Class D

Here is an interesting fact. The IceEdge module has two....yes, two inductors in series on the output. It could be one reason the phase does not measure so well. I removed the last inductor and the last set of caps to ground as part of the last set of mods I did (PS Audio leaves these alone but still the highs are pretty good....please read Michael Fremer"s review of the $6K PS Audio amps where he compared it to the $150K Dartzeel). When I did this it sounded as if I had 2 db more gain. The soundstage came forward....much like my class A amp and the highs were much more extended and airy and the decay went on longer. The depth was now greater but the midrange was more forward.  Very cool.  Many other mods I did to the module improved the highs as well....and they had nothing to do with bandwidth or phase shift. Everything makes a difference.....It is not just one parameter.

@ricevs what happens to the residual when you do this?

gFi it’s shocking that you don’t know the difference between your and you’re/you are you’re- you’re ignorant

You’re ignorant, I meant to say (your amp)
Either, or either, so long as you know. To me the fact is you’re being ignorant to this graph.
.

You still need to let it sink in sunshine, I showed you what your amp that you push incessantly does to the phase integrity of the upper-mids and highs, up to 70’ out of phase!!!!!
Oh yes!! wonder why most gripes about Class-D’s sound, is about the upper-mids and highs, never it’s bass.

https://ibb.co/vvwzGV5

I did not measure the amount of residual after removing the secondary coil and caps.  Since the caps to ground were just 1000 pf....I imagine that the residual looked much the same.  IcePower was probably trying to remove ultra high frequency noise as a precaution.  So many manufacturers put filters and fuses on things to prevent imaginary problems.....not knowing these fuses and filters actually wreck the sound.  Everything you do changes the sound.  The output coils that everyone use are ferrite core coils.  No one in their right mind would use a ferrite core coil in the midrange and tweeter xover of a serious speaker.  Ferrite messes up the sound.  So, why do we have ferrite coils on the output of all class D amps?  It is because they are smaller, cost less, have less resistance, run cooler and have better contained fields so there would be less rf outputting the amp.  It is not because they sound good.  If you use a better sounding air core coil the board has to be bigger, the coil costs more, you have to use a large gauge coil to get the resistance down, and you might have to add more shielding in the amp to make it pass rf standards.  

What is true is that all coils sound different from each other.  So, even different ferrite core coils will sound different.....even using the same gauge wire.  The type of wire and its coating all affect the sound......just like wire used in an interconnect.  The worst being normal copper....OFC is better, cryoing is better, PCOCC is better, etc.  Same with the core material and shape and coating and wire directionality and whether you go into the inside or the outside of the coil.  Many air core coils I tried in the Purifi module did not sound as good as the stock ferrite core coil.  The one I ended up using sounds much better than the stock coil.  When I first heard the difference between the stock coil and the one I am using......I said "its like I am sticking my head down the saxophone".  I could hear so much more information.....real information....space, separation of instruments, lower noise, etc.

We need others to start experimenting with the output coil.....this is more important than what the switching frequency is.  There is always more to learn and more beauty to unveil.

It's often the case that extra filters are added to allow the device to pass FCC requirements and/or to improve stability into arbitrary loads.

If you are making modifications for your own use, you can get away with it, but if you are trying to make a commercial product, you will need to make sure the product continues to meet FCC requirements for emissions before offering the product for sale.