I have recently paired an Audio Research DS225 Class D amplifier with an Audio Research tube preamplifier (SP8 mkii). I cannot believe how wonderful and lifelike my music sounds. The DS225 replaced an Audio Research SD135 Class AB amplifier. Perhaps the SD135 is just not as good as some of the better quality amps that are out there, but it got me thinking that amazingly wonderful sonance can be achieved with a tubed pre and Class D amp. I have a hunch that as more people experience this combination, it will likely catch on and become the future path of many, if not most audiophile systems. It is interesting that Audio Research has been at the forefront of this development.
Kosst, Honestly, and truly have you ever sat down and listened at length to ANY Class D amp? Specifically one in your own system? Set in the listening position and show me or more specifically tell me you hear the ringing distortion or switching for that matter that you hear in Class D amps. Although it might be harder than you think with your choice of loudspeakers......
As good as the NC400 module measures it does not sound as good as the slightly less good measuring IceEdge 1200 module. And this is with the output caps in the NC400 changed to much better sounding modded and correctly oriented Wima caps versus a completely stock IceEdge.
The switching frequency is at 450kHz, no tweeter could possibly reproduce that... Not that anyone would hear it, not even dogs.
You need to understand better, it’s not the switching frequency "so much" but the "output filtering" needed to get rid of it that ’s problem, which gives phase shift problems right down to 3-5khz (the mids and highs of the audio band). (That's why any complaints of Class-D is the upper mids and highs, never bass or lower mids).
If that switching frequency were to be moved up 3 x higher (like the $20k Technics SE-R1 does with the GaN transistors) then that "output filter" can be also moved up by the same amount, then the phase problems move up as well in the audio accordingly. I would like to see 5 x higher.
Oversimplification is usually done by those who have had very little hands on tweaking of amps. I have been designing, modding and tweaking amps, etc. since the late 1970s. When you realize that every single part and execution effects the sound then just going after one measurement or whatever is just plain wrong. Most all of the class D amps till now have switching around 500K........and most use the same type of filtering on the output. However, they all sound different, including the highs. The Merrill probably switches at 500K yet no one says the highs are not great......same with this IceEdge amp.....super clean highs.....and same filtering. Other amps using the same 500K and same filter sound strident or rolled off or compressed in the highs......because there are so many factors that effect the sound. It is not one thing. It is not just the filter effects, it is not just the distortion measurements....it is hundreds of things that make the sound. I am not against wider bandwidth, GaNs, and better distortion figures. But these things will not bring state of the art sound by themselves. For instance, the stock IceEdge modules sounded OK when I first listened to it (all hardwired, no connectors)......but when I changed the fuse to a serious audiophile fuse I said.....Oh Wow....this amp really is good. Want to blow your mind? Damp the heatsinks on your big Class A transistor amps. If you run your fingernail along the heatsink and they sing, then you are adding that sound into the amp. Every person who has done this has heard the same thing.....way less "transistor" sound......which, of course, was really heatsink vibration sound being superimposed on the signal. My Class D amps will have every panel and the modules constrained layer or multiple layer damped.
Hello guys I think the thread has gone to technical for me. Im not an expert, but I've tried some class A amps, SS and tubes, and now Im trying a Nord One UP NC500DM class D amp, wich has just replaced my previous beloved Line Magnetic LM-508IA class A valve amp (single ended 300B), wich had a VERY good reputation among audiophiles. Using both as power amps with the exact same system (a pretty revealing one) I must confess that Im blown away by the superior perfomance on "every" field the class D amp has against the 300B class A valve amp. On every field Im not Just referring only to grip, dinamics and holographic sound, but also on some fields I thought were the 300B amp strengths like warm, delicacy, tone and texture. I still cannot believe the outstanding perfomance of this Great class D amp, even its not burned in yet as it only has about 30 to 40 hours playing and it should get "much" better. Its incredible! It cost less than a half, weights about 30 kg less, produces considerable less heat and I dont need to spend on valves ever again. I was a valve amp lover, but now I found a much better and cheaper solución for my system. To believe or not to believe.
Ric, really good input (NPI) from you;) and likely why Peter Madnick's AA design got such rave reviews. Owning the DPA-1 (stereo amp) the only tim I notice glare is from poorly recorded discs. And yes, I recall ringing whn I had my KBA 75 with chassis long heatsinks
plga, lucky you. Is it the NC 500 Mk II? I am close to pulling the trigger on a pair of Audio Alchemy monos for about the same money as the Nord Mk II. Not surprising, it's out of stock. Wish I could hear them. Im in S Florida
Hello tweak1 No, its not the MKII. I bought it just a few days before the MKII was released because I didnt know! Colin didnt tell me that, otherwise I would have wait for the MKII. Nevertheless, this model sounds "superb" with the Sonic Imagery Op Amps. To have an idea, Hulgich Audio, an australian speaker factory, won the best sounding stand award on 2017, and second best on 2018, on a HiFi Show in Australia, competing against systems that costed hundreds of thousands and the amps used on those shows where Nord One UP NC500DM Monoblocks. My opinion is that you cant go wrong with the MKII.
plga, I just checked Nords site. It would cost > $2.2k for the Mk IIs. I don't mind the wait, but I can get a pair of AA monos for ~ $1500 (MSRP $3990) and that extra $700 I would need to spend now is a big stretch. I realize that the perceived value in the new amps could pay off at some later date, and that when I sell the AAs, they might further drop in value when I decide to sell
Well, thats something you have to think and decide on your own. It will be difficult for me to sell my previous 300B valve amp because its an expensive one and in my country (Argentina) there arent many people that can buy it, but I dont care much because, even selling it at a very low price, I should recover the money I spent on the Nord. And Im not even considering the replacement valves I have in stock and I also have to sell. But everything is now less importante considering that I have now a much better sound, less heat, less energy consumption, a smaller and lighter amp and I wont have to spend on valves ever again. Is up to you and your circumstances.
It is always best to have dual mono......so here is a link to a review from a person that owned the mono Nord one up amps (with the Sonic Imagery op amps) and then bought two stereo amps with the IceEdge 1200AS2 modules in them and then ran each amp as a mono block.....so now we have a fair comparison (fully mono in each case). He says which one he prefers.
And this is with stock IceEdge modules implemented in a normal way. Imagine how much better it could sound with tweaked modules and tweaked execution.......stay tuned......coming soon.
Haven’t found a digital which can compete.Most digital are to clean for my ear.
Sterile with no decaying harmonic structure, creating too much dead time, are the words I believe you should be using.
Dead time is part of the design of the amp, not something that arises from its ’harmonic structure’.
Judging by the measurements I keep seeing, great class D amps still haven’t arrived. Most of them have issues with ringing. All of them have ultrasonic noise that sits on the outputs like standing DC. Upwards of .8 volts of noise!?!?!? That’s hifi, is it? A 1kHz sinewave looks horrible through those things. For all intents and purposes, it’s made entirely out of high frequency noise.
@kosst_amojan Actually a 1KHz since wave looks good on most of them, without any noise. The ultrasonic noise to which you refer is the residual and is itself a low distortion sine wave at the switching frequency.
Show me where it is stated that the Merrill uses higher than 500K for its switching frequency. In fact, Merrill stated (on this site) that higher frequencies for switching were harder to do. I hope Mr. Merrill steps in here and clears this up. What he seems to claim is that the zero dead time using GaNs plus his zero feedback circuit are what makes the great sound.
The advantage of such high performance output devices is that they allow one to build a circuit that has no dead time circuitry in it. This means the circuit is a **lot** simpler! Of course, there is always some shoot-through current, so by going with a lower switching frequency a lot of consequences of that are avoided- one can use a slightly larger heatsink and the shoot-through heating is controlled. But the advantage of reduced distortion via no dead time is profound. So this should be a very nice sounding amplifier.
Go to Stereophile and look at the last 5 or 6 class D amps they’ve measured. Unless JA applies a low pass filter on the AP the output signals look horrendous.
@kosst_amojan I did and found the review at the link below. I think you may have misinterpreted something in JA’s measurement comments. The filter to which you refer above has to be there because all class D amps have a residual sine wave component, which has to be filtered in order to prevent the analyzer from having difficulty; in JA’s words:
As class-D amplifiers produce RF noise that could drive my analyzer’s input circuitry into slew-rate limiting, between the test load and the analyzer I inserted Audio Precision’s auxiliary AUX-0025 passive low-pass filter, which eliminates noise above 200kHz.
Note the cutoff frequency of the filter- 200KHz, and why it needs to be used. Nowhere in this article does JA say or imply anything that you suggest above. He seems to think the waveforms look pretty good.
You need to understand better, it’s not the switching frequency "so much" but the "output filtering" needed to get rid of it that ’s problem, which gives phase shift problems right down to 3-5khz (the mids and highs of the audio band).
Many such filters are 12db, but if only 6 db, that is where you use the rule of thumb that the phase effects extend to 1/10th the cutoff frequency. In the case you state above that would be 45KHz, not anywhere in the audio passband! If 12db, the effects are more constrained; IOW 6 db is a worst-case scenario.
which has to be filtered in order to prevent the analyzer from having difficulty; in JA’s words:
This is just pure BS and you have been sucked in by those words "your just echoing Stereophiles words" that are advertiser driven, and anyone can see it. And I think you know that, as you don’t want your Class-D to look bad when a 1k square wave is put through it.
As no such AP filter was used at Stereophile before, when all Class-D were measured with the same analyzers. And it showed just how bad what was coming out of Class-D’s.
Also when the AP filter was introduced, Stereophile use to give the wave form shots with and without the filter. And then later mysteriously only with the filter, probably because of manufacturers complaints how bad it looked without filter. So one can see it was just the ugliness of the wave form without the filter, that potential customers didn’t like seeing, and this effects sales, and advertising.
Just like ricevs (Tweak Audio) you are both protecting your soon to be released Class-D amps, and just ricevs you do/say anything not to tarnish it’s launch. Again a blind man can see it.
@georgehifiInstead of made up stories, just stick to the facts. If the filter is not used on the AP, it goes into slewing protection.
We don't use a filter since we are using oscilloscopes; any waveforms we see have the residual sine wave imposed. Depending on the waveform the residual might just look like hash on the waveform until you open up the horizontal gain and see that its just a sine wave.
There goes George with his dark conspiracies and kabalas... Fascinating stuff really.... Except that blind men -- e.g. your truly -- use their ears, and he apparently does not.... Perhaps a deaf audiophile?! :)
Isn't it interesting that a guy that continuously blasts active preamps because he manufactures and sells passives would protest so vehemently about his perception of what another manufacturer is doing that may benefit them? The two he is taking exception with have been nowhere near as overt as he has.
Doesn’t matter what spin you put on it, your just in future product protection mode like ricevs.
I suggest all members here to look close at these two scope shots of the same Class-D amp this one without the "AP filter" used, this large % of switching noise is what’s being sent to the speaker, and it is NOT repeat NOT!!! going into slewing protection. https://www.stereophile.com/images/1212AM1fig02.jpg
The this a shot of the same amp exactly the same scope shot, but this one with the "AP test filter" in place, exactly the same save for the deletion of the % of switching noise, that gives the impression that this is what goes to the speaker to make it look good to the buying public, but it’s not, whats above is! https://www.stereophile.com/images/1212AM1fig03.jpg
And let me say, what ever you look at, these are both pathetic looking square wave shots, even for an old cheap 1970’s solid state amp to be producing, yet alone a "today’s state of the art modern Class-D" the only one approaching that is below and now the new GaN transistor equipped Merrill Audio Element 118 monoblocks.
Now look what happens to the GaN transistor equipped Technics SE-R1 with far higher switching speeds. The blue trace is what the Technics can produce (hardly any residual switching noise, and look how straight up an down the sides of the square wave is this indicates hardly any phase shift down into the audio band, unlike the 2 above who’s sides are quite inward tilted which indicates phase shift into the audio band. https://www.technics.com/content/products/r1/images/se-r1-img2-2-uk.png
So, George, are you enjoying the music from the the Technics amp in your system? Does it make good music? Or is this still pure oscilloscopic voyeurism that you foisting on us all?
I am befuddled with georgehifi . he acts like a class d amplifier is just trash, like everyone who has one is listening to a transistor radio or something. I am glad I am not jaded to the extreme he is. I have a class d amp from crown also a class ab from anthem and a audio research ref75 tube amp and a pure digital amp from exogal. I can put any of these in my system and enjoy. Feel sorry for the guy really.
If you like Class-D as it is that's fine. Others say they can't, and it's always the mids and highs that is the problem, never the bass because that's what they're good at ever since they first came out.
And the title of this thread is. "The Future of Audio Amplification" and it will be Class-D one day, when they have a total acceptance in the mids and highs for the hiend, not just with those that can't hear it for some reason.
And that one day is getting closer with amp like the Technics SE-R1 and also maybe the
Merrill Audio Element 118 monoblocks if they did it right like the Technics.
I hereby nominate Koost and George for the Negative Nelly award for incredible Class D bashing. Who do you think will get the award? He who repeats himself the most wins....don't you think?
We need a little humor in these times. Trouble is these guys are serious. To bad, life is really, really amazing. Audio just keeps getting better and better and class D has made it more affordable and more efficient. I just wish these guys would get out and listen to the latest and best class D amps (including those that switch at 500K and use mosfets). Some great sound out there on the cheap.....as many have already posted here and it will just keep growing and growing.
May all be blessed in this new year! Enjoy every moment, for you never know when your time is up. The more you bless and serve others the more happy you and everyone become. Love everyone, love yourself, the earth and be at peace. God's love and joy are always present.
Ricevs, your only protecting your new Class-D baby your soon to unleash on the public, built around the Icepower Class-D modules, it’s as clear as the nose on your face. here’s a free plug, but I think it’ll end up a furphy. http://tweakaudio.com/EVS-2/EVS_1200_amplifier.html
Hello Recevs, how dare you believing in your own class D creations ;) You should instead prostrate yourself and squirm in shhame, while grovelling and begging undeserved forgiveness from the righteous paperholic and Martin colloms-fearing audio morality police, which keeps us in nirvanic purity, whilst protecting us all from straying into the the anathema of visual osciloscopic abominations lurking inside non-Colloms-blessed classes of amplifier operations.
Hello guidocorona...Any time frame on the Rowland M535’s review release? I’m very much interested on what you have to say about them. Wondering how they may compete with Merrill’s Veritas monos. Thanks...
Hello aolmrd1241, I now have most of the pieces of the eval post.... Need to stitch them together, remove burrs, integrate a few more bits of technical information, and audible observations, and then I will post to Audiogon.
Go to Stereophile and look at the last 5 or 6 class D amps they’ve measured. Unless JA applies a low pass filter on the AP the output signals look horrendous. Even with the low pass filter, they all have ringing. I was just looking at the Below Canto Black and that thing isn’t horrible, but .05% of garbage distortion at 200mW!?!?!? That’s ridiculous.
- Kosst
The problem is you are "looking" and not listening.
We apply the low pass because the distortion analyzer’s numbers would pick out signals no human could hear, not to mention those signals could not make it past the speaker drivers. Without those low pass filters, the distortion numbers loose all meaning for our use.
It’s not just enough to have a measurement, but you have to know how to apply it correctly to an application. Blindly accepting a number as true or useful is the root of all evil.
I compared Parasound A23 class A/B amps to my Class D. Could not tell the difference even knowing which was which. Tell me please how much of that ultrasonic ringing I should care about.
The evidence of my ears are telling me Class D must do distortion right. Go figure!
Exactly.
I’ve also heard megabuck class-A amplifiers around the time I got my Class D.
Honestly preferred the Class D.
I’ve had several audiophiles in my home and no one has ever said "Oh, wow, that hypersonic distortion is killing me, this is class D".
In fact usually what happens is when they are getting ready to leave they ask "Oh, by the way, where are your amplifiers??" because they are so small and easy to miss.
I’m not asking you to love my amps, but the idea that Class D are not competitive with the best Class A is nonsense.
I am as big a fan of metrics as the next guy but fact is they never tell the whole story.
So glad I do not let naysayers detract me from trying well documented real and factual new technology innovations. I have yet to regret it. I’d still be living within the outdated constraints of the 20th century if I did.
Thank God Erik and Mapman showed up. I was starting to think I saw a horse & buggy go by.
The resistance to innovation on this forum is frightening. People talking about things they've never listened to, others talking about measurements as if that is hearing. Some serious audio fruit loops going on around here.
Happy New Year! I hope you guys stick around, it was getting a little scary.
The resistance to innovation on this forum is frightening.
There’s a reason for it, it’s there and real, and if you can’t hear it, fine. But please, don’t tell others they can’t, when they can, and the measurements back them up.
And you can’t refute the amount of listeners that can hear the problem with the upper mids and highs. Even the very best of manufacturers have said so, no need to paste up that list again.
There’s a reason for it, it’s there and real, and if you can’t hear it,
fine. But please, don’t tell others they can’t, when they can, and the
measurements back them up.
George,
All you do is tell others they can't be happy with Class D, and that they should be able to hear the same way you do.
The measurements you are hell bent don't back up a thing. There is a gap between a number and perception which you and kosst can't seem to grasp, but most can.
"There is a gap between a number and perception which you and kosst can't seem to grasp, but most can."
As Sam Elliott says "exactly right".
There's nothing wrong with being an engineer, and there's nothing wrong with taking measurements. However measurements and listening are two different items.
All I can say is the good recordings sound scary real including piano brass and vocals and its dead quiet in my little 12x12 office when the music stops.
Squeezebox Touch -> mhdt Constantine DAC -> Arc sp 16 preamp -> Bel Canto ref1000m Class D amps -> KEF ls50s. Klipsch sw308 sub tossed in for good measure.
Exactly Michael, how many threads on this forum revolve around system brightness regardless of amp topology. Get nos tubes, get better cables, toe your speakers in/out, get a power conditioner, better power cables, change your preamp, change your speakers....on and on and on.
And let me say, what ever you look at, these are both pathetic looking
square wave shots, even for an old cheap 1970’s solid state amp to be
producing,
This is the link about which this comment is made:
Obviously the above quote is false, being based on a Hasty Generalization:
Unless you didn't do the math, that's actually a very respectable waveform; 0.05milliseconds is 20KHz! Its pretty hard for **any** amplifier to make a good **squarewave** at 20KHz- to make it really square you need bandwidth to at least 10x the fundamental frequency. We can see a bit of peaking in the waveform- probably the result of the phase shift of the filter, which is probably set fairly low to deal with the rather low 400KHz switching frequency; my guess is about 60KHz.
And the amplitude is pretty low, so the residual is easily seen. The residual is a bit high, about 1/2 volt. The link does not specify if the amp is under load, but if it is, then this is an older amp not representative of amps made in the last 5 years; if not under load that's quite decent despite the low switching frequency.
Listeners having a problem with their mids and highs have a system problem not a Class D amp problem.
They don't have the problem without the Class-D in the system, are you listening to your self, and you call yourself a room tuner.
I wouldn't want to guess what you do to counter the mid/high problem.
Unless you didn’t do the math, that’s actually a very respectable waveform; 0.05milliseconds is 20KHz!
Wrong!!! look at it and think again. It’s Stereophiles, there’s your hint, they’ve NEVER EVER given a Class-D 20khz square wave, as it would look unrecognizable as a square wave.
Ric, I found it, but I don't see anything specific about mono v stereo. That said, my last 4 class Ds were monos. Only my current AA PA -1 is stereo. Too bd your amps aren't ready
I have a chance to do a swap with a guy who has the AA monos for my stereo amp + $$$, but as class D is evolving so quickly, I am concerned that I will not be able to get anywhere near what I am paying, which is 50% off MSRP
Nope, I'm listening to music and working on folks' systems who have Class A, AB and D. No need to guess George when I'm doing. Oh, and since you mention roomtune, go ahead and type roomtune into a search engine. RoomTune started with me George. How do you think the hobby got the term room tuning. Look it up for yourself in TAS, Stereophile or any other audiophile magazine when they covered "RoomTune" from 1990 on. This is where you insert your snappy put down_________:) But just remember George those magazines have already been printed many years ago. It's call audio history. You don't have to like it, just like you don't have to like Class D amps. You also don't have to like me, but your missing out on a fun audio guy.
I think some guys here try to hard to be relevant and it causes them to become the opposite from what the hobby is and is about, the enjoyment of listening to music. I think most here have experience with A, AB and some D. And with that experience a respect is given to all the amp types. I personally think the OP is pretty clear. "the future of audio amplification" It's not a trick question, and it's not a put down for what any may like the most. Trying to tell all of us that we're going to someday see innovation stop, well that's simply not going to happen. I don't care if the next Class is W, innovation is the future.
The person in the thread bought two stereo amps and is using them as monos. He did not A/B using one stereo amp versus mono (however. I have and it is not close....you want dual mono IceEdge). He just listened to dual mono. However, since the Hypex modules are dual mono it makes it a fairer evaluation. Basically he is saying that his dual mono stock IceEdge amps beat the dual mono Nord one up mono blocks (with Sonic Imagery op amps).
As kosst alluded to, class D is not a new technology and was developed largely by Phillips for the sake of specific engineering requirements such as one would find in an hearing aid for example. Class D has had a renaissance of late due in part to engineering or rather manufacturing convenience (who wouldn't want a kit you could pop in an aftermarket box).
No one has provided a logical, technical counterpoint to kosst's argument regarding class D other than experiential vignettes.
I for one have owned the gamut of amplification (including several class D variants with multiple iterations of Hypex and a DIY amp from Class D Audio). Class D was pleasant enough (with a tubed pre-amp), but failed to hold my attention and seemed vaguely flat and bleached for lack of a better description. I have regressed back into the archaic world of tubes (Trafomatic 300B integrated) and the music is back. To each his own. With audiophiles, the rubber meets with the road with duration of ownership.
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