And then after all the likely causes that may lead to an audible difference; Conrad Hoffman has brought up the external field caused by the transformer iron.
What the hell does it matter? A lot of audiophiles agree on subjective terminology to define what they hear. "Punch," "pace," "timing," "PRAT," "dynamic," whatever. Ten years ago I bought an Arcam irDAC based on a completely subjective review from WhatHiFi. I have never once regretted the purchase. I wasn't interested in numbers, I was interested in enjoying my music collection. Everything they talked about in that review is what I hear, and after comparing it to other DACs I've heard in my system, I still agree and I couldn't be happier.
A friend asked me to repair his Orchid DAC. He trashed the PCB when modifying it and I managed to put things back together. It sounded okay. It's a well-regarded DAC. I wouldn't trade it for the Arcam. To me it sounded dull and flat. Maybe to him, in his particular system, it sounds great. What does that prove?
Everything--let me repeat that--EVERYTHING in audio reproduction is subjective, regardless of what you choose to believe. What floats one listener's boat may sink another's. Over time you learn to trust reviewers and amateur listeners whose subjective tastes reflect your own.
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Yeah, that's a great point. I'm a newb so am still trying to understand so much... Thanks for your thoughts.
touche! really good point. he didn't use that exact word, but several others, so I picked that word.
EI and toroid trafos are rarely the same if the “specs” are the same. Toroids in general have better regulation. If you were to buy a 300 VA 300 volt EI and a 300 VA 300 volt toroid, the EI would measure HIGHER with no load and LESS at 2X rated VA compared to the toroid. They could not simply be used interchangeably. In order to get the same “light load” B+ to keep from overvoltage on your caps and over dissipation in the tubes at idle, you would need a lower voltage EI. In order to get the same output power, you would need to design with the higher B+ with an EI and need to be able to tolerate it.
And EI’s can go from bad to worse as far as regulation. Split bobbin types are horrible. They can be 20-25% high with no load because they drop like stones under load. Even the big ones do.
And EI’s can go from bad to worse as far as regulation. Split bobbin types are horrible. They can be 20-25% high with no load because they drop like stones under load. Even the big ones do.
I design and build my own transformers and in general, with one notable exception, aim at "punchy" amps , which means low DCR > good regulation.
In my book, largest losses are resistive, way more than magnetic ones, so try to use as much copper as possible, filling the window completely.
Wire does not rest as a perfect square or rectangle on the bobbin, specially outer layers, , corners are rounded and sides are rounded convex, so after winding I press them flat using a hydraulic press and shaped hardwood dies, go figure.
Core shape per se does not have any influence, except toroids for geometrical reasons have huge "window" surface available so designer is free to use thicker wire with no restraint (except $$$ of course), also sometimes average turn length is smaller, reducing DCR.
But again, it´s not "shape magic" , simply it often allows for lower DCR which is the main parameter..
PS: also prefer square section EI instead of rectangular ( extra stacked) cores, allows for shorter average turn, solower DCR.
Ideal would be a round core, like on some ferrites, but stamped sheet cores prevent that.,
Have also used so-called semi-toroidal cores: from above you´ll see a square or rectangular core, made out of steel strips stacked and joined by the corners.
They use 2 log narrow bobbins, on 2 parallel sides, large window and small core makes them practical "toroids, and because of the inevitable small gap at each corner, no problem with Mains DC.
In a way, best of both worlds.
In my book, largest losses are resistive, way more than magnetic ones, so try to use as much copper as possible, filling the window completely.
Wire does not rest as a perfect square or rectangle on the bobbin, specially outer layers, , corners are rounded and sides are rounded convex, so after winding I press them flat using a hydraulic press and shaped hardwood dies, go figure.
Core shape per se does not have any influence, except toroids for geometrical reasons have huge "window" surface available so designer is free to use thicker wire with no restraint (except $$$ of course), also sometimes average turn length is smaller, reducing DCR.
But again, it´s not "shape magic" , simply it often allows for lower DCR which is the main parameter..
PS: also prefer square section EI instead of rectangular ( extra stacked) cores, allows for shorter average turn, solower DCR.
Ideal would be a round core, like on some ferrites, but stamped sheet cores prevent that.,
Have also used so-called semi-toroidal cores: from above you´ll see a square or rectangular core, made out of steel strips stacked and joined by the corners.
They use 2 log narrow bobbins, on 2 parallel sides, large window and small core makes them practical "toroids, and because of the inevitable small gap at each corner, no problem with Mains DC.
In a way, best of both worlds.
Maybe not BS, but 'just' a personal view. If you go through the motions of overspeccing a xformer, it's impossible for it NOT to sound better unless there is a pathological defect. That's basic stuff, and not my personal view, this is backed up by a myriad of studies and research. But your ego will make sure you're not going to look that up.
Jan
And that makes them a good choice for a preamp. The split-bobbin designs makes tham less susceptible to mains junk getting into the secondary, and the relatively high impedance doesn't matter much for a light preamp load.
So, again, there is no universal rule, decide what you need and determine the best fit.
Jan
A lot of commercial mains transformers are built to a price which means they are made to run at or near the flux density limit for the core material used ie using the smallest core they can
get away with. This applies to EI,toroids, c-cores, r-cores or whatever. This means its easier for these transformers to saturate causing distortion on the power waveform which might
be audible. In my experience its one of the main reasons that mains transformers can sound different and why I specified in my designs transformers that ran at a lower flux density ie a 300VA
transformer with a 500VA size core. This didnt please the bean counters.
get away with. This applies to EI,toroids, c-cores, r-cores or whatever. This means its easier for these transformers to saturate causing distortion on the power waveform which might
be audible. In my experience its one of the main reasons that mains transformers can sound different and why I specified in my designs transformers that ran at a lower flux density ie a 300VA
transformer with a 500VA size core. This didnt please the bean counters.
I see "O core" toroids in some Chinese audio products lately. Having what seems an oval cross section stacked core. Should be controlling better the external magnetic field emissions I suppose. Has anyone used such a type or knows more about it's pros and cons?
Yes, split bobbins were not invented to make "better" transformers but to help them meet "official rules": primary to secondary HIPOT insulation and reduced EMI coupling ... which is not bad of course.
Only reason you'd avoid a toroidal transformer is that the cores tend to be smaller and saturate easier compared to an E-I core. Only really a problem if you use half-wave rectification or you have full-wave rectification and it becomes unbalanced, e.g. using a voltage-doubler to generate split rails, then loading one rail more than the other.
The problem arises that "PRAT" and the other terms you mentioned when used as a subjective assessment cannot be related back to an objective measurement. Say you design a product and it has bad "PRAT" (or whatever), where do you begin to re-engineer it to improve on that?
If instead I take objective measurements and see the powersupply to be drooping under load, or the output distortion to be high, I can then go make specific engineering improvements to the product to improve those objective performance criteria which hopefully results in a subjective improvement to the sound.
Having a subjective opinion of a product is fine and generally products which objectively measure favorably also tend to be subjectively favorable and vice versa. If a product objectively measures like garbage, likely it'll also sound subjectively garbage.
The problem arises that "PRAT" and the other terms you mentioned when used as a subjective assessment cannot be related back to an objective measurement. Say you design a product and it has bad "PRAT" (or whatever), where do you begin to re-engineer it to improve on that?
If instead I take objective measurements and see the powersupply to be drooping under load, or the output distortion to be high, I can then go make specific engineering improvements to the product to improve those objective performance criteria which hopefully results in a subjective improvement to the sound.
Well it has a split bobbin ...
What is the application for this xformer? Is it a high voltage transformer?
Jan
What is the application for this xformer? Is it a high voltage transformer?
Jan
Yes, I think it's a flyback and one of the pairs from the primary is probably for the CRT heater.
Yes looks like it. These are often special in the sense that the spread L and capacitances are tuned to the 3rd or even the 5th harmonic of the flyback pulse. Adding harmonics to the secondary pulse makes it broader thus having more energy content.
This was a trick used with HV supplies in color TVs with a picture tube.
I know because I designed some of them ;-)
Edit: the primary usually is the exitation, and would be in series with a current, like the horizontal sweep. By resetting the current (the flyback when the beam returns to the right side of the tube) a large voltage pulse is generated.
Jan
This was a trick used with HV supplies in color TVs with a picture tube.
I know because I designed some of them ;-)
Edit: the primary usually is the exitation, and would be in series with a current, like the horizontal sweep. By resetting the current (the flyback when the beam returns to the right side of the tube) a large voltage pulse is generated.
Jan
As a general rule the more compliant you make anything to a set of rules the more **** poorly it performs in all other metrics. (You could even call it the 4th law of thermodynamics - work in industry long enough to see just how universal it is.) You just have to use these trafos where the load is constant and you know exactly what it will be ahead of time. Or if for some reason you want a lot of sag. I cringe when I see them in HT receivers - you know that one is going to be blowing output transistors if you play it louder than Muzak levels - or listening to the protection circuit clipping if the load impedance drops below 6 ohms. I won’t even try to use one with power tubes.
Those old flyback trafos have intentionally poor coupling - the inductances are tuned to give a high conduction angle. Same as any other flyback-type SMPS - which tend to work best with constant DC loading.
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