Usb audio vs onboard digital audio

**nasa** · 02-21-2007, 09:09 PM

Hi,

I am trying to determine wether to use a usb soundcard or go with the audio provided with my VIA EPIA EN15000 Mini-Itx Motherboard. From my searching it seems there are the following pros with using USB:

Better sound quality (higher S/N ratio, louder volume)

the cons being:

Higher cpu usage
Higher usb bandwidth usage
Higher power usage

The pro that I read about is caused mainly by removing the audio source from the case, thus removing noise from the cpu/harddrive/fan. Everywhere I read this was mentioned in regards to analog signals.

So the question is... Is that still true given a digital signall (via the S/PDIF) connection?

Additionally, how much more cpu is used given a usb sound card like the Roadie?

Thanks for any hints

Nasa

**XC-C30** · 02-21-2007, 09:33 PM

how much cpu is used depends on the cpu, hardware and software you use.....

**nasa** · 02-21-2007, 09:37 PM

Well,

I noted the MB and cpu... It is using 1Gig of ram and run WinXP SP2 - frontend (right now) is RoadRunner, DigitalFX theme.

Nasa

**XC-C30** · 02-21-2007, 09:46 PM

if you're not using multiple programs at the same time (like some of us for audio-processing), you should be fine with a simple stereo or 2.1 usb-card. what kind of chip is being used for the on-board sound? most-on-board soundcards aren't that great when it comes to sound-quality. I'd do some more reading (yes, I know, there's lots of info and it can be hard to take it all in

). I'd search for the projects durwiid and Red GTi VR6 are on.... Those two have done some great contributions when it comes to audio and audio-processing.

**psyrex** · 02-21-2007, 09:49 PM

Disclaimer: I'm making lots of assumptions and guesses. I think I have it right, but I have nothing substantial to back this up.

USB offloads alot of processing crap to the CPU. This is how tiny products like this can exist and work. I imagine that the smaller the device, the more work depends the CPU. However, for example, the Extigy can be used as a standalone device (I have one and I've tried it. It's kinda cool). I imagine that if most of the audio can be handled by the device, less work is placed on the CPU.

As for noise with S/PDIF on the motherboard, I suppose that depends on how the signal is generated. If it only appears as digital and then sent through the TOSlink, then it's probably fine. However (and I think this might be true), if the motherboard just produces analog signals and a A/D chip converts it to digital, it's not so fine. A S/PDIF connection really only protects the signal as it's being transported from the computer to the device. It doesn't cover what happens before it enters the TOSlink.

Again, I think the above is right, but I might be talking outta my ***.

**nasa** · 02-22-2007, 07:11 AM

So,

I continued my

searching to see if I use SPDIF will the audio stay digital through out....

I have found these points of reference:

http://tjrforum.com/archive/index.php/t-946.html
http://www.linuxis.us/linux/media/ho...tpc/audio.html
http://www.head-fi.org/forums/showpo...75&postcount=7

all seem to suggest:
"The plus you get from spdif is total electrical isolation from the noisy computer."

Do the all knowing members of mp3car agree with that assessment?

That would suggest using a motherboards s/pdif out would be better than using usb and/or a pci soundcard.

Nasa

**durwood** · 02-22-2007, 07:43 AM

I was not impressed with SPDIF from my mobo. Yes, you should have no noise from my experience but it sounded flat to me, not very good D/A-A/D conversion/codec handling.

I am not sure if the SPIDF is still processed by the dacs built into the mobo when using SPDIF, but most mobos do not use high quality dac chips or good codecs unless you are using a newer mobo that supports the new HD codecs.

I am using a Creative Live USB right now for SPDIF and before i was using a PCI Creative Audigy2 on my M10000 ITX. The increased CPU usage from the USB soundcard was about 20-30%. Before I think my CPU ususage was hovering around 5-10% with the Audigy2, now it's about 30-40%.

**HIPPOhifi** · 02-26-2007, 08:23 AM

Originally Posted by nasa

pros with using USB:

Better sound quality (higher S/N ratio, louder volume)

the cons being:

Higher cpu usage
Higher usb bandwidth usage
Higher power usage

Better Sound Quality - In most cases
Higher cpu usage - Yes but not much, for the Bloat (our product) it was about an extra 3%-5% on a 1.8ghz machine
Higher usb Bandwidth usage - Yes but this wont affect sound quality or other USB components
Higher power usage - Yes, to be precise a maximum of 2.5watts (5v @ 500mA) for each USB device.

cheers,
Brent

**nasa** · 02-26-2007, 11:21 AM

Hippohifi:

Thanks for the info. So, if I may ask, how does audio quality over S/PDIF compare between usb and motherboard?

Nasa

**HIPPOhifi** · 02-28-2007, 09:02 AM

Originally Posted by nasa

Hippohifi:

Thanks for the info. So, if I may ask, how does audio quality over S/PDIF compare between usb and motherboard?

Nasa

Hi Nasa

In most cases USB will sound better because the interface between all the components (transmitter, receiver and dac) are on the same PCB and can be designed to deal better with jitter and interference. When using SPDIF out on the PC, the transmitter and receiver/DAC are obviously seperate devices, a poorer design solution and opens the door to more interference and jitter.

Furthermore, the trick is to find a USB Device that uses the I2S interface between USB receiver and DAC. I2S is better than SPDIF as it minimizes jitter. In some cases USB DACs use the SPDIF interface between the USB receiver and DAC within the PCB of external device. Eventhough this is somewhat contradictory to what i said in the previous statement, the interface is still in the same design space, ie on the same PCB. Although, this is still a better option than spdif over a cable into an external DAC.

Hope this is clear, a lot of USBs, SPDIFs, DACs mentioned..

cheers,
Brent