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Classification of USB D/A Converters

January 10, 2014 / Dalibor Kasac / Articles
5

Rational and clear information regarding audio equipment is not available today from mainstream audio literature. We only see unnecessary long treatises on high end audio, concentrating on technical descriptions and pointless analyzing of sound nuances, without any clear statements about the sounds fidelity.

Just like external sound cards, USB D/A converters are an integral part of computer audio systems and we would very much like to present our view of their performance. We are trying to avoid long descriptions by organizing USB converters into 3 classes, thus making the information about them simple and decisive. Placing all USB converters into only 3 groups may seem superficial, but after the following explanations the point shall be very clear:

CLASS 1 converters do not change the characteristic sound of acoustic instruments significantly. Trained or professional ears can easily determine the level of distortion caused by the digital to analogue conversion.

class1
It is always present, but the devices of the class 1 group do not obstruct euphonic lifelikeness during music playback. USB D/A converters in this class should be considered as the best devices available for D/A conversion. Their sound varies from model to model, but all of them share a unique capability to reproduce acoustic music without influence on sound perception, characteristic of a live performance in a concert hall.

CLASS 2. The majority of USB D/A converters are members of this group. CLASS 2 converters lightly distort the analogue signal in a way usually referred to as “digital sound”. It is easily recognized in crescendo passages of orchestral music.

class2
At a crescendo’s climax the music becomes harsh and tiering, especially for the trained listeners, accustomed to live musical performances. Synthetic music (amplified instruments – electric guitars, pianos, etc.) is not so sensitive to digital harshness. The vast majority of popular music is played on amplified instruments, and this makes the converters in this class popular despite of the mentioned drawbacks.

CLASS 3. Artificial sound, the annoying and unnatural timber of acoustic instruments, make the converters in this class completely useless for serious stereo systems. Although some modern music genres like techno-pop could even profit from distorted sound that the class 3 USB DAC can produce, music connoisseurs devoted to high fidelity should not be interested in digital mish-mash, produced from CLASS 3 converters. 

class3

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5 comments on “Classification of USB D/A Converters”

  1. Jesper Heeno says:
    May 18, 2014 at 10:55

    That class 2 usb not always superiour to class 1.1 usb makes no sense to me Dalibor.

    However, I can confirm that the SPDIF out of a Teralink X with an C-media usb 1.1 controller outperforms the usb input on my new NAD D1050 with XMOS. The difference is like day and night, with a more natural, open sound from Teralink X spdif and much less harsness. Less digital sound.

    The question stands if we can improve the sound quality from usb 2.0 DAC devices by forcing a linux system to use usb 1.1 low speed protocol?
    Only method I know to test this is to prevent the usb 2.0 ehci-hcd module from loading use the command: rmmod echi-hcd. The Ehci-hcd module is unfortunately compiled statically into the linux kernel of my current distro Ubuntu 14.04.

    So talibor tell me if it Is possible to remove the ehci-hcd module on AP-Linux, I might give it a try.

    Regards Jesper

    Reply
  2. Wieslaw says:
    July 3, 2016 at 13:02

    This classification is very important, but how it can be determined in relation to specific DACs?

    What defines this natural sound?
    1. what characteristics (eg. Dynamic range, Resolution, Maximum sampling rate);
    2. the processor type – which of known types of chipsets belong to 1, 2 or 3 class? (here are a few: ES9018, ES9016, ES9023, PCM5102, PCM2706, PCM2704, PCM1794A, AK4495, AK4490, AK4399, DSD1796, CS4398, WM8740 etc.)
    3. moreover?

    Regards,

    Reply
  3. Branko Živković says:
    March 15, 2021 at 20:44

    Is it possible to install AP Linux on Compact Flash Card? If YES what size?
    Does AP Linux support touch terminals? Is it possible to set portrait orientation instead of landscape?
    I have TouchDiva Music streamer based on Celeron , 2GB RAM, 15″ touch display and 2*125W IcePower amplifier but boot device is only CF card.
    Should I try to install AP linux on it?

    Reply
    • Marko says:
      March 18, 2021 at 12:25

      Flash cards are bad and slow and it will ruin the sound of AP-Linux so it’s not recommended. Portrait is maybe possible. Check xrandr command on Linux. For touch display, I don’t know.

      Reply
    • lorenzo says:
      June 28, 2021 at 21:23

      Yes, like any Linux you can boot it from SD, even if it’s not the best solution.
      To avoid slow read problems from SD and potential slowdown/stuttering of sound playback you could preload the entire OS in RAM.
      Unless it’s specifically forbidden from the motherboard you CAN boot from USB too.

      Reply

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