D220 Pro from the inside.

[Confused]

It looks as though the PCBs are identical, or nearly so, but the 140 is de-populated compared to the 250.

The 28 black, squarish parts along the bottom edge of the 250's ADH board are (I think) each 4.7 μH inductors.  These might be part of the class-D amplifier output, perhaps acting as a low-pass filter to convert the digital PWM output into analog.

The 140 seems to have fewer inductors (either 10 or 20 depending on what's inside the blue/grey packages), no doubt doing a similar job but catering for a lower output current.  I can't read the part numbers to see what value the inductors have or how many there are per package.

These are some links to the original pictures, they are slightly clearer when compared the pictures attached in this thread, which lose a little resolution.  It is possible to read to part numbers on the 250 / 1000 Pro pictures, not so much for the 140 Pro pictures.

https://on-mag.fr/index.php/topaudio/tes...s-exquises

EDIT:  If you scroll to the end of the article there are some much higher resolution photographs, click on these and the component part numbers are fully legible.

https://www.son-video.com/article/amplis...t/1000-pro