Class D amps are only current limited by the designer. You can make a super high current class D amp (you just need higher voltage rails and larger fast power supplies and maybe a couple more output transistors.....and great output coil). Class D idles at practically zero current....because its output stage is switching at high speed......does not need to be "on" all the time. What you hear in any class D amp is the designers knowledge...nothing more, nothing less. Tons of high end speakers use class D amps for the bass. The big Von Schweikerts for example.....no loss of dynamics there. There are tons of things in any amp that effect the dynamics.....one bad part and dynamics are history......and this is true for high-current class AB types as well. This is why all class A/B amps sound different.....in the bass/dynamics and otherwise. I do various things in my mods to the VTV Purifi amp that allow for better bass and dynamics and speed. There is no end to tweaking.....no end to knowledge. The Purifi module does 400 watts into 4 ohm...and over 500 watts into 2 ohms (25 amps).......this is enough for most speakers but getting it all out of the module in the most tweaky, dynamic and great sounding way is an art.
Purifi Class D: Junk?
So, from the previous thread about high-end class D the Purifi module was brought up. I decided to get a cheap example from VTV, a simple stereo unit with a single Purifi module and matching Hypex SMPS. Standard input buffer. I got it in yesterday. First impression wasn't what I was expecting: weak, congested dynamics is what stood out to me. I expected greater expression through my ProAc D30Rs. The other problems such as poor soundstage, thin / boring character, etc, I marked up to needing burn-in before evaluating. So it's been 24 hours, I would still expect to get at least the high control / damping of high end class D and dynamic power, but it's just not present.
Could it be an impedance mismatch? Other manufacturers selling the Purifi with their custom input buffers are reporting 47k Ohms. VTV doesn't say in the manual or on the site. I checked the Purifi data sheet which reports...2.2k Ohms on SE???? That can't be right?? That's absurdly low! Am I reading the right spec? My preamp has an output impedance of 230 Ohms. Can someone confirm that the stock Purifi has this ultra-low input impedance?
Could it be an impedance mismatch? Other manufacturers selling the Purifi with their custom input buffers are reporting 47k Ohms. VTV doesn't say in the manual or on the site. I checked the Purifi data sheet which reports...2.2k Ohms on SE???? That can't be right?? That's absurdly low! Am I reading the right spec? My preamp has an output impedance of 230 Ohms. Can someone confirm that the stock Purifi has this ultra-low input impedance?
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02-21-2021 7:17pmWhat you are hearing is what class d amps do they produce high wattage with low current to save money on energy and expense of manufacture to make more money for the manufacturer and they will not have the required current to dive the proac speakers you have they like a good high current ab type amplifier i am glad you did not spend much money on the class d amp you dodged the bullet with that decision. More making things up. I really don't consider 25 amps that limited. That's 1250 watts into 2 ohms. Class D amps primarily have thermal limits because real world music is not 1000W continuous, ever. That's a magazine test. |
Class D amps are only current limited by the designerShow us just one that’s not, and can almost double it’s rms measured wattage from 4ohm to 2ohm. The true indication of not current limiting, like many good A/B bjt amp. The Purifi module does 400 watts into 4 ohm...and over 500 watts into 2 ohms (25amps)This is pathetic to show off it’s current ability, some NAD’s can do that current, it’s actually limiting, should read closer to 800w into 2ohms if it were good at current into low impedances. A 175w- 8ohm Gryphon will do 350w - 4ohm 700w - 2ohm 1600w - 1ohm 9000w - 1/4ohm NOW this IS an amp that does current without limiting. |
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You only need the current you need. It does not matter if an amp doubles its current/power down to 2 ohms. All that matters is that it have enough current at 2 ohms to drive a 2 ohm speaker to the volume required. The IceEdge 1200 module puts out 700 watts into 8 ohms, 1200 into 4 ohms and I measured 1000 watts into 2 ohms......so what? Michael Fremer used this amp module on his 2 ohm Wilson Alexx speaker and said it was great in the bass. Of course, if he had a larger room and played way louder then maybe 1000 watts would not be enough......I mean, how many speakers are 2 ohm......not many. Let’s see......Alexx speaker is 91db sensitivity.....and say you are 10 feet back....so that would be around 82db with one watt......10 watts gives 92db and 100 watts gives 102db.....and 1000 watts gives 112db.......I doubt many listen this loud. This is why 500 watts into 2 ohms is plenty for most people and most speakers (most speakers don’t go near 2 ohms). The Merrill class D amps all double their power down to 2 ohms.....all of them. Most class D amps don’t do this because it costs more money for larger supplies and it is generally not needed. Did you know that the big Parasound Jc1+ amp does not double all the way down to 2 ohms? Stereophile measured 500 watts into 8, 830 into 4 and 1200 into 2 ohms. I guess they should make an even bigger amp to satisfy those that need number doubling.......$16K and no power doubling.....too bad. The 60 thousand dollar Gryphon amp doubles to 2 ohm....but it only does 700 watts at 2 ohms.....so my $2K IceEdge amp I sold last year will probably play louder than the $60K Gryphon.......doubling does not matter.....only the power you need matters. |
. doubling does not matter.....only the power you need mattersTell that to a pair of ML-2 monoblocks 20w only at 8ohm and can double all the way to 1ohm, one of the most magnificent amps you’ll ever hear. http://www.hifido.co.jp/photo/05/504/50446/c.jpg You just shot yourself in the foot, listening to you all you need then is one of these Class-D 3000w for only $399aud, that just $313usd!!! get two and bridge them. https://www.bavasmusic.com.au/behringer-nx3000-power-amplifier-with-smartsense?gclid=EAIaIQobChMIqIa... |
If you like or need volume, that "pathetic" 20W amp sound quite anemic. So it doubles to 1 ohm. If I have inefficient mainly 8 ohm speakers it will still be anemic. There is no magic in a 160W into 1 ohm amp that halves in power all the way to 8 ohms. You shot yourself in the foot with this really idiotic argument. I expect most people are shaking their heads reading it. |
Show us just one that’s not, and can almost double it’s rms measured wattage from 4ohm to 2ohm. The true indication of not current limiting, like many good A/B bjt amp.George, seriously, you would do yourself well to educate yourself on how amps work, at a basic level. Your metric seems to be "at full power". That is actually causing you to have confusion; its a misleading and lousy metric. What is important is that the amp behave as a voltage source, and by that I mean that it will make constant voltage regardless of the load impedance, at music power levels. If you exceed the power the amp makes into whatever impedance, it will clip (overload). I'm stating stuff that should be obvious but because you trot this trope so often, I have to assume that everything I'm telling you here is new for you. With any amplifier the designer is faced with limitations; often verses cost. For example, our module has GaN output devices that are rated at 35 amps. This means that we should not exceed 17 amps in the field if we want the output section to survive; employing 50% margins is a good idea with any kind of semiconductor! In addition the heatsink has to be effective, and yes you do need them for GaNFETs if you plan to run the amp at higher power levels, and especially if that involves lower impedances. So far all traditional solid state amps all have this factor in common too. Finally you have to look at how much you want to spend on the power supply. Given you know the limitations of the output devices there's an argument for setting the power supply current to a certain maximum so that current will not be exceeded. So really what this comes down to is what I've been harping to you all along: the current capacity of the output section, its heatsinks and the current available to support the output power of the amp are the variables and these are no different than traditional solid state. What **is** different is that the output impedance of any class D amp employing GaNFETs is several times lower than any traditional solid state amp. That is why they can act as a voltage source to a much lower impedance than traditional amplifiers. So your metric of 2 ohms is not harder to attain than it is for traditional solid state should the designer feel its important. |
It must be getting close to the release of the your new Class-D to respond like that with such verve and virgor with doubling of wattage v halving of impedance loading. Take it up with the likes of D’Agostino, Curl, ect ect manufacturers of the greatest amps that are recognized as being able to drive speakers with loadings that make Class-D’s run for the hills, they will tell you the same thing. Like I said "if" all that matters is wattage with Class-D, and what you and your mate say is anywhere near true, then all anyone needs is this $300 3000w Class-D https://www.bavasmusic.com.au/behringer-nx3000-power-amplifier-with-smartsense?gclid=EAIaIQobChMIqIa... As much as I like my NC500 monoblocks on my easy to drive secondary speakers, they can’t compete in an A/B against my friends Gryphon Antillion on his Wilson Alexia MkII’s, and the Gryphon is less than half the wattage of the NC500’s |
As I said, the latest $16K Curl amp does not double nor is it state of the art.....it is very good.....but no $60K Gryphon or $110K Boulder. Jay listened to the JC1+s briefly and then they went on their way.....not competitive. Of course quality matters. Behringer amps are just so so sonically. Nothing like a tweaked IceEdge or tweaked Purifi. Every single thing you do matters. Power output is only one of an infinite number of things that change sound. A stock Hypex module (less than $150 each wholesale) plus linear power supply versus a $40K Gryphon. I hope the Gryphon would be better. As I said, the power output is only one factor in how something sounds. I made the IceEdge module sound way more dynamic sounding with my mods.....but there was no increase of current of voltage. Nothing is that simple. I hope not one is claiming that a tweaked IceEdge or tweaked Purifi is state of the art. Tweaked IceEdge was $2K....tweaked Purifi is $2.6K. There will be and maybe there is better class D......and it will just keep getting better and better. Those who have more money.....please read the reviews of the AGD GaN amps and the Merrill Class D GaN amps.....they are getting rave reviews.....and they start at $7500. Can you afford that?......most cannot. I bet the average money spent on a high end audiophile system is under $20 grand for everything. All this talk about super expensive gear here is really out of place. Remember, for less than $1000 delivered VTV stereo amp with the Purifi amp modules and the Purifi buffer board is yours......the same basic proto amp from Purifi was A/Bed with $40K Constellation amps and found to be as good. The revolution has begun! |
Nothing like a tweaked IceEdge or tweaked Purifi.Save use all, looks like another one bringing out his new "tweaked" Class-D, probably has an orange fuse in it too Can anyone save us us against boutique Class-D manufacturers using threads to promote their own yet to be released stuff onto the market. BTW Those $300 3000w Behringers are ICE POWERED modules!!!! Two problems Class-D have still. The switching frequency, which is fixable with GaN technology the way only Technics so far have used it. And the second, is current delivery, where wattage goes up almost doubling for each halving of impedance down to 2ohms or even less. |
Take it up with the likes of D’Agostino, Curl, ect ect manufacturers of the greatest amps that are recognized as being able to drive speakers with loadings that make Class-D’s run for the hills, they will tell you the same thing.Actually they won't. They will all tell you the same thing- the limit of any solid state amp, class D or no, will be current the output section can withstand, the ability of the heatsinks to adequately cool the devices and how much current is available from the power supply. I will note one thing though- I've seen a number of SMPSs (Switch Mode Power Supplies) used in class D amps. I think its a bad practice. They work, sort of; the problem is that class D amps go from almost no current draw at idle to quite a lot at full power. SMPSs don't have a lot of capacitance at their output and so can be drained faster than they can replenish. A lot of them will shut down if you put a lot of capacitance at their output. So if you're not running an amp with a regular power transformer and a lot of capacitance available for the class D amp to feed on, you're probably not hearing what it can do. |
So if you're not running an amp with a regular power transformer and a lot of capacitance available for the class D amp to feed on, you're probably not hearing what it can do. Exactly true. That's what allows the H2O Audio S250 Signature to run Scintillas with ease and quality, albeit with old B&O modules. I'll take this old school approach with current class D anytime! |
Ok here is the part I don't get. HOW anyone can charge 7500.00 for any Class D or 20-40,000.00 for any class a or A/B. That is the my problem.. NO BODY is that good... I can see a Rolls-Royce costing 1/4 million, I understand that. The back right side door is a lot more complicated than ANY SOTA amp EVER made. But please explain, why THEY get 200.00 an hour for building an amp in 48 hours and expect ME or anyone to pay for it.. NUTTSO comes to mind.. Jesus help me.. I helped build and repair dams, bridges, aircraft, buildings, rescue people from other countries, on a job in Brazil pulling guys out of fresh bores 1000 feet underground. 50.00 an hour? MAYBE. God give me strength.. something is wrong.. Where is the Roller I been waiting for to show up on my door step with a big ol thankyou and a RED ribbon.. AND Buffy the belly dancer as the chauffeur. She gives wonderful hand massages. :-) Now everyone's point it? Some people like apple, some people like oranges. Me I like mangos. Regards |
I will note one thing though- I've seen a number of SMPSs (Switch Mode Power Supplies) used in class D amps. I think its a bad practice. They work, sort of; the problem is that class D amps go from almost no current draw at idle to quite a lot at full power. SMPSs don't have a lot of capacitance at their output and so can be drained faster than they can replenish. A lot of them will shut down if you put a lot of capacitance at their output. So if you're not running an amp with a regular power transformer and a lot of capacitance available for the class D amp to feed on, you're probably not hearing what it can do. I can't agree with this statement Atmasphere, it really depends on the power supply, how it was designed, and circuit limitations. Most switch mode power supplies for power amps I see for audio are not power factor corrected. They tend to be single stage LLC, with a simple bulk capacitor arrangement on the front end. Poor design choice in my mind, but is what it Is. They store most of their energy on the high voltage side, not the low voltage side. Let's say no PFC boost front end, so at 120V, say a bulk voltage with losses of 160. Pretty easy to put 1000uF, if not more on the front end. At 160V, that's 12.8 joules. That's the equivalent of 16,000uF at 40V. I would be more inclined to put a PFC boost front end with a link voltage of 400V. Now my 1000uF (450V capacitors) is like 100,000uF at 40V. That 450V, 1000uF capacitor is lot smaller than the 100,000uF, 50V capacitor. All that is required is the LLC stage has high surge (added power capability), and suitable continuous capability. |
JUNK? That’s kind harsh.. There are some good sounding class ds. NO they don’t float everyone's boat, but they get the job done for a lot of folks.. Is it my favorite amp? For some things, I think it is the absolute best.. I use 3 12k Behringer for SERIOUS bass duty.. I have 1300.00 invested. Come one come all, unless you have 4 of those things..:-) The best performance is 220 single phase. They can suck a PG&E pole dry, just like the rest of the welding machines can, too. Don't underestimate pro equipment EVER.. Couple of mods and some good cables. Can crumble a house... It's how you got to hear it the first time. Live anyway.. NC500 I have a few, wonderful amp with buffer boards.. George has got them cooking along without, buffers. I didn’t like Ice or the Hypex 400 without buffers. Maybe he’s got something special there. I use them in the hot summer months, with a tube front end. Valves in the cooler months.. Yea I don’t listen to junk. I never have. BUT then I like tone control, Mcintosh, Russco and VMPS speakers, too. I like slower runnin' women too.. That's just me.. There is "too fast" ya know.. :-) Regards |
I can't agree with this statement Atmasphere, it really depends on the power supply, how it was designed, and circuit limitations.The problem I was getting at is for the most part you can't use an off-the-shelf SMPS and get top drawer results. I think you could if you had a supply custom built but IME that's a very pricey thing to do- and not something that most 'high end audio' manufacturers can pull off due to the quantities involved. Obviously storing electrons at a higher voltage allows a lower capacitance, since voltage dominates the energy formula; I think the problem might come in when that conversion to the actual voltage being used has to occur and occur quickly. We were able to use SMPSs for prototyping, but continually ran into current limit shut down issues and the like. After a while (and also once we had sorted RFI issues) it got much easier to simply use a conventional power transformer. We still had to be careful about the power supply since it had to have a number of protection circuits built in. |
Given the price of high end audio equipment, if you are doing 1K units a year, 3 year design, 3000 units, you could amortize the $100K design cost, at $33/unit additional. Most audio companies would be best off contracting that out. Hypex does their own, and I have seen some a company or two offering audio targeted switch mode supplies. |
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I have to say that I am enjoying the sound from my DIY Purifi amps a lot more than the Nord NC500 amps I had last year. I don't know if this is because of my use of a large linear power supply in my DIY amps, the difference between the Purifi module and the Hypex module. the difference in input buffers, or other changes in my system. But these new amps are much more dynamic and engaging. I don't have the experience or knowledge that atmosphere or audio2design have, but based on my 45+ years experience as an audio enthusiast and tinkerer, a good power supply makes a huge difference in the sound quality of all audio electronics. I don't doubt that it's possible to achieve this with an SMPS. But either way, I think many (most?) class D amplifier companies are not making the effort and/or are not willing to increase their parts cost enough to deliver close to the full potential of what class D can offer. |
jaytorNot saying which are better Class-D modules but yes!! my NC500’s took a giant leap also, with big linear power supplies, made me realize smp’s no matter how well designed are not very good for audio. And then there was another jump again going direct in, with no input buffer, so long as your source has the gain, and <50ohm output impedance output stage/buffer. Cheers George |
They are basically compatible. The NC500 has a clip output which the Purifi board does not. The NC500 recommended op amp supplies are +/-15v where as the Purifi module recommends +/- 12V, but the Purifi max rating for this supply is +/- 20v, so you should be ok swapping in the Purifi module in an amp designed for the NC500. |
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After well over 200 hours of burn-in of the Weiss opamps I did my first focused listening test. The low-quality / distorted / unnatural midrange has come back. I could have sworn that issue was largely resolved by the Sparkos, but maybe I was misremembering it or I wasn't paying attention to midrange quality? Anyway it's pretty bad. Sounds sort of metallic, "buzz-y", which is why I want to call it a distorted sound. I switched to a $300 NAP200 clone just to make sure it wasn't something else in my chain -- nope, good quality midrange. I HAVE to ask those of you who own this amp if you really can't hear this low-quality midrange? It's pretty obvious in vocals and horns. |
That can be caused by an offset problem at the input of the comparitor- if its something like that I would regard it as a malfunction.Seems unlikely that this would be the case in both channels (assuming that's the case). Since this is a stereo amp, perhaps an issue with the power supply? I am not noticing anything particularly egregious in the midrange in my amps, but I want to spend some quality listing time comparing to my other amps now that I've got a couple hundred hours on the Purifis. It's been a few weeks since I listened to my Neurochrome Mod-286 amps, and a few months since I used my Parasound JC-5. I am hoping to get some time this weekend to do some critical listening and comparisons, and will report back after that. I ordered a pair of VTV's tube input buffers with Weiss op amps to compare with the Neurochrome buffers. These should arrive later this week, but will require some rewiring since the connectors are not compatible. I may have to order some connectors if I can't find any that fit in my stash, so it may be a couple weeks before I can try these out. |
Seems unlikely that this would be the case in both channels (assuming that's the case). Since this is a stereo amp, perhaps an issue with the power supply?I agree. I don't know how the Purifi module works, but if its anything like ours there is a low voltage side of the module where the comparitor and triangle wave processor reside. If the power supply has a regulator for all that, it could be that something with it is amiss- for example, the regulator is oscillating. At any rate it seems a good idea to get it checked out. |
I spent some time today switching between my Purifi amps (using Neurochrome input buffer), Neurochrome Mod-286 amps, and Parasound JC5. First, I should say that my ears aren't as discriminating as they used to be. I've suffered with Tinitus for many years, and my high-frequency hearing is not what it used to be. So take these observations with that in mind. I used the same interconnects for all three amps, but I had to use longer speaker cables with the JC-5 since it's a stereo amp. The cables were exactly the same construction, just 2.5 meters instead of 1 meter. Also, I used a different (although similar) power cord with the JC-5 since I needed a longer one. I set the levels using a pink noise -10db recording with a sound pressure meter with C weighting measuring 64db. For most of the recordings I listened to, this would be about my average listening level. A couple of the recordings were a bit lower volume than I'd normally listen. The songs I listened to were Sophie Zelmani - Why, Jennifer Warnes - Way Down Deep, Shirley Horn - Beautiful Love, Dominique Fils-Aime - Birds, Ray LaMontagne - This Love Is Over. I turned off my subwoofers for these comparisons since they have their own amps and I didn't want their contribution to influence my impressions. My main speakers (GR Research NX-Oticas) don't play very low without the subs, so I can't really assess the deep bass performance of the amps. All three amps have a fairly similar presentation, although the JC-5 was slightly more laid back than the other two. The overall differences between the amps were not real obvious. The JC-5 is slightly warmer sounding with excellent dynamics and smooth midrange. The highs (to the extent I can still hear them) sound clean and natural. Compared to the other amps, the biggest short-coming is a somewhat narrower sound stage. I suspect this is because the other amps are monoblocks. The Modulus-286 amps were the weakest of the three. They still sounded quite good, but had a bit of honkiness (if that's the correct term) to the upper bass and some unpleasant sibilance on female vocals. At higher volume levels, I've noticed these amps get a bit more congested sounding, probably due to their more limited power, but at the volume that I was playing today, they sounded fine. The Purifi amps were just a tiny bit rougher sounding in the upper midrange compared to the JC-5, but overall cleaner than the Modulus-286. They also had a touch more energy in the bass compared to the other two amps, most obvious on the Jennifer Warnes song. At this point, I'd be perfectly happy with either the JC-5 or the Purifi monoblocks, but I'm hoping I can take the Purifi amps to the next level with the new input buffers I just got. I'm waiting on a couple of connectors before I can install them (hopefully next weekend). The Purifi amps are also a lot more efficient which is particularly nice during warmer months. |
The definition of a shill is " an accomplice of a hawker, gambler, or swindler who acts as an enthusiastic customer to entice or encourage others." So you are saying I am a swindler and he is my shill? Shills get paid to swear false info and to entice. To call someone a shill is slanderous, unless you have proof. You just don’t like me and you don’t like him......so you call us names. This is against the Audiogon rules of conduct. Please grow up. Tweak 1 is an enthusiastic customer.....nothing more, nothing less. I don’t tell him what and when to post nor have I ever offered him free anyting or even given him a discount or any money. Again, please grow up. Shill does not mean to sell or promote. It has a much more sinister implication. You use the word to make it seem you are ridding this place of vermon. Remember, when you point a finger at someone.....3 are pointing back at you. Try pointing the love finger. Then three self love fingers point back to you. Love is much more fun and juicy then being right and making others wrong. Make everyone RIGHT. We are all beautiful. |
I did own one class D amp in an office system NAD M33. Kept it in that system for 3 months and elected to unload it while all the hoopla over this amp was positive. Was just to much for my office and operated at very high temps. Elected to get the Moon Ace all in one. The M33 had good sound quality and is built well. |
George, don’t you ever tire of being wrong, or jumping to wrong conclusions? In the early 2000s I was partner in a audio company named AudioTweakers, and took Tweak1 as my UN. It had (and I have) ZERO affiliation to Tweakaudio, which is ricevs’ website name. I am simply a very happy customer Over 10+ years I owned lots of class D amps going back to a PS Audio GCC- 250, which I bought new when I was a dealer (still in use in my video system). As time went on I have owned several W4S amps, Underwood HiFi 100.2SE monos with upgraded fuses, Audio Alchemy DPA-1, and prior to my EVS1200, PS Audio M700s I bought Ric’s EVS1200 because it had a 30 day money back and I was expecting the Voyager GaN amp within the 30 days so I could compare the 2. We know the Voyager still hasn’t been available, but I remain very happy with my EVS1200. Reviews of PS Audio’s M1200s have been fantastic, so there is at least some comparison to be made, though I am confident Rics pixie dust puts mine on a much higher level. hth |
Wow!! in one post your "suing me" and now your "recruiting me", how polarized can you get, suppose it depends on what it was on tap at the time. This is not a recruitment forum for whatever it is your trying to sell. You can't sell voodoo or snake oil to audiophiles using the love/hippy card, maybe some will bite. |