[mythtv-users] Integrated Sound vs. Sound Card, suggestions ??

[Brian Wood]

On Jun 7, 2006, at 3:56 AM, Chris wrote:

>>
>> The problem is that I am getting a lot of hum and garbage coming out
>> of the line out (lime green) connector on my motherboard.
>
> Define garbage? Clicks and the like that change along with moving the
> mouse, or HD spinning up, etc.?
>
> If that is the case most likely you have a ground loop and you should
> either switch the equipment to share the same ground, or if that is  
> not
> feasible isolate the AUDIO ground(Leave the AC ground completely  
> intact
> for safety reasons)

Since common mode (ground loops etc.) is a common source of this sort  
of thing I tried grounding changes for the AC sources. The Macs pull  
enough current that it was not practical to put them on the  
computer's UPS system, so I tried a solid-state amp with the same  
result.

I'm not sure how I would go about isolating the audio signal ground,  
as it is apparently tied to the DC ground of the motherboard.

Of course single-ended (non-balanced) high-impedance audio running in  
a chassis with all sorts of square waves at many different  
frequencies is a problem waiting to happen, but I think only the  
highest-end audio cards have balanced low-impedance audio outputs.


>
> On the contrary, audible noise from onboard audio is a very common
> complaint with many popular motherboards and is caused either by poor
> decoupling/signal routing in the mb itself or a power supply with poor
> output regulation.  You can quickly establish this simply by  
> plugging a
> set of headphones into that lime green mb jack.

I finally thought of that and plugged a pair of Koss PRO-4AAs into  
the mobo output jack, the "noise and garbage" is definitely there. I  
didn't notice it before as it seems to be primarily low frequency  
stuff that the previous speakers simply couldn't reproduce. The  
garbage seems constant and does not change with CPU, disk or I/O  
activity.

The power supply is a supposedly decent Thermaltake unit and should  
have reasonable regulation.

Googling around it seems this is indeed a very common complaint, and  
it seems the motherboard makers do indeed give just as much attention  
to audio quality as they do to the built-in video :-)

>
> Even a cheap used SB Live card for around $15 will produce much  
> improved
> audio and the newer SB Audigy or Turtle Beach Riviera cards are even
> better.  What you ultimately spend should be determined by the quality
> of the rest of your audio system.

I'm going to pull the SB-Live out of my old Dell and see if it  
improves things, assuming it does I'll just invest in a sound card  
for the Myth machine.

So are most Myth users using integrated sound or sound cards ? Again  
this list sees more video discussion than audio, but that makes sense  
for several reasons.

It seems my "under $200" project to improve my audio will probably  
run closer to $1000 by the time I get a receiver, some good speakers,  
sound card etc. Oh well, that's how it is with hobbies, guess I'll  
just put off buying that Intel-based Mac for a little while :-)