In Praise of Isolation Transformers


#1

Remember the first time you incorporated a P10, or P5 in your system – it was like upgrading all your gear. Add multiwave and boom – yet another level of depth and separation! Well, for those of you who have power amps or monoblocks that are beyond the capability of the P10 (I have Parasound JC-1s), a BALANCED isolation transformer is a way to go.

A few caveats – based on months of tinkering:

  • The transformer should be clean. No MOVs or filters on the input or output
  • Dedicate a 15A transformer for each power amp (if you have monoblocks)
  • Be sure to use outlets of Power Port quality
I started with used Exact Power balanced transformers, disconnected all but one outlet on each, which I replaced with PS Power Ports. The power ports made the difference between using the transformers or not using the transformers. With the Exact Power standard outlets, there was an annoying edge to the sound that detracted from the depth, separation, and clarity the transformers revealed. The edge disappeared with the Power Ports. But in the end, the sound of the JC-1 straight out of the wall outlet was dull, flat and uninvolving compared to the sound with the balanced isolation transformers.

So if you can’t plug your amp(s) into a P10, try a balanced isolation transformer!


#2

This post came upon my search for viewpoints on the use of ITs in conjunction with the P10. So, I took a look through Paul’s posts and the forums here, and maybe it’s because of the multitude of uses of the words “isolation” and “transformer,” but I couldn’t figure out why why @adminpaul hate isolation transformers; why does he?

Anyway, @jah, thanks for this post. I have been looking at all sorts of devices to work alongside or supplement my PSA regens, which I have on every audio system. These include Topaz transformers [pretty good buy new here], Core Power balanced units, ExactPower, etc. Which ExactPower unit(s) did you implement? Topaz get high marks for their build quality, but I haven’t done enough research to see if they meet the criteria you articulate above.

I also came across the Canadian AC regen maker PurePower. I have to admit I like some of their features including and especially the battery pack capability, as well as their approach to power. Good looking units as well. Anyone have experience with them? Not sure

P.S. I am not affiliated with any of the companies in this post, and am only a customer of PSA so far. Thinking about all three though.


#3

I don’t “hate” isolation transformers, but I surely don’t like them nor do I support their use.

They typically make things worse.

Adding these products in series with the AC line does exactly the opposite of what we hope to do: lower output impedance of the AC line and regulate the power. Yes, the isolate, but that’s not important sonically. What IS important is the aforementioned impedance drop.

If you place a large lower power factor device on line—say it has a PF of 0.7 as most amplifiers and equipment do—and then draw high peak current, you will cause a divot to be sucked out of the incoming AC. This is because the resistance (impedance) of the wires connecting your home to the power transformer on the utility pole are relatively high. It’s simply Ohm’s law. Draw too much current through a resistor and you get a voltage drop. We see it all the time (which is why we built an oscilloscope on the Power Plant’s front panel) and want people to understand what is happening.

When you then insert an isolation transformer into this soup, the voltage loss can only get worse. Flat topping and voltage divots can’t get better with an isolation transformer, only worse. They store no energy and cannot make up for losses.

Only a regenerator can.


#4
palerider said I also came across the Canadian AC regen maker PurePower. I have to admit I like some of their features including and especially the battery pack capability, as well as their approach to power. Good looking units as well. Anyone have experience with them? Not sure
I've had the PurePower 1050 for quite a while. I too like the features they highlight on their web site. I'm also somewhat surprised that I've not had to replace it's battery (unlike a Belkin UPS which I used for my Tivo's which only lasted five or six years.) Tho I've not found anything that helps my amps sound better, the PurePower was nice for my EMM Labs equipment (my Switchman preamp and my DAC6e.) I had thought about getting more of them when I bought the first, but they didn't help with my amps so I didn't really need more. At some point I'll probably try some P-10's but in the mean time the PurePower is working fine. Also I upgraded two of the outlets on the 1050 to Oyaide (which was a real pain just because solid core wire jumpers from outlet to outlet were so hard to work with.) At the time the PurePower folks thought I was nuts, but I noticed that they now have an outlet upgrade option.

#5

The Pure Power unit is good for some things, not for others. Because their output is class D sine wave purity is great unless the power factor gets low and current demand goes high. Class D amps aren’t great at delivering peak current under short durations as is required with a regenerator feeding a power amp (for example). In this case, we’ve measured 10% distortion from their device where the wall only had 3%. That divot I referred to. That’s what’s being sucked out by a low power factor load.

For preamps and DACs, as Ted is using, Pure Power works just fine, has low distortion and reasonable noise. I would never recommend the device for higher loads like power amplifiers.


#6

Hmm. Don’t really know if what yielded the substantial sonic improvement was the isolation or balancing of the power, but the sonic improvement to the JC-1s was not subtle, and I have not noted any constriction in dynamics compared to straight out of the wall.

Details I didn’t mention in my initial post are that I have my system on a dedicated 20A circuit, and that I use shielded power cable. In addition, I bypassed the fuses in the Exact Power units. Unfortunately, the Exact Power units I’m using are no longer manufactured.

As an aside, I was able to greatly reduce a noise problem I was having with a couple of old Revox R2Rs by plugging them into the balanced ITs (less noise than plugging them into the P10).

I will just conclude that I use the balanced ITs for my power amps and R2Rs only. Everything else is on a P10. For my system, this is an outstanding combo. YMMV.


#7

@adminpaul and @tedsmith, thanks for this input. Very helpful.