Discussion of AC mains isolation transformers

[YashN]

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.

 

Some people will say "but then the noise injected back into the AC mains can go right into other boxes". Yes it can. BUT recent experiments have been pointing to the leakage loops being a significantly greater detriment to ultimate good sound than the injected noise. Of course different systems are different and this may not be true in all systems, but it is looking like this is a good place to start for many systems.

 

Doesn't the power strip in that case have its Earth rail acting like a star-ground for all the devices? Is that what is helping with the current leakage issue?

 

Furthermore, are the leakage currents the same things as the supposed currents circulating when two chassis of connected gear aren't at equi-potential?

[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.

[YashN]

a couple of small (about 5" cube) inexpensive iso transformers

 

Which ones did you get, Jud?

[YashN]

He got these: Model 1604A, Single Output Isolation Transformer - B&K Precision

Thanks Alex.

[YashN]

Well we think that an RC snubber on a transformer secondary does, by reducing trans ringing back to the wall, reduced the impact of AC cord variations.

But look at a typical power amplifier: Non-regulated PS and big diodes kicking harmonics back to the wall. No wonder AC cords interact especially strongly with power amps.

 

And there's no Transformer snubber for most of these amps either!

 

I've looked over around 10 audio pieces of equipment like that, and none except perhaps a Pioneer DVD player attempt any ring damping right after the transformer.

 

So, one thing I want to do when I rebuild my project studio is to re-do all the power supplies.

I will most probably include a snubber for my SET Tube amp as well.

[YashN]

Well we think that an RC snubber on a transformer secondary does, by reducing trans ringing back to the wall, reduced the impact of AC cord variations.

 

Now that's interesting because I could probably retrofit a snubber into my SS amp and then do an A/B between the old power cord and my DIY one and hear if there's still a difference.

 

Problem: I don't know where the original power cord is

[YashN]

You could try John's typical 2.2nF and series 330 ohm resistor across the secondary winding and see if you can hear a difference.

That's precisely what I meant to do, but in addition, compare the original power cord with my DIY one after the fact to hear if there's any immunity with respect to that.

[YashN]

If you disagree please explain in much better detail how you are measuring leakage current because you would seem to be using a different definition.

 

Interesting observations.

 

Could it be the further induced currents caused by the normal definition Leakage Currents?

 

That's where I think the complexity lies.

[YashN]

I was just reading this comment over on the PS Audio Forum:

The link to the post here: In Praise of Isolation Transformers | Power products | ForumsPS Audio

From the Ted Smith post at that thread, the info on PurePower's site is quite interesting. Hadn't heard of them despite being local.

[YashN]

Lastly, John is coming to visit (work/play) in January, so I just added this very firm queen-size sleeper-sofa to the UPF. No more airbed in the studio!

Sounds like a ploy to keep John indoors so that he can get some new technology from his mind into a worthy audiophile contraption.

 

Good plan.

[YashN]

I am trying to understand the basic electronics behind this. I would understand this better with a schematic than descriptive prose such as "iso" and "leakage". Perhaps that isn't appropriate in this vendor subforum. I thought the point of breaking off this thread from the lps-1 was to allow some non-product based discussion

 

I want to understand it too, so perhaps the better venue for discussing it is the AC Filter, etc. thread where you can discuss it unfettered. For instance, I want to understand whether the breakage of that 'leakage current' also prevents the original issue of 'hash injection' from interfering with SQ with other equipment, asked a question but now I can't even find my post. I thought it was here, but with all the moving of posts and so on, I can't even follow a discussion.

 

Something been on my mind about the difficulty in simulating it, so a post is forthcoming on that but over there.

[YashN]

2 hours ago, JohnSwenson said:

Yes but I think the following way of thinking about it makes more sense to a lot of people:

 

many digital devices have very rapid current load fluctuations as different parts of the circuit turn on and off. These rapid changes in current create voltage across the inductance of the cable, the higher the inductance, the greater the voltage for a given load current change. Thus the lower the inductance of the cable, the lower the noise generated across the cable due to rapidly changing current loads.

 

Very neat!

 

How's life in the new house, John?