Agreed, could also means leakage flux interfering with operation of the amp which may be helped by repositioning the transformer or shielding, happens often enough due to poor layout. A perceived difference described by the OP is an indication to a problem.
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Extraordinary for you who deals with great transformer and perfect layout. Us less blessed mortals have to make do with lousy parts and cheapo amps with poor layout all the time.
I love listening to smart people talk. Especially where he makes it clear the subjective attributes are measurable. Lots of us have great ears which define Nelson's pocket book.
My take is that Lab Instruments are WAY more sensitive, precise, linear and reproducible than Human anything , including hearing.
So IF something is audibly different , preferably confirmed by different Humans acting independently so as to somewhat reduce individual bias , THEN a measurable difference will be found, period.
So IF something is audibly different , preferably confirmed by different Humans acting independently so as to somewhat reduce individual bias , THEN a measurable difference will be found, period.
Sure, he parrots what he said to Guttenburg. When the issue of non measurable differences are alluded to he tempers it with the word "maybe".
I was doing an experiment with two transformers in parallel for output, switching the outputs to a single set of speakers. Several people could tell the difference and stated one switch setting was Clearer / better defined than the other. Then I output level balanced the two (previously 1dB difference) and they couldn't tell the difference.
Sometimes what you hear, is not what you hear.
Sometimes what you hear, is not what you hear.
Great. Now quantify how much the leakage flux changes and, thereby, how much the performance of the amp changes. Even if you don't have measurements you should be able to provide an estimate. How much do you think the field changes? 0.1%? 1%? 10%? How does that impact the output voltage (or whatever parameter you're interested in) of the transformer? How much does that, in turn, impact the performance of the amp?
The transformers I deal with are plain Jane toroidal types. Back when I dabbled in tube amp design I used EI core transformers. There was nothing special about them.
My layouts aren't perfect either. Nothing is perfect. As with any engineering challenge my layouts are the best compromise I could conjure up at the time. In fact, I see circuit board layout as a pretty typical engineering challenge. It's a multivariate optimization problem. There may be one global optimum. There may be multiple optima ... or there may be none. I do my best to juggle those within the battle box imposed by the design constraints.
I'm a mere mortal who bothered to learn stuff. If you'd like to scratch the surface on PCB layout, I recommend Montrose, Printed Circuit Board Design Techniques for EMC Compliance, ISBN: 0780353765. Montrose approaches the topic from an EMC perspective and is mainly high-speed focused. But the laws of physics apply equally to audio. Henry Ott and Ralph Morrison spring to mind as well.
Tom
That's too funny. That's a common audio salesman's trick. I was at an audiophile store in Seattle with a friend at one time. We were listening to a Parasound setup which sounded pretty good. The salesman then discovered that we were using el-cheapo courtesy cables between the preamp and the source. In feigned horror, the salesman exclaimed, "oh, you're not using THOSE are you??!" and proceeded to replace them with some fancier (read: much more expensive) cables. Both my friend and I noticed that he also nudged the volume control up a bit (a few dB). Sure. It sounded better. But none of us could tell any difference with the levels matched.
I surprised a cable salesman at a trade show at one point too. I was exhibiting a headphone amp and used some GLS brand XLR cables between the DAC and the amp. They're about $25 for a set of six at Bezos' Bookstore. So this salesperson shows up with a pair of XLR cables that were about the same diameter as a garden hose and about as stiff as said garden hose at -40ºC. I compared with my cables. Couldn't tell an honest difference. I then used one of his fancy cables on the left channel and my el-cheapo cables on the right channel. The salesman's eyebrows shot to the ceiling. He hadn't thought of that. If there was a difference, I should hear an imbalance, right? Spoiler alert! There was no difference. I did swap left and right and listen again just in case. Yeah... The salesman refused to tell me the price of the cables, but I'd be surprised if they were less than $1k for the pair.
Tom
If what OP said about open and dynamic is to be trusted, I'd suspect the stray field induced slight hum and/or created IM product enough to be perceptible. It is hard to put numbers on because I have not done any related measurement and also relates to hearing acuity of the listener. DIY guys in Pass forum sometimes need to reorient, rotate or shield their Plitron toroidal to reduce hum on their builds even using boards from DIYAudio store. The problem seems to be worse in cases where signal transformer is used such as the M2 or the F6. Your plain Jane toroidal could be somewhat better than Plitron.
For some poor sod mortals, el-cheapo cable often means < $1 while anything beyond $5 is a luxury type. I never have any interest to listen to cables laced with fat extract of reptilian origin.
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Only when the experience is not prematurely dismissed as non existence or a hallucination and somebody makes relevant measurement. Constructive comments from trusted people with more salt below his belt may encourage beginners to dig out, rectify a problem and learn from the experience.
I think Tom's statement was an general one, not a subjective one, just related to himself. Anyone who claims something extraordinary that's beyond any present knowledge, experience, you name it, needs to back it up by proof before publishing. That's good scientific and engineering practice since a very long time. Sadly and mostly driven by the internet good scientific practice appears to be diminishing or even disregarded by now.
Best regards!
Thank you Kay, a lot of us poor sod simply have no access to a descent spectrum, nor network analyzer. The forum used to show "projects by fanatics for fanatics". Fanatics share what they find out of exuberance, you know how it is. I expect those who knows better to present his view in a more scientific manner, but that is rarely the case, perhaps because they are also fanatics. But I do complain when a probable problem is being dismissed as a nonexistence because that promotes sloppy work to newcomers.
Oh, I trust that OP perceived a difference. But was the perceived difference due to a difference in the stimulus that reached their ears or due to other factors? I don't think we have the data to say either way.
You don't need to do that work. There's plenty of documented science on audio perception. All you have to do is to visit a library with access to AES's papers and start digging.
Plitron makes good transformers. I doubt the Toroidy ones I use are significantly better or worse. The Antek ones that are common on DIY Audio are probably worse. That's just my guess (hence, my use of the word 'probably') based on the wiring geometry.
Toroids have the largest leakage field where the wires exit. Also, the wires themselves have EM fields associated with them when current flows in them. So you do need to keep those wires tightly bundled and away from sensitive circuits. Having to rotate the transformer to find a good spot seems reasonable. Perhaps this need could be alleviated with a different PCB layout, but perhaps not. Either way, turning the transformer is cheap and doesn't require a layout spin (-> cost).
I'm curious what you intend to gain from playing this "I'm not worthy!!" angle.
Really? You don't have a computer with a line level input or sound card?
Right. You expect those of us who know to present to you the results of a scientifically controlled experiment that shows the issue is a non-issue. This after many of us have stated that we can't think of a single reason or theory that could explain why the stimulus that reached OP's ears would be different with/without the added transformer, never mind audibly different. I hope you're able to see how unreasonable your expectation is.
Meanwhile all we've heard from you is some mumbling about how the stray fields might be impacted, but no quantification of how that would impact the audible performance of the amp. Instead you hide behind "I'm just a mere mortal".
Does it? I would argue that it does the opposite. You are correct that it is hard to present an idea that seems to contradict established science. Science is conservative that way. But the way to make it through is to be persistent and thorough. Engage a friend. Hide the amp behind a curtain (or sit with your back to it) and have your friend place/remove the extra transformer. See if you can tell when the extra transformer is present and when it's not. If you're able to tell 19 times out of 20 whether the transformer is added or not you have actual data ... and an afternoon of fun.
Obviously this experiment wouldn't meet the standards of scientific rigour. After all, the participant (you) would know that something is being changed and your friend would know whether they'd made a change or not. So it would be impossible to rule out experimenter bias and expectancy bias. But as I said earlier, audio doesn't always have to get turned into science.
Tom
Whatever Tom you are the expert. What you say makes no sense to me, probably over my head.
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I guess no one has tried placing a spare EI core transformer on a working power supply EI transformer. Or they might have but they don't want to share the results.