Trouble is the Levinson sounded like crap. Everything makes a difference....again....the truth is in the listening. It does not matter that Levinson used a bunch of air core coils (one thing does not make a whole).......what matters is the sound. They did not get it right. My modded Purifi uses ONE super sounding air core coil.
Class D
Been thinking of trying a D amp to reduce clutter. Most that I see are not rated at 2 ohms. My PSB Stratus gold's will drop to 3 ohms or lower at some frequencies. So my question is will these types of amps handle this impedance ?
Thanks in advance. Chris
Thanks in advance. Chris
Showing 13 responses by ricevs
Please don't be stupid. It is stupid to respond to George.....he is a rock....he will never move from his position.....and he has to have the last word.......so it will always go on and on and on. Don't be stupid....he does not want to learn....he just wants to be right. Let it go.....let him go. Just let him post what ever nonsense he wants and pretend it does not exist. You will be much happier, if you do. What we really need is feedback from those that have listened to the latest class D amps versus the latest class A and class A/B amps (within the same price ranges). We need actual listening test impressions.....not all this guess work.....it is just a bunch of noise. The Technics amp that is about to be released has tons of stuff inside that could make it sound great. Technics does not even mention 1.5 meg or phase shift in their literature. This thing could be really fantastic.....but there is no way you can say it is because of 1.5 meg or phase shift. Please read all the info....very revolutionary. It has 4 switching power supplies that switch at 500K....It is not really a standard class D at ALL.....it is fully digital (like the original Tact amp and Lyngdorf). It takes an analog signal and converts it directly to high speed PCM and does all kinds of low jitter manipulations to make the distortion go down. The PCM signal is then changed in software directly to PWM (class D). Please read all the lit. https://www.technics.com/us/products/reference-class/integrated-amplifier-su-r1000.html https://www.technics.com/us/about/press/releases/20200901-su-r1000/index.html https://www.youtube.com/watch?v=b-BJifbtjbI George did start a thread on this new goodie....so when this comes out and people have listened then we will have a REAL idea of how good it is. It looks great....I do hope it sounds great too. |
Here are some interesting developments.... 1. Class D audio (under the Premium Audio name) will soon be releasing their "baby" GaN amp.......stereo, 150 watts a channel into 8 ohms, balanced and unbalanced inputs for a mere $699. 100K input impedance. You will see a tiny bit of info here....wait for the second slider to load to see the pic https://premiumaudioproducts.com/ 2. Orchard Audio is releasing a higher powered version of their GaN amp module. You can buy the module fully loaded or you can just buy the board and buy all the parts and stuff it yourself. This new 250 watt a channel module has higher input impedance (44K balanced) and higher gain then before so makes it more universal. The unloaded boards can be bought for $100. The stuffed boards can be purchased for less than $1000 the pair (till the early bird sale goes away). This would be way better than the eval board put out by the GaN companies.....The Orchard amp measures and sounds very, very good.....800K switching and very very little phase shift. https://orchardaudio.com/shop/ols/products/strk-ltr-mdl/v/STRK-LTR-MDL-SSMBLD The phase response and other measurements of the earlier less powerful module can be seen at the bottom of this page. https://orchardaudio.com/bosc#58053fe9-04a5-4030-9e69-e310ee3f6b5a |
You can theorize all you want. What I do is listen. Most EVERYONE who has listened to ferrite core coils in a xover.....knows they suck. I now know they also suck as "full range" coils on the output of a class D amp. You can only know how something "sounds" by listening. If you want to build just for numbers than a ferrite core is fine. I build for sound......the best sound wins. Of course, it is just my opinion. Until others listen to air core coils on the output of a class D amp it is just.....my opinion....based on what I hear. There are lots of opinions where they have used them in speaker xovers.....and the overwhelming opinion is that ferrite sucks. Look at all the pics of the xovers of super high end speakers.....do you see any ferrite core coils used in the mids and highs? Don’t think so. He he.....I am sure someone will find one and post.....just to be right....he he. |
Here is an interesting fact. The IceEdge module has two....yes, two inductors in series on the output. It could be one reason the phase does not measure so well. I removed the last inductor and the last set of caps to ground as part of the last set of mods I did (PS Audio leaves these alone but still the highs are pretty good....please read Michael Fremer"s review of the $6K PS Audio amps where he compared it to the $150K Dartzeel). When I did this it sounded as if I had 2 db more gain. The soundstage came forward....much like my class A amp and the highs were much more extended and airy and the decay went on longer. The depth was now greater but the midrange was more forward. Very cool. Many other mods I did to the module improved the highs as well....and they had nothing to do with bandwidth or phase shift. Everything makes a difference.....It is not just one parameter. |
I did not measure the amount of residual after removing the secondary coil and caps. Since the caps to ground were just 1000 pf....I imagine that the residual looked much the same. IcePower was probably trying to remove ultra high frequency noise as a precaution. So many manufacturers put filters and fuses on things to prevent imaginary problems.....not knowing these fuses and filters actually wreck the sound. Everything you do changes the sound. The output coils that everyone use are ferrite core coils. No one in their right mind would use a ferrite core coil in the midrange and tweeter xover of a serious speaker. Ferrite messes up the sound. So, why do we have ferrite coils on the output of all class D amps? It is because they are smaller, cost less, have less resistance, run cooler and have better contained fields so there would be less rf outputting the amp. It is not because they sound good. If you use a better sounding air core coil the board has to be bigger, the coil costs more, you have to use a large gauge coil to get the resistance down, and you might have to add more shielding in the amp to make it pass rf standards. What is true is that all coils sound different from each other. So, even different ferrite core coils will sound different.....even using the same gauge wire. The type of wire and its coating all affect the sound......just like wire used in an interconnect. The worst being normal copper....OFC is better, cryoing is better, PCOCC is better, etc. Same with the core material and shape and coating and wire directionality and whether you go into the inside or the outside of the coil. Many air core coils I tried in the Purifi module did not sound as good as the stock ferrite core coil. The one I ended up using sounds much better than the stock coil. When I first heard the difference between the stock coil and the one I am using......I said "its like I am sticking my head down the saxophone". I could hear so much more information.....real information....space, separation of instruments, lower noise, etc. We need others to start experimenting with the output coil.....this is more important than what the switching frequency is. There is always more to learn and more beauty to unveil. |
Because the filter is set at 50K does not mean it does not effect the sound. It's intrinsic sound is still there. No free lunch. Everything makes a difference. But you have to listen to know. Years ago I worked for an audiophile company that made tube stuff. They had a zobel network on the output of one of their amps that had a .1 microfarad cap. . I told them to change their junk mylar cap to a polystyrene but the owner said it was operating at high frequencies out of the audio band so it should not matter. He humored me and tried it. Of course, it sounded much better. There are people that sell external zobel networks and the best sounding ones use the most expensive parts. Again, no free lunch.....everything makes a difference. |
Of course, I checked every channel of every amp that I sold and looked at the residual of each channel. I just did not do an exact measurement of the before and after. From what I remember, it was very much the same, about a half a volt or so of pure 500K with no added high frequency noise (but since I did not do an exact measurement then that is what I tell you I did). However, it sounded way better without the extra filter (most class D amps just use one coil and one cap per phase). if I had seen any kind of added noise on the 500K wave or a noticeable increase of value I would of taken note......there was basically no difference (that I remember). The secondary coil is 15 uh and the cap to ground is 1000pf.......so it looks like a 1.3 meg filter......that is not going to make any difference in a 500K sine wave. If you add another 1000 pf for speaker wire than maybe a hair difference. By the way, I first removed the 1000 pf caps to ground on the output and heard no difference. But when I remove the inductor.....OMG When Nuforce started making class D amps I was a dealer. That first amp had all kinds of noise coming out of it. One if the fixes they used was to add a secondary coil right on the speaker output terminal. When I look at the output stage of the latest class D Nuprime amps (Nuforce morphed into Nuprime) then I notice a bunch of coils near the output.....so I believe they are still doing this today. Most everyone just uses one coil and cap. More ferrite coils on the output is not merrier. How many coils (hopefully air coil) are you using on your output? Coils are not good......but you have to have one in a class D amp or you fry your speakers......so make that one the best sounding one in the universe! |
The original UCD module had lots of feedback.....all around the output coil....The Ncore modules added even more feedback and the Purifi adds even more feedback. Most people feel the Ncore sounds better than UCD and Purifi sound better than Ncore. Read the reviews of the "super high feedback" Purifi amps.......they like them. I am not a FAN of feedback....nor am I not a FAN. There are lots of ways up the mountain. Again, everything matters. One amp with 500K switching could sound way better than another at 1meg switching.....or visa versa.....One amp could sound better with more feedback....or with less feedback.....it is not one thing......everything has to be done well. |