On the topic of solid state, what about Class D?

Discussion in 'Power Amps' started by JeffYoung, Apr 20, 2017.

  1. JeffYoung

    JeffYoung Rando

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    The idea of them makes the hair stand up on the back of my neck, but that's mostly because I've had bad experiences with PWM drives in other fields (telescope drive systems and model railroading).

    But I note the Hypex modules are getting some good press, and Class D seems to be taking over the powered subwoofer market.

    So what do you guys think about Class D vs. Class A/B or Class A?

    Cheers,
    Jeff.
     

  2. Armaegis

    Armaegis Friend

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    Class D inherently has issues... basically it doesn't really produce a smooth output but rather chops it up into pulses which get smoothed into something useable on the output stage. Early designs were rather iffy, and while in theory the final output smooths out to resemble what we put in, there was a lot of distortion generated. Newer designs have improved on this drastically, but class D suffers from the reputation of its early days. Plus there's still a LOT of cheap and crappy implementations out there. By that token however, there's also a lot of cheap and crappy class A/B amps too.

    Class D amps have the huge advantage of higher efficiency, less heat, and lighter weight. They can often produce higher peak outputs as well. The cheaper designs can often get very very lightweight. Good designs will start getting heavier again as they start beefing up the power supplies and output stages.

    So what do you need? If you want purity and have a strong back and have cold winters, stick with your class A space heater. If you want five hundred hundred watts of power on tap but don't want to kids to burn themselves on it, class D might be the way to go.

    I used to run a bunch of Bryston amps on my PA rig and they sounded great. I switched out to some cheap Peavey amps that don't sound nearly as good, but I willingly made that choice because now the rack of gear that I have to haul to the car weighs 40 lbs instead of 120 and I'm not tripping the breakers when the beat drops.
     
  3. Priidik

    Priidik Friend

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    Regarding Hypex...
    The NCore will outperform most usual solid states, especially in bass.
    It's cleaner, clearer, there's no mosfet false density and no bjt tizz. Also more natural sounding than any solid state I have tried. I liked the tonality.. ,or lack of any tonal issues.
    Transient performance is second to none, and I say it in context to high end tubes.
    This is the amp that commits no sins of commission, but of course nothing is perfect and I feel in microdynamics and stage tubes are still better.
    There is lack of 'inner life'' to it.
    I have no exposure to real high end solid states, but anything below 5 k$ that I have heard have been at least a strong league below.

    The old gen UcD modules are noticeably more veiled and dull, more reminiscent of run of the mill class A-B, ie significantly and noticeably inferior.
     
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  4. TwoEars

    TwoEars Friend

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    There are definitely good Class D amps around these days, the NAD M22 springs to mind. However - if you're an addict for that smooth velvet like character that some of the best Class A amps have I haven't heard any Class D amps that do quite that yet. But if you don't want a room heater, or a second mortgage for you power bill, Class D is a very valid choice, and class A/B as well. Every manufacturer does things a bit differently on the circuitry level so I wouldn't focus too much on Class A/B or Class D and instead listen to individual amplifiers.
     
  5. uncola

    uncola Friend

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    I had a Phillips ucd based emerald physics ep100.2se Class d amp and it was as good as most entry level ab amps I've heard, certainly no worse. I live in Hawaii with no air conditioning so I'm always considering class d. The amps are just so small and not audiophile looking though
     
  6. strangecargo

    strangecargo Rando

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    I have a pair of Hypex NC400 mono blocks made from the Hypex DIY kits. I've been using them to run in a pair of new Dynaudio Contour 30s and it's only recently that the C30s have started to sound natural, so I don't have a lot of nuanced commentary on the NC400 modules, but my general impression of them echoes a lot of what @Priidik has said. They sound like very, very competent solid state without any of the weirdness that people normally associate with Class D. The bass is incredibly tight and controlled and they don't really seem to color the sound at all. The imaging seems to be very precise, but soundstage is somewhat flat and tight. I'm still working on speaker placement, so it could be that I just haven't figured out how to place the C30s in this room yet. They exhibit some self-noise; I felt that I could just barely perceive the background hiss from my main listening position on ~90dB sensitive speakers, but I don't really notice on the C30s (87dB).

    The kits cost €1300 for the pair and took me about 90m to assemble with a screwdriver and not much else. The DIY aspect was little more than screwing a few pre-assembled boards into the chassis and connecting them with pre-terminated cables. There was no soldering iron involved.
     
  7. JeffYoung

    JeffYoung Rando

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    Interesting. I think Rogue is still using the UcD modules in the Sphinx and Pharaoh, and while I haven't heard either of them, they seem to have a lot of converts. I wonder if they'll update to the NCores....

    On the other hand, I live in Ireland, and every little bit of extra heat is welcome, even in summer. ;)

    Anyone know if JL Audio's or REL's subwoofers use the Hypex modules, or if they roll their own?

    Cheers,
    Jeff.
     
  8. JeffYoung

    JeffYoung Rando

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    One of the few reasons I miss living in California. Ireland doesn't have the population to support much in the way of high-end audio dealers.

    Cheers,
    Jeff.
     
  9. Kattefjaes

    Kattefjaes Mostly Harmless

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    It's worth giving the Sony WM1A DAP a listen- it seems to have some sort of crazy class D output that performs the functions of both DAC output and amp. It gives the thing ludicrous battery life and sounds surprisingly nice for a portable (assuming you run it in "direct source" mode with all the processing off).
     
  10. strangecargo

    strangecargo Rando

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    I think the general idea behind this concept is that the PCM is turned directly into PWM at the amplifier without an intermediate analog stage. I have a pair of active speakers on the desk in my bedroom that implement their crossovers in DSP and have amplifiers for each driver that operate in this way, so if you use the digital input on the speakers, the audio stays digital until it reaches the amplifier at each driver. Pretty cool:)
     
    Last edited: Apr 21, 2017 at 2:09 AM
  11. Kattefjaes

    Kattefjaes Mostly Harmless

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    Yes, that is the general idea.
     
  12. crazychile

    crazychile Friend

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    I've been looking at class D amps quite a bit lately. For car stereo.

    I know about their reputation for sounding like ass. The general opinion is that they've gotten a lot better in the last few years. I can buy a ~100w 2 channel Class D amplifier from a reputable company for <$200 that doesn't get hot, can be concealed in the dashboard of the car, and it's not much larger than a pack of smokes. In a car environment where some of the nuances are lost anyway, this is the perfect solution for me.

    Home stereo is another story. The selling points of Class D don't do much for me. Except maybe cost. But cheap cost doesn't matter if it doesn't sound decent. If these amps are truly getting a lot better, then maybe at some point in the future I would consider one for home.
     
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  13. Hrodulf

    Hrodulf MOT: Sonarworks

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    If I had big hungry passive speakers to drive, I prolly would look at nCores. They're really good. And by that I mean - they trade punches with the good-est Class-AB. People will learn to forget about the old Class-D sins. That's not to say that there aren't bad ones, It's just that there are bad amps of any class.

    P.S. Extra topic for your thought - PWM power for class A/AB! I know that Tom swears by it. Might be good, if one knows how to design high PSRR circuits.
     
  14. sorrodje

    sorrodje Carla Bruni's other lover - Friend

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    I was considering some Hypex UCD180 H&R for my Thiel CS1.5 ( Kinda hard to drive with a 4ohm impedance and 87db/W sensitivy. moreover Impedance goes lower @ 3ohm ) but @Priidik comments are not that encouraging. For sure I don't need as much power as the Ncore provides so UCD180 looked like the sweet spot for me.
     
  15. Hrodulf

    Hrodulf MOT: Sonarworks

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    If you're handy with an iron the FirstOne Class AB modules might do the trick. Heatsink mounting usually sucks, but they're pretty cheap for what they do.
     
  16. SineDave

    SineDave Facebook Friend

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    I was a real skeptic of Class D, but then I discovered D-Sonic, who uses Pascal modules with a proprietary input board. To my ears they are the best I've ever heard class D, and really impressed me. I ended up A/B'ing them against some older Adcom and Krell class A amps, but really preferred the D-Sonics. They currently drive my home theater/stereo setup which is all Legacy Audio.

    I also got to A/B D-Sonic's 600WPC monoblocks against Raven Audio's 20K tube monoblock, and the D-Sonic held its own with better speed and dynamics, but less of that tube character.

    It's easy to speak negatively about Class D, but you have to hear the best implementations to really understand what it's capable of.
     
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  17. earnmyturns

    earnmyturns Almost "Made"

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    I've owned a Bel Canto C7R integrated amp that drove my KEF Reference 1s very well. It was all digital/PWM (all Bel Canto gear is?) It sounded very controlled, solid bass, highs a bit dry, soundstage a bit flat. I like my current Yggy>Hegel H360 better, bigger soundstage and more realistic overall, but it's 2.5x more money and a lot more space (the H360 is big and heavy). I could have lived with the C7R happily except that I started listening to Schiit multibit DACs, loved what I heard, but the C7R was useless as amp after one of those because the first thing it does to its analog inputs is to A2D them into the amp's main digital path.
     
  18. Cspirou

    Cspirou Friend

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    If we are asking what is the best sound we can get below a certain price, then I think class D is an underused tool in that box. When comparing class D vs other offerings reviewers usually compare it on a one to one basis. However the cheaper prices for class D typically mean you can get 2(or more) amps for the price of one similar spec'd class AB, which means bi-amping or active EQ. So if the comparison is just straight class AB vs Class D, then I would say class AB wins every time. But if you are comparing:

    Class AB amp -> passive speakers

    vs

    2 x class d -> biamped tweeter and woofer

    I'd say it's not as clear cut. Especially if you throw DSP into the mix.
     
  19. Armaegis

    Armaegis Friend

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    Or just get an active bi-amped monitor with DSP and digital input. Save money by skipping that silly dac in the first place.
     
  20. sorrodje

    sorrodje Carla Bruni's other lover - Friend

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    How do compete usual Class D amps like those based on Hypex UCD180 modules against something like a Yamaha AS700 ?
     
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