georgehifi Posted September 9, 2019 Share Posted September 9, 2019 (edited) 30 minutes ago, March Audio said: I'm away from the office until Thursday but will measure the phase shift of the Purifi. Really, your capable of doing that, yet nothing from you as a posted screen shot on a 10khz square wave from the speaker terminals, without any A.P. inline filter, to prove your claims. Edited September 9, 2019 by georgehifi Link to comment Share on other sites More sharing options...
aussievintage Posted September 9, 2019 Share Posted September 9, 2019 (edited) 35 minutes ago, March Audio said: George the reality is what it is. Bruno and Purifi have done what you claim is impossible. As a spectator it would appear to me that much hinges on Bruno's explanation that most of the phase shift is simple time delay. Bode plots of a time delay and of a low pass filter (2nd order Butterworth) looking at the Passband, would seem to bear that out. The argument that a time delay doesn't damage music makes sense. Is it possible that his claim of low phase problems at 20kHz could be after time delay is removed - and that, according to the above, would be valid. Edited September 9, 2019 by aussievintage 1 Link to comment Share on other sites More sharing options...
March Audio Posted September 9, 2019 Share Posted September 9, 2019 (edited) 11 hours ago, georgehifi said: Really, your capable of doing that, yet nothing from you as a posted screen shot on a 10khz square wave from the speaker terminals, without any A.P. inline filter, to prove your claims. George you only need a scope to measure the phase difference Not wishing to be un civil, but beleive or not George I do have other things to do apart from pander to your lack of understanding and knowledge of the subject. However from elsewhere You will also note the flat FR beyond 20kHz which will indicate a flat phase response. Edited September 9, 2019 by March Audio Link to comment Share on other sites More sharing options...
March Audio Posted September 9, 2019 Share Posted September 9, 2019 1 hour ago, aussievintage said: As a spectator it would appear to me that much hinges on Bruno's explanation that most of the phase shift is simple time delay. Bode plots of a time delay and of a low pass filter (2nd order Butterworth) looking at the Passband, would seem to bear that out. The argument that a time delay doesn't damage music makes sense. Is it possible that his claim of low phase problems at 20kHz could be after time delay is removed - and that, according to the above, would be valid. So long as the specific phase change is linear as he described it is just a time delay. I beleive his Hypex designs follow this, whilst the Purifi is just essentially flat within the normal passband. Link to comment Share on other sites More sharing options...
ghost4man Posted September 9, 2019 Share Posted September 9, 2019 https://6moons.com/industry_articles/purifi/ 1 Link to comment Share on other sites More sharing options...
genkifd Posted September 9, 2019 Share Posted September 9, 2019 looks like Holton is jumping onto the Class D band wagon https://holtonprecisionaudio.com/blogs/news/coming-soon-holton-audio-to-sell-hq-class-d-amplfiers Purifi models due later on in the year. 2 Link to comment Share on other sites More sharing options...
lemarquis Posted September 9, 2019 Share Posted September 9, 2019 1 hour ago, genkifd said: looks like Holton is jumping onto the Class D band wagon https://holtonprecisionaudio.com/blogs/news/coming-soon-holton-audio-to-sell-hq-class-d-amplfiers Purifi models due later on in the year. Holton Audio has in development our own brand of Class D amplifier based around Hypex Ncore OEM modules, they will have Exclusive Holton Audio True Class A input buffers with the ability to adjust output gain using on board SMD dip switches to allow the best gain structure to be attained. Ncore vs Purifi .. Link to comment Share on other sites More sharing options...
keinesorge Posted September 9, 2019 Share Posted September 9, 2019 (edited) All inputs to Class D threads from georgehifi and his buddy (not dragged in to this thead yet but let wait and see if he makes an appearance) are likely to be financially motivated. I wonder of the ties that they have to Peter Stein / ME amplifiers. Just expose the BS to the the right people and the nonsense will likely stop. It is unfortunate that Gerogehifi does not share his approach to audio enlightenment with the entire diyaudio Class D subforum where the masses "truly" really need conversion. Instead he just dumps on smaller threads / forums. Just wait till he starts going on about how once upon a time, Class D blew up tweeters. And lets see if his ME motivated counterpart joins the thread. Their strategy is obvious. It is a shame that the forum moderators allow for this kind of nonsense. Worst of all, he has projected his carefully worded bias against against a local WA business. Edited September 9, 2019 by keinesorge 1 Link to comment Share on other sites More sharing options...
March Audio Posted September 9, 2019 Share Posted September 9, 2019 (edited) 59 minutes ago, keinesorge said: All inputs to Class D threads from georgehifi and his buddy (not dragged in to this thead yet but let wait and see if he makes an appearance) are likely to be financially motivated. I wonder of the ties that they have to Peter Stein / ME amplifiers. Just expose the BS to the the right people and the nonsense will likely stop. It is unfortunate that Gerogehifi does not share his approach to audio enlightenment with the entire diyaudio Class D subforum where the masses "truly" really need conversion. Instead he just dumps on smaller threads / forums. Just wait till he starts going on about how once upon a time, Class D blew up tweeters. And lets see if his ME motivated counterpart joins the thread. Their strategy is obvious. It is a shame that the forum moderators allow for this kind of nonsense. Worst of all, he has projected his carefully worded bias against against a local WA business. It's not actually anything to be concerned about because all the misinformed points he is making are very easily countered with technical facts supported by measurement data. People can then make their own minds up based on the evidence. Edited September 9, 2019 by March Audio 1 Link to comment Share on other sites More sharing options...
ghost4man Posted September 9, 2019 Share Posted September 9, 2019 7 hours ago, keinesorge said: All inputs to Class D threads from georgehifi and his buddy (not dragged in to this thead yet but let wait and see if he makes an appearance) are likely to be financially motivated. I wonder of the ties that they have to Peter Stein / ME amplifiers. Just expose the BS to the the right people and the nonsense will likely stop. It is unfortunate that Gerogehifi does not share his approach to audio enlightenment with the entire diyaudio Class D subforum where the masses "truly" really need conversion. Instead he just dumps on smaller threads / forums. Just wait till he starts going on about how once upon a time, Class D blew up tweeters. And lets see if his ME motivated counterpart joins the thread. Their strategy is obvious. It is a shame that the forum moderators allow for this kind of nonsense. Worst of all, he has projected his carefully worded bias against against a local WA business. Really? What is the purpose behind this post other than a cheap shot making reference to something that is apparent happening in the background. I have no commercial interest with George. George has clearly expressed his opposition to Alan's remarks on a technical level where there are opposing ideologies at play between the two. Let the technical facts make the determination and let's wait and see how the product ultimately performs. Most of us have heard of Bruno and there's no doubt that Class D has made huge inroads over the last 5 years which I've seeb on other forums getting under the noses of traditionalists. Link to comment Share on other sites More sharing options...
keinesorge Posted September 9, 2019 Share Posted September 9, 2019 (edited) 1 hour ago, ghost4man said: Really? Yes really. Disclose his business interests in non class d amplifiers and let us all reread the thread in a new light. What cheap shot are you talking about ? On page #13 georgehifi references the blown tweeter. And this is not the only forum thread with its mention. Have a look at the diyaudio forums: https://www.diyaudio.com/forums/class-d/ You wont find much of his push back there. After all, there are plenty of "misguided" audio enthusiats who are happily enjoying a whole heap of class d amps. And who is going to save them from the dreaded blown tweeter ? I have not heard the purifi. Perhaps i will contact Alan for a listen. (i have no commercial interests with anyone on these forums). Have you heard it ? If individuals with electronic design experience would chime in and share about creative snubber design to better attenuate carrier content going down the speaker cable, post filter feeback etc, i'd view the comments in a different light. To slam the topology and denigrate the design - with nothing positive to bring to the class d table (and this bring a class d thread) reeks of subversive commercial marketing. Edited September 9, 2019 by keinesorge Link to comment Share on other sites More sharing options...
March Audio Posted September 9, 2019 Share Posted September 9, 2019 (edited) Just to tackle the frying tweeters myth. Whilst I am sure somewhere in the past someone fried a tweeter using a class d amp (just like they have with AB amps) it's just a myth with any quality amp manufactured now. Let's do the math. Just went to Madisound and at random picked a Scanspeak D2604 tweeter. It parameters are below. So we want to calculate the power dissipated by the tweeter caused by the switching frequency. First we need to calculate the impedance of the coil at the switching frequency. We will use 500kHz. Switching risidule amplitude is 350mV. We will ignore a few things but it will be close. Impedance Z = 2 * Pi * F * L Z= 2*3.14*500000*0.00002 Z= 62.8 +R = 65.7 ohms This value is ignoring the effect of any speaker cabling or crossover in circuit which will increase the impedance further. So current = V / Z I=0.35 / 65.7 I= 0.0053A I=5.3mA Power = V * I P=0.35*0.0053 P= 0.00185 W Power dissipated by the coil = 18.5 mW A total non issue, and this is in a directly connected scenerio without a crossover circuit or speaker cables that will reduce this further. Oh forgot to mention the inductive reactance component doesn't generate heat, only the resistive. Edited September 10, 2019 by March Audio Link to comment Share on other sites More sharing options...
aussievintage Posted September 9, 2019 Share Posted September 9, 2019 2 minutes ago, March Audio said: Just to tackle the frying tweeters myth. Whilst I am sure somewhere in the past someone fried a tweeter using a class d amp (just like they have with AB amps) it's just a myth with any quality amp manufactured now. Let's do the math. Yes a few things missed out here for simplicity but it's close. Just went to Madisound and at random picked a Scanspeak D2604 tweeter. It parameters are below. So we want to calculate the power dissipated by the tweeter caused by the switching frequency. First we need to calculate the impedance of the coil at the switching frequency. We will use 400kHz. We will ignore a few things but it will be ballpark. Impedance Z = 2 * Pi * F * L Z= 2*3.14*400000*0.00002 Z= 50.24 +R = 53.14 ohms This value is ignoring the effect of any speaker cabling or crossover in circuit which will increase the impedance further. So current = V / Z I=0.35 / 53.14 I= 0.0066 A I=6.6mA Power = V * I P=0.35*0.0066 P= 0.0023 W RMS Power dissipated by the coil = 23 mW RMS A total non issue, and this is in a directly connected scenerio without a crossover circuit or speaker cables. Look, I have no doubt a bad class D amp somewhere has fried a tweeter, but in properly designed amps its not a problem. In my experience, the most often cause for tweeter, and any driver, damage, is distortion. Hey, many of us never believed the tweeter story. I am currently using a very basic class D tripath chip-based amp. I have no tweeter anxiety, and I enjoy the sound Link to comment Share on other sites More sharing options...
March Audio Posted September 9, 2019 Share Posted September 9, 2019 (edited) Yes this is correct. The harmonics generated when clipping increase the power level delivered to the tweeter. I should do a worked calculation example to demonstrate. Just to note I updated the switching frequency as it was a previous example I had done and copied from elsewhere. Problem is many non technical people without informed technical guidence do beleive the spreading of FUD by some. Fear Uncertainty Doubt. Edited September 10, 2019 by March Audio Link to comment Share on other sites More sharing options...
Addicted to music Posted September 10, 2019 Share Posted September 10, 2019 The issue with it is that no matter what maths is used to prove it, the fried tweeter by ultrasonic freq always show up in any classD thread.... We don’t know the history of those tweeters that got fried, all we know is that it was last driven by a classD when it had issues, doesn’t mean that classD caused the issue either.... just saying! Your are highly likely to fry any tweeter if you pushed a conventional amp into clipping or severely exceeding its max power rating.. Link to comment Share on other sites More sharing options...
March Audio Posted September 10, 2019 Share Posted September 10, 2019 (edited) 3 hours ago, Addicted to music said: The issue with it is that no matter what maths is used to prove it, the fried tweeter by ultrasonic freq always show up in any classD thread.... We don’t know the history of those tweeters that got fried, all we know is that it was last driven by a classD when it had issues, doesn’t mean that classD caused the issue either.... just saying! Your are highly likely to fry any tweeter if you pushed a conventional amp into clipping or severely exceeding its max power rating.. What tweeters though ? Can anybody actually cite a documented example? Where is the evidence of the switching frequency being the cause? It's really just an urban myth. I have indeed fried a tweeter with an AB amp during a party. Edited September 10, 2019 by March Audio Link to comment Share on other sites More sharing options...
aussievintage Posted September 10, 2019 Share Posted September 10, 2019 3 minutes ago, March Audio said: I have indeed fried a tweeter with an AB amp during a party. Classic way to do it. Link to comment Share on other sites More sharing options...
ghost4man Posted September 10, 2019 Share Posted September 10, 2019 8 hours ago, keinesorge said: Yes really. Disclose his business interests in non class d amplifiers and let us all reread the thread in a new light. What cheap shot are you talking about ? On page #13 georgehifi references the blown tweeter. And this is not the only forum thread with its mention. Have a look at the diyaudio forums: https://www.diyaudio.com/forums/class-d/ You wont find much of his push back there. After all, there are plenty of "misguided" audio enthusiats who are happily enjoying a whole heap of class d amps. And who is going to save them from the dreaded blown tweeter ? I have not heard the purifi. Perhaps i will contact Alan for a listen. (i have no commercial interests with anyone on these forums). Have you heard it ? If individuals with electronic design experience would chime in and share about creative snubber design to better attenuate carrier content going down the speaker cable, post filter feeback etc, i'd view the comments in a different light. To slam the topology and denigrate the design - with nothing positive to bring to the class d table (and this bring a class d thread) reeks of subversive commercial marketing. No it is a cheap shot because you have made it personal and in particular the reference to a WA business where you have insinuated that a type of treachery has or is taking place which you wholly attribute to George. So let's be clear about this. During the course of this thread can you point to a specific example where George did that. If not then your narrative is nothing more than unnecessary flame throwing in an attempt to denigrate another person by attributing foul play. I have not heard the purifi. I have heard Class D and have been very impressed with what it brings. A the risk of being judged by association, I believe that another contributor who goes by title Mivera is dead on in his assessment that Class D has progressed incredibly over the last 5 years which will bother many of the traditionalists. I've stated privately to Alan that I'm not comvinced that Class D is necessarily the answer for magnepan speakers. Unless you've experienced Maggie's you won't realise the challenges involved with them and especially to get the best out of them. I take on board Alan's attempt to at least source an impedance curve but that doesn't tell the whole story. If you ask Bill McLean who has more experience with Maggie's than pretty much anyone in Australia the first question thst he asks is what amp do you intend on using with them. That should tell you something about them. There's currently a conversation at the minute on another thread where one of the contributors questions the value of high end McIntosh gear and what he considers their ability to have grip on the bass. Bear in mind that the chap has heard Maggie's with the Jeff Roland Relentless Monoblocs driving them and doing so superbly. We're talking absolute hi end gear here. I'm not saying that good Class D aren't viable. I'm just reserving my opinion until I hear them in action. Link to comment Share on other sites More sharing options...
March Audio Posted September 10, 2019 Share Posted September 10, 2019 As you have mentioned him several times I think it's worth mentioning that (Mike) Mivera has benn banned in many forums including ASR where he trolled my business under a pseudonym. Mods checked IP address to confirm. Link to comment Share on other sites More sharing options...
March Audio Posted September 10, 2019 Share Posted September 10, 2019 (edited) 3 hours ago, ghost4man said: I've stated privately to Alan that I'm not comvinced that Class D is necessarily the answer for magnepan speakers. Unless you've experienced Maggie's you won't realise the challenges involved with them and especially to get the best out of them. I take on board Alan's attempt to at least source an impedance curve but that doesn't tell the whole story. As I asked in the PM, what are your concerns? What is the "rest of the story" if it goes beyond being able to drive complex loads and low impedances? I can't do it from here, on mobile ATM but I will show you some Maggie impedance plots. If anybody hasn't figured yet, I do prefer to deal with technical fact as opposed to teeth sucking oooh difficult load types of comments and unsubstantiated opinion. Edited September 10, 2019 by March Audio Link to comment Share on other sites More sharing options...
rantan Posted September 10, 2019 Share Posted September 10, 2019 I am not involved in this thread as regards to the merits or otherwise of any particular amplification topography, but I really feel that some of the negative, carping and demeaning posts about March Audio and his products are not only unwarranted,but also against the spirit of what form debates should be about. It goes without saying ( although I will say it anyway ) that I have no association of any kind whatsoever, with March Audio and I feel that Alan has conducted himself with great patience and goodwill in the face of some personal attacks. Obviously, he neither requires nor seeks my opinion, or support, but I did feel the need to post about this thread in any case. It is completely acceptable to have a very negative view of equipment, provided that opinion is based on some sort of actuality and personal experience ( One cannot slander something inanimate ) but making it personal and playing the person is 100% unacceptable. 9 Link to comment Share on other sites More sharing options...
Addicted to music Posted September 10, 2019 Share Posted September 10, 2019 2 hours ago, March Audio said: What tweeters though ? Can anybody actually cite a documented example? Where is the evidence of the switching frequency being the cause? It's really just an urban myth. I have indeed fried a tweeter with an AB amp during a party. It’s on another class D threads in this neck of the woods, didn’t really pay any particulars to it because it was just entertaining reading. But every time someone brings up class D there are certain opinions for ultrasonic leakage with comments that it “dirty the SQ “. And if this was a typical conventional amp then it wouldn’t pass noise certifications.... Even the screen shot of a scope showing the ultrasonic hanging around the main fundamental it’s like “really”. It’s that tiny for peak-peak there’s no way that even at that amplitude will have the energy to destroy any tweeter! And what they don’t realise is what you @March Audio have brought back to reality is that at those subsonic freq even though you feed it to the same tweeter the Z impedance is different at 450khz to what it is for 20-20k. Theres also the preconceived idea that all SMPSU are noisy and generate and radiate noise, Some of the SMPSU are actually cleaner than Linear supplies, also most SMPSU would have regulation that keeps a constant voltage, that’s why ASR is so good, we can see on a scope the magnitude and at which frequencies. Link to comment Share on other sites More sharing options...
Addicted to music Posted September 10, 2019 Share Posted September 10, 2019 On 08/09/2019 at 3:21 PM, March Audio said: I havent actually done it with the Purify but I certainly have with Hypex modules. They just shut down. They have a "hiccup" mode where if the max output current is exceeded for more than a set period it shuts down. They have a microcontroller on board which does monitoring. From Hypex NC1200 Purify is even more sophisticated Don’t quote me on it but I think the dedicated PSU also has protection where if there’s an over load it shuts down. When manufacturers produced this type of documentation, I’m not game enough to put it through the test, some of the products I work on use what’s called “fold back circuit “ basically limits the current and shuts down via microprocessor, they theory goes that when the fault condition is removed, the intelligence is supposed to restore to normal, well they never do! So not only you are dealing with the initial fault that caused the PSU to get into this condition, you have to replace a PSU that has the smarts.... where previously it would take out a fuse and that’s it..... Link to comment Share on other sites More sharing options...
rocky500 Posted September 10, 2019 Share Posted September 10, 2019 35 minutes ago, Addicted to music said: It’s on another class D threads in this neck of the woods, didn’t really pay any particulars to it because it was just entertaining reading. But every time someone brings up class D there are certain opinions for ultrasonic leakage with comments that it “dirty the SQ “. And if this was a typical conventional amp then it wouldn’t pass noise certifications.... Even the screen shot of a scope showing the ultrasonic hanging around the main fundamental it’s like “really”. It’s that tiny for peak-peak there’s no way that even at that amplitude will have the energy to destroy any tweeter! And what they don’t realise is what you @March Audio have brought back to reality is that at those subsonic freq even though you feed it to the same tweeter the Z impedance is different at 450khz to what it is for 20-20k. Theres also the preconceived idea that all SMPSU are noisy and generate and radiate noise, Some of the SMPSU are actually cleaner than Linear supplies, also most SMPSU would have regulation that keeps a constant voltage, that’s why ASR is so good, we can see on a scope the magnitude and at which frequencies. I thought the problem people had with switching power supplies is what they fed back into the mains, that supposedly can effect other equipment. Link to comment Share on other sites More sharing options...
aussievintage Posted September 10, 2019 Share Posted September 10, 2019 15 minutes ago, rocky500 said: I thought the problem people had with switching power supplies is what they fed back into the mains, that supposedly can effect other equipment. There'd be a big problem these days if that was a concern with soooo many devices using them these days Link to comment Share on other sites More sharing options...
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