My thoughts on my first Class D amp

The original Tripath amps had the warmth and meat but they were not very high power. The Gan Systems evaluation amp boards had the ability to turn loop feedback off and in that configuration they have a lot of the Pass sound. I prefer the feedback off on those amps personally. Gan Systems made those evaluation boards to demonstrate the higher linearity of the GaN devices and less need for feedback however I do not know if manufacturers followed their lead or opted for feedback and lower THD specs vs pure sonic results. 

Interesting comment I read tonight elsewhere, and it makes one wonder if I change amps to something much more revealing, will it trigger a follow-on desire to replace other components later as well.  Caused a pause.  Here is the comment:  

"Class D amps tend to be very revealing, very low noise, very fast. Upstream gear like a DAC, a preamp, and speaker voicing become more exposed. If something sounds off, people may blame the amp." 

I wonder how many people have upgraded to one of these great new ClassD amps or ClassD monoblocks - now looking to change speakers, DACs, or other components in order to tame something they are hearing too much of now. 

Why I really like this forum.  So many good points made. 

@desktopguy Wyred for Sound.. Heard of them, turns out there is a distributor on Canada, Reverb, who sell new and refurb units. Makes me want to buy a pair, just to try them.

I am now realizing how difficult it is for me to do a blind listening test, as my gear is next to impossible to access.  

@ozzy62 Bel Canto, another brand I know I have seen in a shop, and I think I liked their sound.  It must have been over 5 years ago.

@decooney You are most likely right.  The weakest link shows up.

Some speakers (like 86dB Magnepan's) need high current to shine.  I replaced an vintage entry 50 WPC Levinson amp with a high power 500 WPC class D and it was better sounding but I think that was because the caps on the ML were worn and it could not deliver the current needed.  At high dB's the sound of the Class D got unpleasant, I think because the Maggies were starving for current or the Class D I used wasn't right for my speakers.

I replaced the Class D with a 60 WPC Pass XA60.8 with less than 20% of the rated output of the Class D and night and day difference for the better all around but especially at louder (not loud) levels.  With the Pass the sound swelled as the loudness increased, it's like listening to waves crash on rocks at the beach from 30 yards out and then moving to standing on the rocks.  The Class D did not do this but rather took on a harder honking character as the volume rose.

I found an interesting paper on output filters of Class D amps.  

https://www.eetimes.com/understanding-output-filters-for-class-d-amplifiers/

Apparently the design of the low pass output filter is critical and is referred to as "the heart of a Class D amplifier". Class D amplifiers generally use a low-pass filter to attenuate the switching noise in the output waveform while passing the audio signal to the loudspeaker.

While the paper is above my head in general it does make the statement that the output filter's "Inductance" and "Q value" need to be designed around the impedance of the speaker!  If you change the Impedance (the Speaker) the optimum Inductance and Q value of the filter changes also changes.  It then goes on to describe what to me are compromises to work with a range of impedances.

I suspect that speakers that provide a difficult load will not shine with Class D amplifiers just like Maggie's don't shine without high current amps.  Class D likely sounds best with simple loads centered around the designed output filter's selected optimum speaker impedance.

Of course I am no engineer and I have limited experience with Class D and this is just what makes sense to me.

Interesting answers you guys are giving on class d amps.