Is D for Dry? Class D...

Class D, good for powered subs and car stereo amps, and that’s about it. All my opinion. No class D in my house, except my powered tannoy sub in my dedicated home theater set up. Hifi run by class A.

@mapman As you know, I own the Ohm Walsh 2000s for 11 years now.  A great match with my class D amp, and a great value, IMHO, at full retail.  Used and fully broken in makes them a no brainer, IMO.

Class D, good for powered subs and car stereo amps, and that’s about it. All my opinion.

I agree that a good number of older class D amps were not all that musical. I heard some early examples that I would have thought were a joke were it not for the price.


Class A relies on the bias setting and operating point of the output devices such that you get the maximum linearity out of them. This is important to keep distortion down and for getting a nice first watt.


The advantage of a class D amplifier is that controlling distortion isn't based on the output section. This is a tremendous advantage. At this point its more about how linear the encoding system is.


In a class A circuit, the linearity is important because in most cases, the amount of feedback that can be applied to the circuit is often limited by frequency poles (like coupling capacitors; in engineering terms, this idea is called 'phase margin'), which if exceeded, will cause the amplifier to oscillate. The other problem is that the application of feedback causes distortion which manifests as IMD and higher ordered harmonics through a process called 'bifurcation'. The ear interprets this as harshness and brightness, as it assigns a tonality to all forms of distortion. The ear is also particularly sensitive to the higher ordered harmonics as it uses them to sense sound pressure.


These aspects of using feedback have been known for a long time- Norman Crowhurst wrote about them in the late 1950s. Now you can get around the distortion problem by running enough feedback, but in most class A amplifiers this isn't practical since the amp will probably go into oscillation; you need in excess of 35dB for the amp to clean up the distortion caused by feedback.

Class D amps have a means to get around this problem. You can run 35dB or more of feedback with the expectation that the amp will oscillate- in fact its encouraged. The oscillation is used as the switching frequency, resulting in a fairly simple circuit that has low distortion and lacking the higher ordered harmonics that causes harshness in so many amps.

seems to me that since class d is newer tech with new possibilities for good sounding cost effective builds and a lot of active innovation in the amp modules, there are many new efforts to make good sounding amps using these modules

as in any case with emerging/new-ish technologies, you have older aficianados who will poo-poo it, having been burned before or having experienced poor sound from earlier cruder versions... so while they may indeed have had these experiences, and they are not wrong, their experiences are increasingly out of date, and don’t fairly reflect on what is being accomplished presently by innovative folks working with the latest versions of these 

I have a gut feeling @atmasphere would not be soon marketing a Class D amp if the technology was somehow not up to snuff. Nor would Bel Canto which took the plunge and helped lead the charge a number of years back.

My ears tell me the technology is 100% up to snuff and a threatening challenger to the high end status quo moving forward as a result of not just sound quality but TCO, versatility, and overall ease of use. That might account for at least some of he hostility towards Class D commonly encountered here.

I just ignore it because I have owned good quality Bel Canto Class D amps for a number of years now and know better every time I listen which is pretty much every day. I decided to try the latest and greatest new technology on the block that seemed to fit my needs on paper first  and managed to stay clear of much old tube technology in my system as a result.  Have goals to eliminate tubes altogether perhaps someday soon.     I have to pull myself away from listening usually especially when listening to the Ohms, so that is the ultimate good sign and all that matters.

Of course as always YMMV. Different strokes and all that will never change.