Class A/B Home THeater Receivers

Hi brucew5828,

  This is Darth Vader and I just have a few questions for you:

Do you enjoy having a large and heavy HT receiver?

Do you appreciate HT receivers that tend to operate on the warm-hot side which is a major reason for internal electronic part failures, reduced life span and the need for large heat sinks?

Do you enjoy higher noise levels (lower Signal-to Noise Ratios)?

Do you prefer smaller Dynamic Ranges (reduced ability to go quickly from soft to loud)?

Do you prefer higher distortion levels?

Do you get a thrill out of wasting electricity and paying higher electric bills every month?,

     If you answered 'YES' to the majority of these questions, you are an ideal candidate for class A/B amplification in your HT receiver.

     If you answered 'NO' to the majority of these questions, however,  you  may want to consider joining me on the "Dark Side".  Of course, this will require you to think logically, not emotionally,  eliminate irrational avoidance of class D amplification, keep an open mind and let your ears decide about your HT receiver choice.
     I run separate amps directly from an Oppo-105 to my amps and do not use a HT receiver or external surround sound processor for a 5.1 system.  I would suggest you may want to do the same for your setup since a HT receiver or processor is redundant and not necessary if you're already incorporating the excellent Oppo-105 in your system.  

     Unless you think there are significant benefits from room correction or bass management software often built into the newer HT receivers and processors, which I think there are not, there is really no reason to insert the extra component in your system.
     A few years ago before buyiing the Oppo,, I used a DVD player routed through an expensive 5.1 surround processor.  I used 3 class A/B amps to drive all 5 channels.  Once I upgraded to the Blu-Ray Oppo and understood its full capabilities , I first sold my processor and ran its outputs directly to my amps. There was no detectable reduction in performance and  I ran my system this way for about a year.

     About a year ago, I decided to replace all 3 class A/B amps with class D amps ( D-Sonic mono-blocks replaced an Aragon for the main l+r, Emerald Physics bridged stereo amp replaced an Adcom for the center and a ClassDAudio stereo amp replaced another Adcom for the rears).  I immediately noticed a definite improvement in the performance of my 5.1 system.  The main improvements in the sound were the extremely low noise floor (sounds emerged from a dead-silent background), increased dynamics (the ability to go from soft to loud on all channels was obviously better and, at times, even startling).  

     Other benefits included affordabiliy, smaller size, reduced weight, average reduction in my monthly electric bill of about $40 and none of the class D amps get hotter than luke-warm no matter how hard they're driven.

Hope this was useful to you,
     Tim
     

brucew5828,

     I just wanted to add that many class D amps have a choice of inputs (XLR balanced or RCA unbalanced).  I use XLR  from the Oppo's outputs to my front l+r mono-blocks and RCA for all other amps.
     As for space considerations, if you decide to go separates your likely to gain space because:

1. You won't have to devote space to a class A/B HT receiver which tend to be larger, heavier and require extra space on all sides for adequate ventilation for cooling. No need for a separate surround processor, either.

2.  If you opt for class D mono-blocks for the l+r mains,  each amp is relatively small and can easily be hidden  behind each l+r main speaker.  This has the added advantage of allowing your speaker runs to each main being very short although your single XLR or RCA cable to each would likely need to be longer (typically a trade-off that improves performance) .

3.  Class D amps for your center and rear channels don't require large berths for adequate cooling so positioning them on a traditional audio rack is not necessary.  

      Once I had the Oppo and class D amps, it allowed me to seriously streamline my entire  2-ch/5.1 HT combo system.   I now use a 5' wide and 18" tall metal equipment rack, topped with a 5' wide walnut  platform and extra shelving space below behind hinged doors, that contains all my gear.  I wall mounted a 5'W x 3'H hdtv above this rack, leaving about 1' between the top of the rack's wood top platform and the bottom of the tv.
     
     The result is a streamlined system that is symmetrical and a breath of fresh air.  The Oppo is centered on the rack's top wood platform, flanked at each end by a mono-block on a small maple isolation platform on spiked brass footers. All other equipment (2 class D amps, a 1.000 watt class A/B amp driving 4 subs, 10 TB NAS, 10 TB backup hard-drive, internet router and a cable box) is hidden behind hinged doors below.

     I'm not familiar with your system but I described my system to relate how using class D amps, using a different equipment rack while also eliminating a HT receiver or surround processor can result in significant space saving and streamlining.  However,  I believe you could save space and streamline even if you use class A/B amps as long as you don't use a HT receiver or separate processor and utilize class A/B mono-blocks that are not too large positioned behind your main speakers.  It would just be easier, and your system would likely perform better, if class D amps were used.

I hope this gave you some useful alternatives to a class A/B HT receiver behemoth.

Good luck,
 Darth (Tim)    

Hi David,

I understand that Bruce prefers a class A/B AVR because that’s what he’s always used and he’s comfortable with this traditional technology. Unfortunately, he seems to have gotten some false information that class D technology has had reliability issues and he generally seems poorly informed on the numerous advantages of class D. To be fair, this is likely due to Bruce having little to no exposure to class D.

My view, based on research and personal experience, is that switching from all class A/B amplification to all class D amplification results in superior performance in all areas that audio enthusiasts care about such as a lower noise floor, lower distortion levels, better bass response, greater dynamic range and generally coming closer to the audio ideal of a ’straight wire with gain’. There’s also other benefits not directly related to sound quality such as smaller size, less weight, affordability, no heat sinks required,less heat emitted, significantly higher efficiency and reduced electricity usage. To further tip the scales, all these benefits are gained with zero costs or negatives that I’ve become aware of during the past 2 yrs I’ve used class D amps.

So, as the owner of an A/V company, I’m interested about your views on class A/B vs class D amps and just have a few questions if you’re willing:

1. Do you recommend class A/B to all your customers?

2. Can you name any important performance measure or quality in which class A/B is superior to class D?

3. Can you name any important performance measure or quality that could be in any way accurately be described as a cost, ’negative’ or sacrifice of switching from class A/B to class D? I honestly cannot.

4. Have you ever compared one of your popular A/V systems using all class A/B amplification to the identical one using all class D amplification? If so, can you share the results?

5. Does your company even carry or sell any class D amps or receivers?

I’m not familiar with your A/V business but I’m fairly sure you have extensive experience in selling and installing many A/V systems. Because of this, I’m sincerely interested in your viewpoint.

Thank you,
Tim

Bruce,

  You stated:

" I actually thought the Class D sounded a little cleaner and more detailed... but then I started researching customer reviews of those AVR, and I was surprised to fin that there are TONS of technical problems, and outright failures, of the Class D amps."

     Tons of technical problems with class D amps?

    First I've heard of this, I hope you're not a believer in 'alternative facts' ala Kellyanne Conway.


Tim

toddverone,

Good points about all types of amps can break and that Bruce may have been reading about a particular AVR model that had repeated issues.

I’ve been running 3 class D amps (a pair of mono-blocks and 2 stereo) left on 24/7, and often played at high volumes, for a couple years now without any problems. They don’t even get any warmer than luke-warm no matter how hard they’re driven.

There seems to be a lot of anti-class D bias being spread along with some false information. My theory is that class A/B amp makers, sellers and biased fans may be the impetus behind this.

I believe Class A/B amp makers and sellers justifiably feel threatened. Class D already clearly equals or betters class A/B in every audio performance criteria along with every other criteria that is important to amp buyers such as price, size, weight, reliability, operating temperature and efficiency. I honestly cannot think of a single advantage that A/B has compared to class D.
In my opinion, class A/B amps have managed to remain viable longer than they merit for a few reasons:

1. Class D amps are mainly sold internet-direct with free or low cost in-home trial periods. Many potential customers are either unaware of this or reluctant to shop or buy via this method. This is slowly changing as more class A/B amp makers, concerned with their company’s future, are offering class D amps of their own that are sold through traditional stores.

2. Some, such as the OP Bruce, either have a bias against class D or mistook anti-class D info as truthful and decided to not even consider class D.

3. Not all amp buyers, being less knowledgeable than those active on audio blogs, even know of the existence of class D and its extraordinary attributes. The awareness of class D by this group is likely to only grow since there are so many ways (friends and family, chance reading or listening) to become aware that only increase over time.

As if the above wasn’t enough bad news for class A/B amp makers and sellers, they realize that their technology has peaked while class D technology is likely to continue to improve and only widen the performance gap.
It may be hard to believe, given my admittedly pro-class D bias described ad nauseam above, but I have no financial interest in the manufacturing or selling of class D amps. I’m just a big fan based on research, the facts and my experiences switching from all class A/B amps to all class D amps over the past few years.

I could go on but I’m going to bed,
Tim

David Campbell,


     It's been over a week since I asked you on 1/22/17 a few questions on your thoughts on class A/B and D amps.  You have not responded to any of my 5 questions.
      I'm assuming  your work responsibilities are keeping you too busy to respond.  I understand work duties are of primary importance.  Therefore, I've reduced my 5 questions to a single one I hope you'll respond to:

Can you name any important performance measure or quality that could be in any way accurately described as a cost, ’negative’ or sacrifice of switching from class A/B to class D amplification?

Thanks
  Tim 

" Can you name any important performance measure or quality that could be in any way accurately described as a cost, ’negative’ or sacrifice of switching from class A/B to class D amplification?"

     C'mon!  The silence is deafening.

     There is ABSOLUTELY NOBODY who can name A SINGLE, AS IN  ONE,  performance measure or quality in which class A/B outperforms class D?

     Well, I guess that means there is absolutely no reason that anyone should even consider continuing to use or consider buying any product that utilizes class A/B amplification.

     Don't feel bad, I can't think of a single benefit of class A/B either.  When I replaced my amps from all A/B to all D, I thought that there might be some performance area or quality that would suffer.  But that was 2 years ago and I still cannot name a single   performance measure or quality that could be in any way accurately described as a cost, ’negative’ or sacrifice of switching from class A/B to class D amplification, either. 

    Case closed, right? 

     To be fair, let's see if ANYONE can think of ANYTHING, just ONE performance criteria or quality that class A/B betters class D in the next week.  If there is no response in a week then I think it's safe to perform a eulogy for class A/B.

Tim     

Hi Bruce,

     Your post drew my attention because you referred to class D as the 'dark side'.

      I understand you want a class A/B AVR because your 'old school' (behind the times) and think class D means digital which it does not.        

     Then later in the thread you cast further aspersions on class D claiming there have been numerous amp failures without explaining where you read this, whether it was a problem with one brand/model, whether it was an AVR or an amp or even knowing whether the reports are accurate.
       Many on this thread, including myself, have no idea what you're talking about and have used class D amps for years with no issues.
       Class D is extremely reliable and outperforms class A/B in every performance criteria while also being less expensive, cooler running,  smaller, lighter and more efficient.  You even admitted the class D AVR you auditioned sounded 'cleaner and more detailed'.
      
       The truth is that nobody, including yourself, could name ANY advantage that class A/B has over class D because there aren't ANY; zilch zero and nada.  
      Of course, you're free to disregard the facts and the opinions of posters who have owned and used both types of amps.  I didn't mean to hi-jack your thread, I just thought you should know the facts before purchasing your future class A/B door stop.
      Someone with your lack of experience with,and lack of knowledge about, class D amplification should just keep their 'old school'  pie hole shut.

Later,
  Tim   
  

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

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