- Sunfire TGA-7401 or TGA-7201
- NAD M27
- Lexicon RX-7
- Anthem PVA7
- Marantz MM8077
- Emotiva XPA Gen3
- Outlaw Audio
You said no fan, but, the one I would recommend does have a fan. However, it only runs when thermostatically required, which is not often. That amp is the Datasat RA7300. There are few 7 channel amps that will better your Krell. The ATI signature would be a close second. PM me if you would like pricing on either.
If heat is a concern, you should be looking for ICEPower or Hypex based amplifiers. They'll stay quite cool.
nuForce, Jeff Rowland, NAD, Bel Canto and Theta are making amps based on their modules.
I personally own ICEpower 250 modules and they not only stay quite cool, they are perfectly neutral and to me indistinguishable from the A/AB amps they replaced.
Thank you all. Never thought class-D before. It seems Class-D made a lot of progress in the past few years. They can be found in some real high-end brands. Many of them just use modules from ICE or Hypex which is also available to end customers. Does any one know diy kit available for multichannel amp including case and power supply? it will be fun to build one on hands. This will be for HT only, I will still keep my ARC VT100 for 2 channel listening.
Class D amps can be engineered to be a perfect circuit. However, you must include the speaker impedance itself as part of the circuit. A Class D amp can provide perfect frequency response if the speaker is a very constant impedance (i.e. like a straight 8 ohm resister). However, a real speaker is almost never a perfect resistor and its impedance curve is typically all over the place (such as ranging from 3 ohms to 16+ ohms in different frequency areas). Some speakers are harder to drive with a Class D amp. In these cases, the speaker itself tends to drive the frequency response of the Class D amplifier and you get things such as tube-like midrange, weak bass/sub-bass, less punch/slam, high frequencies rolled off. A regular Class AB amp will still be affected by the speaker impedance curve, but not nearly as much (this is a significant difference). I played with Class D amps for a while until I figured all this out.
Sure, the Class D amps will run very low heat and are very efficient (and they are very small), but if you have hard to drive speakers, a normal Class AB will always be superior. I had some Focal speakers that are very easy to drive and they worked well with Class D. However, when I moved to B&W 805 Diamonds, they just did not do as well. An Emotiva XPA-1 monoblock just stomped all over the Channel Island Class D. (yes, I do understand that the Emotiva is a much heftier amp, but still high-current Class AB).
I’m not sure what advances have been made in Class D over the years, but I would really keep this in mind if you want to research and try Class D. In my opinion, the B&W 805s that you have can really sing, but they really need a high-current Class AB amp (which does heat up in any amp you choose). If you do choose Class D, I would suggest you mate it with a speaker that has an almost constant impedance curve.