Has anybody direclty compared Class D and Class A A/B amps?

Popspin

Active Member
Apr 28, 2015
70
5
38
#1
Hello;
I had posted this question on AVS but was it was suggested that responses here on Whats Best Forum may be better different. So I am posting the same question here:
I am in the process of choosing new amps to power KEF Blade Two's and KEF Reference center and surround speakers. I have had Class D amps for the past 7 years (W4S SX-1000 mono blocks) and have been considering 3 different Class D options; Jeff Rowland, Mola Mola and Theta. W4S is about to release a new amp named the Statement, perhaps by late January but nobody has listened to it critically yet.
My Class A A/B preferences are from Accustic Arts and Mark Levinson.
I read comments by several members of this board lauding the Theta, But those laudatory comments, in isolation, don't answer my question:
Do Class D amps sound just as musical as Class A A/B amps in a direct side-by-side comparison?
I want to hear from those who have really directly compared one of these current highly regarded Class D amps with a similarly regarded Class A A/B amp. What did you hear? What were the strengths of each? Did you have a preference? Did one make your toes tap or get you more into the music?
Thanks for your input!
popspin
 

cjf

Well-Known Member
Nov 19, 2012
337
7
248
#2
Hello,

I've compared my Hypex NC400 DIY amps to my previous Pass Labs X250 head to head. In my system I preferred the sound (or lack there of) of the Hypex amps better. The key for me was the Hypex's lack of sonic signature that the Pass Labs amp had in spades. I certainly didn't dislike the Pass but there was no mistaking that it had a sonic signature that leaned towards warmth and a bit of bloat. It seemed to be a slower moving/reacting amp in comparison to the Class D Hypex.

In terms of power output I would say it was a wash. I later added a total of X 4 Hypex modules powering my B&W 803 D2's and things got real fun then.

I also noticed that the Class D amp seemed to have a greater control of the bass drivers as the volume level increased. A quick look at the damping factor specs between the two easily shows that as well.

In terms of noise floor and S/N ratio there was no comparison. The Hypex is the definition of Dead Silent! The Pass labs always had a bit of hum to it that annoyed the hell out of me. I should add, before anyone claims local power grid problems as being the cause, that nothing was changed in terms of mains power when I swapped amps. The Class D was silent, the other amp wasn't.

I've recently acquired the Merrill Audio Veritas Amps and am now using them solely. These amps are just like the NC400 amp was in terms of sonic abilities/attributes but only with much more power. This is something I needed in my configuration due to a recent speaker swap (Magico S3) where the added power into a non bi-amp/bi-wire speaker was needed.

So in summary, in my system and based on my sonic presentation preferences the Class D amp was the winner between the common Class A/AB unit I compared it to. I know there are many who dislike Class D amps and think they sound "Dead/Flat/2D..etc" but that is there opinion. I suspect many who say that have never heard the new breed of Class D amps out there now which go against the old stereotypes from the dinosaur age. In any case I can't argue with them about not being able to adjust to the lack of distortion many are used to hearing and it did take me a while to appreciate the differences between the two flavours. Now I find it hard to go back and probably never will.
 
Sep 30, 2015
3,049
1
0
#3
Hello,

I've compared my Hypex NC400 DIY amps to my previous Pass Labs X250 head to head. In my system I preferred the sound (or lack there of) of the Hypex amps better. The key for me was the Hypex's lack of sonic signature that the Pass Labs amp had in spades. I certainly didn't dislike the Pass but there was no mistaking that it had a sonic signature that leaned towards warmth and a bit of bloat. It seemed to be a slower moving/reacting amp in comparison to the Class D Hypex.

In terms of power output I would say it was a wash. I later added a total of X 4 Hypex modules powering my B&W 803 D2's and things got real fun then.

I also noticed that the Class D amp seemed to have a greater control of the bass drivers as the volume level increased. A quick look at the damping factor specs between the two easily shows that as well.

In terms of noise floor and S/N ratio there was no comparison. The Hypex is the definition of Dead Silent! The Pass labs always had a bit of hum to it that annoyed the hell out of me. I should add, before anyone claims local power grid problems as being the cause, that nothing was changed in terms of mains power when I swapped amps. The Class D was silent, the other amp wasn't.

I've recently acquired the Merrill Audio Veritas Amps and am now using them solely. These amps are just like the NC400 amp was in terms of sonic abilities/attributes but only with much more power. This is something I needed in my configuration due to a recent speaker swap (Magico S3) where the added power into a non bi-amp/bi-wire speaker was needed.

So in summary, in my system and based on my sonic presentation preferences the Class D amp was the winner between the common Class A/AB unit I compared it to. I know there are many who dislike Class D amps and think they sound "Dead/Flat/2D..etc" but that is there opinion. I suspect many who say that have never heard the new breed of Class D amps out there now which go against the old stereotypes from the dinosaur age. In any case I can't argue with them about not being able to adjust to the lack of distortion many are used to hearing and it did take me a while to appreciate the differences between the two flavours. Now I find it hard to go back and probably never will.
What are you using for a preamp?
 

cjf

Well-Known Member
Nov 19, 2012
337
7
248
#4
What are you using for a preamp?
I'm currently using a Classe CP-800. Now that I am no longer Bi-Amping this may change in the future but I'm in no rush at the moment to swap it out. Although I do keep at least one eye on the Mola Mola Pre at all times :)
 
Sep 30, 2015
3,049
1
0
#5
I'm currently using a Classe CP-800. Now that I am no longer Bi-Amping this may change in the future but I'm in no rush at the moment to swap it out. Although I do keep at least one eye on the Mola Mola Pre at all times :)
If your open to an easy tweak that can drastically improve the sound of the NC1200, Pop open the case and move the little jumper pin on the NC1200 to the "unbuffered" position. This will bypass the onboard LM4562 IC opamp based buffer. If your preamp has enough juice, the sound quality will be greatly increased. It's also not hard to retrofit an external buffer to drive the amp unbuffered. This is the only difference between the Mola Mola Kaluga and the Veritas. The input buffer.


Edit: Was checking out the specs of the CP-800. looks like it can put out a max of 18 Vrms with 14dB gain via the balanced outputs. That's massive. I would seriously try this. The best sounding buffer, is no buffer, if it's not required.
 
Last edited:

cjf

Well-Known Member
Nov 19, 2012
337
7
248
#6
If your open to an easy tweak that can drastically improve the sound of the NC1200, Pop open the case and move the little jumper pin on the NC1200 to the "unbuffered" position. This will bypass the onboard LM4562 IC opamp based buffer. If your preamp has enough juice, the sound quality will be greatly increased. It's also not hard to retrofit an external buffer to drive the amp unbuffered. This is the only difference between the Mola Mola Kaluga and the Veritas. The input buffer.
From what I understand the Veritas uses a Balanced Differential Input. I don’t know enough about the differences between that and the one in the Mola Mola. I thought I read the Mola uses the same Discrete one found in the NC400.

In any case, I'm not prepared to void the warranty of the expensive Veritas to give it a try but thanks for the info.
 
Sep 30, 2015
3,049
1
0
#7
From what I understand the Veritas uses a Balanced Differential Input. I don’t know enough about the differences between that and the one in the Mola Mola. I thought I read the Mola uses the same Discrete one found in the NC400.

In any case, I'm not prepared to void the warranty of the expensive Veritas to give it a try but thanks for the info.

It won't void the Warranty. It's much easier than you think. It's pretty much the same as just simply flipping a switch. Your preamp has more than enough juice. It will probably result in a bigger upgrade than that Mola Mola pre.

Simply move the jumpers to the unbuffered position like in the photos.

View attachment 23811 View attachment 23812 View attachment 23813


I have the exact same LM4562 buffers here for the NC500's. Comparing going from my pre without them, to with, is night and day. You don't realize how much coloration they add until you hear them without it. And with a pre as powerful as yours, they aren't required at all. They are just there for if you have a pre or DAC with only around 4v output.

If you do this it will be better than the Mola Mola amp. Because there's no buffer better than no buffer if it's not required. Think of it as connecting 2 preamps back to back. No matter how good they are, it won't be better, if 1 preamp has enough drive on it's own.
 
Last edited:
Apr 3, 2010
15,814
9
0
Seattle, WA
#8
I did a comparison once. It was a four-way test, comparing Crown Class I (interleaved class D), Mark Levinson No 53 class I (interleaved class D), Mark Levinson Reference 532 and Devialet (hybrid class A and D?).

Of these only the Reference 532 was a classic linear AB amplifier. All digital amps beat the 532 in bass. There simply is more power there in these switching amps due to high efficiency and low output impedance. At high frequencies, I found the 532 to be superior to Crown and Devialet. The only amp that matched it for high frequency was the Mark Levinson No 53. It was the only one with the great bass performance and neutral high frequency reproduction.

Note that while I tried to do this test methodically, it is still a non-rigorous test and could be all wrong :).
 

Popspin

Active Member
Apr 28, 2015
70
5
38
#9
Hi;
What interesting responses. Class D amps are coming of age with enough strengths to make them competitive with quality Class A A/B amps.
Thanks for the input, cjf. It appears you are staying happy with your Merrill's. They look very interesting.
It seems there is a dividing line in Amir's informal test though; the no.53 did it all...for $50k.:)
Trying them out will be the only way to know for sure...
Thanks!
popspin
 
Nov 19, 2015
1,537
175
180
Hutto TX
ibelieveinhifi.com
#10
I have tried a number of class D amps against the A/AB variant. If you go class D I would stick with Kharma MP150's as they are the best of the class D brand I have used rr Jeff Rowland a close second although I would get some Model 7's over the new class d stuff if you don't mind a high electricity bill
 

Popspin

Active Member
Apr 28, 2015
70
5
38
#11
I have tried a number of class D amps against the A/AB variant. If you go class D I would stick with Kharma MP150's as they are the best of the class D brand I have used rr Jeff Rowland a close second although I would get some Model 7's over the new class d stuff if you don't mind a high electricity bill
Hi Josh;
Your sentiment is one i have come to agree with. Class D amps have their strengths and distinctive qualities but I prefer living with something else for the foreseeable future.
I just made my final decision on amps today. I am leaving Class D to return to a Class A/B design that I feel has the musical, build and physical qualities I have been looking for. The fact that very few people know about them really prolonged the decision process as it took a while to get comfortable with my choice. I am now excited about getting them. The month it will take to get them built and delivered will seem endless! They are Accustic Arts Mono II's.
 

Popspin

Active Member
Apr 28, 2015
70
5
38
#13
Hi Andrew;
Yes, very excited about the Acoustic Arts Mono II's!! I hope to take delivery some time in mid-February. It will be a long wait...
I see you are from Oz. I just attended a performance in Ft. Lauderdale by a singing group from your country, the 10 Tenors. Very enjoyable performance!
I will provide my take on the amps by late spring.
popspin

Congratulations on you fine choice. I bet you are very excited.

Enjoy in good health, my friend.
 
Oct 26, 2015
229
1
0
Sydney, Australia
#14
Oh yes, the 10 Tenors can belt out a tune. Glad you liked them.

Please let me know how you go with the AA's. I really like their gear. Beautifully made and sounds heavenly, at least what I have heard.

Were it me, I would be counting the days ha ha.

Wishing you peace and joy this New Years.
 
#15
Yes, compared Class A, Class A/B , Class D ( three different modules) , PSE, SET ,P/P hybrid valve input and SS output.
I have tried to ensure that every amp was capable of driving the loudspeaker properly, for the most part the loudspeakers used have all been pretty efficient horns, it has been interesting.
Keith.
 

bonzo75

Member Sponsor
Feb 26, 2014
14,421
3,736
740
London
#16
Yes I compared a set of Belles 200mb with some modification with a TAD M25000 no contest in my system. The class ab Belles bought music the TAD was hatefully harsh and nasty. Ones £7000 + 1500 upgrades the the others £19000.
I am no soft and cosy loving slipper wearing old man either.
And you said the Belles sounded better than the AR Ref 110 I sold you. I can verify in those days over the phone you spoke better than you spell ;)
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,464
6
255
#17
If the Devialet is a Class D (Yeah I know AHD) then they have arrived. I haven't heard many Class D but the Devialet in my book is a world changing product. Class D et al.
 

Groucho

New Member
Aug 18, 2012
680
0
0
UK
#18
What a delightfully down-to-earth data sheet for the Hypex NC1200. It goes against everything that high end audio enthusiasts like to imagine goes on in their favourite b̶o̶u̶g̶h̶t̶-̶i̶n̶-̶d̶e̶v̶i̶c̶e̶-̶w̶i̶r̶i̶n̶g̶-̶a̶n̶d̶-̶p̶u̶t̶t̶i̶n̶g̶-̶i̶n̶-̶a̶-̶f̶a̶n̶c̶y̶-̶b̶o̶x̶ ̶c̶o̶m̶p̶a̶n̶i̶e̶s̶ ̶ designers' secret lairs, basically saying "Wire it up like this. That really is all you need to do."

I particularly liked the part:
Externally supplied voltage should be >15V and <25V, otherwise quality is not important.
http://www.hypex.nl/docs/NC1200_datasheet.pdf
 
#19
What a delightfully down-to-earth data sheet for the Hypex NC1200. It goes against everything that high end audio enthusiasts like to imagine goes on in their favourite b̶o̶u̶g̶h̶t̶-̶i̶n̶-̶d̶e̶v̶i̶c̶e̶-̶w̶i̶r̶i̶n̶g̶-̶a̶n̶d̶-̶p̶u̶t̶t̶i̶n̶g̶-̶i̶n̶-̶a̶-̶f̶a̶n̶c̶y̶-̶b̶o̶x̶ ̶c̶o̶m̶p̶a̶n̶i̶e̶s̶ ̶ designers' secret lairs, basically saying "Wire it up like this. That really is all you need to do."

I particularly liked the part:


http://www.hypex.nl/docs/NC1200_datasheet.pdf
If you get the chance google one of Bruno's lectures ,he is a proper engineer one of the very few IMO.
Keith.
 
Sep 30, 2015
3,049
1
0
#20
What a delightfully down-to-earth data sheet for the Hypex NC1200. It goes against everything that high end audio enthusiasts like to imagine goes on in their favourite b̶o̶u̶g̶h̶t̶-̶i̶n̶-̶d̶e̶v̶i̶c̶e̶-̶w̶i̶r̶i̶n̶g̶-̶a̶n̶d̶-̶p̶u̶t̶t̶i̶n̶g̶-̶i̶n̶-̶a̶-̶f̶a̶n̶c̶y̶-̶b̶o̶x̶ ̶c̶o̶m̶p̶a̶n̶i̶e̶s̶ ̶ designers' secret lairs, basically saying "Wire it up like this. That really is all you need to do."

I particularly liked the part:


http://www.hypex.nl/docs/NC1200_datasheet.pdf
This is because of the superior PSRR and CMRR of the onboard HxR regulators. They render the need for old fashioned LPS supplies obsolete. You will notice DAC manufacturers like Nagra and Merging have realized this as well.

It just so happens I have one of these beauties sitting in front of me on the table :)

image.jpg
 

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