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Discussion of AC mains isolation transformers


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5 hours ago, One and a half said:

and are only a problem is the earth/ground to neutral voltage is higher than a 0.5Vac.

Unless a large permanent transformer is wired as a Separately Derived System,  there will almost always be more than a 0.5 VAC difference between the Neutral and Safety Ground/Protective Earth when a large amount of current is flowing.

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9 hours ago, One and a half said:

Not a fan of the PS audio power gear, since the design is essentially a UPS without the battery. There's a lower impedance from the wall outlet than the PS audio gear.

Certainly the Topaz can be used on the output of any UPS to remove the common mode noise that inherently UPS produce. I've played with this concept in the back of my mind, but an online UPS is noisy for audio powers, both acoustically and electrically on the front end.

 

Harmonic distortion affects transformer's abilities by reducing output power. Harmonics in the order of >3% are common for houses, and are only a problem is the earth/ground to neutral voltage is higher than a 0.5Vac. Equipment will still run, but the harmonics can get into DC supply rails in amps where it can be heard. Have a look on page 15 of the pdf to see measurements. I tested my own amp, and a spectral analysis revealed only the frequency I has playing and nothing else, so the construction of the amplifier has a great deal of influence. There's also scope photos of different power cables on amps also interesting.

 

For a power strip use a plain type, no suppressors.

Studies On Residential Power Line Noise.pdf

Thanks for the reply.  

 

From the pdf, it looks like were using ps audio power regenerators and liking the results,

but now have moved away from them?

 

Have you ever looked into the Richard Gray products?

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7 hours ago, Speedskater said:

Unless a large permanent transformer is wired as a Separately Derived System,  there will almost always be more than a 0.5 VAC difference between the Neutral and Safety Ground/Protective Earth when a large amount of current is flowing.

Agreed, you'd open your eye to what sort of current is down that neutral. Not so much domestic dwellings, but apartment blocks with all those SMPS and inverter type aircons. From memory (which is kinda bad) the neutral needs to be min. 1.3 times the size of the conductors for sub mains to cope with harmonics. The voltages above the 0.5V are usually the domain of harmonics out of control or some problem with the earth/grounding system.

AS Profile Equipment List        Say NO to MQA

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4 hours ago, wwc said:

Have you ever looked into the Richard Gray products?

Their website doesn't say much technically, other than per pound engineering. I like a lot of iron for transformers, which Richard Gray provides. The voltage suppression at a type 3 means it can be used with regular gasoline, doesn't mean much other than it's local to the appliance. For the Power purification products, a balanced voltage suppression could mean two VDR worth $2 each front and back, unless it's explained, they are only words. This review gives some insight on what's inside and if accurate is a good idea. For the money and performance though, the Topaz and their kind provide more bang for buck.

AS Profile Equipment List        Say NO to MQA

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19 hours ago, One and a half said:

From memory (which is kinda bad) the neutral needs to be min. 1.3 times the size of the conductors for sub mains to cope with harmonics.

That's a 3 phase problem only, it doesn't happen in single phase systems.  A modern SMPS design has reduced the problem.

It's 'K' factor or rating in 3 phase transformers.

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.005pF interwinding capacitance of your Topaz is not going to reduce common mode and normal mode noise as well as the .0005pF Topaz units.

 

You need to make sure it is wired correctly for the voltage you plan on using. Each side could be wired differently so you need to open it up and check that out. Just because it says both ends are 120v does not mean it is so.

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7 minutes ago, diecaster said:

.005pF interwinding capacitance of your Topaz is not going to reduce common mode and normal mode noise as well as the .0005pF Topaz units.

 

You need to make sure it is wired correctly for the voltage you plan on using. Each side could be wired differently so you need to open it up and check that out. Just because it says both ends are 120v does not mean it is so.

 

Thanks, Diecaster,  I appreciate your reply. 

 

I'm aware of the reported improvement (according to some) in performance of .0005 vs .005, though John Swenson didn't feel this was meaningful per on an earlier post of his and uses a .005 (2nd post in this thread, which is why I went ahead and bought this). 

 

For now, I've got an inexpensive $175 unit I can try out while looking for a 31 or a 32 at a low price.  

 

I'll open it up and send pictures tomorrow, as I won't know by looking at it (opened up) what the voltages are, or what to rearrange in order to get the voltages right (if needed).  Because of the cord, the input side may be difficult to remove.  

 

Rick

 

 

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11 hours ago, diecaster said:

Wow, that unit does not appear to be configurable for voltages. Interesting.....

The difference in noise suppression between the .005pF and .0005pF is something like 30dB. Not insignificant but not critical either. 

It's doubtful that there is any meaningful difference where it counts!  Heck there may not be any (repeatable & reproducible) measurable difference.

So just where does it count?

Why at the audio output of your hi-fi system.

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1 hour ago, Speedskater said:

It's doubtful that there is any meaningful difference where it counts!  Heck there may not be any (repeatable & reproducible) measurable difference.

 

116dB vs 146dB of common mode noise suppression is a meaningful difference and of course the measurable difference is "repeatable & reproducible". That doesn't mean that the 116dB number isn't great. It is great...just not as great as 146dB. I'd rather have the later but the former is excellent.

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Thanks for the replies, the Topaz seems to be working fine in my system but I will need to address the noise it makes, haven’t done thorough listening.  The main benefits seem to be mis and high at this early stage.  This is without the Tripp Lite PS3612–20HW, yet.  It has a black and white pigtail at each end with no ground pigtail and fortunately no circuit breaker.  There are two ground wires at each end which connect the last outlets to the chassis.  It has a knockout at each end.  I need to decide whether to hardwire it or to put an IEC on it so I can try different audiophile power cords.  Any thoughts?

6A354F8B-2CCE-493F-970B-A286A17DD0ED.jpeg

A2EBCED0-37D4-4FA6-B78B-B84DDD66F905.jpeg

3037E5FC-79EA-4AD0-8BE2-011B8D69D234.jpeg

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A8F9D3E2-B3EA-43B0-854B-71ECD2E6AA9B.jpeg

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  • 1 month later...
On 8/8/2017 at 7:06 PM, zilch0md said:

Having finally taken the plunge to get a Topaz 0.0005 pF (91095-32), I'm very pleased with the results had vs. the Tripp-Lite is500 I'd been using.  Here's my current setup/guide:

 

Affordable_Power_Conditioning_with_Serial_Isolation_Transformers.jpg

1561147211_Topazdiasgram1.thumb.jpg.46e356897ea4e8a7ebed423db1efd899.jpg

Hi,

 

Got a couple of noobish questions regarding grounded neutral secondaries and also balanced supplies that I hope someone can help me with: @One and a half, @zilch0md ?

 

Just discovered my Topaz doesn't have a grounded neutral secondary (i.e. it's floating) and is currently supplying a low power intergrated DAC/amp and a separate music server which according to the info above is not ideal (Warning: Plug only ONE load into an Iso T with a floating neutral secondary). If I understand correctly the way to go is to ground the Topaz secondary neutral to enable more than one load to be connected for better performance?

What if I convert my Topaz to a Balanced mode output; is a Balanced output configuration still good for using more than one load or should only a single load be used as per a floating neutral secondary?

 

Second question: When in Balanced mode, does this mean the Topaz's output is reduced?  My stereo draws around 400-450VA which is close to the recommended limit for my 750VA Topaz and I'm concerned that switching to Balanced mode may not be ideal if output power may come down? I have 240v mains power in my country.

 

Thanks for any replies.

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11 minutes ago, tims said:

1561147211_Topazdiasgram1.thumb.jpg.46e356897ea4e8a7ebed423db1efd899.jpg

Hi,

 

Got a couple of noobish questions regarding grounded neutral secondaries and also balanced supplies that I hope someone can help me with: @One and a half, @zilch0md ?

 

Just discovered my Topaz doesn't have a grounded neutral secondary (i.e. it's floating) and is currently supplying a low power intergrated DAC/amp and a separate music server which according to the info above is not ideal (Warning: Plug only ONE load into an Iso T with a floating neutral secondary). If I understand correctly the way to go is to ground the Topaz secondary neutral to enable more than one load to be connected for better performance?

What if I convert my Topaz to a Balanced mode output; is a Balanced output configuration still good for using more than one load or should only a single load be used as per a floating neutral secondary?

 

Second question: When in Balanced mode, does this mean the Topaz's output is reduced?  My stereo draws around 400-450VA which is close to the recommended limit for my 750VA Topaz and I'm concerned that switching to Balanced mode may not be ideal if output power may come down? I have 240v mains power in my country.

 

Thanks for any replies.

 

I have my Topaz 2.5kVa .0005 wired as balanced and it really helps the overall sound quality. But you can’t really do that as this lowers the output somewhat. 

 

Aren’t 240v mains already balanced (120v per leg)? You can check with a multimeter. 

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2 hours ago, diecaster said:

 

I have my Topaz 2.5kVa .0005 wired as balanced and it really helps the overall sound quality. But you can’t really do that as this lowers the output somewhat. 

 

Aren’t 240v mains already balanced (120v per leg)? You can check with a multimeter. 

Thanks,

I'm in New Zealand - 240vac is on the hot wire leg, so not already balanced.

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55 minutes ago, tims said:

Thanks,

I'm in New Zealand - 240vac is on the hot wire leg, so not already balanced.

It might be balanced, but floating, but otherwise you can adjust by wiring for balanced and maybe non floating too. 750v is much more than the 250 your system is asking....

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8 minutes ago, esmit said:

It might be balanced, but floating, but otherwise you can adjust by wiring for balanced and maybe non floating too. 750v is much more than the 250 your system is asking....

 

His system is asking up to 450va and that is probably not peak. Wiring the transformer for balanced out will reduce the power output somewhat. 

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22 hours ago, tims said:

1561147211_Topazdiasgram1.thumb.jpg.46e356897ea4e8a7ebed423db1efd899.jpg

Hi,

 

Got a couple of noobish questions regarding grounded neutral secondaries and also balanced supplies that I hope someone can help me with: @One and a half, @zilch0md ?

 

Just discovered my Topaz doesn't have a grounded neutral secondary (i.e. it's floating) and is currently supplying a low power intergrated DAC/amp and a separate music server which according to the info above is not ideal (Warning: Plug only ONE load into an Iso T with a floating neutral secondary). If I understand correctly the way to go is to ground the Topaz secondary neutral to enable more than one load to be connected for better performance?

What if I convert my Topaz to a Balanced mode output; is a Balanced output configuration still good for using more than one load or should only a single load be used as per a floating neutral secondary?

 

Second question: When in Balanced mode, does this mean the Topaz's output is reduced?  My stereo draws around 400-450VA which is close to the recommended limit for my 750VA Topaz and I'm concerned that switching to Balanced mode may not be ideal if output power may come down? I have 240v mains power in my country.

 

Thanks for any replies.

 

Hi tims!

 

Unfortunately, I'm not able to go back and edit the post you are quoting:

 

https://audiophilestyle.com/forums/topic/29662-discussion-of-ac-mains-isolation-transformers-started-wposts-moved-from-quotlps-1-troubleshootingquot-thread/?page=31&tab=comments#comment-704749

 

Quite some time ago, I updated the graphic to correct an error in my understanding, thanks to the teachings of John Swenson.

 

The punchline is that Common-Mode noise is attenuated by Isolation Transformers, whether their secondaries have floating neutrals or grounded neutrals.

 

Here's my current version of that graphic:

 

9992956.jpg

 

... as found on the first page of this thread at Head-Fi.org:

 

https://www.head-fi.org/threads/topaz-low-capacitance-isolation-transformers-for-affordably-clean-power.857448/

 

In answer to your questions, I personally wouldn't bother to convert to balanced operation, even if it's possible and yes, for safety reason, you should not plug more than one load into a transformer with a floating neutral secondary.  I don't believe any Topaz units shipped with a floating secondary, so yours must have been modified.  I recommend you ground the neutral, but if you don't know how, you should get an certified electrician to do the work for you.   It's either that or just get another one and keep this one for powering a single DAC or any single audio component that uses a switch-mode power supply - both of which are suspect for backwashing noise onto the mains - where a floating neutral secondary can prevent that from happening.

 

 

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10 hours ago, zilch0md said:

 

Hi tims!

 

Unfortunately, I'm not able to go back and edit the post you are quoting:

 

https://audiophilestyle.com/forums/topic/29662-discussion-of-ac-mains-isolation-transformers-started-wposts-moved-from-quotlps-1-troubleshootingquot-thread/?page=31&tab=comments#comment-704749

 

Quite some time ago, I updated the graphic to correct an error in my understanding, thanks to the teachings of John Swenson.

 

The punchline is that Common-Mode noise is attenuated by Isolation Transformers, whether their secondaries have floating neutrals or grounded neutrals.

 

Here's my current version of that graphic:

 

9992956.jpg

 

... as found on the first page of this thread at Head-Fi.org:

 

https://www.head-fi.org/threads/topaz-low-capacitance-isolation-transformers-for-affordably-clean-power.857448/

 

In answer to your questions, I personally wouldn't bother to convert to balanced operation, even if it's possible and yes, for safety reason, you should not plug more than one load into a transformer with a floating neutral secondary.  I don't believe any Topaz units shipped with a floating secondary, so yours must have been modified.  I recommend you ground the neutral, but if you don't know how, you should get an certified electrician to do the work for you.   It's either that or just get another one and keep this one for powering a single DAC or any single audio component that uses a switch-mode power supply - both of which are suspect for backwashing noise onto the mains - where a floating neutral secondary can prevent that from happening.

 

 

Thanks for your reply and the updated info.

 

Prior to your response I changed my Topaz to balanced mode  and was  pleasantly surprised as the SQ increase was better than expected plus my Topaz is running a little cooler.

But now I'm not sure if this is due the fact that it's running in balanced mode or now the secondary is now not floating as before?

 

I may try the following:

Revert back to unbalanced mode but this time ground the output neutral to make it non-floating and then try both components connected and compare the SQ to balanced mode SQ as described above. 

and then:

Just have one audio component plugged into the Topaz and have it floating as per your diagram and again compare to the other versions.

 

Would love to have another Topaz 000.5pf but their as rare as hen's teeth where I am and not cheap! 

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  • 2 weeks later...

Hi

I just purchased a BK Precision isolation transformer.  When I checked the voltage it is outputting 129V.  When I checked hot to ground I got 19V & neutral to ground 28V.  I called BK Precision and they said that this is normal.  Does this sound correct to you?

 

I have an MGE ultra isolation transformer.  I have been using it balanced with an output of 124V, X1 to G 62V & X4 to G 62V.  I was not confident using the BK 1604A balanced so I rewired the ultra iso non-balanced.  I got X1 to X4 124V.  X1 to G 38V & X4 to G 77V.

 

Does this sound correct to you?

 

I have the APC LE1200, if the above is correct I will use all of the above together and see how it sounds.  I will use the BK 1604A on my Holo Spring DAC.  Then I will order another BK 1604A.  Before that is it OK to use my Rogue RP-1 Preamp at 107V  and my Rogue Medusa Amp at 107V?

 

Thank you,

Bill

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