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Topic: SPDIF output quality comparison (Read 4485 times) previous topic - next topic
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SPDIF output quality comparison

Hi, I've a simple question: if I use spdif out and play for example a mp3 file, is quality with an high-end soundcard exactly the same as with a low cost one?

SPDIF output quality comparison

Reply #1 –
In general, yes, but the soundcard drivers/characteristics can add differences in the software stage.

Concretely, i mean the known issue with soundcards that resample to 48Khz (most AC97 type ones).

SPDIF output quality comparison

Reply #2 –
You need a DAC to convert the audio data into an audio signal. Using S/PDIF to get outside of the soundcard means it will be the DAC on the other end of the S/PDIF transmission that determines the quality of the audio signal rather than the DAC in the soundcard.

SPDIF output quality comparison

Reply #3 –
If you play back your audio file

a) without some internal "treatment" like resampling (44.1 kHz file -> 48 kHz soundcard internal -> 44.1 kHz output) or playback software DSP,

b) without internal PC noise interfering and

b) if your spdif interconnect is not defective, a cheap soundcard will offer the same output quality than a high-priced one.

Unfortunately, most el-cheapo soundcards stumble over a) ...
The name was Plex The Ripper, not Jack The Ripper

SPDIF output quality comparison

Reply #4 –
Quote from: JeanLuc on
[...]
a) without some internal "treatment" like resampling (44.1 kHz file -> 48 kHz soundcard internal -> 44.1 kHz output) or playback software DSP
[...]
Unfortunately, most el-cheapo soundcards stumble over a) ...

Can't help mentioning that there is an alternative driver for C-media 8738/8768 soundcards (very popular in low cost sector), which allows bit-perfect playback over S/PDIF; [a href='index.php?showtopic=49350']discussion thread[/a] and homepage.

SPDIF output quality comparison

Reply #5 –
Quote from: JeanLuc on
If you play back your audio file

b) without internal PC noise interfering and


Can "PC noise" really affect/change digital output of a sound card? Wouldn't it be similar to "PC noise" affecting, for instance, exchange of data with an external hard drive? I don't know much about S/PDIF but exchange of digital data with external devices (such as hard drives etc.) is certainly not normally affected by any kind of noise, or nothing wold work. For all I know, S/PDIF could be different but I'd like to have this confirmed please. Thanks.

SPDIF output quality comparison

Reply #6 –
Most proper digital interconnects verify data integrity and in case of noise (error) request retransmission. S/PDIF receiver at best can try to hide any errors.

SPDIF output quality comparison

Reply #8 –
I've recently tested the SPDIF of a C-Media 8768 card by connecting the optical output to the input with a 7m TOSLink cable and playing/recording a DTS encoded file (~4min). There weren't any differences between the recorded and the played file, thus errors in the transmission happen seldomly and are negligible.
However, jitter errors (timing) can induce a loss of dynamic range, but since the majority of DACs have a small buffer and are effectlvely reclocking the input stream, this type of error is negligible, too.