Isolation transformer question

here is how a transformer works:

GI GO.

@testpilot I'm skeptical there's any benefit if the equipment you're using has a competent grounding scheme. You always have the issue of pushing any isolation transformer past 50% of its rating- that does not change with balanced power.

A good balanced transformer will have an electrostatic shield which any good regular isolation transformer will too; electrostatic shielding is a really good thing- it prevents capacitive coupling between the primary and secondary windings, which in turn vastly reduces high frequency noise from getting through. I'm curious if this might actually be a larger portion of the 'benefit' people perceive when they go to balanced power.

@atmasphere , what are your thoughts on balanced power isolation transformers?  

The only time I had intrusive hum on the Plitron within my BPT was when I had an over voltage situation with my provider, 125-126V. I also had noisy power trans. in my Art Audio 845 and Coincident 845 amps, I ended up building bucking trans. to quiet those (no amps ever on PC for me).

I also have experience with battery vs AC powered equipment, had Nirvana Electronic Works SS class A amp which ran off 4 wheelchair 12v batteries, Merlin speakers back in the day run a BAM (essentially a preamp, rechargeable batteries), and experimented with battery vs AC power for preamps, dacs. I'd posit if going battery, Stromtank level of design and build quality  may be necessary.

Large capacity transformer in PC and only run front end equipment off PC, no issue with saturation. No doubt grounding is an issue, I completely redid grounding in my house, no more ground loops with potential issues resolved.

@lewm pointed out the difference between these types of PC, this is consequential.

@clustrocasual Isolation transformers are incapable of cleaning up AC power. They can provide isolation, which is useful for solving ground loop problems, but they can actually add to AC power distortion.

It is AC power distortion which causes some of the ills that people seek to solve with conditioners. In particular, the 5th harmonic of the AC line (so 300Hz in the US) causes power transformers to become noisy, power rectifiers to radiate noise and synchronous motors more likely to run in the wrong direction; all with greater heat.

If you run any transformer past 50% of its rating, the distortion will rise and things like the 5th harmonic show up. Here's a nice link to show you what goes on. https://en.wikipedia.org/wiki/Harmonics_(electrical_power)

I found just messing around that feeding the ESL bias supplies from the lowest power PS Audio regenerator does make a small improvement in sonics. Years ago I tried 6 different power cords on my then SL M1 speakers (before I bought the present PX845s), and I heard differences with SQ having no relation to the cost of the power cords. In fact, the OEM SL power cords (basically 14ga hardware store types) were 2nd best of the 6. Go figure. Any noise inherent to the bias supplies can potentially move the diaphragms, much as spurious motion of a cantilever can also cause distortion.

@lewm That is why I said, "well designed".  Sure, there is a lot of equipment that cut corners to keep the price down. However, I once thought the very basic bias supplies on our ESLs would benefit from refined power. I tried it and it made no difference. I moved the transformer to my line level equipment and it made no difference, so I sold it. The most sensitive piece of equipment, my phono stage, is powered by batteries and is isolated from the line during play. 

There’s no attempt in this discussion to distinguish among isolation transformers vs isolation transformers plus regulation and/or additional filtering using caps and inductors vs just a box of HD caps and inductors that filter only vs AC regenerators, which are actually amplifiers designed to take in wall AC, convert it to DC, then output it as 60 Hz at 120V (or variants thereof). These are 4 kinds of very different devices. 
 

I use an AC regenerator on my basement Beveridge speaker system because the AC down there is contaminated by utilities, and it’s made a difference. On my Sound Lab system I use a small PS Audio regenerator just to feed the ESL bias supplies. That was a serendipitous discovery. Anyone who thinks the linear PSs built into our gear are universally well designed and deliver perfect DC ought to invest in an oscilloscope.

@ steakster, you are fortunate.  It is my understanding that the larger the iso transformer, the more likely it is to hum.  IME, there is always some hum on very large whole-house transformers, but they are located outside or in their own room, far from a listening room.  They could be very useful (I think @whart and M Fremer had some installed). I had two "audiophile" transformers, and kept the smaller one (which I use on front-end components with no problems).

A cursory search on Google confirms that transformers hum by nature, e.g: 

"There are actually multiple causes of transformer noise. The main one is the Magnetostriction Effect. This is when the current that flows through the transformer’s coils creates a magnetic field. The magnetic field then changes the dimensions of the transformer’s iron core. The core expands and contracts with the alternating current, which causes a humming sound."  Landmark Electric Inc.

Perhaps one based on a toroid would hum less?

lloydc

You need to know that isolation transformers hum.

Mine don’t.

If there’s a hum, that most likely indicates that there’s a gremlin somewhere else in the circuitry. Possibly a grounding issue.   Yet, poorly made transformers can hum - if the windings are uneven or if the lamination deteriorates.

You need to know that isolation transformers hum. I threw out a 2kv Soundtrapper isolation transformer because the noise of the hum more than counter-acted any perceived benefit to the electronics’ noise floor

There are plenty of good reasons to use an isolation transformer including blocking DC, preventing ground loops and getting a quiet neutral. Of course the biggest variable is the quality of your AC in the first place, which is my case is just dreadful. (The corporate parent of my electric utility has paid tens of millions of dollars in penalties for its bribery and fraud schemes, which only drains money that could be spent to improve local infrastructure.)

I have an Audience AR6 power conditioner. I bought it three houses ago and it made a positive difference. I moved from the big city to a brand new subdivision on the edge of farm country. The people across the street had Moo Cows and the next house rotated crops. Anyway, there, the power conditioner seemed to do absolutely nothing. I left it in for the magnetic circuit breaker, but that’s it.  8 years later, I’m back in the big city and the AR6 makes a very noticeable difference.

YRMV

I use Plitron isolation transformers for all sensitive electronics. These are industrial grade, not consumer-itis.

I have done a factorial Plitron/ Wall x Aftermarket Power Cord two factor experiment, (in all combinations). Source power was high quality 117VAC half a mile from the nearest commercial installation. No AC, no street lighting running in the neighbourhood. Amps Bryston, speakers Quad ESL, source vinyl.

Best sound was with Plitron isolation transformers. With Plitron, all power cords sounded the same. With wall power, more expensive cords sounded better, monotonically increasing with price (best of these aftermarket cords was $4k).

Just how good can it be? Well, comparing an isolation transformer in front of a medical grade power supply, that power is almost as good as NiCad battery (NiCads are so quiet that they fall below the noise floor of most professional test equipment). You have to listen with utmost attention to hear the difference. That is for powering the most sensitive device, the phono/pre.

Other benefits include protection from power surges. You just can’t expect a 5kg transformer (at most) in a component to protect like a 20kg transformer by the panel. The notion that ANY commercially available amp under 50K is going to protect like that is silly. Even on my big (100 lb of transformers,100 kg of inductors, 1F capacitance) brute force power supply, I use Plitron isolation.

For what it’s worth. YMMV.

@mijostyn ASR isn't worth a minute more of my time.

You guys crack me up.  @sns  If any of that stuff makes your system sound better then you have some seriously poor equipment. More likely than not a formal AB comparison would show that it did not make any difference at all. I use to think it was just expectation bias, but now, given my own feelings when I have gone down the wrong path, it is avoidance of buyer's remorse. "I just spent all that money. It's got to sound better!" My last mistake cost me $13,000 and three months wiring, rewiring, resistors, no resistors, more resistors, two transformers and finally one transformer. Not isolation transformers, step up transformers. 

@clustrocasual I’ve used Bryston/Torus isolation transformers for over a decade. The ones I use are listed in my virtual systems. My experience with them: lower noise floor; I prefer the soundstage structure; the system dynamics are excellent. In my opinion, they help the other components in my system(s) to live up to their potential.

IMO a regulator can do much more for you than a simple isolator, but the isolator can eliminate DC on the line, which is kind of rare, increase filtering due to increased inductance and make the incoming AC immune to certain types of EMI/RFI noise pick up.

In various places I've lived though the automatic voltage regulator is what really kept my gear fed consistently well, whether from too low or too high a voltage.

Linear amps in particular may both cause voltage sags and be subject to them.  A regulator will make the incoming AC look much stiffer.

I have Torus TOT isolator. I have everything but my tube amps on it except network stuff which is on clean sine wave UPS. 

The above is complete nonsense. Certainly the transformers and power supplies within individual components are critically important for best performance, this goes without question. Just as those power supplies treat the power going into signal path of those components, power conditioners treat the power going to all those individual components.

Some years ago I tried a wide variety of power conditioners from Cable Co. through their lending library, including conditioners from AudioQuest, Audience, Synergistic, Shunyata, PS Audio, know I'm missing some others at the moment,  also tried different parallel conditioners over the years. All these compared to the BPT 3.5 Signature I had already purchased. It wasn't that I was unhappy with BPT, just that I wanted to find a conditioner to quiet an 845 SET amp I had going into high efficiency speakers (no worse situation for noise with this combo), this without impacting transients one single iota. Not entirely successful with the transient impact issue with any of these conditioners, Audience closest. Anyway, all these conditioners made a favorable impact on my system, BPT continued as my conditioner of choice for system. Now the BPT happens to be the only transformer based conditioner amongst those I tried, take this for whatever its worth.

I'll just say this for conditioners in general, at least in my system with my AC. All contributed to lower noise floor, therefore, higher resolution/transparency. More detail heard as lower level info suddenly heard, more inner detail in that sound staging and imaging far more expansive. I've A/B'd conditioner vs. no conditioner many times over the years, with wide variety of equipment, all higher end, difference can be detected within minutes.

I\'d suggest if you took a poll, vast majority here using power conditioners, don't know the percentage using trans. based. One last thing, not all trans based conditioners created equal, the tranny used, AC receptacles, filtering caps can all make a difference. I changed out AC receptacles and filtering caps on my BPT, all for the better. BPT  sadly no longer in business, one man operation, I guess became too much.

@jasonbourne71 1+ This is exactly the case with well designed, regulated power supplies. The best equipment even has multiple power supplies, one for each section or stage to keep them from interfering with each other. 

People would be much better off investing in better equipment than in transformers and power conditioners or regenerators. 

It will do nothing! Your gear has power supplies that adequately filter the AC and produce pure DC to the circuitry.