Discussion of AC mains isolation transformers

[Superdad]

I'm copying below the post that John just made in the other thread as it is as relevant (maybe more so) here. Don't think he is trying to put a damper on discussion of isolation transformers, but as usual he is bringing at bit (a lot?) of clarity to the big picture:

 

 

OK, this talk about isolation transformers has gone far a field from my original intent. It was supposed to be about ways to decrease the effects of leakage loops.

 

The PRIMARY part was to decrease the AC mains impedance between devices in the audio system. Many people have power conditioners that as a byproduct of filtering line noise significantly INCREASE impedance between outlets. My recommendation is to get rid of these power distribution devices and use a simple power strip that just has wires between outlets. No filters, no MOVs.

 

BUT that can lead to a situation where noise from the rest of the house and neighborhood can get into the audio system and it leaves the system unprotected from AC line surges.

 

This is where my recommendation of a SPECIFIC type of isolation transformer comes in, these have extremely low inter-winding capacitance and carefully designed magnetics which result in a very high amount of noise suppression AND very good surge suppression in one simple device. Most isolation transformers do NOT have these parameters.

 

This is NOT the only way to do this, there are other devices that filter the line noise and provide surge suppression, BUT it needs to be something that you can drive the power strip with.

 

So look at your power conditioner, if there is ANYTHING other than wire between outlets you will not have the lowest possible impedance between audio devices. If the power conditioner just has its "filtration" upstream of any outlets and just wire between outlets it will probably give good results.

 

But be aware that very few power conditioners will be as effective as the specific isolation transformers mentioned.

 

So a few ways you can do this:

 

a power conditioner with all the filtration/surge suppression before any outlets and all outlets connected with just wire.

 

A filtration/ surge suppression device with a simple power strip plugged in.

 

A special isolation transformer being used as a surge suppressor/filter with a simple power strip plugged in.

 

The third option is, in my opinion, the best way to go for most people.

 

This should give you a way to determine whether a particular system meets my criteria.

 

NOTE I am NOT saying you HAVE to do any of this!!!!! The LPS-1 is a very effective tool for breaking some leakage loops, the above is a way to decrease the negative sonic impact of other leakage loops which cannot be broken with an LPS-1, such as a DAC with its own PS, preamp, poweramp etc. Once you hear what dealing with some leakage loops, which the LPS-1 can do, you might want to think about decreasing the impact of others. This is a way to do that.

 

John S.

[JohnSwenson]

Hi All, I have posted a message in the other thread which I would like everybody to read:

 

UltraCap™ LPS-1 Troubleshooting, system grounding, etc. - Page 3

 

I have received many PMs with people asking me if a specific power conditioner is good, bad better etc, the truth is I simply do not have the time right now to research every one of these devices and give informed opinions on them. I hope this post will give you some tools to evaluate them for yourself and make an informed decision about what to do.

 

I'm sorry if this feels like I'm putting a wet blanket on things, but If I did the research for everybody to the degree I would like to do, I would not have time to get any new products out!

 

Another thing in general is to realize that most isolation transformers are not the ultra low inter-winding capacitance ones, they will not have anywhere near the same degree of noise suppression or surge suppression. If they ARE they will probably let you know in the marketing literature. So if a specific transformer does NOT say anything about very low inter winding capacitance, it probably doesn't have it. You can always contact the manufacturer to find out.

 

I'm not going away or anything, I just have to cut down on the individual recommendation thing.

 

Thanks,

 

John S.

[asdf1000]

I've just ordered a CABAC Power-Mate: POWER MATE 10A | CABAC

 

There are $20 ones at JayCar but I wanted something built well (this is built in Australia) and will last. Right now is definitely not the only time I'll be interested in my system's overall power consumption. This one is pricey at $170 but I've heard it's well built and accurate enough so should be a good investment for years to come.

[joelha]

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.

 

Those are impressive purchases, jabbr.

 

Thanks a lot for the information.

 

Joel

[joelha]

For those of you who have purchased one of the Topaz units, did you hear a meaningful difference after connecting the unit?

 

Is it beneficial even when you don't originally hear any noise our hum on your system?

 

Thanks in advance.

 

Joel

 

Joel

[One and a half]

snip

 

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?

 

The immediate and obvious change in using a balanced transformer from Equitech was the quiet. Fade outs went forever, it was easy to listen to. Bass improved as it should. Since the noise was lowered, the quality of the sound improved, naturally increasing the volume level.

 

Objectively, measuring low level harmonics (3rd, 5th, 7th....) line to line on the AC side, IIRC reduced by 35db compered to plugging into the wall. The harmonic voltages were in the microvolt levels, there's a graph at CA shows this. Conclusion is the crud (harmonics anyway) from rectifiers and SMPS are indeed knocked on the head on the AC side. I didn't measure any RF, by the time you reach the 35th harmonic and it's all noise floor, who cares.

 

Equitech have a lot of information on their site, but I would not buy from them again. After repeated request emails to buy a larger unit, the questions remain unanswered. Plitron have shyed away from balanced transformers publicly and offer an isolation transformer which supposedly does the same thing...they did at one stage supply Equitech with balanced transformers to Equitech spec. There was another lot in CA that also supplied transformers to Equitech, I will do some research as to the name and post.

 

The reason they are not cheap is to do with the construction of the bifilar windings of the secondaries. To achieve effective cancellation, the voltage regulation must be be very tight from one winding out to the other. To ask that of a magnetic device is a tall ask and complex since the regulation needs to be <1.0%., or better of course.

 

To substitute the balanced transformer, it's possible to use solid state programmable AC voltage supplies with +/- 0.1% regulation, 2kVA for USD5500 a piece (California Power or ELGAR), you need two of them of course. Makes a rotary system a very real prospect. More on this later.

 

I did read somewhere (here at CA?) that balanced transformers restrict dynamics. That's BS. The recordings are the limitations to restricting dynamics, if sized correctly, transformers can withstand quite a bit of overload before they melt and reduce the voltage.

[fob69]

Hi

 

Isolation transformer by they inductance are known to impact the sound spectrum of amps and preamps. I have one and i don't use it anymore because of this. None of you had this kind of issues ?

 

B.

 

 

Sent from my iPhone using Computer Audiophile

 

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[Superdad]

Hi

 

Isolation transformer by they inductance are known to impact the sound spectrum of amps and preamps. I have one and i don't use it anymore because of this. None of you had this kind of issues ?

B.

 

Yours was likely too small and also not of the caliber of the Topaz units under discussion. Yes, a transformer will always increase impedance by a few percent, but sized right it will be very little at the 50/60Hz frequency we care about, and the benefits--again with the ultra-low interwinding capacitance of the good ones--when applied in the manner John explains, outweigh the slight impedance issue.

 

And I say that as someone who has disliked many a "power conditioner" and always plugged my gear direct into the wall.

[asdf1000]

Hi guys, I've borrowed a power meter while I wait for my own to arrive. Plugged in my PS Dectet power board into the power meter with my pair of 1600watt subwoofers and 350watt integrated amp and microRendu plugged into the power board. Cranked up the music to louder than normal.

 

Apart from my ears still ringing, the other interesting thing is the meter shows 0.7A of current being drawn but a power factor of 40-42 (fluctuating).

 

Can someone help me to understand what these figures mean? And how do I convert this to the amount of current being drawn, to size an appropriate iso transformer?

 

Just as a sanity check, I went to the kitchen to test it with a kettle and it showed 8.7A with power factor of 100.

[asdf1000]

Just as a follow-up:

 

Can I use this: Power Factor = True Power / Apparent Power

 

Therefore: Apparent Power = True Power / Power Factor = 0.7 / 0.42 = 1.75A = current to be used to size an iso transformer?

 

Allowing for even significant measuring equipment error, if I'm using < 3.5A then it sounds like my 8A (2.5KVA) Elgar Iso transformer should be fine.

 

Voltage at the wall here is ~ 249 Vac

[One and a half]

Just as a follow-up:

 

Can I use this: Power Factor = True Power / Apparent Power

 

Therefore: Apparent Power = True Power / Power Factor = 0.7 / 0.42 = 1.75A = current to be used to size an iso transformer?

 

Allowing for even significant measuring equipment error, if I'm using < 3.5A then it sounds like my 8A (2.5KVA) Elgar Iso transformer should be fine.

 

Voltage at the wall here is ~ 249 Vac

 

Yes, you're on the right track.

 

Power factor is always is equal to or less than 1.00. So Power Factor = True Power / Apparent Power and

 

Apparent Power = True Power x pf and

 

VA (apparent power) = Volts x Amps

 

Watts = Volts x amps x pf

 

If your load is 0.7A at 0.42 pf at 249V, then the Watts = 249 x 0.7 * 0.42 = 73.2 Watts.

 

The ISO transformer in this case is a minimum 73.2 Watts / 0.42 pf = 174VA.

 

If the pf can be improved even to 0.8, the size of the ISO transformer can come down 73.2 / 0.8 = 91.5 VA. Power factor can be improved using a combo of mainly capacitance and inductance. BUT. No free lunch here, possible resonances between the load and the power factor correction gear can occur. The load has harmonics which usually add voltage and also resonate with the frequency of the LC filter, which the capacitor tries to support, so an over voltage occurs. If the load decreases, then too much capacitance can makes things worse as well. Oversizing a capacitor bank can attract harmonics from other appliances in the house or your neighbour.

 

In audio case, it is simpler and less painful to buy a bigger ISO transformer.

 

BTW, you buy electricity in kW, not VA, eg. $0.25 / kWH, not kVA per hour.

 

The kettle 8.7A at 1.00 pf 249V = 2166 Watts.

 

The ISO to supply the kettle (silly but for exercise only) VA = 2166 /1.00 = 2166 VA

[asdf1000]

Yes, you're on the right track.

 

Power factor is always is equal to or less than 1.00. So Power Factor = True Power / Apparent Power and

 

Apparent Power = True Power x pf and

 

VA (apparent power) = Volts x Amps

 

Watts = Volts x amps x pf

 

If your load is 0.7A at 0.42 pf at 249V, then the Watts = 249 x 0.7 * 0.42 = 73.2 Watts.

 

The ISO transformer in this case is a minimum 73.2 Watts / 0.42 pf = 174VA.

 

If the pf can be improved even to 0.8, the size of the ISO transformer can come down 73.2 / 0.8 = 91.5 VA. Power factor can be improved using a combo of mainly capacitance and inductance. BUT. No free lunch here, possible resonances between the load and the power factor correction gear can occur. The load has harmonics which usually add voltage and also resonate with the frequency of the LC filter, which the capacitor tries to support, so an over voltage occurs. If the load decreases, then too much capacitance can makes things worse as well. Oversizing a capacitor bank can attract harmonics from other appliances in the house or your neighbour.

 

In audio case, it is simpler and less painful to buy a bigger ISO transformer.

 

BTW, you buy electricity in kW, not VA, eg. $0.25 / kWH, not kVA per hour.

 

The kettle 8.7A at 1.00 pf 249V = 2166 Watts.

 

The ISO to supply the kettle (silly but for exercise only) VA = 2166 /1.00 = 2166 VA

Thanks so much. I was worried a 2.5kVA iso transformer @ 249Vac could be an issue (undersized) since I thought my pair of subwoofers and integrated might get close to 10A. But today's measurement and your calc of <100 watts consumption by my gear is awfully low. That's a good thing I guess !

 

Just another question. If a 2.5kVA iso transformer itself has a power factor of 0.8, then it's good for 2.5 x 0.8 = 2kW = 8.3Amps.

 

If someone accidentally put a 10A fuse on the inlet of the iso trans (or they thought it should have a 10A fuse on there despite my above calc) and the iso trans had a 9A load applied.... what would happen to the iso transformer? And what could happen to the gear connected to it?

[One and a half]

Thanks so much. I was worried a 2.5kVA iso transformer @ 249Vac could be an issue (undersized) since I thought my pair of subwoofers and integrated might get close to 10A. But today's measurement and your calc of <100 watts consumption by my gear is awfully low. That's a good thing I guess !

 

Just another question. If a 2.5kVA iso transformer itself has a power factor of 0.8, then it's good for 2.5 x 0.8 = 2kW = 8.3Amps.

 

If someone accidentally put a 10A fuse on the inlet of the iso trans (or they thought it should have a 10A fuse on there despite my above calc) and the iso trans had a 9A load applied.... what would happen to the iso transformer? And what could happen to the gear connected to it?

 

An ISO transformer doesn't have pf. The load does.

 

Inrush currents and protection on larger transformers can be an issue. There are ways to get it right, but not tonight Josephine.

[asdf1000]

An ISO transformer doesn't have pf. The load does.

 

Inrush currents and protection on larger transformers can be an issue. There are ways to get it right, but not tonight Josephine.

Thanks mate. So a 2.5kVA iso transformer is actually good to provide a full 2.5kW of power?

[One and a half]

Thanks mate. So a 2.5kVA iso transformer is actually good to provide a full 2.5kW of power?

 

Yes, if the load is a kettle pf of 1.00

[asdf1000]

Yes, if the load is a kettle pf of 1.00

 

Ok I get you now all depends on the load. Took a minute to finally click.

 

But from a safety perspective, a 2.5kVA iso transformer in my place can have up to 2500 VA /249 A = 10.04 A of current pass through without damage to the iso trans? Obviously it would need to have a 10A circuit break though (here in Australia). But a full 10A can pass through without damage to the iso trans?

 

I previously (wrongly) assumed there was a power factor needed to convert kVA to kW which is why I thought perhaps a 2.5kVA iso trans wouldn't be able to supply up to a full 10A current, if required.

[sandyk]

But today's measurement and your calc of <100 watts consumption by my gear is awfully low. That's a good thing I guess !

 

Many people in typical domestic situations vastly overestimate amplifier power requirements !

[asdf1000]

Many people in typical domestic situations vastly overestimate amplifier power requirements !

 

Me included - until I actually measured the consumption today. This entire thread has been a good learning curve for a muppet like me ! :-)

[sandyk]

Me included - until I actually measured the consumption today. This entire thread has been a good learning curve for a muppet like me ! :-)

 

A typical average listening level in many Aussie lounge rooms is likely to be in the vicinity of 1 or 2 watts !

Not so many years back, a 30W per channel amplifier was considered adequate in many Pommy homes.

In fact, I have never been able to use my 15W/Ch. into 8 ohms Class A amplifier (30W Class AB into 4 ohms) at anywhere near it's maximum power into speakers of 87.5dB/1W @ 1 metre sensitivity at home. It's far too bloody loud in a room about the size and width of a master (large) bedroom or for that matter, in a typical Aussie lounge room.

Many of our American cousins appear to have listening rooms far larger than most Aussie homes do, judging by the amplifier ratings they often mention of >700W per channel. They mustn't have neighbours right next door to them ?

[asdf1000]

A typical average listening level in many Aussie lounge rooms is likely to be in the vicinity of 1 or 2 watts !

Not so many years back, a 30W per channel amplifier was considered adequate in many Pommy homes.

In fact, I have never been able to use my 15W/Ch. into 8 ohms Class A amplifier (30W Class AB into 4 ohms) at anywhere near it's maximum power into speakers of 87.5dB/1W @ 1 metre sensitivity at home. It's far too bloody loud in a room about the size and width of a master (large) bedroom or for that matter, in a typical Aussie lounge room.

Many of our American cousins appear to have listening rooms far larger than most Aussie homes do, judging by the amplifier ratings they often mention of >700W per channel. They mustn't have neighbours right next door to them ?

Very true. I feel silly and embarassed having mentioned my pair of 1600W subwoofers and 350W integrated. But I literally had no idea up to now, what my actual consumption is. I'll never mention those figures again ! ;-)

[Jud]

Is it beneficial even when you don't originally hear any noise our hum on your system?

 

Thanks in advance.

 

Joel

 

 

Hi Joel. I have not purchased an iso transformer sized for my entire system (though I plan to for the house my wife and I will be building in the near future). I have purchased a couple of small iso transformers for (1) my MacBook's SMPS, and (2) my preamp. I also placed a network isolator (though not a transformer) on one Ethernet connection from the router supplying network service to my system, and am awaiting delivery of a second isolator for the second connection from that router. Like iso transformers, it is a function of network isolators to stop leakage currents. https://en.wikipedia.org/wiki/Network_isolator

 

While making these changes, I have had in my system a device that serves the function of a "noise sniffer" (see for example Welcome to AudioPrism Noise Sniffer). It takes whatever noise you have in your system and amplifies it to the point where it is plainly audible. I can tell you that iso transformers and network isolators do work to reduce noise, since they made noise in my system inaudible even with the "sniffer."

 

A very interesting thing that I remarked about to a friend is that when the noise was inaudible, these measures subjectively resulted in the sorts of classic changes we've all described in these pages - better soundstage and imaging, more detailed intonation in vocals and instrumental playing, a greater sense of ease in listening.

 

So I know for a fact these things work to reduce noise, and my subjective impression is that even when noise was not audible they were beneficial in my system.

[joelha]

Exactly what I wanted to know, Jud.

 

Thanks for the great information.

 

Joel

[ted_b]

I'm sure this is a very small sample size but I will ask anyway:

* has anyone who uses a Topaz/Eaton quality iso transformer ever used it with or replaced an Uberbuss (my power conditioner for my front end).

 

Also,a more general question, is the attack plan to first size and use a Topaz for the front end or for the amps (assuming one cannot find or afford to size for both)?

[sockpit]

Can someone who uses a smaller to medium size Topaz comment on how much heat these units generate?

 

When sitting idle (with equipment also sitting idle but powered on) and when playing music?

 

Thanks.

[fob69]

Once full digital part has been isolated, why not isolate only the dac with AC isolation instead of DAC + (preamp) + amp ? The transformer will be chapper and smaller.

HF are not critical for amp as they are for the DAC (except mabe for D class amp) and "leakages" the way J.S. describe them would be blocked.

 

 

Sent from my iPhone using Computer Audiophile

 

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