Hi o,
I know the early Belden cable, very good for XLR runs due to the inherent noise-cancellation characteristics of differentially balanced circuitry (not applicable for SE circuitry). Once you get your room acoustics in order and you can really hear what your equipment/speakers are capable of doing, I predict a new interest in your quest: cabling and power.
Best to you o,
Dave |
Dave, I think it done snuck up on you too.
The cable I use to make my own, was once sold by Belden in 100 ft rolls to radio and TV stations; that lets you know it's some good stuff; they both demand the highest quality at the cheapest price. Belden no longer sells that cable to the masses. I asked for some replacement cable, and if it was food, the dogs wouldn't eat it.
Fortunately, I'm working on my last major improvement, and thanks to your excellent ideas, I know it's going to be a success.
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Oh no, o! Say it isn't so! What about the sonic influence of various dielectrics (smearing of the sound due to signal "absorption and release" time-misalignment), the winding geometry (reducing RF/EMI noise and phase shift), the use of active shielding (accomplishing the same as the first two to an even greater extent), and Graphene (improving conductivity), not to mention optimally matching capacitance and inductance to the input/output sweet spot of your equipment and speakers?
I don't know what cabling you are using, but I hope that some good ones "snuck up upon you when you weren't looking" for the sake of your excellent preamplifiers (and your ears).
Best to you o,
Dave |
I will try Class "D" when it get's as common as "bacon and eggs". In the meantime I will maintain my staunch prejudice against Class "D".
Did you know that the vast majority of people who hate "Black" people have never seen one up close and personal. If that can be accepted, I'm sure my stance on Class "D" amps can be accepted; in both cases there is no logical or rational reason for such a stance.
But seriously, I have already "verified" that computer sonics, and analog sonics, are impossible to tell apart, if the computer is done right; evidently it depends on the level of switching; but there are many indistinguishable differences that "audiophiles" claim to hear; such as six 9's copper; 99.9999% pure.
While there is a difference in the quality of interconnects, and it is due to the composition of the wire, the composite of silver plus copper for example, but that also has a scientific variable in ohms. When so many minute differences are carried to such great extremes, accompanied by extreme prices; without any scientific merit, I for one am quite dubious, as in the case of interconnects. I strongly suspect that almost any difference is interpreted as better; how else could you explain a 1K price for a 6 foot piece of copper wire?
Some of these differences are at a "subconscious" level; tube, and solid state for example. I think SS is best for rock, and tube best for "smooth sounds and female vocals"; but I am speaking of a tube pre and SS amp, where the difference is even smaller; when both are SS, then it's audibly obvious.
There are many dubious things on this forum, that I "strongly" suspect are no more than opinion, but "placebos" are good for one's mental health; that is, if the health of one's bank account can accommodate this feel good luxury.
I suspect I have become an "Audiophile"; it snuck upon me when I wasn't looking.
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Here is part of Lamm Industries ML3 Signature amplifier by Michael Fremer in 9/2013 Stereophile. The ML3s produced the most glorious, palpable, airy, detailed midrange I’ve ever heard from reproduced music. That part is easy. They pushed that performance envelope without going all greasy and congealed over time, as some tube amps do after the initial appeal of warmth wears off. The ML3’s standout features were its natural re-creation of instrumental attacks, generous sustain, and lifelike decay—all as close to live as I’ve heard, if nowhere near the real thing. It was quiet, fast, detailed, dynamic without reservation, transparent, airy, and extended on top. No sharp edges unless the recording had them, and no boredom-inducing global softening. The pair of them produced an enormous sense of space when that was appropriate, and, within that space, images of exceptional delicacy, three-dimensionality, and body.
It should be good for $140k/pair. This amplifier has measured -3dB bandwidth at about 50kHz - which is 15kHz less than my class D amp, that supposed to suffer from wrong harmonics summing. Please notice words "airy, and extended on top". Imaging also did not suffer. |
Are you going to be producing an amplifier anytime soon? Nope. Not my lot. I’m just a critical listener reporting what I hear and trying to understand why. I already have two generations of Bel canto Class D amps. I have yet to hear any hint of brightness ever with the newer one. Even with Dynaudio Contour monitors known to lean that way with the wrong amp. It is an all in one integrated the C5i so less to get wrong or right when matching . In fact one of the reasons I bought it was to be able to compare and contrast with what I had. And guess what, better bandwidth and improvements in general with a newer and still evolving technology is exactly the thing that leads me to keep testing the waters. As I said I do not doubt the relevance of bandwidth in theory, only is it an issue of enough magnitude in practice that most people would care these days when things are done well otherwise. Some people report brightness in some Class D amps. Same true with other SS amps. Probably even with tube amps to a lesser degree. But I am not hearing it at all ever, in fact less than ever, with my latest and greatest Class D amp. So I do not find the fears bandied about with the technology in general to be warranted at all in practice. Nor am I saying all Class D amps perform equally well either. Only the ones I own and know well for sure. That just proves to me it can be done now and today. I am not alone there I would say. YM always varies. Its nice to hear a maker of tube amps and another of passive pre-amps gives the competing technology some credit. Its only fair to point out where the achilles heels lie. Every product has one. All good information for the educated consumer to mull over when making a decision. |
So based on a combo of facts and experience I still see it as one of
theoretical things that exist but do not add up to much if anything in
practice for most.
Are you going to be producing an amplifier anytime soon? If an amp cuts off at 20KHz then expect phase shift artifacts down to 2KHz. If an amp cuts off at 60KHz then its 6KHz. If the cutoff has a steep slope the artifacts can be more severe. The trick, if you can't get bandwidth the way you want, is to not have a severe rolloff. You'd think this stuff is inaudible but it isn't. Many factors add up to how a given amp sounds and its plain foolish to attempt to focus on any one factor by holding it above others **or** below. They **all** affect the result. So you are right in a sense. But I'll give you an example of how phase shift can manifest. Years ago a dealer brought an MFA Magus preamp to me with the complaint that it was really bright in the phono section. In fact I had heard this problem in the preamp myself. I put it on the bench and found that in the RIAA equalization there was a circuit that caused the equalization to go to flat at 50KHz. This is a ways above human hearing. Normally the RIAA curve would be rolling off at 6db per octave. So I took the circuit out, thus restoring the RIAA curve (FWIW the RIAA did not spec the curve past 20KHz but it usually designers assume that it will continue with its 6db per octave rolloff as frequency goes up). The **very audible** brightness was eliminated! The dealer was thrilled, and MFA changed their production so that this circuit was omitted. Apparently they didn't like the brightness either, but had not made the phase shift connection. They said it was there to "improve square wave response". I'm sure it did that! If your amp does not have lot of bandwidth then you are in the same boat as a lot of SET owners and they seem to like their amps just fine. The fact is that its not the most important thing in the world. But don't confuse that with it not being audible at all! In a class D amp, most of the artifact that its going to have is coming from the input circuit and in that regard whatever amplification it has (probably an opamp) which imposes its own signature. That's a lot better than the signature that many transistor amps impose; opamps if treated right can be pretty musical. If the bandwidth is limited then the amp might not seem very bright and a lot of audiophiles (myself amongst them) cringe when things get too bright. You like your amp a lot so if your hearing isn't too off than I have to assume that the designer chose a reasonable set of compromises in the design. I guarantee though that the designer would prefer to work with greater bandwidth if possible. When they come out with the latest greatest replacement for your amp (which will happen sooner or later), take a look at the bandwidth spec and see if they didn't improve on it. |
atmasphere, I’ve pretty much heard it all , including Atmasphere amps. phase shift is just one factor that might acount for an expansive soundstage. You can’t equate the two or infer a large soundstage necessarily means phase shift being heard. if its truly phase shift that is there and not being mentioned then the reviewers need to go back to school perhaps. For example, my setup has expansive soundstage only on recordings made a certain way conducive to that. on others it is quite the opposite. So there is no evidence there of artificial effects of phase distortion that would persist constantly. Certainly nothing that I can hear with any of my speakers large or small. You might measure something but I doubt anyone could single it out listening. Maybe young pups with 20-20khz hearing and speakers with awesome bandwidth, but frankly there is a good chance that other forms of noise and distortion are what’s mostly occurring at the highest frequencies for various reasons, phase shift being one of many nasty things that occur there predominantly. Very little music does. Mostly just "air" at 20khz.. See the reference here: http://www.independentrecording.net/irn/resources/freqchart/main_display.ht So based on a combo of facts and experience I still see it as one of theoretical things that exist but do not add up to much if anything in practice for most. |
Wading through this discussion, I found myself reminded of the late neurologist, Oliver Sacks. He was, as I’m sure you all know, hugely interested in music and how we experience it. He was an enthusiastic devotee of the music of Johann Sebastian Bach, and was pretty indifferent to the music of Beethoven. He volunteered for a brain-scan to see how he reacted to the music of each composer, and the results showed that Bach noticeably increased his brain’s activity, while Beethoven showed no such effect. http://mentalfloss.com/article/23288/inside-oliver-sackss-brain-he-listens-musicI mention this because what I’m taking away from this lively discourse (apart from the technical details which is mostly beyond me) is that we all have our innate preferences. A sound that lights one person’s candle might have no effect at all on another, and some of these sounds might be actively irritating to a few. Our ears and our brain-wiring are all different, so what appeals to one group of us won’t appeal to another. Hence our differing preferences for and reactions to various classes of amplification. Personally (and I’ve alluded to this subject in my review of the Wyred4Sound reclocker, q.v.), as a professional musician, I like to be "inside" the music, that is, to be able to discern its details and building-blocks, but I still want the overall sound to be pleasing (musical) enough to be enjoyable. It’s a balancing act. As stated in my previous post in this thread, my ARC STi200 achieves this for me. It might not for you, though, which is fine. I’m not a tube-person, but I certainly can see (hear) why this sound appeals to so many of you. Would be very interesting to see what MY brain looks like on music. |
Companies such as Devialet are creating hybrid AD Amplifiers. In theory, that could be the best of both worlds with sound & efficiency. Are the hybrid amps subject to the same issues with phase & bandwidth?
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BTW has anyone ever noticed a reviewer complain about phase shift when
reviewing gear at a show? They can find all kinds of faults but seldom
if ever that. Are they not listening right or is it just not there?
Gotta wonder..... You see them writing about it all the time. Don't look for them to use the expression 'phase shift' though. Look for them to talk about the soundstage, how deep and expansive it is. That's one indication (but not the only one). The thing is, you can build an amplifier that only goes to 20KHz or so that can still sound pretty good (lots of SETs only go that high). The effects of phase shift are more subtle but they do exist. So you might be happy with what you have (which is good) but ultimately its all in comparison to what, and if you've not heard that 'what' then you just don't know how much better it can get. That's why many people listen to boom boxes. They just don't get how much better it can be. |
Kijanki 11-21-2016
One can argue that this phase delay might be beneficial since many
speakers have positive phase shift at these frequencies. I don't have
data for my speakers, but I picked one of the speakers reviewed by
Stereophile. As you can see on the phase diagram (dotted line) speaker
actually accelerates phase at the highest frequencies. Phase delay
caused by the bandwidth limit of my amp would improve summing of
harmonics (Al, am I missing something?).
No, I don't think you're missing anything, Kijanki, and that's an interesting point. As is frequently the case it's possible that non-ideal behavior in one part of a system can to at least a loose approximation offset or compensate for non-ideal behavior in another part of a system, and turn out to be subjectively preferable. And it is true that dynamic speakers in particular commonly have impedances in the top octave or two that are inductive, meaning phase angles that are positive. On the other hand, though, there are of course many other factors besides impedance and bandwidth that contribute to a speaker's overall time domain performance. Best regards, -- Al |
I had a fellow agoner over to listen to my gear a while back. He is a fan of David Berning ZOTL amps. I heard these at CAF last summer and liked those very much as well. He indicated he really liked my setup running off the C5i which is latest and greatest Icepower and pure digital integrated amp as well with both phono and line level analog inputs. I do not know the bandwidth. Its a non issue in regards to what I hear personally so I haven’t even given it a thought. But I still gotta know so need to look it up. The ZOTL tube amps I heard and the C5i had quite a bit in common in regards to the sound IMHO. More evidence its the overall execution that matters more so than the technical approach of individual quality parts.
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BTW has anyone ever noticed a reviewer complain about phase shift when reviewing gear at a show? They can find all kinds of faults but seldom if ever that. Are they not listening right or is it just not there? Gotta wonder..... It is a little of negative placebo effect - if you really believe that class D cannot sound good it will not.
I suspect some truth there as well. I went in not totally sure but willing to believe anything. I think.
SMPS in mapman's amp can deliver 36 amperes for a full second!
And....loving it! |
Phase shift and wrong summing of harmonics argument might look plausible (I claimed it myself) if not for the fact that my speakers already limit bandwidth to 22kHz creating larger phase shifts in comparison to 65kHz amp's bandwidth. This 65kHz amp's bandwidth is responsible for about 20deg phase delay at 20kHz (that I cannot hear) and about 10deg delay at 10kHz (that I can hear). One can argue that this phase delay might be beneficial since many speakers have positive phase shift at these frequencies. I don't have data for my speakers, but I picked one of the speakers reviewed by Stereophile. As you can see on the phase diagram (dotted line) speaker actually accelerates phase at the highest frequencies. Phase delay caused by the bandwidth limit of my amp would improve summing of harmonics (Al, am I missing something?). http://www.stereophile.com/content/monitor-audio-platinum-pl300-ii-loudspeaker-measurements#Oze7AYHq...There are many class A or AB amps that have bandwidth much lower than 200kHz (including Krells that have -3dB at about 100kHz) but nobody makes claims about bad sounding highs. It is a little of negative placebo effect - if you really believe that class D cannot sound good it will not. As for the hefty H2O power supply - it is unregulated and as such requires huge bank of capacitors to keep voltage steady and to filter out 120Hz ripple. Jeff Rowland uses only very quiet SMPS, line and load regulated that operate at 1MHz switching frequency that is very easy to filter out. In fact, he uses SMPS in preamps (Capri), where efficiency is not important, to lower the noise. SMPS got bad rap from crude computer applications. Either way works but traditional "linear" supply generates a lot of switching noise. Also low inductance capacitors (like slit foil) are very expensive. Why only a few companies use SMPS? Perhaps because it is not easy to design good switcher and also because of market demand. Many people believe that it has to be very heavy to work right. Tiny ferrite transformers can carry at high frequencies as much power as huge transformers operating at 60Hz - not to mention wide supply voltage range and DC operation. SMPS in mapman's amp can deliver 36 amperes for a full second! |
My good buddy Glen (shibui). A fantastic friend, an all-around great guy, and an ardent and experienced audiophile/music lover with a superb-sounding system. What more could anyone ask?
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Shibui,
Thanks for your real world experience driven insight. I will always place more weight on actual use and listening experiences than the hypothetical/theory argument. Ironic given the contrary opinion of some on this threat that tube and class D amplifiers are superb driving your 1 ohm load Apogee speakers.
Charles |
Al, thanks for that.
I was aware of the phase shift concerns and recall looking at measurements and reviews prior to buying to get a feel for what is going on. Knowing no gear measures perfectly in all regards I decided to give it a try and was glad I did.
I have to say to whatever extent my amps and gear may be imperfect or not, listening enjoyment is not affected. I can listen for hours and never grow fatigued or tired. That's not something I could lay claim to with my system prior to Class D.
So as we know in the end it always comes down to what one hears and can enjoy or not. Measurements help scope out the likely candidates in advance, and their technical strengths and weaknesses but never tell the whole story regarding how things actually sound.
So while nobody including me has argued that more bandwidth done right is always a good thing, I do still think its unfair to dismiss Class D technology and products as a whole these days based solely on that. The benefits will far outweigh the disadvantages for many but probably not so much for those who are put off for whatever reason.
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Assuming nothing is there to start with isn't a phase shift of 0 = 0? Nope! The point is that if you don't have the bandwidth in the amp it will cause phase shift at lower frequencies- down to about 1/10th the cutoff frequency is then its considered negligible (of course, 'negligible' by whom is a different story; obviously some designers don't care about that so much). IOW the ear might hear 20-20KHz but to reproduce that in an amplifier without phase shift you need 2Hz to 200KHz if you really want to do it right (the same rule applies on the bottom end; otherwise the bass loses impact due to phase shift). For this reason Stuart Hegman, who designed the h/k Citation 1 and Citation 2 was a big fan of wide bandwidth. I
did not know vinyl has frequency bandwidth so high. Most home hifi
always talked of 20-20K frequency response. Is this in practice or
theoretical? I'd agree theoretically vinyl could do more but
practically its news to me. The best digital (higher res) sounds as
good as most vinyl to me these days. RTR is better but look where
that got us practically. Its not just theoretical. Its true that most LP systems don't spec past 20KHz but you would be very much mistaken if you think it stops there. Most phono cartridges and phono sections made since the mid 1960s go much higher than that (although it does not show in the specs as at the time there was no thought that it made any difference). Our cutter head is an early Westerex 3D, made about 1959 and it has no worries cutting 30KHz which can then be played back by a 1970s Technics on a 1970s h/k receiver (the Westerex mastering system has a filter that cuts it off at about 42KHz). By contrast RTR does not have this sort of bandwidth; about 25KHz or so is the best you're going to get at 15 i.p.s. IOW LPs have wider bandwidth than tape and its been that way since the inception of reel to reel. Every time a new system has come into the scene the previous knowledge of the prior engineering often goes by the wayside for a while until the new technology gets its pants on. This happened with digital; its only been recently that its begun pressing bandwidth past 20KHz and we're seeing the same thing with class D right now. In time this will all get sorted out as the technology improves to the point that such bandwidths are routine; until then essentially what you will see is the industry collectively placing its head in the sand as if these facts don't exist. But this is not rocket science and we've known that bandwidth is essential going on half a century now. But people have short memories when new technology comes in... Look how long people put up with unruly fuel injection while carburetion was pretty figured out and actually performed better. But fuel injection was 'new' so people put up with it. Now days its sorted and no-one would consider a carburetor. But literally it took 3 decades to get there! |
Also what is the math relationship between bandwidth and phase shift? Where does 10X bandwidth number come from?
Hi Mapman, If I'm not mistaken class D amplifiers typically use an output filter consisting of a series inductor and a shunt capacitor. Together with a primarily resistive load that will form what is known as a second-order low pass filter. "Second-order" meaning a filter that increases the amount of attenuation it provides by 12 db/octave (12 db per doubling of frequency) above the frequency at which it has rolled off by 3 db (that frequency usually being what is referred to as the bandwidth of the filter). The equation defining the phase shift introduced at various frequencies by a second order filter is complex, and is shown (approximately!) as equation 3 on page 2 of this reference. To provide some perspective, however, it may be helpful to consider the much simpler case of a first order filter (6 db/octave rolloff), which is what would be formed by the combination of a series inductor and a resistive load, without the capacitor. A first order low pass filter will shift the phase of a given frequency f by an amount equal to: Phase shift = arctangent (f/bandwidth) So a first order filter having a 3 db bandwidth of 200 kHz would shift a 20 kHz signal by arctan(20/200) = 5.7 degrees. The 10x figure is a rule of thumb, as Ralph indicated, chosen to limit the phase shift introduced at frequencies of interest (e.g., at 20 kHz and lower) to amounts that are presumably inaudible. It should also be understood that while for a pure sine wave at a single frequency any amount of phase shift will be inaudible, a musical note consists of a combination of many frequencies that are simultaneously present. And the goal is to achieve proper alignment of the timing of all of those frequency components relative to each other. Best regards, -- Al |
shibui,
Sounds to me like you pretty much nailed it in all regards based on actual experience seeking the best sound possible with some of the most challenging speakers to drive well ever.
That a Class D design can even compete in that arena says all that needs to be said really. There is no reason to categorically reject the approach. From there it comes down to personal preferences and case by case details that vary widely most likely. Plus things can only continue to get better as/if needed as bandwidth continues to increase over time. Better performance always tends to come for additional cost. class D is no different there except it lowers the price barrier for what most would consider good performance especially when more power is needed to get the most out of less efficient speakers. Ability to get the most out of more challenging speakers is the primary value added use case for Class D these days I would say though I find the newer ones to be top notch as well with easier load speakers I own. Class D has kept me from pulling the trigger on a tube amp now (and associated speaker changes that would be needed) for several years.
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Dear Audio Friends,
I write this as one who is rather un-technical but possessing excellent 'ears'.;-)
As one of the few who have all 3 main amp designs in house and active in-system, and who owns 6 pair of priastine and extremely detailed Apogees, including a purely1 ohm Scintilla pair completely rebuilt by Rich Murry of True Sound Works, I am making a rare post here to clarify a couple of things re my experience with amps of all persuasions:
In my room as I write this I have 2 of Henry Ho's H2O SE amps driving my Scintillas, and the staging, imaging, frequency response and range are world class. I gave up a pair of beloved Class A Nelson Pass XA100.5s for them, as I could tell very little difference whiule getting some serious power benefits for my room and speakers. Please note that Henry Ho first made his name as a successful and well-reviewed Class A amp builder, and his Class D amps have Class A grade power supplies. They weigh 60lbs each, and mine have some extra-fine caps, to boot.
I also have a pair of custom Bob Carver built-for-me-by-Bob-Himself KT120 tube amps that he designed specifically to drive 1 ohm Scintillas. They have a 1 ohm tap, and sound exquisite, with a slight wider stage and image than the H2Os, but not as tight a control over the transducers, of course. These are NOT like my Kronzillas which, though superb
and with unrivalled detail and finesse
on my other Apogees, can NOT drive a 1 ohm Scintilla - nor would I ever try!
I have other amps, hybrid Vincents, Wyred4S SX500s, a fine Class A Coda 3.2 Stage, and the H2O and Carvers out-do them all by a wide margin in every particular.The only exceptions at all are the T1610-tubed Kronzilla DX MkII monos.
I hope my personal and ongoing experience with these amps might lend a bit of boots-on-the-ground substance to an otherwise thorny and subjective discussion.
My final and main point, really is this: From my experience it seems - and I have discussed this in detail with both Bob and Henry - that each style and design philosophy has its strengths and weaknesses: HOWEVER, as the designs and designers progress to the pinnacle of what is possible to each, the differences become a matter of diminishing returns. They each become less distinguishable in a blind test, with almost equally transparent and less 'visible' between listener and music.
That is and has been my experience.
All the Best
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Also what is the math relationship between bandwidth and phase shift? Where does 10X bandwith number come from? is there something akin to Nyquist that is used to determine this? Did the engineers making high end Class D amps miss the boat on this somehow? it does not sound like they did in practice based on listening, at least the good ones seem to know what they are doing.
From my perspective there is understanding the theory which is useful and how things sound, for which there is no mathematical equation to properly represent that. Pundits focus on the strengths of a supporting theory and skeptics the weaknesses. No approach is perfect and holds all the cards. That’s clear by the variety of successful amplifier designs out there today.
Ralph sounds like you are actively prototyping your own class D designs? that tells me you think there is in fact something worthwhile there if done right.
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Assuming nothing is there to start with isn't a phase shift of 0 = 0?
I did not know vinyl has frequency bandwidth so high. Most home hifi always talked of 20-20K frequency response. Is this in practice or theoretical? I'd agree theoretically vinyl could do more but practically its news to me. The best digital (higher res) sounds as good as most vinyl to me these days. RTR is better but look where that got us practically.
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Atmasphere why does 200khz bandwidth matter if there are no sources
practically (record or CD res digital) that can even come close to
delivering it today?
I did explain this in my post but here it is again: In order to reproduce phase correctly bandwidth is a requirement. Put another way, if the bandwidth is not there phase shift is the result. You are correct that digital doesn't have bandwidth and that is one of the reasons that the LP sounds better and is still around after all these years of being 'obsolete'. Nevertheless, to prevent phase shift in the amp you need bandwidth even it its not there in the recording. In fact the recording doesn't matter. To put this another way: phase shift components can be heard to 1/10th of the cutoff frequency. So if you are cutting off at 20KHz there will be phase shift to 2 Khz. 100KHz cutoff means that phase shift will exist down to 10KHz. We older adults don't hear so well at 10KHz so you can sort of get by with 100KHz bandwidth but if you really want to do it right you better have 200KHz so your kids will like the stereo (unless you're the type that just wants them off your lawn...). What prominence does the heft of the power supply play in the sonic performance of Class D amps relative to SS or tube amps? The supply should be clean else IMD components related to the noise in the supply and the scan frequency will show up in the output. IMD is pretty audible to the human ear (shows up as brightness and grit or 'grundge'). Since the scan frequency is pretty high the power supply had better be properly bypassed to be effective at the scan frequency! But it can't have any sawtooth going on either. Otherwise the supply has to be able to support the operation of the amp at full power, even though most of the time the supply will see a fraction of the current draw that a traditional amplifier supply would see, so most of the time the power draw from the wall is minimal. Traditional power supply design or SMPS is irrelevant so long as the supply is quiet (SMPSs have the advantage of being easier to regulate...). |
Power supply is no less important with class D than with other amps. A lot of vendors focus on optimizing it and it is a common theme among better reviewed and received designs.
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Well said, atmasphere. One of things that stands out, at least to me, about the H2O Class D amp is that it uses an extremely robust power supply comparable to the great SS/Tube amps. http://www.6moons.com/audioreviews/h2o2/1.html http://iceh2oaudio.com/What prominence does the heft of the power supply play in the sonic performance of Class D amps relative to SS or tube amps? Best to you atmasphere, Dave |
Atmasphere why does 200khz bandwidth matter if there are no sources practically (record or CD res digital) that can even come close to delivering it today?
Seems like a purely theoretical argument.
I agree and have stated on many occasions that higher bandwidth alone is better theoretically all other things aside and Class D can still get much better there. It certainly cannot hurt assuming it is done well/right like most things.
But practically I am less sure. I expected my Class D amps to not sound nearly as good as they do given the theory. I’m glad I did not let that stop me from trying because it seems to be a non issue already practically, at least for me.
Thanks.
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but nobody talks about phase shifts. I do and all the time. The ear can't hear phase shift in single notes, but over a spectrum it can hear phase shift in a variety of ways- as a tonality or as a change in the soundstage. The engineering rule of thumb to prevent phase shift is to have bandwidth exceeding the highest frequency to be amplified by about 10 times. Now that is generally interpreted to be a bandwidth of 200KHz (but might be higher- for example nearly all LPs have bandwidth well past 30KHz in record and in playback; usually this is limited by the source tape or file or the microphones themselves...). However you need the bandwidth in the playback electronics even if the source lacks the bandwidth if you expect to reproduce all the phases correctly! We get that out of our amplifiers but to do that with class D is still a bit of a trick. We are barely getting switching speeds much past 250KHz which means true 200KHz bandwidth isn't there yet. Now the AES says that if you can get about 2 octaves above the limit of human hearing (80KHz IOW) that you are doing OK for a monitor amplifier. Audiophiles routinely operate gear that has performance in excess of that. And one of the things I don't like about many of the class D amps I've heard has been the lack of speed and spaciousness on the top end. Like mapman, there's no way my hearing is as good now as when I was in my 20s but I still notice this stuff nevertheless. So if you're going to get that 200KHz response you need a switching speed of around 1 MHz and even then its going to be a bit spotty (2Mhz would be much better). There's no problem getting the converters to run that high. A prototype we're building here in the shop can do conversion at 3MHz easily no worries (the chips we're using have a bandwidth product of about 50MHz). The real problem is the switching speed of the output devices (and whatever junk occurs between the output of the converter and the inputs of the output devices...). If one were to spend the extra cash to get the really high speed stuff then one of the primary advantages of class D goes away real fast: low cost/high profit margin. Really fast, powerful switching transistors aren't cheap and you don't see them in 99% of all class D amps! So to compete against traditional solid state and tube amplifiers in a nutshell Class D has to improve bandwidth, and you don't have to be a bat to appreciate the difference. This is one reason why class D is still a rising star. Its also why some class D amps are quite diss-worthy and others are not too bad. |
I used the DR-25 and Krell with my Apogees for years before trading for the equally-difficult-to-drive Thiel CS-5i’s.
I assume that you had the same seeing you compared them to your friends. Why would I need opinions of "gurus" when I have actual real-life listening experiences regarding this exact subject?
Because the ones I would ask, you’d have difficulty in dismissing them as well. Just ask and it will be done. Cheers George |
READ my first post George. It was talking about MY FRIEND’S H2O Class D amps with his Scintillas in challenge to your statements trashing all Class D amps as inferior as if there was no difference between them.
I normally do not need to qualify my posts with details of my system. I felt it to be unavoidable in this case.
Why would I need opinions of "gurus" when I have actual real-life listening experiences regarding this exact subject?
Best to you George,
Dave |
Please let me know if you want, I’ll post in Tech forums for guru’s to respond. Tech advise needed, Apogee Scintilla in 1ohm mode which amp?
Krell FPB-600c or is there any Class-D you can recommend to equal the Krell? And yes even any of the ones you just mentioned would be fine, why weren’t these mentioned instead of just the tube ones you tried before, as they had no chance, and you should have known that. Cheers George |
georgelofi:
"The Apogee’s in 1ohm mode were never meant to be driven with tube amps, especially ones like you mentioned, they needed big s/s amps like Krells, Classe, Mark Levinson, yes and even the earlier big JR’s, ones that could pump current into most loads down to 1ohm."
Oh, you mean like my Classe’ Audio DR-25, dual bridged-mono DR-9s, or my Krell FPB-600c (6000w/ch@1 ohm with 143 amps of current according to JA’s bench test in Stereophile)?
I had no idea that those would work well with Apogees. Oh, wait, I used the DR-25 and Krell with my Apogees for years before trading for the equally-difficult-to-drive Thiel CS-5i’s.
Best check people’s Virtual System page before spouting off. Where’s yours?
Best to you George
Dave
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Can’t "see the forest through the trees" even though they are presented to you.
The Apogee’s in 1ohm mode were never meant to be driven with tube amps, especially ones like you mentioned, they needed big s/s amps like Krells, Classe, Mark Levinson, yes and even the earlier big JR’s, ones that could pump current into most loads down to 1ohm. You should know this being an owner of a Krell FPB-600c and why didn’t you drive the Apogee’s in 1ohm mode with that, I’m sure you would have changed your mind about the classd-.
Only condescending to the posts that believe that Class-D can drive a speaker to "it’s full potential", when most of the load it represents is around 1ohm, and we’re not even mentioning -phase angles yet. Though I think they will be pretty benign being a planer speaker.
Cheers George |
It’s about sound George. Obviously from your many condescending posts, you consider yourself the foremost "guru". Try a little humility and you might learn something.
Best to you George,
Dave
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I understand your just protecting your JR120 investment, that "if" you had the knowledge you could have built for 1/8th of the price. http://www.usaudiomart.com/details/649188442-icepower-200asc-modules/ And I’ll bet you’ll be the first to sell it when the technology comes that get’s rid of the switching noises problems without effecting the amps sound. Cheers George |
It is far from mud slinging, buy it appears that you make strong technical statements on the subjects that you are completely unfamiliar with. I pointed out units just to show that you don't have any electrical engineering education. This thread is not too bad, but your crusade against Delta-Sigma converters is plain insane. Cheers. |
I believe you won’t find one tech guru here on Audiogon that would recommend a Class-D amp over "big current" linear amps for these kinds of loads, sure they may work, but are you getting the best from them? I think not. 2nd graph http://www.lippaudio.org/old/MySystems/Scintilla/impedance.html BTW: Carver 120 and Kronzilla Mark II are NOT big current amps, sure they consume big current, but they won’t push it into speakers load like these Appogee’s Cheers George |
So it's come down to mud slinging.
Not from you sunshine, I think everyone knew I meant megahertz as there's 1,500,000,000 difference between the two.
Cheers George
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"One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results."
georgelofi:
"Then I feel sorry for this person as he has never heard his Scintilla’s at their best. It may work, but at their best?? FAR FROM IT!"
Hi George,
My good friend Glen, a BIG tube fan, has the best sounding Apogee-based system I have heard (and that is more than a few). Had the Carver K-120 monos, then Kronzilla Mark II monos, and now living very happily with two H20 Class D stereo amps from Henry Ho running bi-amped into his Scintillas.
Proof is in the hearing and not found in blanket statements unfairly encompassing hundreds of products with one fell stroke. Glen’s Kronzillas are for sale if you are interested.
Best to you George,
Dave
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Before you offer your "expertise" get things right - mhz is millihertz, proper unit is MHz (megahertz). Keep posting - you might learn something one day. |
randy-11
It sounds like a Class D amp would be best for a sub-woofer, based on a comment above
If the new MOSFET designs will be out (as products) soon, I would not want to sink too many $$ into an amp right now... You are correct Randy, really good for bass Technics have lead the way and developed a very expensive one http://www.technics.com/us/products/r1/se-r1.html with double the switching frequency as it is today @ 1.5mhz. This is a step in the right direction, but it really needs to get to around 5mhz before the right effective filtering can be done, and then able to get rid of todays Achilles heel that Class-D has. So just go the cheaper not so glitzy ClassD’s if you want to dabble in it, or even do your own clone if you or a friend are able, and purchase the Icepower/Hypex?etc modules and the power supply modules they sell. They are very much a pluggable build to do, hardly maybe no soldering to do. Cheers George |
It happens that this person (muralman1) knows everything there is to know about Scintillas and he adores them with class D amp. Nice try :(
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One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results. Then I feel sorry for this person as he has never heard his Scintilla’s at their best. It may work, but at their best?? FAR FROM IT! As they are a great speaker and should be driven with the right amp and Class-D is definitely, absolutely, not one of them, not yet anyway, give it some time and in the future it will be. Cheers George |
It sounds like a Class D amp would be best for a sub-woofer, based on a comment above
If the new MOSFET designs will be out (as products) soon, I would not want to sink too many $$ into an amp right now... |
The best reason to buy is that the good ones sound great even with harder to drive speaker loads due to lots of power and current delivery possible out of a smaller package due to efficiency.
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Back to the OP's question (really two questions);
So my question is, if it weren't for efficiency & power, would there be any reason to own a Class D amp? Do they beat Class A in any other categories that count for sound quality? The obvious reasons to buy a Class D amplifier are power per dollar, efficiency, and form factor (i.e., small). They should also work well in powered speaker implementations. From a sound quality viewpoint, some, like Guido who posts here, have had good luck with cutting edge designs from Rowland and Stereophile certainly gushed over the Theta
Prometheus that uses NC1200 modules with a linear PS. However, even the Mola Mola that 6moons praised has received some responses that it is not quite ready to compete with the best. Based on my singular experience with a pair of Ncore NC1200 monos, the one sound quality based reason I can think of that somebody may like Class D over (high quality) Class A is low noise. The Ncore NC1200 amplifiers were dead nuts quiet. My Class A Clayton amplifiers are not as quiet as the Ncores but they are certainly no noisier than other Class A and AB amps I have owned, quieter than most, and quiet enough that noise is a non-issue. Sonically, the NC1200 amps came close to the Claytons in several respects such as having a nice tonal quality and full, powerful bass, but even in those strength areas, the Class A Claytons offer a bit more realism and enjoyment. In some other areas, such as high frequencies and soundstaging, I find the Claytons to be clearly better. With respect to sound quality and listening enjoyment, of the amps I have owned, I would rank the NC1200 amps about fourth. |
The output filter vs switching noises frequency is the bottleneck for Class-D HF distortion and low impedance drivability. It is ill minded and made up. There are many amps that have similar bandwidth and great reviews. My tiny amp is listed as 3 ohms minimum and it drives 3.6 ohm min. Hyperion HPS-938 speakers. Larger modules, like one used in mapman's amp, can drive 2 ohm (this module can deliver 40 amperes for 0.5 sec and 36 amperes for 1s - not many amps can even do that). One of our audiogon friends uses class D amp (H20) with Apogee Scintilla in 1 ohm mode with great results. Please stop making pseudo-scientific reasons - it is not funny anymore. |
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