I'm a big fan of class D amps, however, I've noticed that they do tend to truncate the natural decay times on bass notes, which I believe is due to their very high damping factors. I find this a bit ironic, since class D is often dismissed as only good enough for sub amplification.
I'm wondering if others have noticed this because I've never read about this unnatural class D shortening of decay times here or anywhere else. It's important to note that this class D bass note decay time truncation issue is not something that is easily and immediately discerned by listeners, mainly because it's more distinct on certain instruments, notes and types of music.
When I listened to my first class D amp, a Class D Audio SDS-440-CS with a rated damping factor of over 1,000, driving my former Magnepan 2.7QR speakers, for example, I distinctly recall perceiving the bass performance as the best I had ever heard on them since I bought them used about 6 years earlier. I perceived the bass as clearly being more prominent, powerful and dynamic as well as tauter and, at least initially, seemingly more detailed through my new class D amp than through my prior class AB Aragon and McCormack amps.
It wasn't until about 6 months later, after installing an Audio Kinesis Debra 4-sub distributed bass array (DBA) system with all subs driven by a separate class AB 1K watt amp with a DF about 300-500, that I first became aware of this class D decay time truncation issue on bass notes.
I ran my Magnepan panel speakers full range knowing they only had a rated bass extension of 35 Hz. My main purpose for installing the AK DBA system in my room was to provide full bass extension down to 20 Hz and provide the bass power and dynamics that my Magnepans lacked between 20 and about 40 Hz.
I clearly noticed the bass quality was much improved being reproduced through the AK DBA system. The bass was even more powerful and dynamic, as expected, but it was also smoother, faster and much more detailed. I believe it was this added detail that enabled me to notice the stark difference between how the AK DBA reproduced the decay times of bass notes in much finer articulation, without any truncations and with more natural sounding durations than the class D amp was able to reproduce them through just my main speakers.
Of course, I realize there's likely more factors involved in achieving high quality bass performance in a system and room than the type of amp used and its rated damping factor. The truth is that, more than anything else, I was surprised by the truncation of bass notes through just the class D amp driving my mains and the vast improvement in their reproduction, along with other benefits, provided by the addition of multiple good quality subs driven by a class AB amp.
Currently, it's just my theory that the DF of the amp(s) utilized in a system is an important factor in determining the quality of a system's ability to accurately reproduce the decays of bass notes. This is all based on my personal experiences, however, and I understand that I'm no expert and that we typically don't know what we don't know.
Which suggests that there are likely other important factors involved.
Tim
