Discussion of AC mains isolation transformers

[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

[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

[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

[joelha]

Exactly what I wanted to know, Jud.

 

Thanks for the great information.

 

Joel

[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

[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.

 

 

Sent from my iPad using Computer Audiophile

 

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

[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

[joelha]

John,

 

Thanks so much for your contributions to this thread. I for one have benefited tremendously from your suggestions.

 

My question is, since my power amps are too far away from the front end (or from each other) of my system to be plugged in to the same power strip, is there a value to putting each a separate Topaz device on each of the amps?

 

Thanks again.

 

Joel

[joelha]

You do not want a separate iso transformer on each amp, that makes the leakage loops through the power amps even worse, not better.

 

Probably the best configuration is a sub-panel for the listening room with an iso transformer driving all the outlets in the room. This will give you about as good as you can get if you can't plug everything into the same strip.

 

John S.

 

You're great, John.

 

Thanks so much for the reply.

 

In the meantime, to get my amps on the same box powering everything else, I could have to run a 30 - 35 foot power cord.

 

Given that length, as an interim move, would using that long cable be worthwhile?

 

Thanks again. You've helped a lot of people here.

 

Joel

[joelha]

From an electrical standpoint a power cord with 12 gauge wires is pretty much the same as 12 gauge wires in the wall so there should be little difference in electrical parameters.

 

The big issue is electrical code in your area and whether you are talking about an actual power cord built in to the amp or an extension cord. The code in my area will allow an extension cord as long as it has a circuit breaker at the load end that is appropriate for the gauge of wire in the cord. A 30 foot power cord would be suspect because the inspector would be concerned that the cord was NOT the original manufacturer cord and thus the inspector would not know if the fuse/breaker in the amp was appropriate for the aftermarket cord.

 

I don't want to be telling anybody to do something that will be violating your electrical code!!!

 

Another possible option is to do something like a wiremold setup.

 

John S.

 

 

Thanks for the very quick reply, John.

 

Whatever I do, no matter the result, you're officially absolved.

 

Greatly appreciate all the help.

 

Joel

[joelha]

I finally hooked up my power amps to my Topaz iso unit and then I could hear the hum more clearly. Obviously a bigger load on the iso device is causing the louder hum.

 

My question is, as I'm using a 1KVa unit, will substituting a larger unit, say 2KVa, create more of a hum because of it's greater capacity or less of a hum because it will not be taxed as much by my equipment?

 

Joel

[joelha]

Transformers hum and can rattle. They can also play tunes of different frequencies. If you hear tunes on the audio systems iso transformer, there's real problems.

Rattle is caused by loose laminations caused by hum.

 

Hum will go away if the Transformer has the right load on it, say 80%. Unloaded transformers rattle more.

 

For balanced transformer, rattle occurs on the primary side due to the transfer of the secondaries harmonics which causes lumps of current to develop. I use an iso transformer to smooth out the noise and this is effective. This practice is recommended by Equi-tech in their manual for the model Q.

 

Assuming this was in response to my question about an increased level of hum on my Topaz, the hum I'm hearing is not being heard through the music. The hum is being heard only from the Topaz. And the hum was virtually inaudible before I hooked my power amps to it. Then the hum became much more prominent.

 

Just out of curiosity, what happens if an iso unit is near or even exceeds its limit? Will it overheat, kick off, something else?

 

Joel

[joelha]

An iso transformer follows the usual path of just about every transformer. For most of the range (power through the transformer) there is a fixed efficiency, as more power goes through the transformer the heat dissipated goes up linearly. Near the upper end the efficiency goes down slightly, so heat goes up a little faster near the max.

 

Then the core magnetic material saturates, this causes two things, the efficiency drops dramatically, but the output voltage also goes down. The latter tends to prevent the transformer from going into thermal runaway. The result is that there is a maximum amount of heat a transformer will produce. Note that your device has probably stopped operating properly before it reaches this point which may prevent the transformer from reaching its maximum heat.

 

How HOT the transformer gets depends on the above maximum heat and how much surface area it has and if there is something between the metal core and air etc.

 

Modern transformers are designed with the saturation point just barely above the rated power limit, this results in smaller cheaper transformers, which unfortunately produce high temperatures when in the overload region.

 

These low cap iso transformers we have been discussing are at the other extreme, their saturation point is way above their rated power, which produces a much larger transformer, which means that if you do manage to actually get them into saturation (which will be quite above the rated power) they won't get that hot because they have so much surface area.

 

The end result is probably the safest high power transformers ever made.

 

I wouldn't worry about it.

 

John S.

 

Thanks so much for the detailed answer, John.

 

I'll take off my lead suit and helmet now.

 

As for the louder humming I'm hearing after adding my power amps, will I likely get less hum by using an iso device with a larger capacity or will the larger iso device add the same or an even louder hum?

 

Thanks again.

 

Joel

[joelha]

Keeping the power constant and using a bigger transformer will usually result in lower hum since the magnetic field per core volume is lower.

 

Sometimes you can lower the hum by tightening the bolts holding the core laminations together. Don't worry about them being too tight, crank them up as tight as you can, it might just help.

 

John S.

 

Thanks, as always, for the advice, John.

 

And bolt tightening just barely falls within my technical capabilities, so I'll give that a shot.

 

All the best.

 

Joel

[joelha]

Plug in a heater or two, nothing else on the output a little in excess of what the ISO transformer is rated at to get it hot. Once the steel is hot, it's easier to clamp, but use heat resistant gloves like 5min+ oven mitts for example and tighten the screws right after the power is off.

 

Thanks to you too, One and a half. Another good piece of advice.

 

Joel

[joelha]

2 hours ago, Em2016 said:

 

I would be interested in somebody else doing a measurement of this too. To cross check / validate your results and the Topaz values. Unfortunately I don't have the equipment or the expertise.

 

I assume John has measured the real inter-winding capacitance of his own Topaz units though as he has both the expertise and the equipment. @JohnSwenson

 

PS: you don't work for Noratel do you? Lol, I'm only joking....

 

 

I have a pair of Audionet Max amplifiers, outputting 400 watts into 8 ohms and 700 watts in 4 ohms.

 

Their quoted specifications say that the maximum electrical draw per amp is 2000 watts.

 

I don't have an easy way to measure what the actual draw is for these amps in real world usage.

 

And I'm not anxious to buy a 4Kw+ isolation device if I don't need it.

 

Is there a capacity of isolation device that would safely cover me in the case of my amps?

 

I realize I have to factor in the draw of my other components, but that's a much easier calculation.

 

Thanks in advance for any help anyone can offer.

 

Joel

[joelha]

1 minute ago, elcorso said:

 

Your ISO Transformer should cover the possible maximum current draw from your amplifiers (plus the other gear).

 

The real world current draw of your amps. depends on speaker efficiency, kind of music and your listening preferences regarding SPL.

 

Roch

Thanks Roch.

 

Not the answer I was hoping for, but the information I needed nonetheless.

 

Joel

[joelha]

If this question has been asked already, I apologize, but a searching this thread for an answer would be tough.

 

I'm currently using a Topaz Ultra Isolation device for my front end devices and love it by the way.

 

My power amps are on a completely isolated circuit.

 

Also, because my amps are located in my basement (they're attached to the ceiling directly beneath my speakers) the run of power cords to a single isolation device would be quite long.

 

Even an isolation device for my amps alone, set between my amps, would call for a power cord run of several feet each.

 

So my questions are:

 

1. If my amps are on their own circuit, do I still want to plug them and my front end devices together into one isolation device?

 

2. If the answer to "1." is no, do I want an isolation device set between my amps even though the amps are on their own circuit?

 

3. Finally, does having to run a longer run of power cord (6'-7' between amps and probably 30' from my furthest amp to my front end) mitigate the benefit of using an isolation device?

 

Sorry for the long message, but hopefully the answers will benefit others besides me.

 

Thanks in advance for anyone who can help me out.

 

Joel

[joelha]

Thanks a lot for the reply, Em2016.

 

The variable here is having the amps on an isolated circuit.

 

Otherwise, I know I would need to put the amps on the same isolation device.

 

But with the amps on their own circuit (and with nothing else on that circuit), I'm wondering if the amps still have to be on the same isolation device as the front end.

 

Joel

[joelha]

Hey Daudio,

 

Thanks very much for the reply and suggestions.

 

My current front-end transformer can't handle my amps let alone my amps plus front end.

 

That's why I've been considering getting a larger transformer but I'd hate to do it as an experiment.

 

Thanks again. I'll welcome any additional thoughts from others as well.

 

Joel

[joelha]

You're right to reference that quote, Imitche.

 

My only question is whether having amps on a completely separate circuit provides an exception to that statement.

 

Joel

[joelha]

Thanks Imitche.

 

Just to be clear, you know this to be the case yourself or you're interpreting John Swenson's message to include amps on a separate circuit?

 

Joel

[joelha]

Only my amps are in the basement, on shelves attached to the ceiling, to give them the shortest speaker cable run to the speakers immediately above them.

 

That configuration also allows me to keep the speaker cables and XLR cables to the amps out of sight

 

So the entire front end is on the main level. Only the amps are in the basement. My concern with plugging the amps into the main level isolation unit (if I were to get a unit with enough capacity to handle them) would be the very long runs of power cables necessary to connect them to that isolation unit.

 

Joel

[joelha]

Welcome to my system.

 

Yes, there's a hole in the floor directly behind each speaker and there are a couple of holes in the floor of the audio equipment cabinet.

 

So the cables run from the pre-amps run through the holes in the cabinets, under the floor, and then back up through the holes behind each speaker.

 

What we do for this hobby.

 

Joel