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Thoughts on a bunch of DACs (and why delta-sigma kinda sucks, just to get you to think about stuff)

Discussion in 'Dedicated Source Components' started by purrin, Dec 5, 2013.
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  1. ultrabike

    Something like that it seems. Would be interesting to know roughly what the quantization Noise Transfer Function (NTF) is (or the equivalent to whatevs his deal is) as that determines to some extent the level of out of band quantizaiton noise filtering needed. That's quite a large oversampling rate also. So is he interpolating the imput signal to the (maybe) delta sigma? If so, using what type of filter? WTA?

    Maybe that's why he needs a lot of taps. Because running the delta sigma that fast might require a fairly large interpolation filter before actually hitting the delta sigma (or PDM, or PA, or WMD).
     
  2. evillamer
    [​IMG]

    System diagram of chord Hugo
     
  3. negura

     
    Where imo some of the studio monitors (in my experience mostly PMCs - have had two different models of these) are really good compared to some "nice" consumer speakers, is the former don't have any design goals in exaggerating or colouring to please. That would not impress their core market. It could be an error of commission, but likely not intended. They try to stay accurate and transparent to the source, which, while may sometimes not instantly impress, in the long term can actually be more pleasant and enjoyable imho, by sounding well a bit more realistic. That's not to say other non-monitor speakers don't achieve the same goals of course.
     
    Harshness/Shrillness: Usually source material and upstream rig would be the cause of this. The PMCs I have are surprisingly well behaved, for how resolved and transparent they are. One of the reasons is that say comparatively to my HD800s, the PMCs don't have audibly nasty treble peaks and (in my room, which isn't that special) reflections like the unmodded former. That said if I were to hook the PMCs to a bright/harsh sounding DAC running bright records, I would always hear that. There are other factors too. Hardly surprising - most good transparent speakers would react the same. 
     
    I would encourage anyone to try and hear a pair of studio PMCs or ATCs on a good R2R DAC or vinyl and a good amp. With my Theta Gen V the PMCs sound noticeably that notch or two warmer/softer compared to the Yggdrasil, or the PWD2. But then I realise preferences are everything and some people would be enamoured with a different type of sound.
     
  4. bmichels
    Has someone heard the new BAKOON DAC-21 ?  It is battery operated, with SATRI connection to connect to the BAKOON HPA-21 amp.
     
    BAKOONDAC-21.png
     
    wmedrz likes this.
  5. skeptic
     
    I'm inclined to think that linear is a misnomer here, and the standard array of published audio measurements just isn't telling us the full story.  On the feedback front, I don't think it is so much about odd or even harmonics but rather disproportionate high order distortions.  According to Pass ( https://passlabs.com/articles/audio-distortion-and-feedback), feedback designs with superlative conventional measurements manifest more complex non-linear distortion products than higher THD nonfeedback designs.  Depending on their analog output stages, I would think dacs could share the same traits since opamps require negative feedback to operate in a linear mode (i.e. as an audio amplifier), and many dacs employ opamps in the output.  
     
    That said, although I tend to prefer nonfeedback amps, some opamp based gear really does sound good to me, and not at all harsh, with the right headphones.  So I think even the above must be oversimplifying what is really going on.  
     
  6. ultrabike

    To some extent it makes sense. To some other, not so much. That's a lot of interpolation filters and one obscure "noise shapper". Who knows. If it's a multi-bit 5th order delta sigma, I guess it's not much different from some consumer audio DACs ICs out there. The sampling rate is quite high though. Maybe that's what they are trying to market as their differentiator.

    Having a high sampling rate may result in lower quantization noise, in paper. Depends on the actual implementation.

    Wish things were more up front with those guys though. Given impressions by some it may be that they are over designing for one set of requirements and neglecting others. I dunno.
     
  7. maverickronin
     
    Doing the crossfeed in the digital domain on a portable device is pretty damn cool though.
     
    It's a shame that it looks like toy for toddlers though.  It might as well be Fisher-Price My First DAC or something...
     
  8. evillamer
     
    The advantage of Hugo over other sigma delta dac is that it has a dedicated FPGA which has more processing horsepower which means more complex digital filters can be implemented. If you look at higher end dacs that feature ES9018s/ES9018K2M(e.g. Audiolab MDAC, Grace design M920) they usually have their own custom filters and also may bypass the ASRC/PLL on the Sabre.
     
  9. ultrabike

    LOL! Yup. Looking at it brings to my mind "brick", which is not a good thing.

    Crossfeed in the digital domain is not too bad IMO, but a good feature to have. You know the Sansa Clip+ Rockboxed does some of that. It works to some extent. But it lacks head tracking which I found to be very important after giving the Smith Realiser a shot.


    The FPGA is more flexible, but not necessarily higher performance. Depends on implementation details I guess.
     
  10. DreamKing
     
    If the recording is at fault or the headphone is harsh (which is demonstrably more plausible) , why should the dac and amp roll off harshness in them? I mean they could but does that mean that they're superior because they roll off everything and should every electronic strive for this? Where this harshness is coming from should be evaluated before coming to the conclusion that the dac or amp is at fault. And then you're in the realm of perception with all of these terms, so it's all relative.
     
  11. maverickronin
     
    I'm just glad that another 'high end" company is taking the idea of crossfeed seriously.  A full on convolution DSP like the Realiser uses plus the head tracking can help quite a bit, but if you're listening to stereo recordings any kind of crossfeed is better than nothing.
     
    It's the biggest problem in the fidelity of headphones that almost no one is addressing.  IMO not using analog crossfeed or a more advanced DSP is the headphone world's equivalent of just throwing a pair of speakers wherever they'll fit and not bothering with toe-in, stands, room treatment, etc.
     
  12. hans030390
     
    I'm curious where you got this rule that more components and larger boards = harder to make transparent. I'm also wondering if your idea of "transparent" is different than how others describe transparent (and it probably is).
     
  13. wahsmoh
    Seriously. Check out Legacy audio.. they have some serious $$$$ speakers I have heard once in a music room at a high end stereo shop. 
     
    http://legacyaudio.com/products/dsp-solutions/
     
  14. Sapientiam
     
    If you're looking for technical reasons - its poor PSRR, coupled with power supplies which haven't low enough impedance.
     
    Simple experiment to try on the O2 - add lots of low ESR capacitors across the supply rails for the NJM4556s which are doing all the heavy lifting. I'd suggest a dozen 3,330uF/10V, six each side. The reason for the power supply noise is that the opamps are operating in classAB, meaning nasty non-linear currents are drawn.
     
    These are the caps - they're bulky so the whole thing will no longer fit in the case. But its a $10 upgrade.
     
    http://www.digikey.com/product-detail/en/EKZE100ELL332MK25S/565-1651-ND/756167
     
  15. aqsw

    Please dont feed the troll.
     
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