It is silly, to avoid using stronger word. You originated this thread pretending you want to learn about class D, while knowing you hate it.
I will remember your login and will be careful to answer your posts next time.
I've learned a ton about Class D from this thread and I appreciate everyone's input (including yours). I began this thread after having a poor experience with Ice Power. I wanted to like that tiny powerhouse and kept trying to talk myself into getting used to its tonal qualities. My goal has been to learn about Class D in general as well as limitations and strengths of the technology. It's hard to not step on toes when seeking to uncover information that is potentially upsetting to promoters of the technology. I would not have began this thread if I had given up on this technology as the internet has enough trolls. Happy New Years to all classes of amp lovers. |
In learning about Class D, it appears that after the linear signal is destroyed and turned into a saw tooth wave form, the output filter? tries to put the signal back together...doing an incredible job considering the complexity of this task...but ultimately is unable to restore micro details to recreate the original signal...which people such as myself notice very quickly, while others either don’t notice or enjoy the new coloration.
It is silly, to avoid using stronger word. You originated this thread pretending you want to learn about class D, while knowing you hate it. I will remember your login and will be careful to answer your posts next time. |
G.,
You are correct and I shouldn't make generalizations. |
Hi Richard, actually what the performance comparison between CS2 and the M625S2+Corus combo highlights is that the latter com bo was designed to a price point Three times higher than Continuum S2, and that it contains circuit sophistications not possible to meet CS2’s pricepoint.
Were you to compare the performance of the class A/B M625 S2 to the class D M925 monos flagship, which costsover three times as much as M625 S2, you might be tempted to draw an equally unwarranted conclusion that class D is inherently superior to class A/B... Which of course would be a fallacy as well.
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One of the best systems I have ever listened to, with my ears anyway, was being driven by a pair of Anthem Statement Monoblocs. When I get the funds to change my amp I'll definitely consider Class D. |
There have been many positive reviews of the NC1200-based amps but for another perspective, read near the end of the linked review of the Mola Mola Kaluga.
http://www.monoandstereo.com/2015/08/mola-mola-makua-and-kaluga-review.html This review perfectly describes my experience with ICE Power. In learning about Class D, it appears that after the linear signal is destroyed and turned into a saw tooth wave form, the output filter? tries to put the signal back together...doing an incredible job considering the complexity of this task...but ultimately is unable to restore micro details to recreate the original signal...which people such as myself notice very quickly, while others either don’t notice or enjoy the new coloration. Perhaps my understanding of Class D that I mention above is incorrect and someone can correct me. |
I’ll repeat what I’ve said several times on this forum. I had a Jeff Rowland Class D Continuum S2 Integrated amp and to my ears it was musical and did all of the "audiophile" things very well. I rate it above every amp I’ve every had in my system; except the Class AB Jeff Rowland 625 S2. To be fair I have the 625 S2 with a Jeff Rowland Corus preamp and together they are in a totally different price category. In my system the 625 S2/Corus is just more musical and I submit highlights the shortcomings of Class D. At least in direct comparison with products made by the same manufacture. |
Absolutely, "musicality" is indeed subjective . I am not trying to convince anyone. My intention is to point out the inaccuracy of making broad generalizations about folks here who still like the sound of their Class A or AB amps better than the Class D amps they have compared against, and how that doesn’t necessarily mean they are only comparing against old Class D technology or less expensive Class D implementations.
I may not have defined "musicality" adequately but would add, the sound of the Mola Mola Kaluga described in the review linked to my prior post is not unlike what I heard from the Atsahs. Again, I thought they were good amps, just not as good as my other options. |
mitch2
Isn't the term "musicality" subjective??? Meaning not everyone will hear it the way you do...... |
I'm concerned that comments like yours, and other posters earlier in this thread, may give readers the false impression that switching to class D involves some sacrifices in sound quality. Class D did exactly that at my house. I want to make it clear to everyone considering a switch from class A/B to class D amplification that these sort of comments may have been accurate for some early lower quality class D amps but are definitely not valid for current good quality class D amps. Not sure what you consider "current good quality class D amps" but to confirm, my comments are based solely on comparisons with the Ncore NC1200 Acoustic Imagery Atsah monoblocks ($10K/pair). Once you've experienced the extraordinary improvements a good recent class D amp will make in your system, you'll begin to realize how inaccurate, no longer relevant and simply untrue these types of comments are. Again, not here. My evaluation started with four amplifiers, all of which I owned and the Class D Ncore amps were the first eliminated. There were indeed sonic trade-offs and the Ncore amps did some things quite well (bass, tone, power, body and lack of noise). For some, those attributes at would be enough since they were enjoyable to listen to but, for me, there was a missing musicality factor that ended up being a deal-breaker, at least in my system and to my ears. The Atsahs, like Merrill's Veritas, use the stock NC1200 amplifier and power modules. I would like to hear those amplifier modules with a linear power supply as in Theta's Prometheus and I would also like to hear the NC1200 modules with an input buffer, as some are using like, I believe, Mola Mola in the Kaluga. I can only rationalize these sorts of comments by assuming that these individuals have obviously never auditioned a recent good quality class D amp in their system or anywhere else. Although it's possible they're just parroting comments they've heard years ago about early examples of class D. Again, be careful painting with a broad brush. Some of us have indeed auditioned and even owned amps considered to be "good quality Class D amps." I ended up voting with my wallet. Class D amps are obviously getting closer to sounding as good as really good Class A or AB amps and in some specific implementations may sound better. The Atsahs were good sounding amps but they were not as good-sounding as my other options. There have been many positive reviews of the NC1200-based amps but for another perspective, read near the end of the linked review of the Mola Mola Kaluga. http://www.monoandstereo.com/2015/08/mola-mola-makua-and-kaluga-review.html |
Classes G, h have the same advantages of reduced weight and size that class D allows to a lesser extent. The power supply is "variable" based on the signal.
BTW, is the highly rated Benchmark AHB2 amp considered Class D? |
savdllc,
You stated: "
but if one is chasing greater efficiency than Class A without sacrificing as much fidelity as Class D tends to do, Class G and H amplifier tech would seem to be the best choice."
This statement implies that class D requires you to sacrifice significant fidelity when compared to class A/B. As a user of various decent quality class A/B amps exclusively for about 30 yrs (beginning with Adcom and then McCormak and most recently Aragon) before trying various good quality class D amps (beginning 2 yrs ago with a budget ClassD Audio SDS440SC then an Emerald Physics EP-100.2SE and currently D-Sonic M3-600-M mono-blocks), I can assure you I never felt I was sacrificing any fidelity with class D.
With all 3 class D amps I actually experienced quite the opposite; immediately noticing significant improvements in noise level, bass response, mid-treble fidelity being very similar to class A/B with my initial budget class D and clearly superior to my former class A/B amps with my admittedly better quality most recent class D amps.
I know there are many here on Audiogon who have discovered switching to class D is all gain with honestly no pain. I'm concerned that comments like yours, and other posters earlier in this thread, may give readers the false impression that switching to class D involves some sacrifices in sound quality.
I want to make it clear to everyone considering a switch from class A/B to class D amplification that these sort of comments may have been accurate for some early lower quality class D amps but are definitely not valid for current good quality class D amps.
Once you've experienced the extraordinary improvements a good recent class D amp will make in your system, you'll begin to realize how inaccurate, no longer relevant and simply untrue these types of comments are.
I can only rationalize these sorts of comments by assuming that these individuals have obviously never auditioned a recent good quality class D amp in their system or anywhere else. Although it's possible they're just parroting comments they've heard years ago about early examples of class D.
I'm grateful I ignored these class D myths and opted for an open minded home trial and suggest others do the same.
Concerning class G and H, I have never heard either but I'm interested in hearing them. Being an extension of class A and A/B amps, however, I would expect them not to have the same advantages of reduced weight and size that class D allows.
Thanks,
Tim |
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savdllc
I'm afraid I don't buy your premise that class D is always behind A/B, or even behind class A universally. I'm listening to class D precisely because they were as good as heavily class A biased linear amplifiers, though just like linear amps, I can see them having limitations with specific difficult to drive speakers.
Further, I don't buy that ranking tech in order really helps us understand sound quality very much at all. I assure you I can make a terrible sounding class A amplifier. :D
I think while it's cool, and fun to understand what's different, and how compromises and problems are solved, and how dac X is different than dac Y, I'm not one who puts this above personal impressions.
Best,
Erik
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Thanks for the link Tim. This quote tickled me. Much the same with converters. If you know exactly what to look out for in a chip, you can find chips that are really suited for use in a $1000 product that, for the price, will offer fantastic performance, simply incredible value. Speakers ditto: You wouldn’t believe the performance of some $10 drive-units, but if you’re hung up on exotic cone materials, you just won’t discover those. |
I’m not sure if anyone has covered this (I didn’t read all 8 pages), but if one is chasing greater efficiency than Class A without sacrificing as much fidelity as Class D tends to do, Class G and H amplifier tech would seem to be the best choice. For those unfamiliar with this tech, voltage is constantly varied across multiple supply rails to the output transistors, allowing current to flow based on the constantly changing demands of the source material.
This greatly improves both efficiency and headroom, and perhaps most relevant in this discussion, allows the amps to run in pure Class A bias for a relatively large portion of the listening range with massive Class A/B power reserves for handling peak demands. Arcam (Class G) and AudioControl (Class H) are the most accessible options for this tech, though I’m sure there are others out there as well. About the only downside is that it’s an expensive design compared with more traditional tech, but as we head into the future where efficiency requirements are becoming more stringent, this is the best option I see for preserving audio fidelity. Just my .02. :)
-David |
seanheis, I thought that anyone wanting to learn more about class D amplification may want to hear from the horse's mouth,inventor of UcD (Universal class D) and the much newer NCore class D devices Bruno Putzey,, from interviews he has given on the links below.
http://ultraaudio.com/index.php/feat...audio-part-onehttp://ultraaudio.com/index.php/feat...audio-part-two
He discusses many interesting specifics about class D in a manner that is articulate and informative without needing to be an electrical engineer to understand. I found his discussion of the feedback loop (" there is no such thing as too much feedback") and switching frequencies ("A reasonable switching frequency for a class D amplifier is just under 500khz") especially relevant to this thread's content thus far. Please read these attachments. Thanks, Tim |
call me stupid but what do you mean by a "Output Filter" ? A L/C for you amp? Thanks, I am thinking about a Bel Canto but have never heard them.
You might want to hear them first. They are not for everybody. Most people feel that they are incredibly clean sounding with great control of the bass. However, some people also feel that they sound lifeless in the midrange compared to high end linear amps. Of particular importance is the module that is being used. Of less importance is the brand name responsible for putting the module and power supply in the case and tweaking the input stage to create a house sound. Tube preamps can help with the lifeless sound, although some prefer that sound. Good luck. |
call me stupid but what do you mean by a "Output Filter" ? A L/C for you
amp? Thanks, I am thinking about a Bel Canto but have never heard them. Class D amps usually have an L/C filter at their outputs to prevent radiation of their switching frequency. |
Hi RSA, you are safe with Bel Canto... Like Merrill Audio, Rowland, Theta, and D-Sonic, they are reported to make make wonderful amps. Several years ago I review the now withdrawn Bel Canto REF1000 Mk.2 monos for PFO.... Here is the article:
http://www.positive-feedback.com/Issue43/bel_canto_ref1000.htm |
call me stupid but what do you mean by a "Output Filter" ? A L/C for you amp? Thanks, I am thinking about a Bel Canto but have never heard them. |
Hi keeponrockin, it is fabulous that you had an exceptional experience with the Leviathan.
Admittedly, I audition Leviathan several times at length, using my standard test tracks of piano, chamber, jazz/Krall, orchestra, and sax/vocalists, but only at RMAF.... What often happens at shows is that manufacturers bring along brand new devices fresh off the factory floor, with little or no break-in.... So, it is possible that I was experiencing the limitations of units which were not properly broken in.
Regards, Guido |
The snag class D still deals with is the control loop (feedback). Its easy enough to build a class D amp that does not use loop feedback. |
I feel very well qualified to report on my time ( 10 yrs.) with a pair of Class D, Red Dragon Leviathan monoblocks. I LOVE them. ... I don't hear the harsh and dark that guidocorona reports. The reviews were also just shy of stunning when new. With no mention from any one of such shortcomings.
I have been using an EAR 868 pre though. And it is a very nice "warm","sweet" and "tuby" tube pre. So I confess to "tuning". When I used a Mark Levinson 380S it was more bright. But not fatiguing , or harsh in any sense.
I will tell you that the sound is my number one criteria. However their absolutely effortless control, and comparatively light weight are very nice pluses.
My current listening room is mid sized, and the amps are great space savers. I have some Bob Carver Cherry 180s that I haven't even set up because I am so happy with the Leviathans. And I would also love to have a pair of brute solid state monos. But every time I look to see what the weight is. And going over 100 lbs. makes me think what I'd pay to not have a slipped disk. ... I'll still go big SS when the opportunity presents itself.
But if setting up a surround sound system, I'd have to sample the new line at Red Dragon. ... I'd buy them by the bunch !!!!
I don't know about all the other stuff out there. But RD is OK+++. |
Class C is great for ham radio! Ha!
Folks, most class D designs are really a type of Single Ended amp. Something we've been going back to last couple of decades. This may explain why D is finally getting there. The snag class D still deals with is the control loop (feedback). We're still learning - so expect class D to get better and better.
Sound quality depends on the inherent linearity of the amp w/o feedback. Tube guys know this well. Some of us are trying to do this concept with D. Won't happen overnight.
A is just another version of A/B. Bias is used to increase the operational linearity of the devices. It works to a point. Cost is serious $$$$ and heat. Some day, D will incorporate all these factors that are pluses in other topologies. Then we'll all stay cool dudes.... |
timrhu,
I agree, class C amps are not for you. But have you heard about the latest class D amps? WOWIE WOW! Where should I start?......
Later,
Tim |
AFAIK, class C is a poor choice for audio (better for FM transmitter).
Hate it when I make stupid mistakes like that. |
AFAIK, class C is a poor choice for audio (better for FM transmitter).
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My advice for anyone on the fence is do your homework, listen and decide for yourself. Only then will you know.
Well Mapman, if you would’ve said this at the beginning of the thread, we could’ve saved a lot of typing. It’s what I did, and decided class C wasn’t for me. |
Not much doubt that class D noise is independent of signal levels, and poses no unusual threat to speakers.
I own the Spectron monoblocks. Superb sounding amps, amazing value relative to cost.
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I'm not sure what NuForce are doing. It is possible that they adjust supply voltage to signal level, but that would only mean much lower noise (than for instance Icepower) at low signal levels. Noise level at max loudness would be the same as for the amp that doesn't do that (assuming same switching frequency and the filter) - equivalent to about 4mW on 8 ohm speaker. Icepower doesn't adjust the rails and I'm pretty sure Hypex uses constant supply voltage. With constant supply voltage amount of switching noise at 90% or 10% duty cycle would be most likely 1/2 or even 1/3 of the one at 50% duty. |
I’ve seen it on the scope, with Nuforce 9se V3, you need to see it for yourself.
Lower or raise the signal level at the same frequency, then increase or decrease the scopes sensitivity to the same visual appearance, and you’ll see the SF noise remains the same. Forest and trees sunshine.
BTW it was this amp that gradually cooked the WP8’s tweeter voice coils, and the owner (a reviewer) was never abusive with high level, if anything he was anal about playing too loud, he now ones Gryphon Antillions, and has not looked back at Class-D.
Maybe in the future when they can rid this SF noise demon totally without any effects down into the audio band, even he concedes to this after what he went through.
Cheers George |
You might damage membrane from overheating, but most likely not from 500kHz switching frequency. As for switching frequency level following signal level - your understanding of class D output is poor. Amount of switching noise is constant independent of the signal level and in your Stereophile example equivalent to power of 4mW (of inaudible frequency) on 8 ohm speaker.
This switching noise is only dependent on the switching frequency and the filters cutoff frequency. Amplitude of the music signal has nothing to do with it!!! If anything, switching noise at extreme duty cycles will be lower. Signals of 10% or 90% duty cycle represent lower amplitude (in comparison to no signal represented by 50% duty cycle) of the root frequency (500kHz) and a little bit higher harmonics. After filter amplitude of 500kHz will be lower (and not higher) at high music levels.
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Sorry your wrong kijanki, the switching frequency to signal ratio follows the signal level in a proportional manner. and that 20% pod SF noise in the links I provided above, the SF noise does not disappear at certain levels of playing, it stays proportional to the level your playing.
And I didn’t ask you about tweeters playing 500kHz, but seeing you mentioned it, ask the poor sod I had to replace both the Wilson 8’s tweeter diaphragms on, because they were blu’ed with heat abuse from this 500kHz noise. They still worked but never sounded quite right, but they did when I replaced them. BTW he won't use a Class-D again, until he's convinced that the SF noise won't harm his tweeters again.
Cheers George |
Switched voltage 50-80V represent the highest output voltage. They show switching noise riding on a very small signal. This signal of 1V peak represents 63mW of the root frequnecy + harmonics on the 8 ohm speaker.
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Stereophile test shows about 0.5Vp-p - that is about 1% since switched voltage is in order of 50-80V. It comes from the fact that output filter is 2-pole making it -40dB/decade while switching frequency is about decade above filters cutoff frequency suppressing noise by 40dB. -40dB is 1%
As I posted before, speaker cables have no chance to radiate for many reasons. Tweeter won't play 500kHz, not only because of membrane inertia but also because of its impedance rising extremely high.
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There is about 1% of switching voltage noise on the speaker cable You need to rethink this. Look at the switching noise ringing on the test square waves Stereophile show when they don’t use their special Audio Precision’s auxiliary AUX-0025 passive low-pass filter to hide the switching noise ringing from view. This is what’s on the speaker cable on the $7K Anthem Statement M1 monoblocks, and it more like 20% of the wave form. Without Audio Precision’s auxiliary AUX-0025 passive low-pass filter http://www.stereophile.com/images/1212AM1fig02.jpg With Audio Precision’s auxiliary AUX-0025 passive low-pass filter http://www.stereophile.com/images/1212AM1fig03.jpgCheers George |
Talking about Spread-Spectrum during cold war could put you in a prison (top secret). Today all CDMA cellphones (Verizon, Sprint etc.) use spread spectrum. It is interesting application for class D, especially when receiver reacts only to average value (no keying needed). |
The difference, way back when, was in the highs, where Class D was kind of grainy compared to a single-ended transistor amp used for comparison. |
Perhaps this explanation will be easier to understand: If you make loop of a wire conducting electric AC current the radiated EMF will be proportional to loop area. If you reduce area to almost zero (like wires together in a cable) the radiated EMF will be almost zero. |
There is about 1% of switching voltage noise on the speaker cable since
filter is not perfect but, as I said before, 1/300 wavelength antenna
won't radiate. In addition, electricity in speaker cable flows in both
directions canceling the most of RF (if any). When you place radio
directly on the wire you might get some capacitive coupling, but I doubt
it. Many speaker cables are twisted making it completely inefective
(better than shield) for electromagnetic radiation or capacitive
coupling (both ways - from cable or to cable). You may find this of interest: https://www.maximintegrated.com/en/app-notes/index.mvp/id/3977scroll down to: Minimizing EMI with Spread-Spectrum Modulation |
When electricity flows in two wires in opposite direction it tends to cancel radiated EMF or capacitively coupled noise. Same goes for receiving - the closer two speaker wires are - the less susceptible they are to pick up anything. Twisted pair exposes both wires symmetrically to external fields making them almost immune to coupled or radiated noise. That's why in any circuit design signal and return should always go closely together to avoid any loops. The point of my post was that cable (two wires where electricity flows in opposite direction) is a very poor antenna for radiating and receiving. Twisted pair is practically no antenna at all. |
kijanki ... electricity in speaker cable flows in both
directions canceling the most of RF (if any) ... There's nothing inherent about an AC circuit that makes it immune to RF, so it isn't clear what your point is here. |
There is about 1% of switching voltage noise on the speaker cable since filter is not perfect but, as I said before, 1/300 wavelength antenna won't radiate. In addition, electricity in speaker cable flows in both directions canceling the most of RF (if any). When you place radio directly on the wire you might get some capacitive coupling, but I doubt it. Many speaker cables are twisted making it completely inefective (better than shield) for electromagnetic radiation or capacitive coupling (both ways - from cable or to cable). |
Hi all, in olden days, with the NuForce and M312, RF leaks were of some concern... My old FM tuner did pick up hash from the amplifiers if when held less than 2 feet from the power supply of the amps.
However, newer amps like the Merrill Veritas and my current Rowland M925 do not radiate at all.... AM and FM bands are not affected at all, not even if the tuner is placed on top and is in direct contact with the amps.
Without making a broad generalization, I suspect that FM leakages might today be less common than in the past. Perhaps more of historical interest than anything else.
Worth checking out though, particularly when testing older class D amps.
Regards, G. on the |
georgelofi,
Thank you for the further clarification. I just tried your suggestion with an older (non-muting) portable radio in the 500-800 khz am/band range on my amps with results being no discernible change in sound.or level. Reassuring results.
Thanks again,
Tim |
I read a tip that a portable am/fm radio could be used as a crude detector for any RF radiation emitted by a component.
Yes for smps leakage, should also work not that I tied it for Class-D switching frequency leakage. Tune down low and try at different frequencies between 500-800khz on the am/band, so it’s off station not getting a station signal just white noise (some portables mute these are no good to use), then switch on the smps/class-d, and go close to it with the radio, and see if you get a change in sound or level. Cheers George |
atmasphere,
Good points about class D amps being immune from noise due to their modules or the smps but that RF radiated noise could be a problem for other equipment nearby and even pacemakers and other electronics either within or separate from one's system. I was warned of possible RF radiation about the same time I purchased my first D amp.
I read a tip that a portable am/fm radio could be used as a crude detector for any RF radiation emitted by a component. The instructions were to tune to a spot on the dial that is between stations that is relatively quiet, turn the volume control to about 3/4 and move the portable radio slowly around all sides of the tested component. The point being that if the component is radiating any RF signals/interference it will be indicated by the portable radio producing a change in sound once it is in the proximity of any component being checked. I did this test on my D amps on the am and pm bands (since the tipster didn't specify a specific band) and I noticed no changes in sound coming from the portable radio but I hope this was a valid method for RF radiation detection.
Seanheis1 stated:
"
Maybe we will start seeing Class D pre-amps then... "
My understanding is that class D pre-amps would not have any significant advantages over traditional tubed and ss pre-amps, that I believe all operate in class A. This is mainly due to the signal amplification being so small in class A pre-amps that heat and energy efficiency are not significant issues as they are in tubed,class A and class A/B amps.
Tim |
NCore1200, not on the lower end NC500 module... My bad!!!! The NC500 is their newest most advanced module not mentioned anywhere on their site, avalible only to selected few, and is in the BelCanto Ref 600 monos, but BelCanto used their own filters instead of what comes with it. Cheers George |
Maybe we will start seeing Class D preamps then...
Perhaps. Delta-Sigma D/A, A/D converters, SACD and DSD are already class D. |
