[mythtv-users] "Do you really need a discrete audio card ?"

[James Courtier-Dutton]

On 22 November 2010 21:41, Christopher X. Candreva <chris at westnet.com> wrote:
>
> Tech Report has release an interesting review, comparing the Asus Xonar
> cards to the common built-in Realtek chips, with the low-end ($29) Xonar
> comming out as a worthwhile upgrade.
>
> Aside from the article being interesting, it made me wondering if switching
> audio cards would help with the "WriteAudio: buffer underrun" problems I
> have with untranscoded content, which hasn't gone away with 0.24
>

Having worked on ALSA for many years, I agree that on-board sound
cards are considerably worse that even cheap PCI ones.
The worst offenders are laptop ones though.
While sound output is not so much a problem, the real problem comes
with the "mic" input when using a VoIP product like skype.
While developing a VoIP app, we were adding noise cancellation
features to the software.
I had a discrete PCI sound card, and the Mic input had something like
12dB (a lot) better S/N ratio than a laptop mic input.
I also talked to some sound hardware engineers at EMU, and they told
me the problems with laptop mics are all solvable, but require the
addition of about 3 extra capacitors/resistors to the motherboard, and
the motherboard manufacturer prefers to save a few pence and not
include those components.

It is true that you only need to spend money on the Analogue
components in your audio system to get good sound.
1) DAC
2) ADC
3) The AMP with the analogue speaker outputs.
4) Speakers/Headphones.

So, a graphics card with audio over HDMI will sound identical to any
other graphics card with HDMI.
Just like, for less than 4 Meters, any v1.3 HDMI cable will work. No
need to buy expensive ones because it is digital.
You might have to be more careful with long HDMI cables, due to
electrical transmission reasons. Much like Ethernet cables, although
digital in nature have limits on how long you can make the cables.
HDMI is sort of equivalent to a 10Gbps copper Ethernet cable if one
existed.

I would prefer it if the speaker industry moved to speakers with
direct digital inputs, so the speaker unit would have a SPDIF or Audio
over Ethernet input, and the speaker itself have the amp and speaker
drive unit all in one. One could even move of a standard of something
like ethernet audio over mains to get the sound to the speakers and
cut down on cables used.
Then, one could buy cheap everything else because it would be digital,
and the only component that would make any difference to the sound
output would be the speaker unit itself. You could then make the
speaker perform better because you could implement feedback mechanisms
so the circuit could detect where the speaker cone is at any one time
and modify the drive to better match the input digital PCM signal and
further reduce distortion.

Kind Regards

James