Critic's Corner

Who were contenders? Most DACs have USB as an afterthought, so it's not surprising. N/T

129.33.19.254

carcass93

In Reply to: RE: I enjoy TAS and read the USB articles in the August issue. posted by AbeCollins on July 1, 2009 at 09:48:10

N/T

Follow Ups:

Benchmark, Bryston, Bel Canto USB Link 24/96... - AbeCollins 16:54:21 07/1/09 (5)
...and perhaps some I'm forgetting.
- RE: Benchmark, Bryston, Bel Canto USB Link 24/96... - fmak 23:07:23 07/1/09 (0)
  And Audio Research
- Bryston - talk about afterthoought... but Benchmark and Bel Canto results should be concerning,... - carcass93 17:58:14 07/1/09 (3)
  ... since supposedly some actual design went into those. However, I do recall that Stereophile measurements for Bel Canto's jitter were pretty subpar.
  - They did a followup on the bel canto - JA had a problem adjusting his software volume control - keith_d 11:54:23 07/2/09 (2)
    And that threw the measurements off.
    
    This is from memory, btw.
    - Er, no - John Atkinson 15:59:09 07/06/09 (1)
      > They did a followup on the bel canto - JA had a problem adjusting his
      > software volume control...And that threw the measurements off.
      > This is from memory, btw.
      
      You can find the review at the link below. I am not sure what I wrote
      that gave rise to your perception that I "had a problem adjusting [my]
      software volume control." I was driving the Bel Canto with my Mac TiBook,
      using Bias Peak to play back test tone WAV files. This is what I wrote in
      the review:
      
      "there were very slight changes in output level apparent when I fed [the
      DAC 3] a continuous tone via USB. (This didn't happen with the other
      inputs.)" I wasn't having problems with any "volume control"; instead,
      the output level of the DAC3, fed USB data, continuously varied, not by
      much, perhaps a couple of millivolts on a 2V output, but that's not
      something usually seen with DACs and not with the Bel Canto via S/PDIF.
      This behavior didn't change significantly when I switched to the Mac mini
      that I use as my general music server.
      
      I did check that CoreAudio wasn't changing the sample rate, BTW.
      
      I did have other problems listening to music using my TiBook as source:
      "Selecting the USB Audio Codec as the computer's default audio output in
      the System menu and playing back 44.1kHz-sampled files with iTunes, the
      sound was accompanied by what sounded like FM "birdies"; ie, silence when
      no music was playing, but a random whistling when it was. I couldn't
      eliminate this no matter how I tried�wondering if it was a grounding
      issue, I tried using the laptop in battery-powered mode, but no luck."
      
      I solved this by switching to the Mac mini.
      
      John Atkinson
      Editor, Stereophile
      http://www.stereophile.com/digitalprocessors/1107bc (Open in New Window)
      - RE: Er, no - keith_d 10:32:53 07/14/09 (0)
        
        In Reply to: RE: Er, no posted by John Atkinson on July 06, 2009 at 15:59:09
        
        Here is what I was thinking of:
        
        "Repeating these tests feeding the Bel Canto's USB input, I wasn't sure what to expect, as the bit and word clocks are no longer embedded in the data; in fact, the data clock is generated locally. While the jitter with 24-bit data was even lower than with TosLink data, at just 63.2ps (fig.10, black trace), 16-bit data gave a moderately high 637.3ps, dominated by data-related sidebands (fig.10, grayed-out trace). Does this measured performance correctly characterize the DAC3's performance via its USB input? Was, for example, the very low 24-bit figure due to the data being truncated to 16 bits? Test-equipment manufacturer Audio Precision recently loaned me a sample of their state-of-the-art 2722 analyzer; in subsequent issues I will be further investigating this aspect of the Bel Canto's behavior, along with some other new digital processors."
        
        "Other than the jitter performance via its USB input, the Bel Canto e.One DAC3 is the best-measuring digital component I have encountered."
        
        I don't have the follow up which may have explained how to avoid this high jitter you got via USB in some way. I thought it had to do with your using a software based volume control somewhere, maybe in iTunes. I also could be confusing your review of the Bel Canto DAC with a review of another DAC entirely which had this issue. Perhaps a Benchmark.
        
        If I had the print issue I could look at the manufacturer's comment and your follow up, but I don't save them. If I cared enough I could ring up Bel Canto...but they don't me and they have other priorities, as I am sure you do also. (BassNut.)
        
        And my memory is not so reliable, so....
Exactly - Presto 16:31:45 07/1/09 (1)
A lot of lumping USB solutions into one bin going on.

The "afterthought" methods are often adaptive move or just use the "USB Codec chip of the day". Very few are doing an asychronous direct-I2S method like wavelength, empirical or Scott Nixon.

And which firewire approach are we talking? Some here have testing SPECIFIC firewire applications and they were terrible.

I think generalizations are the bane of this forums existence lately...

Cheers,
Presto
- RE: Exactly - fmak 23:08:12 07/1/09 (0)
  Read the article

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