Thread: What’s the big deal with class ‘D’ anyhow ?

OK, I do not have enough posts here to be able to post links or images yet. If you go to the Hypex website, and find the data sheet for the NC-500 OEM module, you will see all the relevant measurements, including distortion vs. frequency. Note that the distortion stays below .01% throughout the entire frequency range, even at 500 W into 4 ohms!

BTW, I never suggested that class A, A/B amplifiers sound bad (huh?) there are quite a few class A, A/B amps which I love.

Weird, or maybe I can!

Originally Posted by a.wayne

I will later put up a couple more of each to explain my position a bit more clearly and no its not necessary to be super smart and deaf to like class-D nor old fashioned and stupid to like class a/ab , each has their own virtues and warts ....

Mr Wayne, I have performed large scale blind listening tests of audiophiles who swore on class A etc...when their ears were actually hearing class D!! The key is that they had no idea they were listening to class D. I'm talking literally hundreds of people, including reviewers, "experts", etc.
The folks who claim "trust ears" listening reveals all. It does!
Now I'm not saying when folks know they are listening to class D that all sorts of melodrama can ensue. As they said in the Matrix, the mind makes it real.
However, if someone actually believes they can identify well designed class D like Hypex, vs class A or AB (SS, no high output impedance tube SFX processors), then I will be happy to oblige them with a controlled "trust ears" session, where they easily identify the classes.
Of course, I have one caveat, in that I will record the session to post on Youtube, for the entire world to see how golden ears can easily identify class D vs A/AB. None of this he said she said ether banter, but plain for whole world to see. The resolution of the camera will be sufficient to identify different shades of red when the results are revealed. All takers welcome.

The bottom line is what you hear. When I got back into this fun journey exploring amplifiers I did not bring a preconceived notion. Instead, since I was jumping back in, assuming a lot had changed I used my ears as the judge. From my list in an earlier post it can be seen that I tried a lot of different types of amplifiers, that I could afford. So I cannot make any comparisons to the extreme high end. I also listed my general feelings and reasoning why a particular amp did not become my long term solution.

In the final analysis the Class A First Watt I felt was something special, but the downsides were to great for it to be my long term solution. A lot of wasted power (low on my consideration list), very hot requiring ventilation considerations (a little higher on my list), but most important, just not enough power for long term with my new KEF.

The new mono PS Audio Class D have done it all for me. After having the W4S Class D early on, I felt Class D was probably not for me, but then with all the rave reviews on the new PS Audio I decided to give them a try. Sound wise just what I have been looking for, and all the upsides made this a fairly easy decision for me.

A friend has come over and listened to the S300 when I had it. He is a big tube guy. He said that it sounded excellent but he felt his personal adversity to Class D was probably clouding his judgement. He wants to come over the listen to the M700. He said after reading all the reviews he is going to try and not let Class D cloud his judgement towards these new mono amps.

Originally Posted by Randy Myers

He said that it sounded excellent but he felt his personal adversity to Class D was probably clouding his judgement.

He is a wise man. I have found when that cloud is accounted for/suppressed, the ears hear a very different tune.

Originally Posted by a.wayne

Those measurements are not independently verified and Hypex wont answer nor indulge when questioned..


there's alot to explain in those graphs i posted , its not just the amount but the shape, odd or even order content and percentage of change , which gives each their sonic signature, a signature you or I or anyone for that matter either loves or hate , as we all listen and accept these signatures differently...

I will later put up a couple more of each to explain my position a bit more clearly and no its not necessary to be super smart and deaf to like class-D nor old fashioned and stupid to like class a/ab , each has their own virtues and warts ....

Enjoy the music , we are all here for that ....


Regards

Hahaha! I am sure that many of Hypex's OEM customer's would not be very happy if they posted bogus measurements. I know of at least two Hypex amp manufacturers who own AP units can easily verify themselves. I trust Hypex, they are not BSers, and if you have ever had any interaction Bruno Putzeys you would experience this for yourself.
You asked me to post measurements and I did, then your only defense is to suggest they are bogus, hahaha.

The measurements i posted show distortion performance at least as good, if not better than, the absolute best measuring class A, A/B amps in the world, even at high frequencies where you suggest their is a problem. Show me a class A or A/B amplifier with less then .01% distortion across the entire bandwidth while delivering 500 watts into 4 ohms...

Meanwhile, you do not even specify what your measurements are of? Or the source of them?

BTW, the NC-400 DIY modules are even better, with .002% distortion across the entire bandwidth while delivering 100 watts into 4 ohms.

When you get distortion levels this low, it matters not whether the distortion products are odd or even, or low order or high order, the distortion products are inaudible entirely. That is the whole point of Hypex's work, to reduce distortion to such low levels that it is inaudible.

As to your comments about square wave response at 10 kHz you are correct. The waveform is a little slow, but there are many, many, many highly beloved tube amplifiers (and pure class A amps) with even worse 10 K square wave response.

Of course you are free to prefer what you like, I have no problem with that. But suggesting that the latest generation class D amplifiers have technical issues which can be shown in measurements is factually false as I have demonstrated, and it is misleading to others.

Originally Posted by a.wayne

I said not independently verifiable ..... Bogus is you projecting ...

My exact words were: "then your only defense is to SUGGEST they are bogus", that is exactly what you did. I have no reason to doubt Hypex's published specifications, just as I would not doubt Pass Labs published specifications. Mr. Putzeys is a straight shooter, and always has been in any interaction I have had/seen with him.

From your list it seems quite likely that you have not listened to an Ncore amplifier, unless the bel canto was a very recent model. Ncore is the first class D amplifier to make it into my system and stay (replacing Pass Labs), although I do hear that the latest tech from iCEPower (only available in the 1200AS 1 & 2 modules) is as good, or perhaps better. I have not heard it myself.

BTW, just listened to Hilary Hahn's Bach Concertos here, last night was Rachmaninoff's Symphony no 2, in DSD from Channel Classics. Both sounded wonderful.

Never took it as anything at all about my decision, just relating my fairly recent journey . It would be impossible to get the same wattage Class A amp in my budget. I did have some Class A/B that were fairly high powered, such as the SST...

Originally Posted by a.wayne

I did say this in my ramblings , we lock onto the sonic signature of what we like and or find negative about any topology genre ..

Except when one doesn't realize one is listening to a certain topology...as I found with literally hundreds of audiophiles. Those "sonic" signatures turned out to be not so sonic. Belief can have a powerful affect on the mind.
It is certainly true that some of the old class D tech had sonic sigs, especially in the highs, as the HF output filtering affected both load dependent frequency and phase. I think that is where a lot of the expectation bias "sonics" arise.
The new Hypex (et al) are load invariant, extremely powerful and transparent to human ears ability to detect distortions of any metric. At least when audiophiles are unaware they are actually listening to them.
Now, with awareness, that is another matter entirely.

Originally Posted by a.wayne

Set it up , very easy to identify IMO, i can pass thru anytime , I'm sure the Audio society can accommodate...

Will do, get ready to be a Youtube star
Now, what class A will suffice?

Originally Posted by a.wayne

Read again Sir , i said we compared the crowns to NC400, i did not own them ... I did own the others except the devialet i had access to it in my system...

Oh good, sorry I missed that. I have direct experience with the NC-400 modules. I have seen a lot of what I would consider poor builds by DIYers of NC-400 modules, so they can be a moving target. When I built mine I compared directly to my Pass X 150.5. The NC was resolving more detail and was quieter overall, but the Pass was a bit warmer and rounder. The NC was a little bit thin sounding in comparison, but I did not want to give up the extra resolution it had. By changing the AC input wiring to the SMPS 600 in the NC amps, I got the body/fullness I was looking for, and kept the additional details. I went from the stock Hypex supplied 18 AWG cheapo tinned copper wire to 15.5 AWG Cardas litz, nearly doubling the gauge. At that point after about 6 months of comparisons of the NC vs. the Pass, the Pass left my system as I fully preferred the NC without and qualms. since then I made one further change which improved the NC amp performance, I changed the footers from Stillponts minis to Herbies Tall/Soft Tenderfoots, this eliminated the slightest amount of midrange hardness sometimes heard when a vocalist is really pushing it, and allowed for an even blacker background.
These amps are so transparent, that small details of implementation really seem to matter.
Since, i have also heard the Nord One Up (SI OPAs) and the Merrill Audio Veritas in my system-both outperformed the NC-400, and I am currently looking for my next upgrade path to a higher power class D amp.

Originally Posted by AJ Soundfield

Will do, get ready to be a Youtube star
Now, what class A will suffice?

If you use a relatively pure class A, such as Pass Labs XA series I suspect the class A lovers will be able to pick it out for its low damping factor and distortion characteristics (lushness). A better comparison might be Constellation, as they are a bit more neutral/transparent.

Originally Posted by a.wayne

Let me give this a try ,

If you use a relatively pure class D amp , such as Hypex I suspect the class D lovers will be able to pick it out for its over damped weak bass and high NFB distortion characteristics (dry sounding ).

A better comparison might be Devialet ....

An amplifier cannot be overdamped, it's job is to follow the input signal accurately, not to be slow and emphasize low frequency signals. Unless you are looking for an amplifier to contribute a sound of its own to the signal. Personally I do not want my system to be editorialize the recording. That would not be what High Fidelity is.

Maybe I can clarify my point. If one is looking to distinguish between two amplifiers, does it not make sense to use two amplifiers which are both about neutral in terms of coloration?
I would characterize Pass XA series (and much more so aleph, etc) as a bit on the warm, forgiving, and slow side. I would consider Constellation about neutral, with clean transients, well controlled but ample bass response, and neutral balance in the high frequencies. On the sharp end of this scale I would put Solution, with super tight, and perhaps a little anemic bass, super fast and overly sharp transient attacks, and emphasized high frequencies. All of these amps are excellent, but need to matched to the appropriate speakers in order to achieve an acceptable sonic performance in room.
It makes sense to me to use the most neutral of these choices for a comparison of amplifier classes, not one which leans far toward one extreme or the other.

Originally Posted by a.wayne

If you use a relatively pure class D amp , such as Hypex I suspect the class D lovers will be able to pick it out for its over damped weak bass and high NFB distortion characteristics (dry sounding ).

Hey now, you're going to be the one picking, not the "class D lovers"
You're choice of class A amp (no tubes and/or pathological SS). Maybe your own Pass?

Has anyone here heard the Auralic Merak monoblock amps? They are class D.

Originally Posted by Mordante

Has anyone here heard the Auralic Merak monoblock amps? They are class D.

I haven't tried myself but I have heard of people comparing with Nord’s and they preferred the Hypex based class D of the Nord’s. I believe there is a thread on the Nord’s running on this forum you might want to check out. If you can stretch your budget then I recommend one of the Hypex Nc1200 based amplifiers, notably the Mola Mola Kaluga’s which can pretty much drive any loudspeaker with ease and control. I know people that have given up on their five times more expensive class A amps for the Kaluga’s.

Originally Posted by alto

I haven't tried myself but I have heard of people comparing with Nord’s and they preferred the Hypex based class D of the Nord’s. I believe there is a thread on the Nord’s running on this forum you might want to check out. If you can stretch your budget then I recommend one of the Hypex Nc1200 based amplifiers, notably the Mola Mola Kaluga’s which can pretty much drive any loudspeaker with ease and control. I know people that have given up on their five times more expensive class A amps for the Kaluga’s.

I'll look into the Nord's thread. The Meraks are second hand about 2-2.5k for a set. The Mola Mola Kaluga are 7k second hand

Originally Posted by Mordante

I'll look into the Nord's thread. The Meraks are second hand about 2-2.5k for a set. The Mola Mola Kaluga are 7k second hand

MM really worth the stretch. Nord’s are about £2k new.

Originally Posted by alto

MM really worth the stretch. Nord’s are about £2k new.

I'm not sure but I think my speakers could with better amps. I really don't know yet. Right now I use 7m long speaker cables. The idea is to maybe use longer interlink for separate pre/power combo. But I don't know. I love spending money on audio, but maybe I should keep my set as is for a few years.

Originally Posted by Mordante

I'm not sure but I think my speakers could with better amps. I really don't know yet. Right now I use 7m long speaker cables. The idea is to maybe use longer interlink for separate pre/power combo. But I don't know. I love spending money on audio, but maybe I should keep my set as is for a few years.

The Nords and the Mola Mola’s come as monos so it is possible to use much shorter speaker cable runs.

Originally Posted by a.wayne

Bart,

When you switch from toobs and buy your Mola Mola , i will come and listen , until then save your breath ...

Ha!
Maybe for a second system!

Originally Posted by Devg

I have heard the Merak in a different system (but same speakers as mine). In the same system, the Usher audio amps, which is class A/B, sounded better than the Merak. The Merak's do have a Class A input stage with Class D output.

Note also that the Meraks use the Hypex UcD technology, not Ncore. Additionally they are transformer coupled, which probably has more to do with the way they sound than anything else.

Meraks also use a linear power supply versus the switching power supply.

Originally Posted by deangale123

Better not Google the Mono and Stereo review of Mola amps then, seems the reviewer shares the stated opinions of a few here. The bass great but not involving , soulless etc.

Sent from my SM-T113 using Tapatalk

Hahaha! THat is a terrible review, clearly by a reviewer who should not be paid. ESpecially when they state clearly that they have a complete bias against the topic at hand for the entire first third of the review. for each review like that I can link to two which proclaim the Kaluga as one of the best amplifiers aever at any price. Also I have listened to it, so I already know. LOL if you believe everything that you read rather than the truth.

Originally Posted by deangale123

Better not Google the Mono and Stereo review of Mola amps then, seems the reviewer shares the stated opinions of a few here. The bass great but not involving , soulless etc.

This is exactly the type of person that I tested, who raved about the "live music" sound of the Class A amp they were looking at....when in fact their ears were hearing Class D.
I must be missing something, but I don't see a name on that review. I would love to put his face on Youtube, where he easily identifies the Class D vs Class A sound that exists in his mind, when he doesn't know which he's listening to. Would be fun.

Originally Posted by AJ Soundfield

This is exactly the type of person that I tested, who raved about the "live music" sound of the Class A amp they were looking at....when in fact their ears were hearing Class D.
I must be missing something, but I don't see a name on that review. I would love to put his face on Youtube, where he easily identifies the Class D vs Class A sound that exists in his mind, when he doesn't know which he's listening to. Would be fun.

Do all amps sound the same AJ or for some mysterious reason do they only sound the same when people can't see what they are listening to?

Originally Posted by mep

Do all amps sound the same AJ

Nope. Plenty of real differences between amps. A high output impedance high even order distortion SET will sound very different from a typical Class D or A SS amp.

Originally Posted by mep

or for some mysterious reason do they only sound the same when people can't see what they are listening to?

That only happens when there are no real audible differences, as I tested. When they can't see the SET vs Class D above, they still hear the exact same real differences as sighted. Anyone with lots of experience doing things both ways can attest to this.
Btw, some of the early Class D stuff did indeed sound terrible, for good reason.

Originally Posted by AJ Soundfield

Nope. Plenty of real differences between amps. A high output impedance high even order distortion SET will sound very different from a typical Class D or A SS amp.


That only happens when there are no real audible differences, as I tested. When they can't see the SET vs Class D above, they still hear the exact same real differences as sighted. Anyone with lots of experience doing things both ways can attest to this.
Btw, some of the early Class D stuff did indeed sound terrible, for good reason.

At what point do the sound of amplifiers converge so that they are indistinguishable from each other sonically? Let's throw out SE amplifiers from this discussion.

Originally Posted by mep

At what point do the sound of amplifiers converge so that they are indistinguishable from each other sonically? Let's throw out SE amplifiers from this discussion.

When they are equally capable of driving the load without exhibiting audible non-linearities, of which there are a great many metrics. Frequency, distortion spectra, compression, noise, etc, they become increasingly difficult...or impossible, to distinguish via ears.
The "class" matters scant then. Easier said than done, but also easily demonstrable.
Hence my Youtube suggestion. Have the claimant pick whichever non-pathelogical class A (so no SET etc) they believe best highlight the attributes that will allow differentiation vs Class D, I'll supply the Class D and the camera. The whole world gets to see the results of the claimant.

Originally Posted by AJ Soundfield

When they are equally capable of driving the load without exhibiting audible non-linearities, of which there are a great many metrics. Frequency, distortion spectra, compression, noise, etc, they become increasingly difficult...or impossible, to distinguish via ears.
The "class" matters scant then. Easier said than done, but also easily demonstrable.
Hence my Youtube suggestion. Have the claimant pick whichever non-pathelogical class A (so no SET etc) they believe best highlight the attributes that will allow differentiation vs Class D, I'll supply the Class D and the camera. The whole world gets to see the results of the claimant.

So how much do a pair of Class D amps cost that are indistinguishable from a non-SE Class A amp? I'm sure lots of people would like to know the answer for how much it will cost to equal the sound quality of expensive Class A amps with Class D such that no one can tell them apart.