Class D Technology

gdhal I think one of the things switching amps excel at is delivering power and current for very short periods of time which makes for excellent detail and transients. Its a very important aspect of music that often distinguishes great sound from just good. Power and current specs alone as published probably do not indicate an amps ability to deliver power and current quickly and efficienctly for very short periods of time when needed.

One way this is refelcted uniquely with the Class D amps I own and use compared to others is detail and articulation of the bass in particular. It is leaps and bounds more articulate and detailed than any other amps I have owned or even heard. When I first heard it, I was shocked thinking my bass was gone when in fact it had leaped to an entirely different level not heard prior.

My impression is tube amps tend to be a bit softer in this regard (which some may actually prefer) and class a/b SS amps often just miss it altogether.

Class A amps, tube or otherwise are historically the ones that probably do this best, but that is changing.....

Lots of great responses. When switching frequencies are 5x higher than today's, what will be improved? Will that prevent the saw tooth waveform challenge? Or prevent the need for a low pass output filter?

What makes today's class D amps sound cold and dry? I have experienced this firsthand with an ICE Module that I once owned.

Mapman alluded to a totally black noise floor. I also experienced this with the ICE module. So far, this is the only benefit other than efficiency & power output that has been discussed and can be attributed directly to the Class D topology. Or maybe this noise floor issue is unnatural and sounds are being cut off prematurely by not allowing for decay?   

CD's have become listenable....maybe some day so will Class D's

" What makes today’s class D amps sound cold and dry?"


I’d attribute it to the high damping factor in combo with the aforementioned transient capabilities.

Mine definitely sound best with speakers that like high damping. Usually larger ones with larger drivers that are inherently harder to control.

They are more towards the cold and dry on my little Triangle Titus monitors.

Not so on my somewhat larger and more extended Dynaudio Contour monitors or any of my other much larger and more extended speakers.

They are the cats meow on my largest the big OHM F5 series 3 floorstanders with much larger Walsh style driver often cited as benefiting from monster amps with high damping. That is very true!

The switching time is an issue. The output devices have to switch on and off at a pretty high speed. The problem is, they can't both be conducting at the same time. That is to say, it takes a certain amount of time for the devices to turn on and to turn off. If one is not quite off while the other is turning on, you get something called 'shoot though current' as the devices are essentially a short across the power supply without doing anything to drive the speaker. Shoot through current causes the output devices to heat up quite a lot. So it has to be avoided!

To solve this, there is something called 'dead time'. Its a circuit that makes the output devices wait just a little so that one is completely off before the other starts conducting.

The longer the dead time the higher the distortion. So if you can switch faster dead time is reduced and so is distortion. Right now the technology is to the point where the amps have become practical for mid fi, but they still have a ways to go before they can challenge a good class A transistor amp or a good tube amp. There is no question that this is a technology to be watched.