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  1. #1
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    Some observations about the Benchmark DAC1

    See my post here.

    http://www.pinkfishmedia.net/forum/s...d.php?t=137152

    Regards, Darren

    Sent from my HTC Sensation Z710e using Tapatalk 2
    Check it, add to it! http://www.dr.loudness-war.info/

    SB Touch

  2. #2
    Senior Member Archimago's Avatar
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    Quote Originally Posted by darrenyeats View Post
    See my post here.

    http://www.pinkfishmedia.net/forum/s...d.php?t=137152

    Regards, Darren

    Sent from my HTC Sensation Z710e using Tapatalk 2
    Thanks Darren. I like the comment about overshoot handling. Will need to have a look at this when I do my measurements. Will be very curious what the Transporter and Touch looks like in this regard.

    Also, it's interesting to note the worsening of jitter with the USB interface clearly demonstrated. I have actually seen a similar phenomenon with my ASUS Essence One comparing the USB with SPDIF; even though it is supposedly better due to asynchronous protocol.
    Last edited by Archimago; 2013-04-25 at 21:33.
    Archimago's Musings: (archimago.blogspot.com) A 'more objective' audiophile blog.

  3. #3
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    Archimago, you may want to look again at the PFM thread since there has been a bit of question-and-answer! Also screenshots.
    Darren
    Check it, add to it! http://www.dr.loudness-war.info/

    SB Touch

  4. #4
    Senior Member Archimago's Avatar
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    Quote Originally Posted by darrenyeats View Post
    Archimago, you may want to look again at the PFM thread since there has been a bit of question-and-answer! Also screenshots.
    Darren
    Thanks Darren.

    I've tried some preliminary tests. I'm actually not sure what Rockwell is getting at with the overshoot handling plots. When I try to roll over that second image (where he lowered the volume), I'm not seeing a difference (anyone else seeing something?).

    Here's what the AUNE X1 looks like with a 1.00227 kHz square wave (that extra 2.27Hz is because of the 0.1kHz in 44.1kHz):
    Name:  Standard_1kHz_AUNE.jpg
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    Note the bit of even harmonics thrown in and I didn't bother calibrating to 0dB.

    Here's what happens with an exact 1.00000 kHz square wave.
    Name:  Standard_Exact_1kHz_AUNE.jpg
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    The DAC1 doesn't look clean compared to his Sony SACD player output because of the upsampling from 44.1kHz to 110kHz - a non-integer upsampling factor; what is or is not contributed by overload is unclear to me.

    The DAC2 I think upsamples to 211kHz which again is not a clean multiple of 44.1kHz. As such, I suspect again if you look at a 1.00227kHz signal like on the CBS CD-1 which he used, the spectrum will still look ugly compared to the SCD-XA777ES. I don't think this is relevant in terms of the sound itself though; good luck reproducing an accurate pure square wave with speakers & headphones :-)

    Mr. Rockwell did not mention this issue and he's using the $50k Rhode & Schwarz...

    BTW, I believe the Transporter and Touch would have no problem with this... Just a matter of how much extra harmonics thrown in...
    Last edited by Archimago; 2013-04-27 at 09:10.
    Archimago's Musings: (archimago.blogspot.com) A 'more objective' audiophile blog.

  5. #5
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    Archimago,
    Did both your examples use square waves with 0db peaks? The screenshot's a bit fuzzy.

    I thought the fact the DAC1 uses ASRC for jitter would mean integer multiples are irrelevant. Hmm.

    Thanks,
    Darren

    Sent from my Nexus 10 using Tapatalk HD
    Last edited by darrenyeats; 2013-04-27 at 16:29.
    Check it, add to it! http://www.dr.loudness-war.info/

    SB Touch

  6. #6
    Senior Member Archimago's Avatar
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    Quote Originally Posted by darrenyeats View Post
    Archimago,
    Did both your examples use square waves with 0db peaks? The screenshot's a bit fuzzy.

    I thought the fact the DAC1 uses ASRC for jitter would mean integer multiples are irrelevant. Hmm.

    Thanks,
    Darren

    Sent from my Nexus 10 using Tapatalk HD
    Yes, both are square waves at 0dB. Unfortunately the message board resizes the images.

    Integer multiples are *essential* when looking at this type of test with square waves. That's why I suspect that Mr. Rockwell is unaware of this fact despite the fancy gear (I like his camera review BTW) :-). Wondering what he's trying to show with volume reduction.

    Bottom line, the ugly looking spectrum is due to the Benchmark DAC1's 110kHz upsampling (why did they pick this and not something better like 176 or 192!?) unless proven otherwise!
    Last edited by Archimago; 2013-04-27 at 18:43.

  7. #7
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    Archimago,
    Ok, I now understand your criticism of Rockwell's analysis. Good point well demonstrated. It explains the Sony.

    The Benchmark results with strong spurs across the whole spectra at -60db, are still distinctly worse than the dirty one you just posted ... plus Rockwell's (also dirty) spectra for the Apogee and Audioengine. Could we infer that all were non-multiples and this BM difference is due to poorer overshoot handling?

    The much bigger difference in the Sony spectrum and your better spectrum would still be explained by the integer multiple (as well as potentially better overshoot handling?)

    My point is, we know the DAC1 lacks DSP headroom (and the DAC2 has this headroom) and I expect this is at least contributes to Rockwell's particularly bad DAC1 spectra.
    Darren



    Sent from my HTC Sensation Z710e using Tapatalk 2
    Last edited by darrenyeats; 2013-04-28 at 03:34.
    Check it, add to it! http://www.dr.loudness-war.info/

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  8. #8
    Senior Member Archimago's Avatar
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    Quote Originally Posted by darrenyeats View Post
    Archimago,
    Ok, I now understand your criticism of Rockwell's analysis. Good point well demonstrated. It explains the Sony.

    The Benchmark results with strong spurs across the whole spectra at -60db, are still distinctly worse than the dirty one you just posted ... plus Rockwell's (also dirty) spectra for the Apogee and Audioengine. Could we infer that all were non-multiples and this BM difference is due to poorer overshoot handling?

    The much bigger difference in the Sony spectrum and your better spectrum would still be explained by the integer multiple (as well as potentially better overshoot handling?)

    My point is, we know the DAC1 lacks DSP headroom (and the DAC2 has this headroom) and I expect this is at least contributes to Rockwell's particularly bad DAC1 spectra.
    Darren



    Sent from my HTC Sensation Z710e using Tapatalk 2
    Yes, that is exactly what I was trying to get at. It looks like ASRC caused the square wave spectrum to look distorted compared to the clean Sony. As you said, perhaps he's suggesting that lowering the volume will show a significant reduction in the amount of distortion but it's hard to tell from those graphs, especially the 2nd graph in that section since the text suggests there should have been another image if the mouse rolled over it.

    I'm also a little confused about the difference he's seeing between USB and TosLink (first roll-over graph). I would have thought that with the ASRC, the spectral difference would be minimal if even present. It also doesn't look like he's using Bit-Perfect with iTunes to ensure accuracy, furthermore I'm also a little concerned about his decision to use that "six-year-old Belkin 7-way powered USB hub with a 10-year-old, 6-foot USB cord" - nothing wrong if we know for sure this old setup isn't introducing its own noise into the mix (I've seen this kind of problem in tests).
    Archimago's Musings: (archimago.blogspot.com) A 'more objective' audiophile blog.

  9. #9
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    I think the roll-over is merely to compare the two graphs more easily. So when you roll-over the top graph you can A/B with the bottom graph. He mentions knocking the levels but I think it's just a measurement level and the DSP headroom wasn't changed.

    If you compare the jitter measurements you can see there are very tiny differences between transports, perhaps that explains the difference in the square wave test between toslink and USB.
    Darren
    Last edited by darrenyeats; 2013-04-28 at 15:26.
    Check it, add to it! http://www.dr.loudness-war.info/

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  10. #10
    Senior Member Archimago's Avatar
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    Had a look at the effect on the ASUS Essence One which has a "symmetrical upsampling" feature. So 44.1kHz material is upsampled 8x evenly to 352.8kHz.

    No upsampling - square wave, 0dBFS, 1.00227 kHz:
    Name:  1khz_Square_-_No_Upsampling.jpg
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    With 8x upsampling - square wave, 0dBFS, 1.00227 kHz:
    Name:  1khz_Square_-_With_Upsampling.jpg
Views: 378
Size:  19.7 KB

    Nice :-)
    Harmonics remain clean and I don't see any issue with overload - looks like ASUS has compensated adequately for the intersample overhead for this test. Also notice how clean the even order harmonics are compared to the AUNE X1.
    Last edited by Archimago; 2013-05-05 at 23:51.
    Archimago's Musings: (archimago.blogspot.com) A 'more objective' audiophile blog.

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