I’ve been working on familiarizing myself with the various SS power amp classes in an effort to understand basic operating principles, pros and cons, significant design considerations/compromises etc. I have a few observations and questions I’d like to bounce of y’all.
A and A/B designs seem to be homegrown ground up designs employing a few different SS device types that don’t seem to stir up much controversy. Passionate devotees, yes. But, aside from measurement food fights, the technology is mature enough that there isn’t much to argue about.
D class on the other hand seems to be the wild west. Relatively speaking the technology seems to be continually evolving. Most all seem to be implementations of amp/power supply modules from a couple of sources that differentiate themselves by the input stage which may be home grown or another purchased module. More so than other amp types, these modules seems to have spawned a DIY cottage industry though some majors and audiophile centric companies have gone all in w/ D.
I’ve come across more than one pissing contest about the relative merits of different SS devices used in the amp modules, feedback and switching speeds seem to get people all riled up. And comparing D class to everything else is where the measurement debates seem to rage the hottest.
And yet most D class amp reviews I’ve read or watched seem to compare their performance to A class. IF A class performance is the Holy Grail of D class amps, do all the arguments revolve around the non trivial D class benefits such as size, output power, and efficiency?
Am I missing something or misrepresenting the D class landscape?
One other tangential question. If relatively inexpensive dynamic headroom is a major benefit of high powered D class amps, how come nobody complains about poor dynamics in relatively low powered A class amps?
After A/B for many years, I used pure Class D from about 2008. It was a bit early days, dynamic but not the best sound quality. I tried a pure Class A amplifier and complained about poor dynamics. I then used Quad amplifiers, which are Class A voltage Class B current hybrid amplifiers, lots of nice clean power and cheap, but lack a bit of dynamics. For the last 6 years I’ve used a Class A voltage Class D current hybrid amplifier that is ultra low distortion and incredibly dynamic, and no thoughts of changing.
The nCore power supplies and amplifiers perform so well it makes sense to use them as plug-in modules in integrated units., which many manufacturers do. Saves re-inventing the wheel.
Size, output power, and efficiency mean nothing to me if the amp doesn’t sound great and is non-fatiguing. Those are indeed trivial to me.
I have listened to many Class D amps over the years and they don’t have full body and engaging sound that the better Class A and Class A/B amps have. Plus, the Class D amps give me headaches after about an hour of listening at my preferred sound levels.
@Paul I’m very happy with my M700s, which replaced a classic Adcom Class A/B amp. I keep reading about how GaN FETs are the future of Class D. Is PS Audio doing any exploration of building a GaN-based Class D amp in the near future?
My impression about Class D amps also until I auditioned one a very modest (read: cheap) Class D unit a few months ago in my system (Vandersteen Treo CT, PSA Directstream, Kimber Select interconnects and Bifocal cables that WAS being driven via a very musical Hybrid amp).
The improvement was beyond any single upgrade I have ever made before so, of course, I kept it.
Funny enough (since I am, but for a select few, a “reviewer sceptic”), I was most surprised at how accurately both Kalman Rubinson and Robert Harley reviewed the unit and after I had tried it and described very accurately, at least to my ear, essentially the same experience as mine had been…and continues to be. First time in my many decades in this hobby that the “new”, “change”, “different” experience in music is so profound and fresh with each listen, and this after swearing years ago that I could not live without a couple of tubes somewhere in front the “final” amp.
Oh Yeah…It is the NAD C298. I have to believe that any Class D implementation Paul does is and would be as very well done, also, but this one really “ambushed” me.
I have been tempted to try a NAD as well in my second system. You can get some pretty reasonable prices at TMR. My first good Class D experience was with 700s. They are great amps. I would imagine all one would ever need in many systems. 1200s would be fun to experiment with and do a A/B against my two A/B amps.
I just replaced my Rotel rb 1582 MKii with M700’s
I liked the sound better so i kept them
Given much of the internet talk ive been reading i was surprised i prefered the M700’s
I never heard Class D (other than my subwoofer) until getting the M700s about a year and a half ago, so I can’t comment on earlier iterations from other manufacturers. But in the time I’ve had with the 700s I’ve been absolutely thrilled with the sound. Granted, I’m not an inveterate amp switcher like some, so despite being in the hobby for almost 49 years now (!) I don’t have a huge well of sources for comparison. In all that time I’ve only owned a GAS Son of Ampzilla (8 years), a B&K ST-140 (33 years), an Emotiva BasX A-300 (1 year), and the M700s. All of those followed my first system in 1973 (which I don’t usually count), that was built around a Pioneer SX-727 receiver (5 years).
I have the Class D M1200 monoblocks with a tube input stage and absolutely love the sound I am getting. My basis for comparison has been listening to Conrad Johnson full tube pre and power amps for the last 24 years.
Many thanks all. I truly appreciate hearing of your experiences. For some it appears well executed Class D amps are satisfying a need though it almost feels as though in Class D you risk obsolescence. I suppose a good sounding amp will always be a good sounding amp.
I actually have an NAD AVR that I like pretty well for what it does but didn’t know it was Class D for probably 2 years after I bought it. I was clueless and latched onto it because it reportedly ran cool enough to be crammed into a cabinet.
A year or so ago reading about Purifi and NAD’s implementation piqued my interest.
I have a T758 V3i. It’s a relatively low cost 7.2 AVR with a lot of stuff packed in the box. I like it well enough for what it does but that’s honestly not saying much. It’s set up okay for HT but not for critical listening, which has been quite frustrating. I’m also just now learning how to listen and haven’t A/B another so don’t have a good comparison.
That said I’m finally getting a good listening space set up and plan to compare it to the Ragnarok running in that space. The Raggy has been paired with Salk Supercharged SongSurrounds which has sounded okay in another compromised set up. I moved the Salks to the NAD and was immediately surprised by how much they seemed to wake up.
So long boring answer to a simple question is it sounds okay. I need to listen to it in a good environment against another amp I have more time with to really draw any comparisons.
