If you are contemplating having Ric mod your class D amp, have no fear. I am one of the few lucky people who bought his EVS 1200 when he was making them. I still love Love LOVE it
Class D amps that are superior to all or most?
Recently, I have heard about some Class D amps that may be close to the best there is regardless of class. Certainly, this technology has been in development for decades. The main issue has always been the switching power supply. In this regard, I have taken notice of AGD. They have created a whole new power supply that “switches” at a frequency 100 times the normal silicon based MOSFET. The designer uses a gallium nitride based PS. Interesting, it is enclosed in the KT88 glass envelope that sits on top of his amps. I am aware of two more pricey amps that seem to be also at the top- the Solution and the Merrill. There must be others that compete for the title. After my thread, “Is there a SS amp that can satisfy a SET guy?”, I am still on the quest.
Don’t want to spend $50K!
Don’t want to spend $50K!
297 responses Add your response
Ralph, Are you using tubes on the input....or is it discrete solid state or integrated circuits? Have you tried all kinds (types like toroid or enclosed, wire wound or foil...better wire quality, directionality of the wire, cryoing the coils, whether you run the signal into inner or outer winding on an air core, etc.) of different iron core and air core coils on the output? Everything makes a difference. |
You don't need money to get power in class D. Even the new GaN Premium-Audio stereo amp for $699 is rated for 200 watts a channel and they show a graph showing it not even clipping (usually 1% distortion ) doing 600 watts? I am going to email them about this because seems to good to be true....maybe a peak power, or one channel driven only? |
Are you using tubes on the input....or is it discrete solid state or integrated circuits? Have you tried all kinds (types like toroid or enclosed, wire wound or foil...better wire quality, etc.) of different iron core and air core coils on the output? Everything makes a difference.The earlier prototypes used no input circuit at all since our preamps have no problems driving a 2K load with plenty of voltage. But obviously we needed more gain so we set it up with opamp inputs. Initially we had used an input transformer but the opamps did a better job with wider bandwidth and lower distortion- and were more musical. We found off the shelf SMPS to really be hard to work with. They usually have current limiting built in which was problematic. So we went with conventional power transformers and that problem was solved- and for less money by quite a long shot than a proper custom-built SMPS would have cost. The filter chokes do pose their own issues but almost entirely about how well RFI and EMI is suppressed. If that isn't sorted out properly the amp simply won't sound right and no small part because it can affect other equipment if its leaking noise! If I were you I'd be very careful about replacing the filter choke if you don't have access to a good spectrum analyzer with a calibrated antenna as well as equipment to measure the noise the amp might inject on the AC line. |
I picked up a Wyred4Sound Class D amp several years ago to fill in while my M60s were back at Ralph's for refurbishment. I was quite impressed with the sound, and this was a $1k amp, so I'm listening when Ralph says he can build a great amp with the technology in the $5k price point. Heck even those AGD GaN "tube" amps at $32k look interesting. I'd like to give them a listen. (Plus they look cool!) |
AGD GaN amps are not $32K. The Audion’s are $7500 a pair and the more powerful Gran Vivace’s are $18.5K a pair. Also coming out this summer is a new Manhattan amp from Mytek....200 watts a channel dual mono stereo GaN based for $7K......The $20K 500 watt a channel Mytek GaN Empire mono blocks will be released in July. Lot’s of cool class D coming soon. |
when are you releasing your class d amps, ralph...?@jjss49 We've run into covid-related issues with part availability. We've completed the AC line-related measurements (the concern is meeting EU directives so it can bear the CE mark; if it does this it will meet radiation directives pretty much world-wide); right now we're working on the RFI measurements. The plan is to have the first production occurring this summer. |
I just got rid of my class D amp (Chinese Icepower). I liked the sound but I am a ham radio operator who just got back into it after a break and the amp was radiating RFI (radio frequency noise) from the speaker cables. I did what I could to filter it out but nothing worked. Back to class a/b and I like it too so nothing lost. |
Recently purchased ARC DS225 Class D amplifier as a secondary (summer amp and live in Texas) to my ARRC VS115 tube amp. Have not been a fan of Class D, however, the ARC DS225 sounds amazing. Not much heat coming off and has balance inputs. Seems ARC designed to have the same sound signature though you can tell it is not tubes. |
Digital Amplifier Company Cherry Amplifiers. Lots of opinions here on Agon. If you have a negative one, you’re entitled to it, I will give you that. In the end, the only person impacted, is the one who didn’t choose to audition one for themselves. The real winner is the one who discovers a product due to another’s recommendation. |
@atmasphere ralph good luck in your work to launch the amps in the event you want some consumer testing/trial, i'd be happy to help i don’t have torture-chamber speakers to drive (mostly british monitor types - harbeths, proacs bigger and smaller, spendor, also spatial m3s, vandy 3a sigs, fritz monitors and of course old stand by esl63’s), then have quite a few traditional ss and tube amps to compare, ranging from several arc, lta zotl40, air tight, carver 275, pass/fw, hegel, devialet and w4s class d... |
It strikes me that the one other contender not yet mentioned in this thread is the LKV Veros PWR+. https://www.lkvresearch.com/lkv-veros-power-plus.html It's been very well reviewed, but I don't know how many units are out there in the field. |
I think the actual chip used has a lot to do with it too. As time goes on, hobbyists are finding out which chips are preferred over other ones. Like the 3116, 3118, 7297 as opposed to the earlier 3886. Check out the Fleawatts by Derek Sanderson. They sound amazing at a much lower cost than many others |
I haven’t heard all the class D so I can’t comment on them all but I can on the Marantz products! I have listened to the PM-10 and the KI Ruby. They are both wonderful amps and have a very nice lifelike and warm sound. I think most people will love them! Having said that I have a PM-11s3, the last of the Marantz Reference A/AB amps sadly. Listening to the PM-11s3 side by side with the Ruby, with both my dealer and friends, the PM-11s3 sounds much better! Not better, but MUCH better. More powerful, more musical, more detailed! We A/B’d the Ruby and the PM-10, and though the PM-10 was much more powerful they sounded very similar musically. So I’d say no! A/AB still sounds better... |
What if I told you there is a Class D amp that retails for $500.00 (made in Sweden), includes shipping and sounds every bit as good as Class D amps that sell for up to $2,500? Well such an amp exists, the Edge A2-300. Some have referred to it as a giant killer. I refer to it as a great find. You ever wonder why some amps sold by different companies are similar in power and quality but vastly vary in price. Mostly because some companies have much more overhead, more debt and expenses, can't pass the savings on to their customers. So shop smart. |
I think you might have a misconception here! Its true that the output filter is affected by the load. But it won't change the FR significantly because of two factors. First, the load affects the Q of the filter. What this means is with lower impedances the filter broadens a bit and is less effective- so you might see bit more of the residual (sine wave at the switching frequency). The second is that in a self oscillating amplifier there is so much feedback that phase shift and the audio passband FR are unaffected. Quite literally there's enough feedback to correct for issues that might arise if the filter is operating at a lower Q.Methinks not. Class D Output filters are load dependent. From TI: The LC filter response also varies with speaker load impedance. The load impedance determines the damping ratio of the output LC filter and is classified as overdamped, critically damped, or underdamped. It is also important to understand the speaker load impedance variations for the application and select the L and C values that suit the expected load variations. Ideally, the LC filter value is selected for a critically damped, flat passband, and phase response. Two considerations when selecting components for the second-order low-pass filter is the cutoff frequency and Q factor or damping ratio. The variations can be small, but they will vary with every load presented. Hence, the perceived sound of the amplifier can vary with each speaker. This Stereophile image of PS Audio's Stellar M-1200 shows it well damped and relatively immune to load variations. https://www.stereophile.com/images/1220PS1200fig01.jpg Ditto this Schiit Aegir https://www.stereophile.com/images/919SchAegirfig01.jpg Not so much this new Mytek Brooklyn AMP+ https://www.stereophile.com/images/421Mytekfig01.jpg Making a purchasing decision based on the written word is folly. Doubly so for fan-boy recommendations. I'm not knocking Class D. I have one driving the woofers in my tri-amp system. |
Lots of class D amps sound "good" but if one is looking for not good but excellent sound you have to listen to most of what is out there. Cheap watts are exactly that cheap watts. Just as with class A, A/B there is a huge difference between class D amps. If someone is looking for just good there is plenty to choose from if looking for excellent it comes down to a handful and how easily your satisfied. If you strive for excellence listen to AGD or Mola Mola. |
+1 to jjss49’s comment about Wyred 4 Sound. I have the ST-500 in my desktop system, and it has worked with synergy and real impact powering some excellent 2-ways (Aerial Acoustics 5Bs; ATC SCM12 Pro’s; and now the vintage/beautiful-sounding KEF 103.2’s). I do all listening in the nearfield position with the Violectric V281 (very nice sound) as preamp. There is nowhere for a bad-sounding amp to hide in this setup: it either works or fails audibly. The ST-500 works extremely well here. And it does something subtle that tells me it’s an above average amp: whatever its inherent sound is, it takes a back seat to the inherent sound of the speakers. This quality of being self-effacing, in service of the chain, is one I value highly. My impression of the inherent sound of the ST-500 is top-to-bottom smoothness, power, music-first. Not a flash-bang, in-your-face sound at all. Never bright. But when a crescendo comes along, get ready for G forces (very powerful amp). All in all, it’s a consistently suave, relaxed "take" on SS sound. |
Yes and you have to remember all those measurements are made using Stereophile AP Aux-0025 low pass filter Stereophile:The Audio Precisions Aux-0025 is a very steep low pass low power filter filter between amp and analyzer which makes things look even better than what they really are. Used in all the Stereophile measurements in the last 10 years. Without it before (Stereophile got the filter) things looked much worse, but showed was what was "really coming out of the speakers terminal" they looked like this, (same amp) what you get is the 1st picture when buying the amp. (switching frequency noise evident) https://www.stereophile.com/images/1212AM1fig02.jpg When the Stereophile AUX-0025 filter was put in place they look like this (switching noise filtered out by Stereophile’s test filter) https://www.stereophile.com/images/1212AM1fig03.jpg not what you get when buying the amp. Solution to rid the switching noise in the audio band, and it’s by product phase shift: Raise the switching frequency 3 x so to the amps output filter, then the switching noise will also be reduced by 3 times , so to the unacceptable hf phase shift, like this Icepower 1200as2 in red https://ibb.co/kMZd9bF Like Technics do with their SE-R1 Class-D and some say the SU-R1000 integrated also. Cheers George |
@jeales Your statement about frequency response varies by load on class D amps is not necessarily true. I have now built 11 different Class D amplifiers. 3 of them are very good and 2 of them, I was able to modify or add
PFFB circuitry. It is similar to an impedance correction circuit. On my 2 amps that I've added this, frequency response does not vary with load.... I'm not sure how widely this is used, but it is definitely out there. |
timlub1,865 posts05-08-2021 10:31am I believe it is, as the best I’ve heard Belcanto M600 monoblocks (NC500) is through a very benign 6ohm 2 way stand mount, that used a Raven ribbon tweeter, which is basically a load that looks like a 6ohm resistor. On more expensive ML ESL’s and other good floor standers they didn’t sound as good through the upper mids and highs, a little artificial and cold. And as far as measurements go, class-D get exponentially worse distortion figures when differently loaded the higher the frequency is, look at any tested Stereophile distortion graphs done on class-D (new Mytek Brooklyn) rising distortions upward from 1.5khz https://www.stereophile.com/images/421Mytekfig06.jpg Compared to a linear amplifier, much better far lower, and starts to rise higher and gradual, not so savagely rising https://www.stereophile.com/images/1115BAHB2fig07.jpg Cheers George |
frequency response does not vary with load...Define load. Non inductive load resistor, speaker simulator or something like this Elac Debut B6 https://www.stereophile.com/images/416Elacfig1.jpg. or Klipsch Forte III https://www.stereophile.com/images/719KF3-fig1.jpg |
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carlsbad Coincidentally I just got MLs and my tinnitus is quite a bit louder than normal. I've wondered if it was the brighter highs. but it is probably just that I'm listening to it more. I don't listen very loud, in brighter speakers I listen quieter. I'd say you haven't really heard what those ESL's can achieve in the upper mids/highs, until they are driven with a good linear high bias class-A/B amp. Cheers George |
@ieales If you look at my post that you quoted and the information you quoted next to it above, you'll see that we are saying exactly the same thing. TI's information cannot be construed to be seen as a change in frequency response. In that post you see me saying this: Its true that the output filter is affected by the load.To which you responded: Methinks not.If you look at these two statements they are quite similar!After that you followed with: The variations can be small, but they will vary with every load presented. Hence, the perceived sound of the amplifier can vary with each speaker.Its this conclusion that isn't quite correct. It can be true if the class D amp is using no feedback or insufficient feedback. If it has over 35dB, what happens is the feedback is so profound that it allows the amp to correct for minor changes caused by the Q of the filter with respect to the load impedance. The result is that the change to the audio passband bandwidth and phase shift is not measurable; i.e. there is no change. |
@atmasphere Your post began stating I have a misconception. I have no misconception of Class D, filters or Q. There is little change for some products as I showed. For others there is a lot. Designers debate the value of under, critical [for design load impedance ONLY] and over damping. Hence the wide FR variation among competing Class D products. Class D products VARY MORE into varying load impedances than do typical transformerless solid state amplifiers. Hence my caveat that fan-boy recommendations are just so much twaddle. Feel free to post unfiltered frequency response graphs of a Class D amplifier that maintains identical flat output amplitude into several 'rollercoaster real world impedances'. I've yet to see one. NOTE: I only mention FR as it is relatively obvious and most comprehend it. Not so much for IM, THD and dynamic distortion spectra. |
There is little change for some products as I showed. For others there is a lot.It appears to me to come down to this. The reason is the filter isn't the only variable- class D amps vary quite a lot; some have zero feedback, others have feedback and don't include the filter in the loop, others have feedback and do include the filter, still others are self oscillating and those that do might have the most feedback. The amount of feedback is the key. Less than 35dB in any amp simply won't work. We've measured no change in bandwidth of our prototypes and Beta units from 20Hz to 20KHz, with less than 1 degree of phase shift over that range, with the load from 2 ohms to 16 ohms. No change. So depending on the amp we are both correct. I think what is bothering me here is you do not draw a distinction with how the amp is designed and that makes quite a bit of difference to the outcome! Here is an example of what I'm talking about:https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-purifi-1et400a...:) FWIW the guy doing the measurements here isn't what I would call a 'fan-boy' :) |
We've measured no change in bandwidth of our prototypes and Beta units from 20Hz to 20KHzI don't think I ever mentioned bandwidth. BW is not FR. BW is how far. FR is variation over BW. Some amplifiers drive test loads ruler flat and reactive loads not so well. fan-boy: "I have a GigantaRama driving BrontoSpheres and it's great." Frequently, not. |
No, You didn't, here's what you said: However, the driven device forms part of the output filter and thus effects the frequency response. In this case its hard to construe the FR being different from the bandwidth because we are talking about the response of the amplifier in its upper range and how its affected by the filter. But no matter: neither are affected if the amplifier is running sufficient feedback. |
Facts are Everyone likes what good Class-D’s do in the bass on loads that are not too severe, but many hear some thing not quite right with Class-D in the upper mids/highs with many speakers, and this is it’s Achilles heel. Technics (SE-R1/SU-R1000) claim to get rid of it by making the switching frequency 3 x higher, 1.5mhz, so that then the output filter is also 3 x higher and therefore it has little or no influence down into the upper mids/highs. Most Class-D’s that have around 600khz switching frequencies, have output filters that have effects down into the upper mids and highs. And yes throwing a **** load of feedback may fix it, but the best amp "theoretically" would be ones that use no feedback if it can be done without distortions, or very little or local not global. Cheers George |
@ricevs -
I have only seen the blah Herb Reichert review of the LKV (says it beats an old class D amp and is somewhat competitive with a $3500 Rogue tube amp). Are there other reviews?This is the Herb Reichert who in the latest Stereophile said he likes harmonic distortion in his amplifiers. It's no wonder he didn't like a class D amp -- most have vanishingly small distortion. |
It’s no wonder he didn’t like a class D amp -- most have vanishingly small distortion. They have other problems also, like the Ice-Power’s 1200AS2 that has massive phase shift from it’s output filter way down into the mids (red trace) https://ibb.co/J2Hns7s and also (blue trace) a sharp rising output impedance starting at also at the same frequency as the phase shift does. Sure throw maybe a **** load of feedback at it and it could fix it, but to what other detriment. Cheers George |
George, How many times have you posted this info?......a million? Yet, Michael Fremer thought the stock module to be quite good (read the stereophile review of PS audio 1200 amps)....he did not think the mids and highs on the $6K monos were quite as good as the $150K Dartzeel. The modified IceEdge amps I sold are raved about sonically. Then there is the about to be raved about by Doug Schroeder (stock versions from Legacy)......calling it a Tsunami.....he he. He likes them better than big mono blocks from Pass. So, with all your postings....it seems to have very little to do with the sound....yet, you keep harping on it. The only ones that really know about something are those that listen. You don't know anything about how a stock or modified IceEdge amps sounds....you only keep posting some spec you do not like. I personally do not care for the stock IceEdge module....but once modified, it sounds really good. The IceEdge module will never be state of the art......it has flaws......including maybe those "bad specs". But once modded, it sounds really GOOD......and you can have a dual mono stereo modified version (remember.....1200 watts into 4 ohm.....drove the Alexx speakers fine) for a little over $2000 delivered to your door. |
Not exactly. What I can do is modify the Rouge Audio Design Studio N-10DM dual mono IceEdge amp that can be purchased and delivered here in the US for $1600. I then add my mods ($550) to it and it will be identical to your EVS 1200 amp minus the extra copper and aluminum plates I added in that product. https://en.rougeaudiodesign.com/product-page/studio-n-10dm |
Oh SO "blah". "Sound quality and music enjoyment–wise, the LKV Research Veros PWR+ amplifier sits on a higher mountain than any other class-D amp I've encountered. It seems like Bill Hutchins made a slew of listening-inspired design decisions which, in concert, led to this extraordinarily natural-sounding power amp. I will be surprised if it measures super-low THD-wise, but, rest assured, I smiled contentedly every minute it was playing music in my room." "Today, most commercial loudspeakers feature reactive, low-impedance loads. Why? Because watts are cheap? Unfortunately, cheap watts often sound like crap watts. Fortunately, Bill's watts sound like limitless, sensual, tactile, luxury class-A watts. On the speakers I used, the Veros PWR+ put minnows, crappies, and my favorites, bass and catfish, into the once-empty class-D pond. Gleefully recommended." |
but many hear some thing not quite right with Class-D in the upper mids/highs with many speakers, and this is it’s Achilles heel.Complete rubbish. I've explained this many times on multiple threads. Its apparent that faced with facts, George is at a loss; his comments are far too inclusive. The output filter will have an effect on phase shift in the audio band **if the feedback is insufficient**. So if you see a class D amp that has lots of phase shift in the audio band now you know why. To prevent phase shift you can do it two ways: have loads of bandwidth (that's how we do it in our OTLs, by going well past 100KHz at full power) **OR** by using enough feedback that phase shift is corrected (which is in excess of 35dB). Some class D amps that switch at 500-600KHz sound great and others do not. Its very much like the difference between a type 45 SET and and 750 watt behemoth push-pull tube amp- they are two different things and sound different as a result. Class D in general is no different in this regard. The last paragraph is really terrible. You don't 'throw a load of feedback' in an amp to fix the amp, you throw a load of feedback in the amp to *fix the feedback itself*. There is a profound difference; to start with you can't just keep adding feedback as you need gain in the amp to do that and each stage of gain degrades the phase margin of the circuit. So it requires a bit of finesse. To get the required amount in a class D, you have to resort to self-oscillating circuitry (which is also helpful for keeping noise down as opposed to a zero feedback class D design). As a challenge to George: why not work out the oscillation criteria and get back to us here? If you can't don't feel bad, just allow the lesson to sink in that there is far more to this than you think! |
https://ibb.co/gt4qW9x Challenge your self, nothing I said was aimed at you, yet you took it to heart, wonder why. Whatever, your new class-D will tell if it’s remotely equal to the better high A- biased linear Class-|A/B amps, if it ever sees the light of day. |
Since the BASH patent ran out last year, things will slowly evolve and change. For high end audio, or for ’quality’ oriented applications, class D is likely to go the way of the dodo bird. As in: extinct. BASH will be re-worked for high end audio and will be found to be superior to all possible class D amplifier designs. No output filter required, for one. And some other great potentials. It always was sonically superior, in potential (on paper), to anything built and designed akin to a class D amplifier...but had been relegated to cheap Chinese design and build due to predominant use in sub woofers and similar high powered low frequency applications. Then the associated IP ownership and lockout of the basic BASH patent. Which was Asian held. (purchased from the Canadian company that created the BASH design). The design is open technology now re patent violation prosecution. It was likely not done before as the patent would be waved in front of the given designer (via western patent office representation, where it is also held) and they would have to pay for the use of the patent, if it was available to do so from the holders of the patent. Secondly, the lack of respect of IP in some corners of the asian build and sales world re amplifier circuitry. As in, make a superior bash based design, publish it, get sued and cut off from it all... all while asian companies steal the design and issue it themselves. Not an attractive scenario to get involved in. Thus, wait for the patent to expire, to avoid at least the being sued part. Expect the theft, and maybe find a way to ride the thing a bit, re being paid for the expected technological theft. Expect the BASH inquisition to arrive on the Class D shores...eventually. |
Challenge your self, nothing I said was aimed at you, yet you took it to heart, wonder why.I'm not angry George, just disappointed :) I often heard problems with class D some years back- weak bass and the like as you've described. But it was obvious to me even 10-15 years ago that class D was a tech that was on a research and development sigmoid curve- and a rising star on which we should keep our eyes. I commented on that often on this site in the past. Its now evolved to the point that a good class D amp is a player against any other amplifier technology, and has already eclipsed them. I certainly don't/can't take it personally since at the very least none of your comments apply to any of Bruno Putzeys' designs (UCD, Hypex or Purifi) nor ours (and probably a few others for that matter). |
