isolation transformer vs line conditioner

Well, to the best of my limited knowledge, an iso transformer is only that. There are no other parts involved. Line conditioners, on the other hand, use capacitors, chokes, and perhaps resistors to try to clean up the AC, although some designs are very simple.

Iso trannies limit available power if they are not big enough. Line conditioners are only as good as their circuit design. If I understand correctly, a single good-quality capacitor between hot and neutral can short out a lot of hash. More complex circuits may work better, or may not.

That's all I know, and it ain't much.

I use a dedicated AC line, an Enacom line conditioner (a very simple design), and two iso trannies on my digital source and preamp. Each measure made a difference, and the sum is, well, it would be getting there if I weren't having a forced layoff due to fire.

Aball: I would be curious as to the specifics of the make, model and specifics of your testing procedures.

Given proper selection, a transformer can do good or bad things to the waveform. In case you haven't noticed, many "high end" manufacturers are going to transformer coupled or "autoformer" designs in their newest products. Some other companies, much like the Mac gear that you love, have used transformers for a very long time.

If you really want to test the quality of a transformer, feed it a high amplitude signal directly from an audio generator and compare the input vs the output. Since there is no real harmonic content generated by the audio generator, the waveforms should match identically minus a small amount of loss. If they don't, then you know that you've got a junk transformer and it's not worth messing with.

As a side note, you should look at the input vs the output of these transformers on a spectrum analyzer. It is very clear to see pretty drastic differences in various designs.

They Hydra is basically just a very fancy parallel line filter strapped directly to the back of duplex outlet. You have one of these parallel line filters for each duplex outlet. Nothing more, nothing less. Even though the whole thing is built using very high grade parts, the price is still insane for what it is.

As a side note, using a "parallel line filter" directly in front of an iso transformer increases the efficiency of the circuit even further. Using the two different yet complimentary types of filters together will provide the best results. Just make sure that the devices that you use to do this are EASILY capable of handling the max load that you'll pull through them under the most demanding conditions. Otherwise, the cores will saturate and you'll end up with MORE distortion than you started off with and "funky" waveforms to boot. Sean
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The transformers I was talking about were used in power converter applications - granted they were mostly nonlinear applications such as resonant topologies and voltage source inverters but it is still clear to see what impact is on the the waveform. Transformer design is very complex - much more so that I made it seem in my over-simplified general comment above. I agree in some instances, you can get the input very close to the output but in general, the B-H curve of a transformer is totally nonlinear. There are some very linear cores but they are more often than not only inductors - similar to McIntosh's autoformer where the action is self-inductive. My comment didn't apply to that but rather complete transformers with a ferrite core, primary, and secondary. In this case, you are at the mercy of the B-H characteristics which are far from linear unless you operate in a very specific range but that never happens when you are talking AC voltage of course. Many of the commercial isolation transformers are undersized and so you run too close to the saturation region where the flux density starts to level off (i.e., nonlinear). Oversizing the transformer costs lots of $$$ and we all know that engineers are forced by the bean counters to keep cost in check - this means you don't add any more core than is absolutely necessary. If the end result is for electrical equipment in a medical lab, the core WILL NOT BE OPERATING LINEARLY because it will be made as small, light, and cheap as possible. It will be just fine for electrical equipment but not necessarily for human ears. Some audiophile companies may do it right but again, I would check it in the lab before betting my life on it.

Having said this, some people may actually like a nonlinear sound eventhough it is totally inaccurate from a strict electrical sense. One more example of "if you like it, keep it." All I am saying is you need to be careful when using a transformer. It isn't a simple thing.

I looked for the waveforms I was talking about but couldn't locate them off hand (we may not have even saved them). There are many examples online about it if you are interested. I will look for a good example and paste the link. The problem we were having was that the slope of the B-H curve changes depending on the direction of the applied voltage becuse that little bit of loss results in "fattening" of the curve which makes the slope different no matter how linear you make it. This is a problem.

Finally, be sure you realize that an autotransformer is NOT the same as a transformer. The two words are not interchangeable. Arthur

An autoformer is simply an impedance matching device, whereas a transformer can be both a power transfer device and / or an impedance matching device. Then again, anything that alters impedance WILL alter power transfer to some extent, so one can generalize that they have similar purposes regardless of how they are used or designed. Obviously, one needs to choose a product suitable for their specific needs.

As to the core sizes of iso's, i've commented on this extensively in the past and even in this thread. Hence my recommendation to utilize transformers that are rated well above and beyond the necessary amount of power consumed. Larger cores will also help to stabilize the magnetic flux, increasing the efficiency and reducing non-linearities in the power transfer curve. They will also lower self-induced noise prior to saturation and maintain a lower impedance, allowing for better transient response. All of this adds up to increased linearities and better performance for the end user.

Out of curiosity, were the iso's that you were using / performing the testing on toroidal or "iron core" based? This makes a HUGE difference for multiple reasons. I've also mentioned this many times in past threads.

Outside of that, designing a transformer for one specific purpose is much easier than taking a "universal" product and making it work for your specific application. The fact that the units that you were studying were used in non-linear applications i.e. voltage inverters ( very "dirty" to start with in most designs ) etc.. may have tainted your opinions of what can be done and is possible in other areas of transformer operation. Given that we are looking for maximum linear power transfer at one specific frequency with attenuation increasing as frequency rises, the transfer function of an iso transformer IS "non-linear" by very design. The key here is to find one that was designed for this very specific purpose with suitable traits, hence my recommendations of specific brands and styles while avoiding those that we know are less than optimal. Sean
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We are senior electrical engineering PhD students. We know the difference between dirty and clean waveforms.

The cores were custom nickel and molybdenum alloy EE cores which are already much better than most commercial-grade transformers. Toroids are terrible for isolation transformers and so aren't used for that purpose.

Keep in mind too that with any power conditioning, the impact on the sound is largely dependant on the quality of the components' power supplies. Arthur