FYI: The BPT *is* an isolation transformer.
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Glai, I don't know who is quoting you a price in excess of $1,000 for the 5kVA MGE Topaz isolation transformer, but I think that price is inflated by a factor of two. Try Al Magro at Allied Electronics in Bristol, Pennsylvania:
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
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
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
"We are senior electrical engineering PhD students. We know the difference between dirty and clean waveforms."
I would hope so, but then again, that's why i asked. The mass majority of inverters on the market aren't typically known for being "clean" sources of power. Hence, a distorted waveform in would equal a distorted waveform out. That is, IF the transformer was actually "linear" in operation. I had no idea where you were coming from or what you were basing your comments on, hence the need for clarification.
"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."
There are TONS of isolation transformers on the market that are of a toroidal design, but thanks for confirming what i've been saying for several years now. Many of the various "computer grade" or "commercial grade" iso's that come in cute little cabinets are toroidal. In fact, most all newer gear uses a toroidal based power supply because it is FAR cheaper to make, FAR cheaper to ship ( less weight ), FAR cheaper to house ( less weight means less rugged chassis ), etc... Only problem is, they allow GOBS more line noise into the componentry and typically saturate much faster than a well built "iron core" transformer.
The fact that audiophiles have been led to believe that toroidals are "superior" is strictly the marketing department pumping out snake oil by the gallons. The only things that toroidals are superior at is generating a profit margin and they "may" be better at reducing stray magnetic fields. This will depend on the construction of the "old school" iron core transformer though.
"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."
I agree as stated in the above response. On top of that, most power supplies are lacking, hence the great variance in power cord effectiveness from component to component. Some components make use of much better power supply design and parts selection and others make use of parts that "get the job done". There's a big difference in performance levels between the two. Sean
Sean, I know you are characteristically forgiving of ignorance...
... most power supplies are lacking, hence the great variance in power cord effectiveness from component to component.
When a component gains a lot from a power cord upgrade, does that indicate it has a poor internal power supply, or a good one? I would have thought the former, but am I right?
Scotty: You guys are killing me with stuff that can be found in the archives. The more times that i have to repeat myself, the less time i have to help in other areas : )
The two brands that i've had the best luck with were Xentek and Topaz. That does not mean that everything that Xentek and Topaz makes will be suitable for what you want. We are primarily interested in the ultra-isolation types although their standard iso's are still FAR superior to a toroidal design. Just make sure that the max load used by all of the equipment doesn't exceed 60% of the rating of the transformer. Using heavy enough gauge wire in and out of the Iso is also important.
Bare in mind that some transformers of equivalent KVA rating and isolation figures can have different size cores. If both transformers are identical in terms of electrical spec's and power ratings, go with the one that has the largest core. Sean
Sean, Thanks, and sorry, I found the 'archived' posts where you recommend the Xentek and Topaz, after the fact :). I know you were going to post something to the effect of how to make the 'best' out of dedicated lines using Romex....which is what I used...now that you have time in other areas...:)...what are your thoughts on this one? Or, did you post it somewhere else already? Scott
Sean, torrids are much more expensive than "off the shelf" EI transformers. That and just about everything else you have said in this thread is wrong. If you or anybody else would like to know the truth about transformers used in audio amplifier power supplies it is spelled out very nicely at bryston.ca news letters volume 8 #4 and #5. It is nonsense to think that a manufacturer would save money with a cheaper transformer, then turn around and put 2 into every amp where 1 will do! I know that Bryston amps have really grown in popularity and there is no doubt that the amps have improved in sound quality, at the same time they switched from EI to torrids. Strange thing to happen if EI transformers made better audio amplifier transformers, but they don't, torrids do. I should warn audiogoners that the newsletters contain some pretty contrasting information on a few subjects I have read about in these forums. I know this thread is about 115volt utility supplied mains, so for that subject your brutal reality can also be found within the newsletters. merry christmas (dec.24)
Wow, never saw this response from 7b4me and it's a year later.
I didn't read the material that you mentioned on Bryston's website, so forgive me for my ignorance as to their point of view. As far as my comments being wrong, i think that you'll find that most EE's that are both honest and well educated will agree with my comments. Aball's response above the multitude of comments that John Curl has made on the subject are prime examples.
Toriodal transformers only have one real electrical advantage over EI's when used as a power transformer. That is, toroids reduce stray electromagnetic radiation as compared to EI's. They can be placed closer to circuitry with less potential for interference. By placing end caps or "bells" on the EI's, radiation can be reduced to near that of a toroid by itself, but once again, this raises cost and weight. To be fair, applying the same amount of metal to a toroid as a shield lowers the stray radiation to the point that an EI could never come close.
Outside of power transformers, toroids are far superior to EI's for use as impedance matching transformers. This has to do with their capacity to cover a larger cross-section of frequencies i.e. wider bandwidth. For audio signals, this is a highly desirable trait. For a power transformer, it is exactly what we don't want.
In this respect, it all boils down using the right tools / circuitry. Whether or not one wants to get the job done or to design / build something that performs optimally are two different things. Sean
I have a Runnings Springs Audio power conditioner that I have been very pleased with, but I have been very curious about iso transformers for my digital transport and DAC. I just bought a Topaz 500VA ultra isolation transformer and plan to use it for my transport an d DAC. Can anyone tell me the importance of capcitance in the iso transformer. This is something I'm still curious about.
JD: People can believe whatever and whomever they want to believe. All we can do here is share opinions and ideas while trying to learn from one another.
Having said that, most of the Bryston amps are not real strong performers into lower impedances. We have discussed this in the forums here before on more than one occassion.
As most know, these are SS amps with low output impedances and relatively robust output stages. As such, the only reason that this could be so would be due to the limited current capacity of the power supply. Since the power supply starts at the transformer, one should be able to draw logical conclusions as to what is going on here.
Clio09: The higher the capacitance of a power transformer, the more coupling there is between the primary side of the transformer and that of the secondary. As such, the greater the capacitance, the less isolation the transformer can offer. In such a case, a higher percentage of line noise is allowed to enter into the circuitry with a higher capacitance transformer as compared to a lower capacitance transformer.
As a general rule, toroids are typically much higher in capacitance than a well designed EI. This makes them less suitable for isolation purposes, as i previously stated. On the other hand, EI transformers are typically more lossy as frequency climbs, making them less suitable for wide bandwidth circuits. As such, a well designed tubed amp might make use of an EI in the power supply and toroidals as output transformers. This should achieve the best of both worlds i.e. lower noise floor with wider bandwidth / better transient response. Sean
what would you consider a high capacitance for a 1kva toroid?
your comments, as always, are interesting: i found that my old wavac SET, which employed EI-type trannys, was guilty of the rolled off frequency extremes, but glorious at the mids. my SS amps are far more linear, but never as "pure" in the mids or the highs.