Martin Colloms, the editor of HiFi Critic (ad-free mag from the UK) have recently published the review of several different Class-D amps, together with an in depth technical analysys and measurments.
His conclusions were not favourable, to say at least:
"I regret that not a single model merits unqualified recommendation. Price is not the issue; the poor listening tests speak for themselves. (...) At present we have to take the prudent view that good sound might be possible from switching amps, but we haven't heard it yet."
BelCanto REF1000 (ICEpower) - score 10.5 pooints "The ICE power module used has a dependable reputation, and the design is well built and finished as a whole. While I would not suggest that you shouldn't try this amp, on sound quality grounds alone I cannot recommend it for audiophile use."
Channel Islands D100 (UcD) - score 13 pooints "While I have reservations about a number of aspects of sound quality, and advise personal audition, given the solid lab results (...) the overall performance and the moderate price, these CA Audio monos do make it to the 'worth considering' cathegory."
NuForce 8.5V2 (proprietary technology) - score 9 pooints "Yes, the price is good for the power output. Yes it's pretty, light, small and runs cool. However, the sound quality simply does not justify recommendation." (on top of that the NuForce amp measured very poorly - Elb)
Pro-Ject Amp Box (Flying Mole) - score 5 points "I'm sorry to say that Project (...) was a real disappointment in the listening tests, and can't be recommended."
Just as a point of reference, recently reviewed Krell 700CX scored 100 points, CJ Premier 350 - 110 points and ARC Ref 110 - 135 points.
At least someone have had the balls to say it. This is why HiFi Critic is THE mag to subscribe.
9. "Use steep low pass filters to limit the upper high frequency range, partially negating the purpose of wider bandwidth, e.g. SACD, source material while resulting filter phase shifts may be audible in the working band" Don't know what he means - Icepower has 65kHz bandwidth (-3dB) and typical phase shift at 20kHz.
10. "Have input circuits which are highly susceptible to higher frequency input signals including upper band noise shaper noise and DAC artefacts, and which then contribute to poor treble sound" Why input circuit are more susceptible ti higher freaquency - I don't know.
11. "Have output circuits with poor high frequency resolution resulting in high levels of intermodulation products at the high frequency end of the spectrum" Resolution is unlimited (analog) and IM distortions for my Rowland are 0.0005% at 10W 4 Ohm 14kHz/15kHz. How many other amps can do that?
12. "Have 'sampler' noise shaped noise floors which vary dynamically with the level frequency and complexity of the input signals" I don't understand this language - what samplers is he talking about in analog modulator?
13. "Have comparatively small power supply reservoirs, in the light of their low frequency output current potential" My Icepower being smallest of the series has peak current 11A. Larger 201 has 20A and largest 501 has about 50A.
14. "Have thermal dissipation limitations due to the small power module size which means that thermal dynamic variations are present in the performance with time" Nonsense - my amp dissipates abot 5W and runs completely cold. Output switchers (Mosfets) have close to zero resistance when "ON" and switch within nanoseconds - not much power dissipated there (even no heatsinks).
15. "To protect the fragile output stages all kinds of pre-clip, and aggressive fold back protection regimes are included which are frequency dependant and are also programmed for duty cycle" Again - tossing terms. Output is more robust than traditional amps having strong Mosfets in H-Bridge and all sorts of protection. Foldback protection is used only in linear regulated supplies (not used in amps for output power). Someone was testing Icepower at full power with music, sinewave and noise for many hours - found them to be exceptional. I can find it if you want.
16. "Operate at an equivalent sample rate which is insufficient for good resolution above 7kHz. DSD 1 bit pulse-width modulation operates at 2.4MHz, nearly ten times the rate used in Class D amplifiers" It does not sample anything and has unlimited resolution at any frequency (it is analog). Has bandwith limit of 65kHz because of 0.5MHz carrier. 2.4MHz he mentiones or 2.8 MHz with SACD has different purpose (sampled system Nyquist - there is no DAC here)
17. "Deliver high constant DC voltages relative to local ground (up to 70V) at the output terminals (of course not between the +,- terminals) and hence the loudspeaker connections and cable" DC voltage on output of my amp is under 1mV. What he means by "High Constant DC Voltage"? I don't know terms like that. This is garbage - believe me
Just one more comment to pnt. 17 - I said I cannot understand what he's saying. It looks like he things there is up to 70V of constant DC voltage on the speaker terminals???? Please help me to understand this!! I don't know what bothers me more claim of 70V DC on the speaker terminals or terms like "Constant DC" (had impresion that DC is constant by definition)
Kijanki, thank you for your clear explanation. I'm affraid Martin Colloms should go back to school. If he is not chicken he should also give his response! :)
My Icepower being smallest of the series has peak current 11A. Larger 201 has 20A and largest 501 has about 50A.
has an ambiguity. The 50A peak current you mention- is that the output? Assuming a 1 ohm load and 50Amps, that's 2500 Watts. Assuming a 2 ohm load that's 5000 watts... So into what impedance does this spec occur or is it 'marketing'?
I paired the MBL 101Bs with the Spectron Musician III signature. It was great. So good in fact. that a friend purchased both items from me and is thrilled. I moved on to the MBL 101Es and MBL 9008 mono amps. But, for the money, the Spectron/111 combo is tough to beat. If you get 2 and run them balanced in mono you ought to really have something special.
Kijank, I want to thank you for taking the time to unmask this pretender, Cplloms.
I am just a listener. One critic of class D, and tube lover extraordinaire, told me recently he can hear class D sampling. When I questioned how, he used the example of upsampling DACs vs. non-upsampling. I had to agree with him on the difference of those two. I also had to tell him I cannot hear any similar sampling distortion in the ICE amp I am using, H2O.
From what I think I understand from what you said, ICE modules do not sample. Am I correct here? That would explain why I do not hear anything.
I can put my ear directly to my drivers and hear nothing but pure music. There is no noise.
Another question I'd like to put to you is whether you have found everything inserted into the best class D amps has to be as faultless as possible?
Maybe I shoud stay out of this one, especially as I do not have time to read all of the posts, but.......
The critcism that not all of the vendors disclosed all of their specs is no reason to find fault in them. Most here have been around high-end long enough to know that specs, i.e. measurements, are just design tools for the guy who design the stuff. (We have been making and selling amps, conventional and switching, for over 20 years. Without once "disclosing" all of the specs. Is there any reason to?)
Yes, a lot of guys like to look at the numbers, but since when could anyone say how something will sound based solely on numbers? If we could, tubes wouldn't be as popular as they are.
Several have already said so, but let me reiterate as a manufacturer of switching amps:
Synergy.
Not every amp will sound good in every system. If they did, we would all own Carver amps driving Bose speakers. But obviously, that is not the case.
Yes, these amps are not for everybody. I do not know of anyone making them that claims such.
Likewise for fine companies like AtmaSphere. I don't see Ralph telling anyone that tube amps are the only way to go. (I only point out Ralph as I have friends that own his products, and they sound good in the right system.)
Martin Collums and his friends may not like them, and I can accept that. To each his own. To dismiss them all, based on his perceptions would not be an enlightened positition. Listen first, then make up your own mind.
To be perfectly honest, I have heard listeners say that our (switching) amps sound "very tube-like".
Hello Kijanki. Excellent review of the review. I would point out only that
"Have thermal dissipation limitations due to the small power module size which means that thermal dynamic variations are present in the performance with time"
has a lot of sense and if designers did not so proper and extensive thermodynamic analyses then this is exactly what is occuring...with time.
Don't measure tmeperature outside the amp - measure it inside the small power module size and at not in one point... Nobody cheated physics yet
"To be perfectly honest, I have heard listeners say that our (switching) amps sound "very tube-like".
... and it is because in all probability they do. Most published measurments of switching amplifiers distortion patterns are very similar to....that of the tubes. Strong 2nd harmonics and strong even harmonics.
I personally love to read in Stereophile comments of reviewers on most of class D amps they review: "tube-like", warm, musical etc...and then glance to John Atkinson measurments with huuuuge 2nd harmonic distortion etc
I love expression "life-like" be it tubes, snakes or whatever...
ICE modules do not sample - they have analog sinewave oscillator/modulator converting input voltage to duty cycle and drive output switches (Mosfets). They resemble now more of sigma-delta modulator. Hypex is also analog and probably most of the others. (Hypex has half bridge output and sounds more like very good Class AB amp versus ICEPower with Full Bridge sounding more like very good tube amp)
Sampling is not even possible since to preserve 16bit resolution at for instance 1kHz - carrier frequency would have to be 65536*1kHz=65MHz. Just imagine bandwidth of my Rowland would require 65kHz*65536=4300MHz carrier. I wish it could be possible since one could take SPIDIF and run to PWM using just some DSP manipulations.
I heard claims of small amount of carrier residue causing intermodulation with audioband on the tweeter - which is only possible if tweeter can move membrane at this (0.5MHz)frequency.
Oversampling itself was created to allow filtering of the carrier with gentle filters with even group delays (Bessell) preventing wrong summing of harmonics in passband. My Benchmark DAC1 uses statistical manipulation to achieve equivalent of 1milion times oversampling and 24-bit resolution to drive output DAC at only 100kHz (audio DACs have lowest THD at around 100kHz).
Stereophile reviewed CODA S5 class A amplifier and compared findings to older Class D Bel Canto Evo amplifier. CODA was little bit better. In letter to Stereophile president od CODA expressed happiness that his amp came favorable in comparison with as he said "such great amplifier as Bel Canto Evo". There is no more honest praise of the product than one made by competition.
Interestingly Coda had more hiss at the tweeter than Bel Canto.
I chose Rowland since I heard That Jeff Rowland is classy guy and did not released bad or mediocre product in 20 years. He switched now his production to 100% Class D (Icepower). Rowland 102 is built nicer than Bel Canto and was cheaper at the time. I have heard a lot of very positive things about H2O.
Peak current I mentioned is the current limit of the amplifier output to speaker. 20A means that my amp can put that much current on the speaker. Nothing unusual - many amps have similar spects. It is rated 100W at 8 Ohm and 200W at 4 OHm - both with 0.2% THD 10Hz-20kHz. As for impedance - amp can drive 3 Ohms min (larger ICE drives under 2 OHms).
Ar-t I agree absolutely. Synergy is probably one of the most important things.
I respect people who can honestly say "I don't like it" even if it costs $500k, but I don't care much for blindsided people who try to present pseudo-sientific reasoning.
Being subscriber to Stereophile for many years I have a lot of respect for technical knowledge and integity of people there. They present detailed measurements but put more stress on impression with different co-equipment and different music pieces. Technical aspect is always interesting but is secondary to sonics.
Amp is close to 95% efficient and does not have to be large to do so.
"thermal dynamic variations are present in performance" - thermal dynamic variations of what? This is still jibrish to me.
Let me place here results of test made by somebody to 1kW icepower and 100W Icepower (same as mine). Notice that he tests 1kW amp with no hestsinks at all. If you take into consideration that average power in music i very low (only few percent) statements about "Thermal dynamic variations" are complete nonsense. Read below:
"Originally posted by dmfraser I operated a sample 1000ASP on the bench delivering 350W average of pink noise into a 4 ohm load for over one hour with no additional heatsink and the metal case stayed below 55°C.
However, higher levels would make the power supply voltage go down to act as a thermal compensation. Much nicer than just shutting down.
However, with 1214W of sine wave, partly into clipping, after about 35 seconds, the output level would drop to about 600W by the protection circuitry. Remember this is with no additional heatsink.
The 200ASC, I was able to operate with sine wave at 100W into 4 ohms continuously. Turning it up, with sine wave, the module would shut down at about 214W.
However, with pink noise at 100Waverage and a 6 db crest factor, the 200ASC would run all day without shut down, until I was tired of tying up one of my Audio Precisions with it. It would also run all day with music, driven hard where the output limiter was set to a peak limit of 210W maximum. That is, the limiter would allow small amounts of clipping. Driven so the limit light in our external optical limiter was on essentially continuously.
We're quite satisfied and will be ordering production quantities of the 200ASC shortly."
Kijanki, not to detract from your comments of the review of the review, but just so you know the numbers that are quoted are not speaker current. If it were:
First, reality: For 100w into 8 ohms, the current would be about 3.54 Amps. For 100w into 4 ohms I = 5Amps, for 2 ohms I = 7.1Amps
then the 'claim': working it backwards, 50A into 4 ohms is 10,000 watts into 2 ohms its 5000 watts.
So- 20Amps into 4 ohms is 1600 watts. But your amp does not make that kind of power!
I agree these numbers are common in a lot of amplifiers, the 'FWIW' part is that the numbers are *not* current in the speaker. I suspect they are power supply numbers, that number being the current output of the supply when shorted for 10ms. Our MA-2 amplifier which is an all-tube amplifier measures about 80 Amps using this technique...
Quoted current - as I said before is the peak current and has nothing to do with average power. It is used to show how well amplifier can respond to impulse.
Internally my 200ASC Icepower can deliver 48V to speaker what would make at 3 Ohm 16A current. Limiting circuitry is set to 11A. Power delivered to speaker will be 363W.
I don't know how long this pulse can be or what would be crest factor with multiple pulses but would like to point that Bel Canto rates the same module at 300W (10% thd)
Kijanki, On my 1 ohm speakers, there is very very little resistance in the way of the signal. The signal is beautiful and natural when it is left alone. Oversampling, as elegant a circuit as is, cannot operate without introducing some timing error. That flaw is painfully obvious on my Scintillas.
These amps are so good at being faithful to the signal, minute distortions, usually deaf on listeners, work their way through. I have found speaker cables must be bereft of insulation, DACs must be simple.
Muralman - I have no experience with high end DAC circuits but my Benchmark has surprisingly clean and transparaent sound. Part of this is due to anti-jitter circuitry. Jitter produces sidebands of very low amplitude (typicaly -80dB) but very audible since not harmonically related to root signal. It sounds less clean (hash) but often people prefare sound with some amount of hash or thd. They often call clean systems "analytical". Sombody even said, after listening to hi-end system, that everything (instruments) sound separate and he preferes all mixed together. I suspect I have similar hearing limitations with my audio experience.
I will search for more info on oversampling. I just don't know how they can filter out carrier of 44.kHz. With the ratio of 2:1 Bessel filters just start attenuating - no matter how many poles. Usage of other filters will affect the sound.
Kijanki, I hear you. I know someone who told me they feel music should be blended because that is how he hears it in the audience. He went out and bought the same speakers as I, and put a Krell on them. Talk about opposing forces.....
My DAC has no anti jitter circuitry. I believe that is the clock, the same thing that is scalping the crud off the signal supposedly. There is no clock that can get the signal perfectly aligned. There are too many complexities. It's sort of like electron studies. It can't be done, because that which is observing unavoidably effects the outcome of the measurement. It is all explained under Quantum Theory.
Like I said before, I can get right to the ribbons and hear nothing but pure music.
By the way, try a naked wire for your speaker cable, then try a wide ultra thin cable. This is a very interesting experiment.
Muralman - people are often confused and becuse they like guitar sound on 30W Vox (remeber The Beatles)with tubes and no feedback (high thd) and want their home system to be like that - close to real performance. Home system of course should not change sound - even if clean jazz guitar does not sound as lively as distorted one. Issue of real life performance is very interesting because real life performance is often very poor (poor acoustics, bad seat etc) - not the studio level what becomes clear after you compare sound from the studio and the concert records.
Jitter is resolved by means of PLL - single loop in cheaper and double in more expensive CD players. DAC spits out with the rate from the disc (to be exact from internal clock phase lock looped to CD and going thru FIFO buffer at this rate). Good transport means lower jitter but is costly. Another method is to completely reclock signal to DAC's clock, upsample it and send to DAC in corrected intervals. Benchmark is trying to do it (correct)acurrate to 5ps. Both methods produce great results - reclocking gives better supression of the jitter and allows to use cheap DVD player as a transport.
I checked audio DACs at Analog Devices website - almost all of them are sigma-Delta (oversampled). There is still few with traditional architecture carrently being discontinued. All Dacs shown as 24-bit are sigma-delta. Traditional Dacs go only to 18-bit (maybe 20-bit).
Dielectric in the speaker wire is evil (even teflon) - I agree. Latest trick is to use foams (lower dielectric constant than solid material) and wide tubes so that wire has only contact with one wall. Another problem is to compromise between low resistance and low inductance (thick wire) and skineffect free (thin wire). Skin effect starts at gauge 20 at 20kHz and splitting wire into many helps only a little (more surface area but still in the sum of magnetic fields). Tapes are wonderful but not practicall solution. I replaced coils in my cheap speakers with the "tape coils". It sounds better - at least I'm telling myself. Capacitor in series with the tweeter is the reson for brigtness in many speakers. Mylar caps are horrible (high dielectric constant) but Teflon are too expensive. Polypropylene paralleled by small teflon is the ticked. I also changed resitors to non-inductive. Every bit helps.
Kijanki, just reading your description of the path the signal has to go through to be cleansed leads me to imagine just what I hear from those DACs, forced. My music is free breathing, unrestricted. There is absolutely no audible distortion. I just can't listen to SACD, and I don't care to.
The two of us are discovering new rules of engagement when dealing with class D. I am thrilled with my results. It seems you are very happy with yours as well.
I recently heard the Onkyo A 9555 integrated amplifier. It is a Class D amplifier, and sounded excellent, and infact better than my SimAudio i-3. Its a steal for its price. I feel that it rightfully got good reviews from Stereophile and TAS. Onkyo makes profits by volume and selling it at a profit low margin, unlike most hi-end audio manufacturers who try to make profits by selling less volume at high profit margins. Thats the reason many hi-end audio manufacturers go out of business.
Your post mentioning jitter and PLL seems to be off-base, and probably ill-suited to this thread. Perhaps you would like to clarify it, but may I suggest in a different thread.
RF gumby:
Yes, I think I am in the right place. I am pretty sure I did not hit the bookmark for the Insane Asylum.
Or it might have something to do with my being an RF engineer, partially out-of-place in the role of front man for a minor high-end company. (It fell upon me by default. Long story.)
The "talking points" that were mentioned as proof that Class D amps are by design inferior seem to be a mix of technical points and sophistry. I could make a similar list for any number of other technologies. Equally convincing, equally misleading. If I didn't know better, I would come to the conclusion that someone had an agenda.
However...........some points do have a bit truth to them. Some Class D amp modules have an output frequency that does vary with speaker load. The maker(s) of these modules clearly show this in their data sheets. I would think that anyone who truly has a background in electronics design could understand how changing the impedance a second-order LPF operates into could have an effect on its damping ratio.
I believe the voltage on the output that he refers to is the Vcc/2 in the ICEpower-based units. They operate with only one polarity of power supply, and being a full bridge design, will have 1/2 of the rail voltage on BOTH output terminals.
Translation:
Don't grab your speaker cable in one hand, and ground in the other! Not a good idea. (Maybe that is why so many have shook-proof terminals.)
Also, there will be a certain amount of the carrier frequency on the output. Yes, it may be a few volts. Somehow, I don't know of many tweeters that will generate tons of IMD with that sort of voltage present.
As I said, some technical facts, seemingly massaged to possibly scare off the uninformed.
Icepower uses full H-Bridge of 4 Mosfets switching direction of the speaker between +VCC and GND. In spite of VCC/2 on the speaker terminals, voltage between terminals is zero. The only disadvantage of this scheme I know is that you cannot bridge amplifiers. My amp has 23.5V on speaker terminals - it won't zap you (voltage up to 60V is considered safe)
As to effect on the damping ratio - filter is within negative feedback and DF is very high. At higher frequencies it drops as I stated before to about 30 at 10kHz. What about DF of a tube amp at 10kHz? What about zobel networks on traditional transistor amps.
It has about 1% of the carrier - not important (cannot radiate and the tweeter produces IMD only if it's membrane moves - not possible at 500kHz).
Talking about "scare" - the scarriest part of Mr. Colloms presentation is the fact that he believes that amplifiers like Icepower or Hypex (he tested Channel Island D100 - didn't he) are sampling systems and have AD/DA inside with limited resolution.
Sure anyone can find something wrong with any type of amps. The wrong think to do is to pick possible deficiencies of different amplifiers and make general statement about whole class of them. At the same time he did not mention any positives like very low THD, extremely low IMD+TIM etc.
I would advise everybody to listen to Icepower, Hypex, NuForce, Flying Mole and make up your own mind.
"Simontju, Amp is close to 95% efficient and does not have to be large to do so."
1 - Even if efficiency would be 99.99% some heat would be generated and...dissipated somehow
2 - No heatsinks! I am talking NOT about chasses of the amp or whatever but inside the very small power module packed DENSLY with microscopic size electronics
3 - I can re-assure you that each responsible designer and manufacturer of class D module like Spectron, Bang & Olafsen, Philips did themselves or invited outside consultant(s) to make most comprehensive thermodynamic analyses.
If you have a 1000ASP, then it will have much more than 22 V on the output terminals, so I would not advise touching them. (Rowlan uses that module in some of their amps.)
As for the output network, I was talking about the damping factor, or Q, of the filter. Not the damping factor of the amp.
If Colloms believes that they have sampling stages inside, then he is ignorant as to their operation, or else one can conclude that he has an agenda. Modern Class D amps of the self-oscillating style (like ICEpower and Hypex/UcD) are basically an amplifier that is unstable, and use that oscillation to generate a carrier wave. (Unlike clocked designs, which no one seemed to like.) They use some simple circuits, in some rather clever manners, to modulate that carrier with the audio signal. Over-simplified story on how they work.
Imho Martin Colloms should make apologies because he tried to disqualified class D amps by using pseudo scientific arguments that underlie his lack of knowledge. This is funny: What would Mr. Colloms do if class D was the only type of amplification? Kill himself? :)
Increased ownership of class D amps. As little as a year ago, there may have been maybe a dozen posts. Some few of us were championing class D four years ago. We were laughed at then. Now there is strength in numbers. This is great!
I am elated to see in this thread manufacturers discussing merits -- or perceived issues -- with switching amplification. We consumers can only learn from these exchanges. I am however much less comfortable with veiled potshots about one's competition of the type:
"So into what impedance does this spec occur or is it 'marketing'?"
I appreciate a designer being proud of his own products, but there are more effective ways to demonstrate it. . . . than resorting to the 'lower' ground, which is not necessarily deemed a highly regarded marketing technique. Regards, Guido
Guidocorona, I was merely commenting on a spec that clearly was not possible as it was represented. I also demonstrated that with the math.
If you think I was taking a pot shot, I apologize. However, let me point you to a paper:
http://www.atma-sphere.com/papers/myth.html
The paper is about 5-6 years old, written long before class D was commonplace. The fact of the matter is that amplifier manufacturers have been placing specs like this before the public for years. I would prefer that the spec be placed in its meaningful context: that it is not speaker current but something else.
I've been watching the class D technology for some years as you must know if you've been reading through this thread (which has grown quite quickly!). Is it a threat to what we do? I don't think so, not because it might be better or worse, but for the simple reason that I am not going to be so close-minded as to think that nothing can beat what we do: there is no integrity in that.
We've been dabbling with class D for about 4 years and I plan to continue. As I've mentioned before, its a newer technology, and obeys price/performance curves that all new technologies follow. Right now we are in the middle of the curve. What that tells me is that we don't know yet where the technology levels off as it matures: it could go a long way yet! I apologize for my pragmatic outlook, but it is what has kept me in business for the last 30 years...
Ar-t - I have the smallest of the series and 23.5V on terminals. To deliver 5x more power they need voltage around 52.5V. I think it stays below safe level of 60V but agree with you that this might be of concern. I don't touch speaker connectors but with largest unit I would be concern about toddlers. Hypex is free from it.
As far as I know filter set at 65kHz has couple of chokes on one toroid (common mode chokes) and ouput capacitors. Frequency of this is in general fixed execept when Q is changing. Mine is listed at 65kHz at 8Ohm and 45kHz at 4 Ohm. Speaker impedance changes will affect frequency but it happens (if I remember) usually in lower frequency range. B&O lists idle frequency 400kHz-460kHz but for operating frequency they show 0-460kHz. I don't know what they mean - it cannot certainly be in audible range. Maybe they include audio signal in the spectrum? So - there are some changes in the carrier frequency and therfore its attenuation. Audioband should have some phase shift - about 20 deg. increase at 20kHz compare to 1kHz. Is it common?
There is something different about highs of Icepower (might like it or not). Is it caused by limited bandwidth or dropping damping factor?
Some people called midrange of Rowlands 201 being magic and almost everybody likes bass performance but highs sound different.
There is no easy choice in design of amps. Class A has about 1/8 of efficiency and large power units are costly if not impossible. Class AB have nonlinear element in the output and require modesty in design. General problem is setting negative feddback to deep to get specs. THD for instance is difficult to hear below 1% but I would not buy class AB amp with 0.001% THD or very High DF. Sane designer would use the most linear elements setting bias current really high and would bring down thd only below 1% and then would limit input bandwidth to one amp had before feedback to prevent TIM. Unfortunately companies are racing for best specifications. I would advise to take specifications, promtly discart them and just listen.
Class D bypasses many problems and I know this is just begining. Comparing them to traditional amps is fair when is done to units in the same price range.
Atmasphere, Thank you for your contributions to this thread. I was discussing this thread with a friend a few days ago. We both agreed how much we appreciate your contributions and how you participate with a constant high level of courtesy and professionalism. You set a standard we should all strive for.
"Unfortunately companies are racing for best specifications. I would advise to take specifications, promtly discart[sic] them and just listen."
Hmmmmm.. these stupid people from Spectron wrote on their silly web site:
" BLA BLA BLA BLA BLA BLA YADDA, YADDA, YADDA, BLA, BLA, BLA BLA BLA BLA YADDA, YADDA, YADDA, BLA, BLA, BLA BLA BLA BLA Conclusion: We hear time and time again that the numbers on the data sheet do not predict an amplifier's sound quality. While largely true in the past, today more and more parameters, measured correctly and even more importantly - truthfully reported - do reflect well some very important amplifier sonic characteristics. When you are considering buying any amplifier, the first question must be if it can drive your speakers at all. If it can drive your speakers, then can it drive them well. Can it drive them, at the very least, without euphonic coloration, muted treble and veil etc? The right approach is to check the amplifier's distortion level and output impedance at high frequencies(* - for class D specifically - my comment here) . Also look for peak current and its duration, flatness of frequency response, noise level, bandwidth etc. Of course, Spectron also considers the speed of the feedback loop and inclusion of the output filter in the feedback loop to be of great importance, even if an audiophile cannot really check on this. Each and every one of these measurements contributes to a gorgeous musical experience, and each deficiency will be readily apparent to the critical listener."
We have concentrated on the Rowland 201 because the most vociferous defender of class D happens to own that Rowland. I have not heard any of the Rowlands, and have no opinion of their sound.
The builder of my amps, the H2O (a 500A module amp), also makes the digital power supply amps. He makes no bones about it, he feels the 500A module, mated to his massive power supply, sounds better.
The point of this is there are a large number of class D amps. One cannot draw a general opinion through these amps, unless that opinion is derived from a built in love for tubes or solid state sound.
For my ears, Class D amp builders are not trying to achieve a sound like tubes or solid state. They are trying to amplify the truest signal to their ability. If it were the mimicry of tubes they were striving for, they would not have employed a passive filter to peel away the manufactured even and 2nd order harmonics, the very distortion that endears some tube defenders.
Recently I auditioned a higher order DAC. It introduced a lot more tubes into the mix. While the huge DAC did spit shine shine separation, and power, it's three more tubes obviously lent a good deal of color.
My preference, and I must insist it is my preference, is for less coloring, and more raw truth. My amps and preamp (class A) are doing that for me.
I wonder if Class D tends to shine more in certain applications than others. I note that some of the big supporters here have notoriously difficult speakers that would tax most amps. For example the Apogee Scintilla has an impedance curve that drops well under 1 ohm at certain frequencies; the MBLs, while not as brutal, are also tough.
I find it interesting that B&O (maker of ICE module) itself, in some of their active speakers, uses the ICE module for the bass unit, but conventional solid state amplification for the mid and treble amplifiers. Any reason for that?
there are a number of amps that will drive a difficult load, say under 2 ohms. just because an amp can drive a speaker doesn't mean one wants to listen to that speaker with a particular amp which drives it.
as i have said i find pnels and solid state difficult to enjoy for more than about a half an hour.
i am so accustomed to euphonic tube colorations that solid state amps and class d amps sound uncivilized, raw and aggressive by comparison.
The answer is "yes", but.........boy, am I going to step into it here..........the module that one would expect to be best for that particular speaker, based on its low impedance and power requirements, really doesn't work that well in that appication. (There is a reason that I know that answer.) Long story, and perhaps best not dealt with in detail in a non-technical forum.
Anyone desiring a more detailed answer should contact me privately.
That is a good question. Looking into it, B&O does employ class AB amps for mids and highs in their Beolab 7. While their flagship speaker, the Beolab 5, uses all 1CE amps. It's quite a mystery. I sent them a query.
Mr. Tennis, my system sound has evolved from one matching your experience to one now that is on all day long.
It didn't take me long to realize there were things you can do to bring out the best results. A remedy for your complaint, "solid state amps and class d amps sound uncivilized, raw and aggressive," is do not use over-sampling CDPs, and do not choose a digital power supplied module.
The ribbon speaker cable I switched to worked wonders as well. On the whole, music is dynamic, yet relaxed.
For my ears, Class D amp builders are not trying to achieve a sound like tubes or solid state. They are trying to amplify the truest signal to their ability.
This comment sounds like a strawman to me: I know a fair nubmer of conventional amplifier designers (tube and solid state) who have the same goal- this is nothing unique to class D!
Hi AR_T, please try post here a super simplified version of the explanation as you know it.
MRT, I am terribly sorry to learn about your physical and spiritual suffering caused by panels, solid state, switching amplification, and other such admittedly uncivilized, raw, and aggressive sounding technologies. In a sense I deem myself fortunate that -- being somewhat of an uncivilized and unrefined pragmatist myself -- I seem not to suffer from such horribly insidious and generalized malaises. . . . heck, I am so bad I even find tubed equipment can be delightful and eminently listenable.
I use CI D200s to drive my 104db sensitivity Klipsch LaScala and find the results spectacular. My guestimation as to why some people don't like the sound is because they don't like whats actually happening upstream. I find the D200 to be the most accurate amps I've heard. They have no sound of their own. They just get out of the way and let the music come through, like it or not.
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