• RE: Class-D component - svisner 08:55:21 04/16/17 (6)
  In Reply to: RE: Class-D component posted by neolith on April 16, 2017 at 06:29:54

  Thanks. I am grateful for the suggestion. At the moment, I think the NSMT will suffice. We're awaiting completion on work on our house, so we're in a rental now, pending a move to our house. The system I'm using, therefore, is intended as "temporary," though I suspect it will be the desktop system when we move. As it happens, our main system has Maggies driven by a McIntosh 240, but our Maggie center channel is driven by a Crown XLS Class D amplifier. It sounds very good, and I've been thinking of building a Class D-based system. Fun to experiment. (The Crown XLS amplifiers seem to have built a bit of a following.)
  

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  • RE: Here you go - josh358 10:16:21 04/18/17 (0)
    In Reply to: RE: Class-D component posted by svisner on April 16, 2017 at 08:55:21

    I tried out the XLS 2500 and while I think many would be happy with it, there were some oddities to the sound.
    
    My first impression:
    
    My initial impression was that the midbass was fuzzy and uncontrooled. However, it was such a brief listen that I want to give it more of a chance.
    
    Just spent several hours going back and forth with the A-21, listening full range. My impression is that the Crown has plenty of depth, etc. It doesn't sound bad at all and if someone wants a big mother amp for $300 bucks they'll be delighted. But when I switch to the A-21, it's as if the instruments are *there* behind the wall, surrounded by their natural ambiance. It's hard to explain but there's a palpability to the image, my eyes keep moving to look at the violin or cello or whatever. And with the Crown that doesn't happen.
    
    Also, when I pushed the level way high by mistake, we're talking well over 100 dB and the speakers were compressing, the Crown turned into a midrange muddle. So I tried connecting it to the A-21 and the muddle went away, it was just clipping on the peaks. But the Crown's limiter was turned on, so it may have been that.
    
    Also, my setup still coarse, tomorrow I'll match levels with a multimeter, and check that the polarity is the same, then move the amps to the listening position so I can switch between them more quickly -- no time to contrive a switch because I have to make a decision soon. And run them off separate circuits so they don't pull one another's voltage down.
    
    
    A. Wayne added:
    
    Playing Classical Music on the Crown was an eye and ear opener, couldn't unplug it fast enuff, contrast it with Jazz, Horns in particular , i thought it was fantastic, a bit thin and bright but really boogied, then I started to notice the artificial ping on Pianos' every Piano sounded like a keyboard, then the classic Music disaster.
    
    Again , the amp is sensitive to power cords and environment ( RF) so YMMV and it may all be system dependent in my case, but you know how it goes, once you hear a negative, it never leaves yah ...
    
    
    And then me again:
    
    OK, so I did the serious comparison yesterday, levels matched with a meter within a fraction of a dB, polarity matched, amps in front of me so I could switch without moving my head. I listened first to both channels to judge imaging, then to only one channel to facilitate switching, then to one channel, woofers alone. It just reinforced my original impressions, to whit:
    
    - The Crowns sound very nice when you just plug them in. They won't take your ears off. If you have only $300 bucks for an amp, I think you'll be happier with the Crowns than with most alternatives.
    
    However:
    
    - There is something seriously wrong with piano, as you say. The notes are missing their attacks, making them sound more like a keyboard than a piano. Piano has a 20 dB peak/average ratio and it seems that the Crowns are smearing the transients. Maybe the filters?
    
    - Pushed even a very little bit, the sound starts to become metallic and midrangey and stuck in the center -- is this Davey's IMD? Pushed a lot, the effect is disastrous shoutiness, while the A-21 handled the same overload with just brief transient distortion. We're not talking about subtle in that case, but brickbat obvious.
    
    - There's something wrong with the imaging. With the A21, instruments in an audiophile recording of a string quartet seem to be hanging out there, somewhere beyond the wall; they're so palpable that my eyes move around to follow them. With the Crowns there's good depth, but no palpable image forms. My eyes don't move. Much of the time I can't even tell where they are. It's a very strange phenomenon.
    
    - I think there's strong phase distortion from the filters. At least, when I was setting them up, voltage doubled between the hot terminals of the amps at IIRC 2 kHz. So I figured phase was inverted. But when I backed the frequency down to 80 Hz, the voltage difference went down to zero. I don't have a scope here so couldn't investigate further but it does look like serious phase shift from the output low pass filter. I'd be curious to see measurements of group delay and ringing, both of which could potentially contribute to the issues we've heard.
    
    - Again and again, I had the same experience -- the A-21's sounded pure and easy to listen to long term. I didn't want to switch away from them. But I'd listen to the Crown and the subtlety and details were gone and it became fatiguing even though it wasn't making *bad* noises like graininess that I normally associate with listener fatigue.
    
    - I had the sense that small details and ambience were being removed, as in those early undithered 14-bit digital recordings. What seems at first superior cleanness on the Crown's part seems to be that it's suppressing very low-level distortion.
    
    - Since I planned to use these on the woofers, I tried disconnecting the mid-tweeter panel and just listening to the woofer panels, which are LPF'd at 250 Hz. Even then, I could clearly hear the difference between the amps. On walking bass on a jazz recording, with the A-21, one heard a full, round note. On the Crown, that full, round note had gone missing. It's not like you can't tell that there's a bass there or what note its playing, but it seems more fuzzy distortion than the full, round note.
    
    - With mid-tweets disconnected, I could still hear the problem with piano attacks.
    
    Bottom line, it was a fun experiment, but they're going back.
    
    https://www.audioasylum.com/cgi/vt.mpl?f=mug&m=218492
    
    
    

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  • RE: Class-D component - Satie 13:52:56 04/17/17 (4)
    In Reply to: RE: Class-D component posted by svisner on April 16, 2017 at 08:55:21

    There is no inherent problem using class D amps, they just need to be of proper ratings for power and current and as well made and refined as you are willing to pay for.
    
    Maggies, and particularly ribbon models are quite revealing of common nits in the high frequency performance of most class D amps. That said, they have improved substantially over the last decade. And competing class A AB amps of similar power performance are not necessarily that much better at the same price points.
    
    The Crown XLS series amps are powerful and relatively inexpensive and in audiophile terms they are downright cheap. But when compared to similar powered or even lesser powered well designed class AB amps they are loose in the bass and not as resolving on top. What it is most obviously is inoffensive. For actual performance in refinement and bass you can use a higher line of amps from Crown, like the XTI series and even the extremely high power macrotech "i" or "HD" series at an appropriately higher price.
    
    

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    • RE: Class-D component - DrChaos 14:06:05 04/18/17 (3)
      In Reply to: RE: Class-D component posted by Satie on April 17, 2017 at 13:52:56

      I use NAD M22 class-D amplifier (Hypex nCore) with my 3.6R's and it sounds great to me. Then again, that's a substantially more expensive amplifier.
      

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      • RE: Class-D component - Satie 15:39:02 04/18/17 (2)
        In Reply to: RE: Class-D component posted by DrChaos on April 18, 2017 at 14:06:05

        Execution and parts quality (and quantity - i.e. available overhead) make a difference with any design.
        
        

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        • RE: Class-D component - TitaniumTroy 17:47:43 04/18/17 (1)
          In Reply to: RE: Class-D component posted by Satie on April 18, 2017 at 15:39:02

          I use a Parasound A23, 225 watts @4 ohms, seems to work pretty well. I tried one of their desk top models (z-amp v3) at around 60 watts @ 4 ohms, this resulted in thermal shut down after awhile. Plus not enough power in a small bedroom/office, for even moderate levels.
          

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          • RE: Class-D component - svisner 20:28:21 04/18/17 (0)
            In Reply to: RE: Class-D component posted by TitaniumTroy on April 18, 2017 at 17:47:43

            The NSMT seems to have plenty of power. It runs quite cool.
            

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