High end Class D amps?

My active set-up (via separate, outward components) until a few days ago comprised three different amp topologies: Class A for the MF/HF horn section (Belles SA-30), Class A/B for the bass/mids section (Crown Macro-Tech 1200) and Class D/PWM-based for the subs (Crown K2).

The Macro-Tech was a temporary solution to begin with being that its built-in fan sports a considerable noise level - one that I was able to suppress to some degree (though not enough), not to mention the very audible hum from its transformer. The Belles obviously as well as the Crown K2 are passively cooled.
The Macro-Tech’s aren’t youngsters dating back to the 90’s, but they’re build like tanks and the 1200 model in particular (and also the 3600, to my ears) actually sound very good full-range, not least bridged. The 1200 I had was very well kept, but some of them are pretty banged up from tough pro touring duties, quite naturally.

On topic: I’ve now replaced the Macro-Tech 1200 with a Lab.Gruppen FP6400 power amplifier with its variant Class ’TD’ topology for the bass/mids of my main speakers.

https://images.thomann.de/pics/prod/169835_folder.pdf

I’ll leave the distinction of this particular Class TD iteration to the more technically proficient, but it involves leaving out the high frequency switching output filter usually required with the Class D topology. Even though the FP6400 in my system is only used in the ~85-800Hz region, actively, it offers improved clarity, insight and smoothness here compared to the Macro-Tech. Several I know use the Lab.Gruppen Class TD amps full-range, and regard them in the same class as MC² Audio’s S-series amps (Class A/B) that I know quite well - which is to say, to my ears they can hold their own against much more expensive, audiophile high-end offerings. The only minor downside of the Lab.Gruppen amp is that it houses a build-in fan, but its noise level and characteristics is very benign and close to unnoticeable - nothing I consider a problem.

Some may balk at the suggestion of pro amps for home usage like Lab.Gruppen’s Class TD, but I prefer keeping an open mind and use what sounds great whatever its intended segment application. What's more: with pro amps one needn't pay more than strictly necessary, hereby saving a lot of money compared to expensively upholstered high-end amps. 

I wouldn't own class D if you gave it to me

It’s true... you can’t teach an old @dutchydog new tricks. 

I am VERY happy I did not finalize my position on class D and hold it inviolable over the past 15 years. I saw no reason to form an absolute resistance, as though it could not be developed over time. Participating in the process of assessment as it has developed has been fun, and now is nothing short of thrilling. 

@douglas_schroeder Yes, all technologies follow a price/performance curve. Class D was first proposed in the 1950s but really didn't get going until the late 1990s. These early amps were at the bottom of the curve. The curve itself usually follows the same shape: sort of like a stylized 'S' (called a 'Sigmoid') where the cost (horizontal axis) goes up quickly while the performance does not. But after a while it starts to get figured out, then the performance goes up rapidly while the cost is minimal. Then as the technology matures the curve reverts to its original slope; incremental improvement for lots of money to develop it.

If I had to guess, it appears that we are nearing the top knee of the Sigmoid curve. 10 years ago we weren't there.


5 years ago we realized we needed to be taking class D seriously. We're known for making very transparent tube amplifiers- not the usual sort to be messing with class D. But in November a year ago we were awarded a patent in the field. A smaller player like us usually has troubles doing that in a field of mature technology. That is why I say the technology is nearing or just past the upper knee of the Sigmoid curve.