Discussion of AC mains isolation transformers

[mozes]

10 minutes ago, Cornan said:

 

Well, I also share the same problem. I cannot just put any ugly IT anywhere I like. My problem is both space & WAF! ?

 

I will guess that Naims concerns are grounding since their designs are extremely thoughtful in that perticular area. I'll guess what you want is a balanced isolation transformer with grounded secondary. According to many it is the best IT around IF you have a dedicated ground receptacle. Unfortunately not many do and it is impossible, complicated and/or expensive to get a dedicated ground receptacle for many.

 

Next scenario is that you choose between unbalanced or balanced isolation transformer with floating secondary that might defeat the purpose of Naims thoughtful grounding. Might not be what Naim wants!

 

Finally we have the Ultra IT (usually unbalanced) or balanced IT with grounded secondary. That is the ones you should choose for Naim even if you do not have a dedicated earth (balanced or unbalanced with a ac mains voltage regulator) or any powerful devices and a IT with floating secondary (balanced or unbalanced with a ac mains voltage regulator) for the rest IMO.

 

These are just my two cents ofcourse. If I were you I would ask other Naim users what they prefer before deciding on which type of IT to use with their products.

 

However, if you want specifically to optain maximum dynamic response you should size a IT by watt X 0.6 X 3! ?

I used to have an Elgar 2.4KVA IT in front of my Naim when I didn't have a dedicated circuit. It didn't make any difference to my ears so I sold it. I know that Naimees like balanced isolation transformers that has grounding (not floating).

[unbalanced output]

You went straight to the point! I'm not sure of what to do about the groundings. I haven't studied this matter yet (that is, how to properly ground Naim equipment with an IT). My main concern, aside from not ruining the sound, is protection. For the digital part of equipment is, aside from protection especially to the Nas, not injecting noise back to the power components. I can definitely tell that some additional noise is being fed to the amps since I stuffed the power circuit with a Lps-1, Nas, router and computer. Improving the sound would be a plus! And yes, waf factor is a concern - I have plans to conceal everything in some furniture with limited ventilation. That's the other side of the plan (therefore the heat concerns). 

[One and a half]

7 hours ago, spacexpert said:

I think so too.  I will have to buy another one, shipping is a nightmare.    

The Hammond guide posted is a good link. The hotter than Melania transformer is producing heat for the wrong reasons.  Perhaps a winding is shorted internally through old age or a drop to the floor years ago. This means dismantling and costly repair.

 

What really needs is the Topaz to be Insulation Resistance tested at 500V for one minute, winding impedance test, plus a current measurement taken with a scope on the voltage to determine distortions.  That's about two hours work for technician and in my country that cost will pay for the freight on a new transformer. 

 

While it's there, leave it on and have it power the system and listen for clicks as well as music. If you don't hear any clicks,  then the Isolation transformer concept works.  I would not leave it on overnight and have a ceramic tile or brick underneath it to insulate from the floor or carpet. 

 

I'm sorry to say and given the effort to test for the obvious,  the Transformer 's heat will just lead to more problems. 

 

The search would be on to find another one. I'm looking for a 2-3 KVA unit and you're welcome to engage in trading on my 1KVA Topaz. It's sad that we have to buy old gear, let's stir a manufacturer to come up with something similar with a warranty.

[Cornan]

21 minutes ago, unbalanced output said:

You went straight to the point! I'm not sure of what to do about the groundings. I haven't studied this matter yet (that is, how to properly ground Naim equipment with an IT). My main concern, aside from not ruining the sound, is protection. For the digital part of equipment is, aside from protection especially to the Nas, not injecting noise back to the power components. I can definitely tell that some additional noise is being fed to the amps since I stuffed the power circuit with a Lps-1, Nas, router and computer. Improving the sound would be a plus! And yes, waf factor is a concern - I have plans to conceal everything in some furniture with limited ventilation. That's the other side of the plan (therefore the heat concerns). 

 

A more detailed setup would help. As @mozes confimed a balanced IT with grounded secondary is what Naimees wants. That is also what powerful analogue devices wants. If you stay on this thread @One and a half have promised to give details about the safety aspects of a balanced IT.  Otherwise IME all digital devices (incl. DAC) should really have a IT with floating secondary to sound best, preferably powered by floating PSUs where possible (LPS-1 included even if its feeder supply is not fully floating).

 

Oh, when it comes to heat it is usually not a big deal with ITs. They can take heat, but if it is burning hot it is something wrong. I have my 500VA Ultra IT covered inside a cubborn damped with sound isolation materials. Still it is just beyond lukewarm when powering my active speakers.

[spacexpert]

2 minutes ago, One and a half said:

The Hammond guide posted is a good link. The hotter than Melania transformer is producing heat for the wrong reasons.  Perhaps a winding is shorted internally through old age or a drop to the floor years ago. This means dismantling and costly repair.

 

What really needs is the Topaz to be Insulation Resistance tested at 500V for one minute, winding impedance test, plus a current measurement taken with a scope on the voltage to determine distortions.  That's about two hours work for technician and in my country that cost will pay for the freight on a new transformer. 

 

While it's there, leave it on and have it power the system and listen for clicks as well as music. If you don't hear any clicks,  then the Isolation transformer concept works.  I would not leave it on overnight and have a ceramic tile or brick underneath it to insulate from the floor or carpet. 

 

I'm sorry to say and given the effort to test for the obvious,  the Transformer 's heat will just lead to more problems. 

 

The search would be on to find another one. I'm looking for a 2-3 KVA unit and you're welcome to engage in trading on my 1KVA Topaz. It's sad that we have to buy old gear, let's stir a manufacturer to come up with something similar with a warranty.

Sure is a bummer.  I guess I learnt a lot along the way.  I could buy the same model again, and just hope for the best?

Of course if you find a beefier unit, I'd be happy to consider your 1KVA unit.

The current Topaz is doing it's job as far as I can tell.  I'll sit it on something safe and see how it lasts.

As soon as you find a bigger Topaz, just PM me and I'll see if I can afford the 1KVA, baring in mind I'm 230V    

It's shipping that tends to suck, but not having to deal with the uncertainty of a faulty unit is tempting.

Thanks for all your advice, been a pleasure.   

[unbalanced output]

Last post for today then... already grouping by transformer:

 

1. "Power" section (shared grounding):

Lampizator Atlantic -> Naim Supernait 2 -> speakers

Naim Hicap (provision for)

 

2. "Digital" section:

4xHDD NAS, Router, NUC, TV (mostly decorational item)

LPS-1 -> UltraRendu

 

 

 

[mozes]

When I had my IT it was warm to the touch not hot. I got fed up with its foot print and the wires so I installed two dedicated circuits with 10 AWG wire one for digital and the other for analogue for the same cost of the IT. Of course dedicated circuits don't offer protection against power surge. The result was nothing short of spectacular. I never expected this level of improvement. If you live in an apartment it maybe tricky to install dedicated circuits.

[Superdad]

10 hours ago, Cornan said:

 

Here is another 500kVA isolation transformer for reference!

 

 

 

 

Great for isolating all audiophiles within 5km!  I like the face on the left side.  Could make a nice listening partner, but I'd be afraid he would hum along with the music too loudly. 

[Cornan]

6 hours ago, Superdad said:

Could make a nice listening partner, but I'd be afraid he would hum along with the music too loudly. 

 

To make it easier to cope with it you can call it grandma and force yourself to love when she´s humming along with your favorite tunes!

 

[Cornan]

8 hours ago, unbalanced output said:

Last post for today then... already grouping by transformer:

 

1. "Power" section (shared grounding):

Lampizator Atlantic -> Naim Supernait 2 -> speakers

Naim Hicap (provision for)

 

2. "Digital" section:

4xHDD NAS, Router, NUC, TV (mostly decorational item)

LPS-1 -> UltraRendu

 

 

 

 

IMO it should be something like this:

 

750VA Balanced isolation transformer with grounded secondary:

1. "Power" section (shared grounding):

Naim Supernait 2 -> speakers

Naim Hicap (provision for)

 

500VA Balanced isolation transformer with floating secondary*:

2. "Digital" section:

4xHDD NAS**, Router**, NUC**, TV (mostly decorational item)

LPS-1 -> UltraRendu -> Lampizator Atlantic 

 

*Alternatively: AC mains voltage regulator -> 500VA unbalanced isolation transformer with floating secondary

 

** Power these devices with a LPSs or (if you ask me) floating SMPSs/LPSs power supplies (Safety ground is not passed through to the DC negative or chassi).

 

YMMV of course!

 

[Cornan]

7 hours ago, mozes said:

When I had my IT it was warm to the touch not hot. I got fed up with its foot print and the wires so I installed two dedicated circuits with 10 AWG wire one for digital and the other for analogue for the same cost of the IT. Of course dedicated circuits don't offer protection against power surge. The result was nothing short of spectacular. I never expected this level of improvement. If you live in an apartment it maybe tricky to install dedicated circuits.

 

Dedicated curcuits for analogue and digital are an awesome solution!   Still, for example two voltage regulators (one for digital circuit and one for analogue circuit) could possibly do the trick. It will ensure a more "balanced" ac mains and protect against power surges. IME even a cheap one (BlueWalker PowerWalker 1200VA for roughly USD35 excl freight. EU version though) can do magic!

 

 

[One and a half]

13 hours ago, unbalanced output said:

However, dynamic response is quite a concern - Naim recommends to be very careful when putting anything upstream of their power supplies. 

 

This is a myth and I'm not criticsising you, one of those stories that hasn't a foundation.. A Topaz for example has worst case 5% impedance typically 3%. It's short circuit current is (100/5%) x Full load amps of the transformer.

 

Example 2000VA ISO transformer at 120V AC has full load capability of 16.6A. If a dynamic is so strong, that it must demand 20 x 16.6A which is a dead short on the transformer, that's 333A. The transformer can't supply that current for too long, like minutes, but a 60 ms transient....walk in the park. The volts may sag, even if it went to 10%, that's 333A x 12V = 4,000W. Most if not all output transistors will fry first, most likely due to clipping.

 

Rule of thumb : Load watts / 0.6 = VA of the transformer.
 

[unbalanced output]

4 hours ago, Cornan said:

 

IMO it should be something like this:

 

750VA Balanced isolation transformer with grounded secondary:

1. "Power" section (shared grounding):

Naim Supernait 2 -> speakers

Naim Hicap (provision for)

 

500VA Balanced isolation transformer with floating secondary*:

2. "Digital" section:

4xHDD NAS**, Router**, NUC**, TV (mostly decorational item)

LPS-1 -> UltraRendu -> Lampizator Atlantic 

 

*Alternatively: AC mains voltage regulator -> 500VA unbalanced isolation transformer with floating secondary

 

** Power these devices with a LPSs or (if you ask me) floating SMPSs/LPSs power supplies (Safety ground is not passed through to the DC negative or chassi).

 

YMMV of course!

 

 

Thanks a lot, it is interesting why you think the DAC should be on the second transformer. My rationale is the uR is isolated, and the Lampizator does not receive the 5V signal, only the ground. Then the Lampi is itself isolated. However, the analog signal shares the ground with the preamp. My Lampi has a Din output (great work by Lampi guys, nothing short of amazing) therefore there is one single ground conductor. My logic was that I should be more important to minimise the leakage in the analog path, doesn't that make sense?

 

Great contributions, much appreciated!

[unbalanced output]

2 minutes ago, One and a half said:

 

This is a myth and I'm not criticsising you, one of those stories that hasn't a foundation.. A Topaz for example has worst case 5% impedance typically 3%. It's short circuit current is (100/5%) x Full load amps of the transformer.

 

Example 2000VA ISO transformer at 120V AC has full load capability of 16.6A. If a dynamic is so strong, that it must demand 20 x 16.6A which is a dead short on the transformer, that's 333A. The transformer can't supply that current for too long, like minutes, but a 60 ms transient....walk in the park. The volts may sag, even if it went to 10%, that's 333A x 12V = 4,000W. Most if not all output transistors will fry first, most likely due to clipping.

 

Rule of thumb : Load watts / 0.6 = VA of the transformer.
 

 

Thanks for the thoughts. I agree with you, and probably would Naim. Their advise is more towards line filters and related circuits, but I didn't make it clear. I read in the Naim Forum some people contacted them and their engineering actually recommended the use of its. I think the question is more in the side of which size would work best. 

[Cornan]

29 minutes ago, unbalanced output said:

 

 

Thanks a lot, it is interesting why you think the DAC should be on the second transformer. My rationale is the uR is isolated, and the Lampizator does not receive the 5V signal, only the ground. Then the Lampi is itself isolated. However, the analog signal shares the ground with the preamp. My Lampi has a Din output (great work by Lampi guys, nothing short of amazing) therefore there is one single ground conductor. My logic was that I should be more important to minimise the leakage in the analog path, doesn't that make sense?

 

Great contributions, much appreciated!

 

You're welcome!

The "mission" is to separate the analogue section from the digital section as you already know and have accounted for. IMO a DAC is the final frontier to the analogue domain and should be isolated from the analogue section. However, in such scenario it is also worth to consider external grounding where your DAC is most likely a good target. This you will do best via chassi ground. Since you AFAIK do not lift the GND this will possibly still make a difference. As soon as you lift both the GND and the 5v plus have the DAC connected to a isolation transformer with floating secondary the external groudning will not have the same impact, probably not at all. 

IME the analogue section is more sensitive to leakage from the digital section rather than the other way around.

 

[mozes]

5 hours ago, Cornan said:

 

Dedicated curcuits for analogue and digital are an awesome solution!   Still, for example two voltage regulators (one for digital circuit and one for analogue circuit) could possibly do the trick. It will ensure a more "balanced" ac mains and protect against power surges. IME even a cheap one (BlueWalker PowerWalker 1200VA for roughly USD35 excl freight. EU version though) can do magic!

 

 

Yes the voltage regulators is a great idea. I have never tried it so don't know how good it is. I think the dedicated circuit also has to do with not only isolation but using thick gauge wire straight to the breaker panel can also act as a low impedance path for the current and this may also be behind the big boost in SQ. The current no longer needs to go through multiple outlets and switches in the room or sections of the house.

[Speedskater]

Testing Isolation Transformer distortion and frequency response.

If you are set-up to do amplifier tests, then you can test an I.T.

Just insert the I.T. between the amplifier speaker output and the 4/8 Ohm dummy load.

Set the level at a low frequency that the amp and load are OK with.

Expect a lot of high frequency roll-off. (don't change the level)

[Cornan]

11 minutes ago, mozes said:

Yes the voltage regulators is a great idea. I have never tried it so don't know how good it is. I think the dedicated circuit also has to do with not only isolation but using thick gauge wire straight to the breaker panel can also act as a low impedance path for the current and this may also be behind the big boost in SQ. The current no longer needs to go through multiple outlets and switches in the room or sections of the house.

 

I wish I could do a dedicated circuit as well, but living in an appartment have it´s down-falls. Surely it is about a more direct path plus reduced impedance as well. Lucky you (even if it is not about luck at all)!

 

[unbalanced output]

7 hours ago, Cornan said:

 

You're welcome!

The "mission" is to separate the analogue section from the digital section as you already know and have accounted for. IMO a DAC is the final frontier to the analogue domain and should be isolated from the analogue section. However, in such scenario it is also worth to consider external grounding where your DAC is most likely a good target. This you will do best via chassi ground. Since you AFAIK do not lift the GND this will possibly still make a difference. As soon as you lift both the GND and the 5v plus have the DAC connected to a isolation transformer with floating secondary the external groudning will not have the same impact, probably not at all. 

IME the analogue section is more sensitive to leakage from the digital section rather than the other way around.

 

 

I apologise infor the following long-ish monologue in advance :):

 

I think there are (at least) two aspects in choosing where does the DAC belong. First is the grounding. Second is noise of the digital components feeding to the DAC power supply. My idea is that if the DAC shares the transformer with the noisy PSUs, it will "see" all the noise from the switching power supplies since they are all on the same side of the "digital IT" - in other words, the signal will be contaminated at the source. 

 

Back to the grounding. Naim grounds the chassis to Earth, and the signal is grounded at the source. From the SN2 manual:

 

The SUPERNAIT 2 negative input and output connections for each channel are common. The mains earth (ground) should always be connected regardless of what other equipment is used in conjunction with the amplifier. The mains earth only grounds the case and the electrostatic screen within the transformer, and is not connected to the signal negative. In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place.

 

So well, again the signal ground would be connected to the "digital IT" which sees all the noise. Right now, without an IT, when the DAC is connected I can identify two sources of audible noise from the speakers: a 50Hz signal from mains and a clicking noise from the digital SPSs, HDDs etc. (the clicking noise obviously disappears when they are off). The noise is barely audible, but is there (clicking is the louder one). When I disconnect the DAC, the clicking noise disappears, and the mains noise is reduced (currently all the components are in different outlets but sharing the same circuit back to the distribution box). This suggests to me that I'd like to isolate the DAC from the other digital components, doesn't it? Whether or not they belong to the same "analogue IT" is another story - perhaps three ITs? Power IT grounded to Earth, DAC IT with floating ground, and digital IT grounded to Earth - digital IT becomes more of a surge protector. Problem is of course to have space for all this - I'd probably also need a voltage regulator since the voltage here may in theory be as high as 240V!

 

Conclusion: I need a bigger flat

[Cornan]

1 hour ago, unbalanced output said:

 

I apologise infor the following long-ish monologue in advance :):

 

I think there are (at least) two aspects in choosing where does the DAC belong. First is the grounding. Second is noise of the digital components feeding to the DAC power supply. My idea is that if the DAC shares the transformer with the noisy PSUs, it will "see" all the noise from the switching power supplies since they are all on the same side of the "digital IT" - in other words, the signal will be contaminated at the source. 

 

Back to the grounding. Naim grounds the chassis to Earth, and the signal is grounded at the source. From the SN2 manual:

 

The SUPERNAIT 2 negative input and output connections for each channel are common. The mains earth (ground) should always be connected regardless of what other equipment is used in conjunction with the amplifier. The mains earth only grounds the case and the electrostatic screen within the transformer, and is not connected to the signal negative. In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place.

 

So well, again the signal ground would be connected to the "digital IT" which sees all the noise. Right now, without an IT, when the DAC is connected I can identify two sources of audible noise from the speakers: a 50Hz signal from mains and a clicking noise from the digital SPSs, HDDs etc. (the clicking noise obviously disappears when they are off). The noise is barely audible, but is there (clicking is the louder one). When I disconnect the DAC, the clicking noise disappears, and the mains noise is reduced (currently all the components are in different outlets but sharing the same circuit back to the distribution box). This suggests to me that I'd like to isolate the DAC from the other digital components, doesn't it? Whether or not they belong to the same "analogue IT" is another story - perhaps three ITs? Power IT grounded to Earth, DAC IT with floating ground, and digital IT grounded to Earth - digital IT becomes more of a surge protector. Problem is of course to have space for all this - I'd probably also need a voltage regulator since the voltage here may in theory be as high as 240V!

 

Conclusion: I need a bigger flat

 

You must remember that even if a IT is floating or grounded the safety ground connection is intact. A IT with floating secondary will isolate the output from AC main noises, but all the devices connected to the same IT via a powerstrip will share the safety ground path. If you connect both the grounded IT and floating IT to the same ac mains wall outlet all devices will share the same safety ground path, but the floating IT will isolate the output from noises coming from the grounded IT via the AC mains (backwash noises/leakage). 

 

I actually have a special made star earthed and starquad wired power distributor on order for the very same reason that Naim wants it. To ensure that the safety ground is connected in a single star earth arrangement. The starquad wiring is just due to its proven efficiency against AC magnetic fields.

 

When I talked about external grounding in my previous post I was'nt talking about chassi to chassi grounding, but about connecting the chassi to a grounding box to enhance/clean the ground path.

 

Buying a bigger flat is probably easier than dealing with isolation, but you'll need a pretty big wallet to choose that option! ?

 

Oh, if you are hear noises from speakers, SSD etc you should look into different cables (balanced ICs) and/or signal isolation or shielding as well.

 

 

[oneguy]

Subscribed and if you are looking for a 5 kVa MGE unit shoot me a PM. There's s guy on eBay who I was going to buy from but I couldn't get him to ship it to the hotel I was going to be staying at in the US and shipping to Japan would cost an arm and a leg.

 

I instead bought a new old stock 1.8 kVa  MGE for my estimated max requirement of 1100 watts.

[Speed Racer]

22 hours ago, Cornan said:

When I talked about external grounding in my previous post I was'nt talking about chassi to chassi grounding, but about connecting the chassi to a grounding box to enhance/clean the ground path.

 

Do you mean a grounding box like an Entreq?? Why introduce snake oil to an otherwise reasonable thread??

[Cornan]

Just now, Speed Racer said:

 

Do you mean a grounding box like an Entreq?? Why introduce snake oil to an otherwise reasonable thread??

 

Never mind! It was just a passus! ?

[spacexpert]

Just been checking out other IT options in the hope of finding one that will run cooler.

I note that some have a sticker on the black part that reads "caution hot surface, avoid contact" 

 

So I guess these things can get hot enough to warn you not to touch.  That's pretty hot.

 

It wouldn't by chance be a combination of 240V + high capacitance .0005 that is a factor?

Regardless I guess it should run cool with low load...    

[frederick184]

I just picked up a Topaz 91095-32 500 Va isolation transformer on eBay.  My system is split into two parts.  My Comcast modem, wireless router, dedicated music PC, NAS, fiber switch and FMC's are all in an upstairs room.  The FMC's are connected to the NAS and the wireless router, and the PC has a fiber NIC connected to the fiber switch.  All devices are plugged into a single Wiremold power strip with no filtering.

 

Downstairs there is another wireless router connected to the master one upstairs in a mesh network.  An Ethernet cable connects to my Ultra Rendu powered by LPS-1.  This in turn is plugged either into my Oppo UDP-205 players USB DAC by a Lush cable or to my LH Labs Infinity X DAC.  The signal goes from there to my Parasound A21 amp and then to my Magnepan MG 3.7 speakers.  All devices are plugged into an Audience AR6-PDC with no filtering.  This part of the system is fed by a dedicated 20 amp circuit.  The upstairs part of the system is not.

 

I intended to buy an isolation transformer for both, but I'm wondering in the meantime which part of the system would benefit from it most?

 

Colin