Class A/B Home THeater Receivers

Tim,
I'm not sure what your agenda is, but you obviously seem to have one. Class D is not inherently better than any other class, nor is Class A or A/B. The implementation of the Class used is what is the deciding factor. There are plenty of Class D amps that do not compare well to Class A or A/B amps, AND there are plenty of Class D amps that are superior to some Class A amps. You can't make a blanket statement that one is absolutely better than the other. If that were true, no one would bother with making anything else.
Also, in all of your posts you never mention a brand or model, so does this mean that you think that ALL Class D amps sound alike? That is what you seem to be implying at any rate, and that is just not so. That is not correct about ANY class amp, whether it's A, A/B, D, or Q.
Something else you seem to gloss over is how you deal with a Xcross over for the sub in your system. Does the Oppo offer a cross over for the sub? And if you use different amps for your different speakers you need a way to balance their output to each other. Does the Oppo have that capability too?
Just curious how you mange your system with out a pre.

Bruce,
Go with what sounds good to you, and don't worry about what class it is. There are plenty of modern class A/B processors out there, so you should be able to find something you like without too much trouble, but while you are looking, don't be afraid to listen to a Class D. All favors are out there for every taste.
Good listening,
Mike

Hi Mike,

     Here are some responses to your post and answers to your questions about my system I may have glossed over:

1. I really don't have an agenda but admit I've had very positive experiences with several class D amps I own.  I bought my 1st class D amp (a classDaudio SDS-440CS) when my previous class A/B Aragon 4004 MKII broke down due to leaking caps in the power supply.  

    My system is used equally for 2-ch music and as a 5.1 surround system for HT.  My main speakers are an older pair of Magnepan 2.7qr panels.  I use a Magnepan CC3 as a center channel, Infinity in-ceiling speakers as rear surrounds and an Audio Kinesis Debra distributed bass array system as subs.  This consists of 4 67lb subs that contain 10" drivers and are all driven by a separate 1,000 watt class A/B amp. I previously used all class A/B amps but have transitioned over the past few years and currently use all class D amps to drive my 5 channels:  a pair of D-Sonic M3-600-M mono-blocks to drive the 2.7qrs, an Emerald Physics EP-102 stereo amp bridged to mono for the CC3 and the classDaudio SDS-440CS stereo amp for the rear surrounds.

     While these class D amps are from different companies and use different power modules, they have similar sonic qualities:neutral, very good dynamics, very low noise floors with smooth but very detailed mid-range and treble response that avoids harshness.  However, I have to resist claiming all class D amps sound the same due to my limited sample size.

2.  I don't believe class D is inherently better than traditional hi-end tube and class A amps.  I have a great deal of respect for the sound of many traditional hi-end tube and class A amps.

     While I've never used tube or class A amps in my system, I have listened to several hi-end traditional tube and class A amps at audio showrooms and friends' homes and find most sound very good.  I've never been able to directly compare very good examples of tube, class A and class D amps to one another since I've yet to find an audio dealer that carries all 3 types.  These dealers typically don't carry good examples of class D because they're usually sold internet direct and bypass dealers.  I've had to rely on professional audio reviewers opinions for information on how the better class D amps compare to the better traditional hi-end traditional tube and class A amps.

Since you have the excellent, but notoriously hard to drive, Apogee Diva speakers I thought you might want to read this 6Moons review of the D-Sonic M2-1500-M mono-blocks.  They drive a smaller pair of Apogee Duettas  as part of the review.  If you need a cooler running pair of amps than your big Krells, you might want to audition these in your system:

http://www.6moons.com/audioreviews/dsonic/1.html

3.  I do believe, based on my personal experience, that good mid level class D amps are inherently better than good mid level class A/B amps.  This is the one blanket statement I am confident is true.  Now that I've used class D amps for a few years, I can honestly state that I cannot think of a single advantage that my former class A/B amp can claim.  The validation of my blanket statement is that absolutely no one on this thread has identified even 1 advantage of class A/B amps, either.

 My switch from class A/B to class D was all upside with absolutely no downside.  

4.  The Oppo 105 is a high quality component that is very versatile.

Yes, the Oppo has a menu for selecting the sub crossover frequency from 40 to 250hz in 10hz increments.   

The Oppo also has a menu for configuring your speakers and their volume level. There's a tone generator that allows you to cycle through each channel Each speaker/channel can be set as either 'Large' that has no bass augmentation from the sub or 'Small' that does augment the bass via the sub.  Each speaker/channel's volume is adjustable from -10db to +10db in .5db increments.


No class has a monopoly on good ,

  Tim

What would you consider as the best/most cost effective class D amps?  D-sonic? Wyred4Sound?  Bel Canto? NAD? Theta???

I have Aerial Acoustics 7b speakers that they would be powering. 

jrunr,

      Your speakers are fairly inefficient (86 db) so they likely require fairly significant power (I figure at least 50 watts/ch but the higher the better) to sound their best Their nominal impedance is 6 ohms but dip down to 4 ohms at certain frequencies so they also need an amp that can handle this.
      If you're looking for the least expensive  good quality class D amps that would drive your speakers well,  there are a couple that I'm aware of:

The Emerald Physics EP-102 at 100 watts/ch @ 8 ohms.  The regular price is $1,600 but it often goes on sale for as low as $600..

http://www.emeraldphysics.com/category-overview/power-amplifiers


classDaudio SDS-440CS at 220 watts/ch @ 8 ohms for $630.

  http://www.classdaudio.com/sds-series-amplifiers/sds-440cs-class-d-audio-stereo-power-amplifier/

     The brands you mentioned all offer good performance, too, but are more expensive.  I mentioned the 2 above since I interpreted 'cost effective' as meaning the best class D amp bargains.  

Tim