Difference between amps

OK so let's talk amps.  I'm sure this has been addressed before but are there real differences between  multi-channel amps among the various brands in the mid-fi to high end markets with comparable specifications? Adcom, Anthem, Classe, Emotiva, Krell, McIntosh, Marantz, NAD, Parasound, Outlaw, Rotel, etc.  What are the differences in these brands?   I can site one difference.  In multi-channel Marantz amps, the specs never state "all channels driven".  They are notorius for misleading the consumer with their power output ratings.  But that's a marketing decision. What are the real or should I say physical or performance differences among these?  .  
The difference is sound, price, performance, layout, and aesthetics. 
If you are looking for a model by model comparison between 7 manufacturers, I can’t help you there. 
"...I can site one difference. In multi-channel Marantz amps, the specs never state "all channels driven". They are notorious for misleading the consumer with their power output ratings..."

Mass consumer products are made for the mass consumer, not top quality audio. You will find nothing on the spec sheet that will tell you anything about their sound quality or ability to drive a loudspeaker except in very general terms. 
When i was going on the look and search for a really good amplifier at low cost, my only possibility was used, but more than used, vintage and a vintage piece miraculously under evaluated...

I have chose mine after 2 years of search, reading ALL reviews about the main vintage legends and ,mythical products, from the tube Fischer amplifier to the Sansui last model....

It is near impossible to buy an amplifier today without listening to it extensively or if not, then put our faith on a few reviews because the product is new...Is this product would be sold as a mythical good one in 50 years? Or would it be forgottent with the mass of good amplifiers but only good not extraordinary good?

With all this thinking i catched a strike with the Sansui AU 7700... At 100 bucks....

It is my really first good amplifier and perhaps my last.... I bought another one 300 bucks in case so good is the first....


In 1968 Sansui was in the top high end and in the mass market of top high end.... His products were sought and it is so true that the name become synonym of fiability, flexibility, organic sounding first, and refined organic sounding at his best.....It was.... It is till this day in my room....

No product at all actually in the market give so much flexibility and high quality for so little money, better than that no product at any cost give the flexibility and not ONLY good sound.....

Think about that..... I feel right with this purchase more than ever.....

Anyway to come back to the question in this thread most of us cannot afford to compare many amplifiers, and the way an amplifier will be listen to is always indirectly, trough a room, through some specific speakers, and specific analog or digital source? And least but not last,how can we assess his real S.Q. trough a not so perfectly embedded audio system ?

The best method is to buy a product very, very, high end or costly, non criticable design or a vintage legend that cannot deceive , between these two alternatives, beware.....

Actual mass market amplifiers has nothing to do with 50 years old mass market amplifiers for many reasons.... Quality is not the main flag here and now but profit except for very costly high end craftsman product but they dont hope to mass market anymore for decades now.... It is no more either the same people that bought audio.... They sought for efficiency more than elusive refinement.... Audiophile is now an insult.... It was not so 50 years ago.... Correct me if i am wrong, you are welcome....

By the way it seems there exceptions to what i speak about, i dont doubt that Schiit for example may sell quality products and develop a mass market but no way this amplifier can compare to the best of Sansui at all level....It is my opinion only i am not necessarily right like i already said....

My best to all...
Real life performance differences of multi channel amps depends on your application and supporting gear. Most of the modern multi channel amps are built for HT duty. They do a nice job of powering the sound of the chop of a helicopter blade or the impact of an explosion. The power ratings in 2 channels driven versus all 7 may be because in normal HT use, rarely, or only in very brief moments are all 7 channels be driven equally. Usually only the center channel is driven continuously. So, in their mind, continuous RMS across all channels is less important? Ultimately it comes down to how it sounds in your system. Specs can’t tell you that. But do not assume these types of amps can sound as good for 2 CH music as a dedicated 2CH amp designed specifically for music reproduction. Different applications, different design goals. So if music is at least one of your priorities, get a dedicated amp for your mains, maybe a decent integrated amp with HT bypass. This should help maximize your music experience. And then get whatever you like to power the rest for HT (or other) duty. If you are comparing between multi channels amps, you need to level match the volume from one to another. When you A/B them correctly, differences in HT applications can be less significant than you might expect.
"...In 1968 Sansui was in the top high end and in the mass market of top high end..."

Not sure if that was ever true.  The  Sansui AU 7700 could never drive the hi-end loudspeakers of the day like the hi-end Infinities. 
I think we rely too much on power ratings.

It takes 10x the power to double the volume, so do I care a lot between 120W and 100? No, really I don’t. In most homes, with a sub, and speakers run as satellites (not full range) 100W per channel is way more than enough.

Honestly, if you are running satellites, with subs, 75W amps per channel x 5 is more than enough unless you are running a mini theater in your home.

How the amps work with your speakers and how they sound is a much bigger deal. I like NAD for the use of nCore, and Parasound a lot.
They are notorious for misleading the consumer with their power output ratings. But that's a marketing decision.

Correct. All this stuff is. The biggest marketing decision is the one virtually all of them have agreed on, to confuse and mislead with meaningless numbers. All these numbers you're so concerned with are meaningless. Absolutely meaningless. 

What are the real or should I say physical or performance differences among these? 
Drop real, drop physical, whatever these even mean, and stick with performance. Then realize the one and only performance parameter with any meaning at all is how people say they sound. Because that is all that matters.  

It will take you a very, very long time listening to a lot of different stuff to realize this, but amplifier specs simply do not matter. Only one spec matters: speaker sensitivity. Good luck if you buy speakers with less than 92dB sensitivity. Good luck finding an amp. When you read all the problems people have matching speakers and amps first thing you should do is go look up the sensitivity of the speakers they have. Go. Look. You will see. Happens all the time. Guy just the other day took a pass on some very excellent easy to drive speakers, bought some 89dB when could have had 99dB, the ones he got will require TEN TIMES the amplifier power to play the same level.   

Good luck with that. Really superb sounding 50 watt amps are all over the place, and are actually affordable. He needs 500 watts. All because he screwed up the one thing that matter about amps, and that is speaker sensitivity. Good luck. 

So forget amplifier power. Do this one simple thing right, find speakers that sound good and are at least 92dB sensitivity you will have no problem whatsoever driving them with anything from 20 watts on up. So power ratings, forget em. Why I said they are meaningless.  

Or you can obsess with the marketing malarkey in which case, good luck! 

Other thing is, multichannel. Sorry, you want 2 channel. Stereo. Multichannel is a wasteland of crap sound quality. They suck people in with the HT BS that you need umpteen channels to watch a movie. Not true. Not even close. https://systems.audiogon.com/systems/8367 Movies on this stereo system are enthralling. Music is to die for. Posted for a reason. Study and learn.
I wouldn't know. I only buy mono amps. They are the only ones that can be installed correctly. 
Don’t forget about Jeff Rowland amps. You might be able to buy 2 used Model 12 monoblocks for a good price which might be one of your best bets. 350W into 4 ohm.
As a relative newbie, I can second MillerCarbon’s comments.  My only other comment is to make sure no matter who or what you buy, there should be a real return policy.  One week is enough enough.  Even 2 weeks is not enough.  
Everything comes down to the power supply.
You need to scale amps like they are welding machines :-)

A proper amp needs to be able to have about 300-400 watts of supply for every 100 real watts rms class A/B, 600-700 watts of class A of output, all frequencies driven.

So, in a 5 x 100 REAL watts/channel amp, 1500 - 2000 watts of power supply is needed for class A/B and 3000 - 3500 watts of supply is needed for class A. Since that is one HUGE COLLOSAL supply, it is very difficult to have a multichannel amp having the full dynamic range over every channel. Look at the power supplies that come with Pass Labs amplifiers and you will know what I am talking about. And remember that those are only for 2 channels. Imagine what they would be like for 5 or 7 channels.

Otherwise, there are not that many differences between them. Amplifier design is pretty well established & known. The rest is dependent on the quality/longevity of the components used.

hey dude, my new harbeth 30.2s are under 90 dB sensitivity and easily driven with my pass xa30.8. Sound phenomenal. I’d take a breath before making all these new rules.

interesting points. Perhaps a bit overstated? What kinds of amps and speakers are you talking about?
I'm with cakyol on this one all the way.. I have an older Adcom 7500, it shares a common PS. It works well for what it was intended 20 years ago.. It still works quite well as far as sound and easy to maintain. AB unit doubles watts to 4 ohm. Workhorse.. They used good parts too.

I have a Nord. Class d. It has 3 separate SMPS 1200A700 power supplies, one for each of NC500 amp module. Weird thing, a single 15 amp IEC fused AC plug.  Left me scratching my head. I'll tell you what. It is a sweet 3 channel amp, the BEST I've ever heard That's saying something.. Three separate amp with GREAT class A Sparco pro OA and Sparco regulators.
15 times lower output noise than IC regulators. They have 52dB (about 300X) better rejection of any noise coming into them, and 4X better load regulation than any other 3 terminal IC regulator.

I also have 3 pairs of their NC500 monoblocks.. (surround system). Very sweet when I use it. Pure analog surround, C45 with Class Ds. cool.
No fancy tool there..

Parasound.. I think is one of the best bang for the buck products out there. Hands down..

Mac. I've never owned a multi channel
I've owned Mac 50 years this spring. I love Mac.

Krell, I've owned monoblocks and stereos.  Powerful, and clinical. Paired with good speakers.. NO JUNK.. Good Electra Stats..small planars, Speakers that use Seas drivers.. good components. Krell like that,,

Nad is good. I don't own one. The neighbor does.. Very nice HT both the 2 and 5 channel Nads sound good. He uses a Krell 7.2 surround..That pre though it's older is a Heck of a stereo unit also..

Outlaw, never heard one

Emotiva, has its place.. I don't use them.. Adcom and Rotel are better SQ wise..

You had quite a cross section to choose from, too..


"...Only one spec matters: speaker sensitivity..."

I know you have posted this over and over but why limit yourself? Sure efficient loudspeakers make it easy to buy amplifiers, but that eliminates a lot of VERY good top end loudspeakers. I'm not willing to do that but I'm willing to buy an arc welder of an amp if I need to. .   
@redwoodaudio  Check out the impedance of your speakers.


If you averaged it over the entire spectrum it would be well over 8 ohms.  Sensitivity is not the only measurement that matters.
@twoleftears that's my point... easy to drive, yet sensitivity under 90 dB (87 per stereophile measurements as you linked).  limiting one's self to "highly efficient" speakers over 90 dB sensitivity, without regard for other factors, would be senseless except when using flea-watt amps.
Thanks everyone for an excellent response and participation.  This has so far been a very active thread with very meaningful feedback.  I've learned a ton with many takeaways.  Although I do have a 7.2 surround sound system for movies, etc, music is still my first priority.  I listen mainly in multi-channel stereo.  One thing I learned here (and others have implied this to me but I forgot about it) is to use a separate higher output two channel amp for my mains and then a 5 channel for the surrounds and center.  I'm going to make this change right away.  Another thing is that for the $$, it seems Parasound is a super choice.  I may sell my Marantz MM7025 and purchase a Parasound two channel amp.    THANKS again.
I ended up with an ARCAM AVR 550.  However, I wish I could have afforded to pay $5,800 for the ARCAM AVR 850.  Their G technology is incredible, as the first 50 watts are pure A.  I had a real problem with their customer support and they are probably the worst in the business.  He was a real jerk and hid behind his phone.  Not sure what I would buy less because I want to be able to have an amplifier that can handle both 2 channel and home theater.  When the time comes I will call upon this group to help direct me.  
Hello PDN.  You almost never need more than 10 watts per channel. Receivers generally don't have power supplies that can really supply the "rated" 100+ wpc they might advertise. The gear sold in chain stores is made to a lower standard than so called "audiophile" equipment. That said, I have in daily use, multi channel amps from Emotiva (5 ch), Starke (4 ch), and Integra (9 ch). All get good to rave reviews and work beautifully for me. I don't know how many channels you need, but the Starke AD4-320 is absolutely fabulous and supplies four channels at 220 watts into 8 ohms, and 320 wpc into 4 ohms. I have two of these amps powering two 4 way speakers (one amp channel per driver, electronic crossover). Stick to a serious brand and you should be fine. My pal has a 7 channel Emotiva and loves it. Enjoy the music.
that's my point... easy to drive, yet sensitivity under 90 dB (87 per stereophile measurements as you linked). limiting one's self to "highly efficient" speakers over 90 dB sensitivity, without regard for other factors, would be senseless except when using flea-watt amps.

This is good information, I have  80 db sensitivity speakers that aren't as hard ony amp as 92bd sensitivity speakers and they are both 4 ohms. So figure that out millercarbon.
pdn, you mentioned listening to music in multi channel. I assume you are using an HT receiver or pre-pro as your preamp? If so, you may find that a dedicated music preamp, or integrated amp might make a larger difference in your music enjoyment (for 2CH listening) than adding a better 2CH amp to your current preamp. I get it that multi channel music may sound better in your current setup. But personally, I found that moving into a quality dedicated 2CH pre was a revelation in sound beyond my previous multi channel experience. That is why I recommended a good integrated amp with HT bypass. Get a loner from a local shop if you can and listen before you buy.