Discussion of AC mains isolation transformers

[sandyk]

This post didn't come over.

 

The leakage currents on 120V systems is half those of 230V systems a bonus for audio equipment.

 

The voltage drop across 120V mains plugs and sockets is much higher, resulting in many members replacing supplied mains plugs with much higher quality expensive plugs, and even replacing AC mains receptacles with higher quality types too for greater reliability.

 

Perhaps your post, and my reply, were both deservedly removed by Alex C due to the wording of your original post, and my tit for tat reply to you ? .

[joelha]

+1 These are great -- I have several of the .005 pF ones. They can be found for very reasonable prices -- downright cheap if you are willing to rewrire the plugs etc.

 

Hey jabbr,

 

Could you give an example or two of "reasonable prices" including the output of the units your referring to?

 

It's times like this where I feel the cost of not knowing how to solder.

 

Thanks.

 

Joel

[Superdad]

Hey jabbr,

 

Could you give an example or two of "reasonable prices" including the output of the units your referring to?

 

It's times like this where I feel the cost of not knowing how to solder.

 

Thanks.

 

Joel

 

Hi Joel:

 

Here is a nice 500VA unit for $120 which has a cord and a duplex outlet. Nice size for front end gear.

Topaz Line Noise Suppressing Ultra Isolator 91095-12 | eBay

 

 

As part of my just completed facility addition we built a utility room (for new high-efficiency, duel-fuel house HVAC system, new mains panel, etc.), and I am seriously considering a big 5kVA (or even 7.5kVA) transformer to locate in there. My office/studio has its own sub-panel fed with 25 feet of 000awg wire from the main panel, so feeding it from a transformer would be easy. And in the studio there are both house-fed outlets and sub-panel outlets which have only hi-fi gear plugged in.

 

I would use the iso transformer as 240V in/out since I run both sides of the line to my studio (someday I'll reconfigure my Hovland RADIA-i power amp trans for 240V operation).

[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

[joelha]

Hi Joel:

 

Here is a nice 500VA unit for $120 which has a cord and a duplex outlet. Nice size for front end gear.

Topaz Line Noise Suppressing Ultra Isolator 91095-12 | eBay

 

 

As part of my just completed facility addition we built a utility room (for new high-efficiency, duel-fuel house HVAC system, new mains panel, etc.), and I am seriously considering a big 5kVA (or even 7.5kVA) transformer to locate in there. My office/studio has its own sub-panel fed with 25 feet of 000awg wire from the main panel, so feeding it from a transformer would be easy. And in the studio there are both house-fed outlets and sub-panel outlets which have only hi-fi gear plugged in.

 

I would use the iso transformer as 240V in/out since I run both sides of the line to my studio (someday I'll reconfigure my Hovland RADIA-i power amp trans for 240V operation).

 

Hey Alex,

 

Thanks for the great information.

 

How does one do the math on figuring the output required for one of these transformers?

 

Hope you and John continue to have success with your company and outstanding products.

 

Joel

[One and a half]

The voltage drop across 120V mains plugs and sockets is much higher, resulting in many members replacing supplied mains plugs with much higher quality expensive plugs, and even replacing AC mains receptacles with higher quality types too for greater reliability.

 

Perhaps your post, and my reply, were both deservedly removed by Alex C due to the wording of your original post, and my tit for tat reply to you ? .

 

The larger rated wall sockets or more a tighter connection is related to power amps and powered subs. For signal sources 120V with the lower leakage currents would prove advantageous. For my system at home I power the RUR, Icron from 120V supply. The Icron PSU is a SMPS 24V with leakage current of 3mA max on the 120V side. That's about as low for a commercial OTC. Unless the linear psu's transformer has lower AC leakage depends on the shielding used and mitigation of unwanted artefacts as per JS-1 for example.

[sandyk]

For my system at home I power the RUR, Icron from 120V supply.

 

But your system at home is far from typical isn't it ?

You also use a couple of Isolation transformers.

 

AC Power Distribution

2000VA Isolation Transformer

Equitech 1000VA Balanced (Symmetrical) Transformer

Furutech Schuko Outlets FP-SWS(G) (6)

Furutech TP-660e AC 6 Way Distributor for source components

Furman PS-8R II Sequencer, relay outputs switching Equitech output

[One and a half]

But your system at home is far from typical isn't it ?

You also use a couple of Isolation transformers.

 

I design the AC for purpose. The 120V is derived from a couple of Jaycar small ISO transformers, which get a bit warm... used to have 2 x 1kVA 230V-115V transformers, still have them, in the process of rebuilding that network. RS components have a 26kg 2kVA ISO with wireable for 2 x 115V or 400V to 2 x 115V. It needs an enclosure and ventilation though. There's no shielding, so the search continues.

 

The key though is distance and keeping the transformers and switching nasties away from the audio equipment. This includes the audio playback computer. I thought to install the playback PC on the same network close to the audio gear with a small ISO transformer, but it was a disaster. The SMPS that powered the computer (19V, 6A) threw back so much shite, it affected the USB transmission very badly. Now the computer lives 25m away and there's very little degradation, however it's not eliminated. Currently input to the DAC is AES3, that seems to be the most optimum. Unless there's a really super dooper USB front end built into a DAC, a separate DDC is the way to go like BADA.

 

The SACD player is still king for SQ, but it's a long road to tinker with computer audio.

[jabbr]

Hey jabbr,

 

Could you give an example or two of "reasonable prices" including the output of the units your referring to?

 

It's times like this where I feel the cost of not knowing how to solder.

 

Thanks.

 

Joel

 

I have the 91001-32 which is 0.0005 pF 1000kV and $75

 

I also have the 91002-32 (30 amp) unit

 

These versions have the lowest interwinding capacitances I've seen.

[Jud]

I have the 91001-32 which is 0.0005 pF 1000kV and $75

 

I also have the 91002-32 (30 amp) unit

 

These versions have the lowest interwinding capacitances I've seen.

 

Where did you find the 91001-32 for $75? I'm going to be talking to the electrical sub for our planned new home this week, and was thinking of finding a 91001-32 to isolate the audio system from the rest of the electrical system in the house. (I'll have a TV, Blu-ray player, DVR, etc., plugged into the system too, so let me know if 2.4kVA isn't enough.)

 

Edit: Sorry, I mean I'm looking for the 91002-32, which is the 2.4kVA model.

[ted_b]

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.

 

John S.

 

So, as others have said, this advice from you, John, is quite provocative, and has me questioning the synergy of putting a Topaz or two into my system that already has the front end on simple poower strips ino the PI Audio Uberbuss, a power conditioner explained here:

 

"The BUSS-Line Design Criteria

 

Power conditioning can be a mixed bag when it comes to high performance audio and video. Almost all of the available power conditioners are comprised of three components in the noise reduction end of the equation. These are: inductive components – either chokes or transformers; high frequency capacitive filters; and MOVs (metal oxide varistors). The purpose of the inductive components is to either provide transformer isolation, balanced power or to introduce a 6dB/octave high frequency roll-off. The capacitive filters increase the roll-off slope above their corner frequency. The MOVs are used for local surge protection.

 

The problem with these commonly used components is that they are only partially effective in most cases. The inductors are either too small to be effective at audio frequencies or too large and cause current limiting in the circuit. Balanced power is a good thing, but the transformers used for this are generally limited in instantaneous power delivery. The capacitive filters are too small to be effective below ~ 100KHz in most instances. The MOVs will begin to produce noise after a while and are “used up” over a period of time and need to be replaced to prevent them from producing noise.

 

The BUSS-Line from PI audio group, LLC was developed as a result of many years of research in noise reduction for use in the recording industry. The design targets were easy to set, but hard to achieve. The BUSS had to be non-limiting in current, effective well down into the lower midrange of audio frequencies and be absolutely reliable. This meant the elimination of MOVs in the circuit. The UberBUSS and RevB MajikBUSS are not surge protectors. They are leading edge power filters that produce dead silent backgrounds at audio frequencies. In addition, they incorporate a Power Factor Correction section that will increase instantaneous current delivery to equipment attached to them. Dynamic contrasts are immediate and transparent. This has to be experienced to be appreciated. For those that want surge protection there is the BUSS-Stop. It is a combination of surge limiting components arranged in a manner to be as quiet as possible during operation."

 

I have enjoyed the lower noise floor of the UberBuss but now question if the combination of UberBuss (or any other good power conditioner) and a Topaz-like device is overkill or even detrimental.

 

I have my monoblocks plugged into the wall, btw.

[jabbr]

Where did you find the 91001-32 for $75? I'm going to be talking to the electrical sub for our planned new home this week, and was thinking of finding a 91001-32 to isolate the audio system from the rest of the electrical system in the house. (I'll have a TV, Blu-ray player, DVR, etc., plugged into the system too, so let me know if 2.4kVA isn't enough.)

 

Edit: Sorry, I mean I'm looking for the 91002-32, which is the 2.4kVA model.

 

eBay with patience. $150 for the 91002-32

[Jud]

eBay with patience. $150 for the 91002-32

 

Perfect, thanks.

[Daudio]

eBay with patience. $150 for the 91002-32

 

jabbr,

Does that figure include shipping ?

 

-------------------------------------------------------------------------

 

To the many folks asking how to calculate their system load - Do Not Calculate - MEASURE !

Dig out (you should have one), or buy (eBay, Amazon, etc.) a Kill-a-Watt, then power off your components and insert the Kill-a-Watt in series at your power outlet(s), and watch the VA and/or Watts scale as you power up, and put your system through its paces (all extremes). Record the highest readings, and add up multiple outlets, if necessary.

There ! Now you know exactly how big an isolation transformer you need. Trying to calculate it with all the variables and missing information is a fools errand

-------------------------------------------------------------------------

 

 

John Swenson,

How does your recommendation for isolation transformers hold for balanced transformers, which, I believe, also function as isolation devices ??

 

TIA,

Dave

[jabbr]

I've seen prices all over the place for these transformers. The 91002-32 which I last purchased included shipping for $150. It's really heavy so I got a great deal.

[ericuco]

 

To the many folks asking how to calculate their system load - Do Not Calculate - MEASURE !

Dig out (you should have one), or buy (eBay, Amazon, etc.) a Kill-a-Watt, then power off your components and insert the Kill-a-Watt in series at your power outlet(s), and watch the VA and/or Watts scale as you power up, and put your system through its paces (all extremes). Record the highest readings, and add up multiple outlets, if necessary.

There ! Now you know exactly how big an isolation transformer you need. Trying to calculate it with all the variables and missing information is a fools errand

 

 

Thanks Dave. Got one on order from Amazon.

[JohnSwenson]

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

 

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.

[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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[Superdad]

 

John Swenson,

How does your recommendation for isolation transformers hold for balanced transformers, which, I believe, also function as isolation devices ??

 

TIA,

Dave

 

Not John, but I can say that what are referred to as "balanced transformers" are just 1:1 (or maybe 1:1.08 or or something to compensate for losses) isolation transformers with a center tap for ground. The unknown is what the interwinding capacitances are in comparison to the known ultra-low spec of the Topaz units. The specs I have seen for balanced transformers do not list interwinding capacitances.

Part of the idea of the balanced transformer (60/0/60)--at least as espoused by the manufacturers of such--is that the leakage currents balance (cancel?) each other out.

 

I am sure there are some very high quality balanced units out there with extremely well made transformers, but they are not cheap. Some are toroids, and some are EI style.

 

Would love to see balanced transformers brought into this discussion as I know a lot of audiophiles have had good results with them. One question is if the results are due to the "balanced" output or due to reduced leakage current. Or is it that one leads to the other?

 

I did get in on the deal that Larry arranged a year or so ago with Bridgeport Magnetics, scoring a 1kVA, 8-outlet balanced isolation unit in a very nice 3-inch tall, thick aluminum case for a terrific price. Embarrassingly, I have yet to try it out.

[JohnSwenson]

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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Sorry, that was supposed to be 0.5 and 0.85.

 

John S.

[YashN]

Not John, but I can say that what are referred to as "balanced transformers" are just 1:1 (or maybe 1:1.08 or or something to compensate for losses) isolation transformers with a center tap for ground. The unknown is what the interwinding capacitances are in comparison to the known ultra-low spec of the Topaz units. The specs I have seen for balanced transformers do not list interwinding capacitances.

Part of the idea of the balanced transformer (60/0/60)--at least as espoused by the manufacturers of such--is that the leakage currents balance (cancel?) each other out.

I am sure there are some very high quality balanced units out there with extremely well made transformers, but they are not cheap. Some are toroids, and some are EI style.

Would love to see balanced transformers brought into this discussion as I know a lot of audiophiles have had good results with them. One question is if the results are due to the "balanced" output or due to reduced leakage current. Or is it that one leads to the other?.

 

Good question about Balanced Transformers and Leakage Currents.

 

Plitron in Toronto builds the Toroids used in some of the best Balanced Transformers.

 

There were several posts and questions about how best to do Bal + Iso + AC Filter in the AC Filtering, Grounding Boxes, Linear PSU and Balanced Power thread.

 

If I remember correctly, I wrote about how Jon Risch advised about a setup with both AC Filter and Iso transformers as needed, Superbad wrote about how he also uses Isos before some of his gear.

 

I had also found a post on AA by Jon Risch about how to build your own Balanced Transformer (very interesting and not too expensive!).

 

Some of the best Balanced Transformers mentioned above were made by Equi=Tech (lots of good articles and info on their site), Furman and BPT. Last I heard, the gentleman owning and building BPT had some personal issues to deal with which threw off his business activity unfortunately.

 

Lots of info already on this subject over there.

 

Too bad the posts couldn't be moved over there - would have saved fishing for info on different threads. But I did re-post some of John's observations on Leakage Currents as they will most probably change the design of my setup with the AC Filter or the design of the filter itself!

 

If you guys don't mind, I may also take some of the info here and re-post over there.

[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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[sandyk]

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

[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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