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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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."
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
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The more responsive the component is to power cord changes, the poorer the design of the power supply. Sorry if this was unclear. Sean
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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
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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
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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
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