transformers on power amps.

 

is that a good idea or not so much?

 

Thanks,

 

Joel