CLASS D INTEGRATED AMPLIFIER SHOOTOUT 2012 - AVS Forum
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post #1 of 30 Old 10-29-2012, 10:38 AM - Thread Starter
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AMP SHOOTOUT

First of all if you think all amps sound the same then please ignore this post and forgive my audacity for posting a review based on personal opinion with very little if any scientific facts. My only wish is that perhaps someone out there would find it useful. My knowledge is obviously infinitely inferior compared to the masters of audio in this forum so I will go ahead and disappear quietly.

Why the comparo? Each of these represents the current Class D best of specific amp modules or brand. The ultimate goal is to note the perceived differences of the different designs and whether it is necessary to spend upwards of $500 to get not just a different sound but “a better sound”. There is a public interest to check whether today’s technology is able to provide similar or better sound quality to expensive amps of old while being very efficient and small in space AND packed with features. Is there a need to spend any more if the specs look similar on paper? Even compared with highly regarded Class D amps such as the new ICE or an ultimate power DAC from NAD the C390DD?

Supporting Equipments: Onkyo C-S5VL SACD Player + Ascend Acoustics Sierra Tower RAAL toed in. And Blue Jeans 75 ohm coax & 10 gauge speaker cables ultrasonic welded bananas (if they even matter). Bliss Quiet Letter CD, Pharos CD, Usher demo music CD. Room size is 16.5 x 19.5.

Setup: All amps are reviewed as complete products and that includes the internal DAC. Only SPDIF digital coax connection to the internal DAC is used for this comparison as the whole point of having these amps is to have a 1 box solution. Two of these amps have USB input but I will stick with SPDIF coax. All amps were run in direct mode with no EQ or any other signal altering option enabled. All amps volumes are level matched as best I can using the good old ratshack SPL meter. Unfortunately I’ve disposed of my old Tripath and other proprietary Class D amps of gone era so they won’t make it here but you can’t buy them anyway so won’t matter. The Onkyo CD player is the cleanest sounding one I got at the moment, better than the sweetened NAD C545BEE. Sierra Towers because obviously it’s one of the most popular accurate ribbon based speakers that’s also highly efficient.
Here we go…


NAD C390DD: 150W @ 8 ohm, Zetex chip, 2012 version, $2000 (street net price). http://nadelectronics.com/products/hifi-amplifiers/C-390DD-Direct-Digital-Powered-DAC-Amplifier

This “power DAC” (direct digital amp) is the smaller brother of the M2 and uses Zetex chip instead of the typical TI chips. More expensive the others in the bunch even at the discounted price I got it for (the first and only unit to enter this country from the local NAD distro). Highly touted as the next generation in amplifiers that beats old school Class A integrateds, loaded with whatever input you can think of short of firewire, upgradable module slots, etc etc… it resembles a small PC rather than an amp which is a good thing. This amp is as big as a typical NAD receiver which is a minus in placement flexibility but who cares about that right? Impressions below are made only 3 hours after installing so if you believe sound may change after “break-in” then too bad. The USB port also requires the NAD drivers installed to be able to play bit perfect.

Perceived Differences:

Highs: 5 stars. With the black silent background the highs are clear, very clear. Total absent of noise and distortion. When I put my ears 1” from the tweeter I hear zero hiss, totally nothing! That’s what separates this amp from everything else… What is also remarkable is the total lack of fatigue even after half a day of cranking with whatever kinds of music thrown at it. Usually at that high end resolution and volume my ears would be bleeding after 15 mins. Nothing else I’ve heard in decades of experimenting with different Class A and AB amps exhibits this character. Realism and accuracy without distortion. That in IMO is the real game changer with this latest generation of power DAC.

Midrange: 4 stars. Vocals are a bit forward and drier than usual but that’s probably the way it’s supposed to sound if it’s to be accurate to the recording. Sounds transparent as any clearest amp I’ve heard. True as is, no sugar, no catering to old school audiophiles looking for the sweet.

Bass: 4 stars. Not super deep but tight, very fast, controlled. Probably the way it’s supposed to sound as is the recording. Not sure yet as I don’t have time to play with the built in room correction feature or I’m just used to the mINT’s overpowering bass.


QLS QA100: 60W @ 8 ohm, 2 x TI TAS5162 chip, 2012 version, $300. http://qlshifi.com/en/wzcapi/qa100.htm.

Represents the last true direct digital amp chip from Texas Instruments before they added closed loop analog feedback. This is in spirit the successor of the infamous Panasonic SA-XR and TACT Millennium of the past. A true PCM – PWM conversion without the addition of anything analog in between = absolute ultimate purity if not accuracy ala power DAC. So this amp has no additional DAC, no analog input, no headphone out, no feedback. Of course that comes with all the issues associated with that design (high distortion, low impedance…) but in theory nothing else can be more transparent sounding than this. In fact I still prefer the sound of the old Panny compared to everything else I’ve got since 2003 when I can stand the distortion. The QA100 uses one TAS5162 for each channel so it sounds powerful. Even when driving an inefficient speaker such as the Usher Be-718, the average volume range I use is 11-16 out of 80 which is the max with these TI chips. The chassis is small and ultra light. Remote quality is good. Makes a neat looking inexpensive office room amp.

Perceived Differences:

Highs: 3 stars. The overall image of the sound is very clear, crisp, and transparent. When you want all the background ambiance music in a song this has it.

Midrange: 1 stars. Vocals are the clearest of the bunch and effortless but slightly edgy which makes them less natural and fatiguing to my ears.

Bass: 2 stars. Not deep but tight. Surprisingly acceptable (which is the opposite of the old SA-XR57) even when used with an inefficient Usher Be-718.


Sinewave “Genius” G33D: 75W @ 8 ohm, 1 x TI TAS5630 chip, ADI DSP, 2012 version, $295. http://www.csinewave.com/product.asp?pid=162.

Represents the current most powerful TI chip with closed loop topology. Alas, I found out about the new $380 G36D which uses 2 x TAS5630 a minute too late after placing my order for the G33D. The G36D is twice more powerful, has 2.0 24/196 USB input, and comes with remote. But then Sinewave most likely is going to release an amp based on the even newer TAS5624A which was released by TI on May 2012. The new TAS5624A chip has 0.025% THD compared to the 5 year old TAS5630’s 0.03%.

Compared to the TAS5162 in the QLS, the TAS5630 has flat freq response but with much lower dynamic range rating although to me the bass is more than acceptable. This amp is designed to be a 2.1 with stereo + sub speaker posts. In fact, it uses a fully user programmable ADI DSP chip instead of a standard DAC and myriad options for stereo main + sub integration options. Aside from the insane amount of options in a slim small box, added features are headphone out and USB input that doesn’t need the PC to be rebooted if the amp is ever turned off like the W4S mINT. Better yet playback resumes right away after I change the input from anything else back to USB. Plus I didn’t have to install a driver as Win7 automatically loads an external DAC driver.

Downside? Only 16 bit USB input accepted. No remote but the G36D will come with one. Now the major downside: Visually the built quality is lower than the other amps in this shootout and alas it only reaffirms the fact that it kept breaking down. The first one was blown the moment I first pressed the power button. I had it shipped back to China and they resend it back with 3 unplugged cables inside including power cables. Once I took care of that myself, I noticed the main board is bent. Now the amp would only run for about 15 mins until it heats up before the right channel shuts off. Sinewave customer support is top notch though. They respond to emails within 1 hour and they shipped a new replacement the same day we corresponded. The replacement is working good for 2 months then start exhibiting slight distortion and the input button takes 10 secs to switch. Also it seems I’m not the only one that’s having problems with Sinewave products.

Having said the above, watch for the newer $380 G36D as it may very well be the ultimate plug and play integrated amp / soundcard replacement to get under $1000 that’s futureproof. And by that I mean, you can even program the DSP as a 3 way digital crossover to run a single 3 way speaker or a 2 way single speaker with a sub. You just need to get 2 amps to get stereo if you’re gonna go that route. The possibility is infinitely more than other amps in the market. Sinewave releases a newer amp every year with features and specs that are quite impressive for the price as long as they last.

Perceived Differences:

Highs: 4 stars. Still has all the ambiance details of the QLS without the tiring edge. I can crank this up at my loudest limit for a few hours and my ears would still feel ok.

Midrange: 3 stars. Like QLS but without the edge but with a slight veil. Certainly not as transparent as the QLS but pretty damn good.

Bass: 1 star. Lacking authority and lean compared to even the QLS.


Wyred4Sound mINT: 102W @ 8 ohm, 2 x ICEpower 125ASX2 modules, ESS Sabre ES1023 DAC, 2012 version, $1500. http://www.wyred4sound.com/webapps/p/74030/117839/612512.

4x more expensive than the other amps here except the obviously large NAD. Lots of big names in one hell of a micro box. Hyped Sabre DAC + ICE’s newest amp module that’s supposedly fixes the treble cutoff that most people complained about = ultimate single box solution? With damping factor >500 I expect the usual powerful bass I’ve heard from the past ICE products I’ve owned. Has USB, Toslink, Coax SPDIF, analog RCA inputs along with RCA stereo output and headphone out. The chassis is smaller but taller compared to the QLS and Sinewave. That much power and features but as light as a cheap Samsung DVD player. Driver needs to be installed on PC prior to using it through USB.
Perceived Differences:

Highs: 1 star. More extended high than old school ICE but dark and lacks spark which makes it great for jazz and solos but definitely not for complex musics. However, this sounds like a characteristic of the Sabre DAC and not the ICE amp or is it? They should’ve fixed the rolled off treble issue with the ASX2 series. Listening to Bliss Kissing’s last half is like
listening in a new song, that is with the ambiance part omitted. Very disappointing coming from a brand that touted accuracy in their slogan.

Midrange: 2 stars. Vocals are natural and believable top to bottom but the singer seemed farther from the listener than the other amps. I prefer a forward presentation of vocals so could be just my preference. Tonally the vocals sound just right. Guitars sound like being played in an anechoic room. Strong and impactful but with very dark background which some people attributed to the Sabre DAC’s character. Where’s the timbre?

Bass: 5 stars. The best of the bunch. As expected from the high damping factor of ICE, the bass is controlled, tight, and deep. Has the proper realism as in you’re in the club.


Onkyo A-5VL: 40W @ 8 ohm, Onkyo’s proprietary Class D module, Burr Brown 1796 DAC, 2009 version, $350. http://www.intl.onkyo.com/products/hi-fi_components/amplifiers/a-5vl/index.html.

Heaviest of the bunch, 10kg, built like a brick just like true high end audio products, solid quality all around that makes the mINT looks like an amateur DIY. Most people are expecting Onkyo’s newer Class D to sound similar to the “warm” A-9555 or A-9755 which I owned and were excellent in some regards. I believe most are disappointed to hear this cold sounding but more accurate amp. This amp represents the last Class D amp ever released from Onkyo since 2009 as they’ve gone back to huge traditional linear separates. This amp has a bunch of inputs including phono, toslink, and SPDIF coax in but no USB. The most interesting thing is when paired with the matching C-S5VL player, it would play SACD and stream through digital coax. Probably downgraded to PCM first…

Perceived Differences:

Highs: 2 stars. Detailed but without the fatiguing edge like the QLS. Not sure if it’s the effect of their vector linear technology or something else but it tries to present everything as
transparent as possible without forgetting to make it smooth, too smooth...

Midrange: 5 stars. Vocals sounded forward and full bodied. Female to male vocals are smooth and believable. I guess I prefer this over the C390DD simply due to the lack of slight dryness which makes vocals more believable. Acoustics though sound more realistic on the C390DD.

Bass: 3 star. Uncontrolled, not tight and fast enough = not musical. However the presence is balanced to the rest of the sound unlike older class d amps. Acceptable.


Summary:

I didn’t have time to set up the speakers in the optimal position, do measurements, etc etc. But the difference between a $300 integrated and another that cost 5 times as much is just a matter of taste. Well except for the NAD which sounds like on another level of goodness and has more virtues than flaws (which could be found by nitpicking beyond accuracy). Which means like any other electronics, technology has caught up and there’s no excuse not to get these cheap fully loaded integrated class d amps as long as they are durable. The amp chips are designed by big names in Europe or US anyway. All of these amps sure sound a lot better than the Krell, Bryston, Sim Audio and other top branded amps I had in the 90’s. Yes you get some plastic cheap knobs but none fell off yet unlike the one on a Yilong DAC. As long as you don’t need more power these cheap amps sound just as good as the established names in the market. Of course as long as the speakers used are easy enough to drive. I’ve also heard that tube and linear chinese amps are excellent as well.
Those who love the old Panny would want to give the QLS a try. It uses the newer (and last) direct digital (power DAC) TI chip than the Panny’s, sounds similar but more powerful. The fact that someone is still selling a pure integrated amp dedicated to this chip at a bargain price is a boon to those in the Panny cult. The QLS goes well with the Newforms just like how John Meyer keeps recommending the Panny to go with his speakers. But it is currently paired with some KEF Q500 at the office that replaced the Usher Be-718. The pairing lacks bass so I wonder if a similar direct digital design that uses a different chip such as the Infineon chip in the $550 Nu Force DDA-100 (direct digital / power DAC) would be more balanced.

The Sinewave is basically less dynamic, less distortion, and more accurate frequency response than the QLS. Yes it’s not a pure digital amp anymore but is the improvement more than makes up for giving away some transparency? YES! The G33D doesn’t have the bass control of the mINT or the smooth high end of the A-5VL, but it is the most balanced in the group. Even throwing sound quality out, the features alone would make the choice amp for anyone looking for a highend soundcard or an all purpose amp not only suitable for poor college kids but anything outside a true reference system. It’s also the only 2.1 Class D integrated amp that I know of. Having said that, a broken amp is nothing but a piece of sh__ brick and should be treated as such.

Those who like to listen to live music, tubeheads, old timer audiophiles, solos, or those only interested in SPL and bass would most likely prefer the mINT. Heck, actually the mINT is powerful enough to be used for a frat house party (until Sinewave G36D comes out). It’s the audiophile choice but certainly not for those interested in ultimate transparency or accuracy as hacking a piece of high end information means the signal has been severely altered. Could be because I hate dark sounding equipment as it takes out the realism of the overall presentation. This is especially true when pairing with the Newform R630 ribbon arrays. I admit prior to ordering I was highly concerned about the potential of missing high end details with a dark DAC mated with an ICE. Having said that, I know many people shy away from anything bright and welcome products like this. An alternative is the $370 TEAC A-H01 which also has 2 x 50ASX2 ICE module but with a more balanced sounding Burr Brown PCM5102 DAC and vastly superior chassis quality to the mINT (just check out the pics). Sure it only has 40% of the mINT’s power but it sure sounded balanced top to bottom to my ears when I demoed at the store. I can see that only in a really large room the mINT would be the preferred choice over the 60% cheaper TEAC. But the TEAC has an ultra cool high quality casing that’s probably the best one out of any amps listed here so that’s a plus.

The Onkyo A-5VL got lots of bad rap when people expected it to sound sweet like the high end A9755 which I was fortunate enough to own once. I didn’t expect it to do well as it seemed a great deal of the budget goes into the chassis and build quality. But compared to these newer generation class d amps it held its own and sounded more natural. Would’ve been perfect if the bass is as tight and powerful as typical linear or ICE amps. Also the problem with it being the older generation (3 year old design) is the lack of USB input but that can be fixed by getting one of those USB to coax converter. In any case, for $350 it’s a lot of amp especially considering the superb built quality which is similar to the TEAC A-H01.

So which one do I actually prefer to pair with the Sierra Towers? Truth of the matter is I can live with any one of them except for the mINT, so that’s out for sale. The Onkyo is limited in connectivity so it will eventually be replaced with something else (most likely the TEAC). Broken amps are good for USB headphone amp from the PC. The QLS is decent for the office or baby’s bedroom playing Twinkle2 Little Star. So that leaves the obviously most expensive NAD with the Ascends. This is also the wife’s favorite pairing. Keep in mind that the Ascends are quite efficient and less efficient speakers may result in the something else being more suitable. In the next shootout the comparison would be strictly for amps with USB input as it would be the standard connectivity given that media servers are replacing CD players. cool.gif

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post #2 of 30 Old 10-29-2012, 12:35 PM
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forgive my audacity for posting a review based on personal opinion with very little if any scientific facts. My only wish is that perhaps someone out there would find it useful.
The first sentence pretty much precludes the second. frown.gif

If you can't explain how it works, you can't say it doesn't.—The High-End Creed

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post #3 of 30 Old 10-29-2012, 02:47 PM
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My knowledge is obviously infinitely inferior compared to the masters of audio in this forum so I will go ahead and disappear quietly.

false humility doesn't enhance the value of your opinion. But thanks for the warning.

In your list you also do not include the hypex amps - which I use to drive my kef 104/2 speakers (and bash 300 for the DIY subwoofer).
I was unable to differentiate between those amps and the Bryston 4Bst/ 4B I used to drive them with. So much for my opinion.
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post #4 of 30 Old 10-29-2012, 06:10 PM
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I've owned a Class D amplifier for almost three years. I like its size, weight and relative lack of waste heat, but it doesn't sound any different from the various AB amps I owned before that.

I suspect, under properly controlled objective conditions, that the attributes you describe would vanish. I mean, deeper/leaner bass? How on earth could that elude test equipment? Is it some kind of secret bass?
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Originally Posted by Brownstone322 View Post

I suspect, under properly controlled objective conditions, that the attributes you describe would vanish. I mean, deeper/leaner bass? How on earth could that elude test equipment? Is it some kind of secret bass?

 

It was a little-known secret until you blabbed it to the whole world!

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Highs: 5 stars. With the black silent background the highs are clear, very clear

Too much of stereophile and sixmoonies.
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Heaviest of the bunch, 10kg, built like a brick just like true high end audio products

What significance does weight have to do in a class D amp?
The only thing that comes to mind a non smps?
And why would that be a good thing necessary? All the dsp's I have used using a smps worked perfectly fine and noiseless.
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I admit prior to ordering I was highly concerned about the potential of missing high end details with a dark DAC mated with an ICE.

WTF does that even mean? A "dark" dac? Get a silver one....
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post #7 of 30 Old 10-29-2012, 11:23 PM
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Class D amps can have load dependency that results in both measurable and audible differences. Here is the NAD M2 measurements based on different loads:

310NADfig01.jpg

The mandatory passive output filter combines with the speaker+wire load and causes the variations seen. They can also be sensitive to power supply fluctuations although copious amount of negative feedback can mask that. Low switching frequency can also mess with smoothness of high frequency response.

Here is some data on listening tests performed by Sean Olive while at NRC (Canadian government funded audio research group) as posted on WBF Forum:
Quote:
Originally Posted by Sean Olive 
Years ago I tested various commercial Class D amp solutions only to confirm that they were very sensitive to the loudspeaker load due to their high output impedance. Which amp you preferred depended ultimately on the loudspeaker you hooked up to it. In my view, that is not a good characteristic of a well designed amplifier.

So if there is one class of amps where it is plausible that there are differences, this is it.

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Founder, Madrona Digital
"Insist on Quality Engineering"

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post #8 of 30 Old 10-30-2012, 12:42 AM - Thread Starter
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Originally Posted by kraut View Post

false humility doesn't enhance the value of your opinion. But thanks for the warning.
In your list you also do not include the hypex amps - which I use to drive my kef 104/2 speakers (and bash 300 for the DIY subwoofer).
I was unable to differentiate between those amps and the Bryston 4Bst/ 4B I used to drive them with. So much for my opinion.

It's the truth, nothing false about it unless you feel offended for some reason. Hypex Ncore is expensive unless you go DIY which is beyond my skills and still expensive as time is expensive. People's ears are different pending on age so my 36 year old ears may be more perceptive or defective than others. But that's just my (ignorant) opinion.
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Originally Posted by amirm View Post

Class D amps can have load dependency that results in both measurable and audible differences. Here is the NAD M2 measurements based on different loads:

310NADfig01.jpg

The mandatory passive output filter combines with the speaker+wire load and causes the variations seen. They can also be sensitive to power supply fluctuations although copious amount of negative feedback can mask that. Low switching frequency can also mess with smoothness of high frequency response.

Here is some data on listening tests performed by Sean Olive while at NRC (Canadian government funded audio research group) as posted on WBF Forum:
Quote:
Originally Posted by Sean Olive 
Years ago I tested various commercial Class D amp solutions only to confirm that they were very sensitive to the loudspeaker load due to their high output impedance. Which amp you preferred depended ultimately on the loudspeaker you hooked up to it. In my view, that is not a good characteristic of a well designed amplifier.

So if there is one class of amps where it is plausible that there are differences, this is it.

Yes, people need to remember that it is only good amplifiers that sound the same, not the substandand junk.

Any modern switchmode amp that is 6 dB down at 20 KHz with a reasonable load, is pretty much junk.

BTW, the source of the plot above is http://www.stereophile.com/content/nad-m2-direct-digital-integrated-amplifier-measurements , and the proper annotation for the graph is that

"Fig.1 NAD M2, >8 ohms speaker compensation, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green). (2dB/vertical div.)"

Right away we see that the test arguably violates the reasonble constraint of the test being with a reasonable load. That really wicked green line is for a 2 ohm resistive load, which is beyond the pale as far as modern, reasonably-designed audiophile speakers go.

The 4 ohm line (cyan-purple) is only about 2 dB down, and would probably be hard to pick out because of its relatively narrow width and the insensitivity of the ear at frequencies those high. While this seems more reasonble, fact is that almost all 4 ohm speakers are only 4 ohms below 10 KHz.

This is a more typical speaker impedance curve:

http://www.stereophile.com/content/emotiva-x-ref-xrt-52-loudspeaker-measurements



While there are substantial regions just above 4 ohms below 300 Hz, at 20 KHz the impedance is close to 8 ohms and we are now in a realm where the response variation is only about 1 dB, and that will sneak almost all if not all listeners. The following is Clark's criteria for level matching, from his landmark JAES article about DBTs:

http://home.provide.net/~djcarlst/abx_crit.htm



Finally, the following is the response curve of a well-designed class F amp into a more typical speaker load:

http://www.class-d.net/MCD-255%20datasheet(test%20version%201.1).pdf



It's actually better than most class AB amps!

And another modern design with excellent frequency response:

http://www.hypex.nl/docs/papers/ncore%20wp.pdf

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post #10 of 30 Old 10-30-2012, 11:04 AM
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Thanks for the review.

Do you have a chance to listen to the Peachtree Grand Int. with ICE?

I see the atoms free and fine,

That bubble like a sparkling wine;
I see the songs Electrons sing,
Jumping from ring to outer ring;
              - Lister, The Physicist
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Originally Posted by arnyk View Post

Yes, people need to remember that it is only good amplifiers that sound the same, not the substandand junk.
Any modern switchmode amp that is 6 dB down at 20 KHz with a reasonable load, is pretty much junk.
BTW, the source of the plot above is http://www.stereophile.com/content/nad-m2-direct-digital-integrated-amplifier-measurements , and the proper annotation for the graph is that
"Fig.1 NAD M2, >8 ohms speaker compensation, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green). (2dB/vertical div.)"
Right away we see that the test arguably violates the reasonble constraint of the test being with a reasonable load. That really wicked green line is for a 2 ohm resistive load, which is beyond the pale as far as modern, reasonably-designed audiophile speakers go.
The 4 ohm line (cyan-purple) is only about 2 dB down, and would probably be hard to pick out because of its relatively narrow width and the insensitivity of the ear at frequencies those high. While this seems more reasonble, fact is that almost all 4 ohm speakers are only 4 ohms below 10 KHz.
Despite amirm's disguise uncovered, he continues to repeat the same marketing over and over again. It's a typical trait of shills. They have certain material and presentation method set, memorized and then just repeat:
http://www.avsforum.com/t/1340051/seeking-education-about-those-ultra-expensive-interconnects/780#post_20613201
http://www.avsforum.com/t/1340051/seeking-education-about-those-ultra-expensive-interconnects/90#post_20572423
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post #12 of 30 Old 10-30-2012, 02:09 PM
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Originally Posted by dwong View Post

Thanks for the review.

Do you have a chance to listen to the Peachtree Grand Int. with ICE?

All I know is that ICE is another technology that performs to modern standards/

Here's its performance with various resistive loads:

http://www.stereophile.com/content/bel-canto-ref1000m-monoblock-power-amplifier-measurements

"Bel Canto e.One Ref1000M, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (blue), 4 ohms (magenta), 2 ohms (red)."



This compares with the NAD M2 below:

"NAD M2, >8 ohms speaker compensation, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green). (2dB/vertical div.)"



It would appear that the ICE power amp has about 3 times better control over response variations with the same loads, which is a good thing. Not quite up to the standard of the other two amps I mentioned.
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post #13 of 30 Old 10-30-2012, 04:38 PM
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Never have hear the BC amp.

Did a quick listen of the NAD M2, like the PT Grand Int.'s sound better but maybe all due to the tube-pre.
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Originally Posted by arnyk View Post

All I know is that ICE is another technology that performs to modern standards/
Here's its performance with various resistive loads:
http://www.stereophile.com/content/bel-canto-ref1000m-monoblock-power-amplifier-measurements
"Bel Canto e.One Ref1000M, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (blue), 4 ohms (magenta), 2 ohms (red)."

This compares with the NAD M2 below:
"NAD M2, >8 ohms speaker compensation, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green). (2dB/vertical div.)"

It would appear that the ICE power amp has about 3 times better control over response variations with the same loads, which is a good thing. Not quite up to the standard of the other two amps I mentioned.

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post #14 of 30 Old 10-30-2012, 08:30 PM
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Hypex Ncore is expensive unless you go DIY which is beyond my skills

the only diy is to hook up the right wires from the smps and find a decent enclosure. If you can't do that - can you replace a light bulb?
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post #15 of 30 Old 10-31-2012, 01:29 PM
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Veda
Thanks for taking the time to post your thoughts.
It is definately appreciated by alot of readers.
Chris
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post #16 of 30 Old 11-01-2012, 09:48 AM
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Strange, although I've only listened to it via asynch USB, I wouldn't consider the mINT dark at all. IMO, it sound pretty neutral connected to a pair of KEF Q100s.

Mike
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post #17 of 30 Old 11-08-2012, 06:00 PM
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Thanks for the comparisions.

I love my nad c390dd paired to a 6 ohm impedance GS 20s.I can attest to the silent background and great midrange.I used to have the wyred dac2 with a mc5 (500 w,250w) combo.the wyred dac was pretty detailed but too bright with my iTunes downloaded music.

The nad dac/amp combo is very listenable for long hours into the night.biggrin.gif:D

Cheers
Ks

Minimac=>iTunes+AudirvanaPlus=>Peachtree x10 USB to SPDIF=> MRX 510=>Sonus faber Auditor M
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post #18 of 30 Old 01-02-2013, 06:33 PM
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You need to add to this group the Nuforce DDA-100. It received a glowing review in the latest issue of Absolute Sound. I just received one I ordered from Amazon last week and i must say I'm very impressed after a couple of hours of initial listening on a pair of Golden Ear Triton 2's. The digital stream came from a Logitech Squeezebox Touch playing CD's ripped to Apple lossless. I've always been of the mind that all competently designed electronic components sound pretty much alike. However the clarity of the sound of the Nuforce was impressive when compared to the same music played via a Emotiva XDA-1 DAC and UPA-200 amp. The added clarity seemed particularly noticeable on vocal duets, where it seemed much easier to differentiate between the voices.

Of course, this all may stem from an overactive imagination or infatuation with a new toy, but I'm still happy with my relatively thrifty purchase.

The Triton 2's have a built-in powered woofer, so I don't know how the Nuforce would deal with an unpowered woofer.

MIKE

For every complex problem, there is a solution that is simple, neat, and wrong.
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post #19 of 30 Old 01-17-2013, 02:56 PM
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Veda, thanks for the shoot out. Awesome. Great you know about the Panny at this young age :-) . I am still running a Panasonic SA-BX500 bi-amping my NewForm Research speakers. My TACT S2150 is boxed up because the family needs the HDMI switching of the Panny. As mraub suggests, it is good to check out the Nuforce too. If I sell of the TACT, I might try the NAD.
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post #20 of 30 Old 05-23-2013, 05:10 AM
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You are misunderstanding the Stereophile measurement of the NAD M2. The graph shows the amp being driven into 8 Ohm load, and ONLY into 8 Ohm load! If measured into 2 Ohms with the 2 Ohm setting the response would be flat. Likewise, using the 4 Ohm filter and driving a 4 Ohm load the response would be perfectly flat. This filter, which is generated in the digital domain using DSP, was created to offset the effect of the potential interaction of the reconstruction filter with the speaker load. In practice the effect of the filter is pretty subtle as it only effects the top octave and thus mostly overtones and harmonics. But careful listeners can hear its effect and the amplifier sounds best when this is set correctly. The exact setting can only be determined by listening. The impedance indication is just a starting point because the exact impedance of a speaker at 20kHz is not necessarily the same as its rated nominal impedance.
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post #21 of 30 Old 05-23-2013, 06:41 AM
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Running an amplifier into a resistive load for test purposes tells you almost nothing about how the amplifier will interact with a REAL load; a speaker.

A speaker is a capacitive load at some frequencies, and an inductive load at some frequencies, and this can cause the amplifier to become unstable and produce harmonics (distortion).

This can be particularly severe at those frequencies where the speaker impedance is below 4 ohms and speaker reactance is greatest.

It is well known to engineers and experienced audio technicians that many speakers have greater inductive and capacitive reactance than others, and that some amplifiers react badly when trying to drive that kind of difficult load.

You will note that Stereophile graphs not only the impedance of the speaker under test, but its reactive phase shift also; for good reason!

These problems can occur with any amplifier, but Class D amplifiers, as a class, are more prone to instability and distortion when driving a REAL non-resistive load (a speaker) than Class AB amplifiers.

This is why many Class D amplifiers do not sound good with many speakers. Lab testing with a resistive load does not give you a clue about why they do not sound good.

It is also the reason why the industry has been slow to embrace Class D amplifiers; they have performance problems due to instability that are well-known to design engineers and well-documented in the industry. One thing that helps to avoid these problems is a massive, well-regulated power supply. Something like the better NAD designs have a good power supply, but most HT receivers with Class D amplifiers are made too cheaply for a good power supply to be included. It's not in the budget.

Testing the performance of an amplifier with a resistive load is like testing the performance of a car on a dynamometer in a test facility; it is no way to evaluate its real-world performance characteristics.The rubber has to hit the road.
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post #22 of 30 Old 04-14-2014, 05:21 AM
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Regarding the Wyred 4 sound opinion that is Incorrect information, only in their. Mamps ans New StMK-2 amps
Is their latest technologies a totally new Input stage with Parralleled quad FET input stage,as well as a
Balanced differential in put stage this with the latest gen3 stage make this a Excellent performer top
To bottom there are at least 4-5 reviews that back up this statement . Unless you hear the latest runin
Then you cannot make a informed statement . Check out the reviews,and the facts !!
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post #23 of 30 Old 04-14-2014, 05:52 AM
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Quote:
Originally Posted by commsysman View Post

Running an amplifier into a resistive load for test purposes tells you almost nothing about how the amplifier will interact with a REAL load; a speaker.

A speaker is a capacitive load at some frequencies, and an inductive load at some frequencies, and this can cause the amplifier to become unstable and produce harmonics (distortion).

This can be particularly severe at those frequencies where the speaker impedance is below 4 ohms and speaker reactance is greatest.

Speaker resistance tends to be the same at all frequencies related to the operation of the relevant driver. It is mostly based on the DC resistance of the voice coil and that is stable but does increase as the voice coil heats up.
Quote:
It is well known to engineers and experienced audio technicians that many speakers have greater inductive and capacitive reactance than others, and that some amplifiers react badly when trying to drive that kind of difficult load.

Back in the day this was far more of a problem then it is now.
Quote:
You will note that Stereophile graphs not only the impedance of the speaker under test, but its reactive phase shift also; for good reason!

Agreed. one irony is that Stereophile's speaker simulator is far easier to drive than many of the speakers that they review.
Quote:
These problems can occur with any amplifier, but Class D amplifiers, as a class, are more prone to instability and distortion when driving a REAL non-resistive load (a speaker) than Class AB amplifiers.

The most audible problem is not instability and distortion, but variations in frequency response > 10 Khz due to interactions with the output low pass filter.
Quote:
This is why many Class D amplifiers do not sound good with many speakers. Lab testing with a resistive load does not give you a clue about why they do not sound good.

Interestingly enough, the tests with lower value resistive loads demonstrate the problem due to the output filter pretty nicely.

For example, the NAD M2 below:
"NAD M2, >8 ohms speaker compensation, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green). (2dB/vertical div.)"



If the above does not scream "trouble"...???? Here the resistive load test portrays the problem quite nicely, thank you!
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post #24 of 30 Old 04-25-2014, 04:32 PM
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The NAD C390DD has an adjustment/compensation setting for nominal speaker impedance. I've never seen the M2, but there may be a similar adjustment, or else this is a feature added to counteract the high-frequency attenuation at lower impedance.

FWIW, the background really is absolutely dead silent. It was the single most striking feature. Negatives included that it ran very hot, even while idle, surprisingly so for a ClassD-like amp. Dynamic range seemed a wee bit compressed, but this was a subjective impression vs. my DIY Class D amp.
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post #25 of 30 Old 04-25-2014, 07:10 PM
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Originally Posted by wgscott View Post

The NAD C390DD has an adjustment/compensation setting for nominal speaker impedance. I've never seen the M2, but there may be a similar adjustment, or else this is a feature added to counteract the high-frequency attenuation at lower impedance.

FWIW, the background really is absolutely dead silent. It was the single most striking feature. Negatives included that it ran very hot, even while idle, surprisingly so for a ClassD-like amp. Dynamic range seemed a wee bit compressed, but this was a subjective impression vs. my DIY Class D amp.

Such adjustments are anathema to mainstream amplifier designers. One of the major goals of an professional amp designers is their inherent adaptability. Adjustments are anathema.
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Quote:
Originally Posted by arnyk View Post

Such adjustments are anathema to mainstream amplifier designers. One of the major goals of an professional amp designers is their inherent adaptability. Adjustments are anathema.

I can't tell if this is tongue-in-cheek, but assuming face value, the relevant thing is it is not a main-stream amp. Everything is in the digital domain until the final output stage, so this adjustment, the volume control, as well as the DSP room mode correction at the lower end, happens before the conversion to the analogue signal. The aim is to get the flattest, most neutral, uncolored response plot.

Page 16, column 2 of the manual (link to PDF) describes this.
Quote:
Originally Posted by NAD 
Digital impedance compensation filter allows fine tuning of the top octave to match the speaker impedance. This will result in perfectly flat frequency response at 20 kHz. The effect of this filter may not be audible* but it is measurable, and it compensates for the small effect of the digital reconstruction filter that eliminates the 844 kHz sampling frequency of the amplifier.
*The exception may be some electrostatic speakers that have very low impedance at high frequency. The lower the HF impedance, the greater the deviation from flat response.
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post #27 of 30 Old 04-25-2014, 08:24 PM
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I just checked the manual for the NAD M2, and it also has the same digital compensation settings, so the measurements represented in the posted graph aren't telling us much if the appropriate setting (albeit manual) has not been made for each of the lower-impedance measurements.
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post #28 of 30 Old 04-26-2014, 02:04 AM
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Quote:
Originally Posted by wgscott View Post

Quote:
Originally Posted by arnyk View Post

Such adjustments are anathema to mainstream amplifier designers. One of the major goals of an professional amp designers is their inherent adaptability. Adjustments are anathema.

I can't tell if this is tongue-in-cheek, but assuming face value,

Suggests to me a lack of understanding of the role of power amplifiers in audio systems. When a good engineer builds a power amp one if its key characteristics is delivery of predictable results.

Consider this.

Engineer one tells you: "Buy my amp, once you get it, its going to deliver great sound no fuss no muss, just plug and play."

Engineer two tells you: "Buy my amp, once you get it, you are going to have to fuss and fiddle and just maybe you might stumble into an adjustment taht might get pretty fair but not necessarily the best sound."
Quote:
the relevant thing is it is not a main-stream amp.

Isn't it supposed to be better than mainstream?
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Everything is in the digital domain until the final output stage, so this adjustment, the volume control, as well as the DSP room mode correction at the lower end, happens before the conversion to the analogue signal.

Which makes it different from your choice of several different Yamaha AVRs how?
Quote:
The aim is to get the flattest, most neutral, uncolored response plot.

Which makes it different from your choice of several dozen different mainstream AVRs how?


I feel like I'm standing in front a store window looking at The Emperor's new clothes... ;-)

Why am I the only who notices that the manikin is naked?
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post #29 of 30 Old 04-26-2014, 08:04 AM
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Originally Posted by arnyk View Post

Why am I the only who notices that the manikin is naked?

Self-congratulatory expectation bias might be interfering with your vision. I admire your tenacity and dedication to debunking audio mythology. (I've been fighting the same, rather thankless, fight elsewhere on the internet.) However, in this case, I have to question your choice of target.

The manikin you think you are looking at is one that is made of straw.

Yamaha AVRs are direct-digital? I must have missed that somehow.

Didn't we have this same conversation on the DAC thread a few months ago?

In the case of the NAD C390DD, It is digital right up to the output stage.

What Yamaha (or any other) AVRs have this design?

I hardly think addressing a perceived shortcoming of Class D amps is somehow itself a defect or engineering incompetence, or are you suggesting all Class D amplifiers are the result of engineering incompetence, ipso facto?.

Most people have 8 ohm speakers and would never even need to make an adjustment, but it is there as an option for people who want it, just like the lower frequency room correction DSP is there for people who want to make use of it. The goal is a flat, accurate room response, a very readily measurable and audible quantity. This is the antithesis of the usual audiophool bull-shi'ite.

As for comparison to AVR setup, the NAD was far simpler. (I have a Marantz 1402, the least expensive in their 5.1 line, but I suspect the setup is similar for most of these. Compared to the hoops I had to jump through for the Marantz, setup of the NAD is much simpler, even if I had to change the checkbox from 8 ohm to some other value. I even managed to do it with a broken ankle.)

I decided not to buy one, mainly because I would be paying for a number of features I didn't require, and my current el cheapo DIY class D amp sounds more than adequate for my own needs.

NAD itself is a completely "mainstream" company with more than competent engineers. This isn't audiophool designer jewelry.

The direct digital power-DAC/AMP units that NAD, Nuforce and a few others are starting to produce are genuinely different. The idea of keeping the signal path in the digital domain as long as possible (right up to the output stage) strikes me (as an outsider to the audio world, but a somewhat competent scientist) as a laudable goal. Whether this results in a clearly identifiable audible improvement is a different issue, one that I would have to test objectively.
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post #30 of 30 Old 05-25-2014, 03:58 AM
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Quote:
Originally Posted by wgscott View Post

Yamaha AVRs are direct-digital? I must have missed that somehow.
NADs are direct-digital? Well... only in their names. They have error correction, so they are not really direct, but over-complicated form of modulator with feedback instead.
What is more direct - good DAC with a power amp on the out that have pure analog negative feedback (i.e. - "ideal" instant feedback). Or a poor DAC on power elements and then ADC (which is Analog circuit!) that feeds DSP with an error (with significant delay obviously) that corrects the DAC... I really do not understand how can anyone call this "Direct". Except for marketing purposes or to make such design as a method to workaround the marketing department "requirement" to have "direct" output stage and still have some sound pretending to be any good. The word "Direct" is so audiophile... and sells good.
Quote:
Originally Posted by wgscott View Post

The idea of keeping the signal path in the digital domain as long as possible (right up to the output stage) strikes me (as an outsider to the audio world, but a somewhat competent scientist) as a laudable goal.
Then you have to read Bruno Putzeys papers, where he very well explains (also as a former believer and also creator of the best class D amps and also the best DAC in the world) why "Direct Digital" is not a good idea.
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