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

[Thomas Vecchione]

> 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.
> 

Of course that is why I was specific about what type of noise, general 
electrical interference is typical of onboard sound cards, but if it 
changes along with Disk IO or mouse movements, or other interrupts, then 
in my experience typically that has meant a ground loop.  You are 
correct in how to test it though, as long as it is not connected via 
audio to the other equipment any other way.

> 
> 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.

Not the highest cards, but midrange typically have them(For recording). 
  However just because you put a non onboard card in there doesnt 
nessecarily mean you will never hear interference, video cards in 
particular are notorious for inducing interference into audio cards if 
the two are close enough.  However putting in a different audio card 
will almost certainly help and be much better than the onboard.

Also just because a card has balanced outputs, doesnt mean the signal on 
the inside isnt running unbalanced and capable of picking up 
interference, that is why many people prefer external boxes for 
recording purposes;)

> 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.

Yea as long as it wasnt connected anywhere else to your audio equipment 
you can probably rule out ground loop.


       Seablade