I did a research on Youtube and found few videos where people have recorded coil whine. I also found some discussion on the web where a person tried to RMA his PSU because of the noise it produced, but Seasonic sent it back with notice that nothing was wrong with that PSU. I checked info on their webpage, and they do market it as defined by "complete silence" https://seasonic.com/product/platinum-520/, so I sent a mail to check if I am eligible for RMA if my unit result in buzzing, crackling and other noises avialable.
I got really fast and friendly answer from real human with name Walter, within minutes of posting a question through the mail form on their page. Here is answer I got:
(I have cut out non-essentiol parts as greetings etc.Please note the PSU may react differently based on system configuration and coil whine can be the result of MB or VGA card’s non-compliance to Intel standards for dynamic load.
As well, the fanless units have been updated and therefore should not have any issues but if you do experience coil whine and or strange noises, please note, the distance to measurement is 50cm, then please contact us and start a RMA here: http://www.seasonic.com/rma/
I asked him back if I can somehow determine which products are compliant with that Intel standard, and here is answer I got back (edited to bare essentials):
I interpret this answer as if it this load on gfx card i combination with certain mobo will give same result from any PSU, not only those fanless, but maybe it is more perceived from a fanless PSU. I am not an engineer myself, and have not much knowledge about electrical components, so I can't either confirm or negate that explanation, but I suppose there are more knowledgeable people here who can give more details about coil whine.Sorry there are so many MBs & VGAs on the market and each with so many revisions it is nearly impossible to keep up.
A quick bit about dynamic load profile….. this is mainly focused on the 12V rail, for example with a VGA, if there is heavy graphics usage, then possibly the uptake and the drop of the 12V rail by the VGA will be very fast due to the quick change of graphics etc. This speak of change on the 12V rail must be within a certain guideline set forth by Intel and if it exceeds the range, then the PSU cannot react fast enough and a by product of this inability to react is… the expansion and contraction of the coils on the windings resulting in… coil whine…
My question is, have you noticed coil whine with other PSUs, and is there any way to know what components will work fine together other than trying them out?