Poor mobo audio

goodguys

Member
2011-02-23 3:51 pm
Hi And thanks for reading this post.

I have a gigabyte ga-ma785gpm-ud2h mobo, which has a xonar d2x soundcard in the pci-e slot.

The audio coaxial out of the xonar goes to an external audiolab m-dac.

The m-dac is then hooked up to a quad 405-3 amp (£3k) and b&w nautilus speakers (£6k)

When i hook up the audiolab m-dac directly to the mobo's usb port the sound is not good.

But when i hook up the m-dac to the coaxial out of the xonar d2x the sound is a lot better.

Do you know why this may be.

The m-dac won best dac under £1k for four years in a row in what hi-fi magazine, i thought hooking that up to the mobo's usb port and taking zeros and ones directly would give the best sound quality, but this has not turned out to be the case.

Is the mobo at fault, for some reason it is not passing the audio information to the dac very well.

Or is it the xonar doing something better than the mobo can do.

Many thanks.
 
The spdif coax output probably has an isolation transformer on it. This blocks low frequencies that might otherwise get into the power supply rails, etc. With USB you might have "dirty" power from the computer, or other problems related to ground loops, etc.

If you have a powered USB hub around you might try plugging that into the computer, and then the DAC into it, and see if this improves the situation. This will support the dirty power theory.
 
It might help for you to describe what "not good" means to you, and what "a lot better" means.

What kind of differences do you hear? What makes the USB connection "not good"? In theory, as long as you get bits out the USB port, your DAC should be perfectly fine, as should your Xonar... Giving us more detail might help us understand what you're looking for, and then be more helpful.
 

goodguys

Member
2011-02-23 3:51 pm
Hi. Thanks for the replies, much appreciated.

CharlieLaub I don't think it is a dirty power problem. The m-dac is mains powered and takes all its power from there.
The audio information is input to the m-dac via a usb connection. i don't think it actually takes any power from the usb hub, although i have read on some of the other forums people snipping away the usb power lines and experiencing better sound quality as within a usb cable the audio and power lines are close together and may be causing interference problems.

Jplesset Hmm, not sure how to answer. The audio from the usb sounds a little thinner and lacking in detail compared to the soundcard, the soundcard is more punchy and dynamic.
Is it perhaps the soundcard is specalised for sound duties so may be performing better because of that, or is the usb connection maybe more of a general purpose pathway and have have all kinds of other signals passing through it at the same time.

On a side note, what i want to do next is buy a motherboard as my present gigabyte one does not support gpt partitioning and my 3tb discs are not being recognised.
Are there any particular makes or models better suited for top end htpc duties, something good at passing usb signals to external dacs hopefully.
I have a quad 405-3 amp (£3k) and b&w natilus speakers (£6k) so need a really good board

Many thanks. John.
 
John, honestly, I suspect that there's simply a volume diffrerence, and perhaps an expectation difference. Maybe, though, your Xonar card is adding something you like via some kind of processing?

On the motherboard front, I've had very good luck over the years with the various Asus boards, and most of the MSI boards. I must have 8 or 9 old ones lying around my place. Consider an AMD-based board, lest cost and plenty of performance.
 

goodguys

Member
2011-02-23 3:51 pm
Hi. Thanks for the reply.

You probably are right about the processing.

Could you possibly name names concerning the motherboard I don't really know much about them.
I already have an amd phenom II processor from the last mobo, could continue using that, as you say best to stick to amd.

Kec Could you name the msi board. I also heard that hdmi output is supposed to be superior to usb, higher bandwidth or something but haven't noticed too much difference myself

Many thanks.
 
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What it seems to me is happening here is the usual common-mode noise problems.

Inside your PC is a dirty switcher which induces an ultrasonic noise voltage between mains neutral and the screen/0V of the USB port of your computer. When you plug the m-dac's USB input into your PC, and the m-dac is also mains powered, there's a loop formed for those ultrasonic noise currents. They do damage within the m-dac, polluting the signal grounds, inducing noise voltages between terminals supposed to be all at the same potential (0V).

To get better sound you'll need to raise the impedance of that loop which then reduces the magnitude of the noise currents. This can be done in a number of ways - for example a common-mode choke on the supply to the PC, or on the supply to the m-dac, or a USB isolator between the PC and m-dac.
 

jiiteepee

Member
2007-03-22 3:43 pm
Hi And thanks for reading this post.

I have a gigabyte ga-ma785gpm-ud2h mobo, which has a xonar d2x soundcard in the pci-e slot.

The audio coaxial out of the xonar goes to an external audiolab m-dac.

The m-dac is then hooked up to a quad 405-3 amp (£3k) and b&w nautilus speakers (£6k)

When i hook up the audiolab m-dac directly to the mobo's usb port the sound is not good.

But when i hook up the m-dac to the coaxial out of the xonar d2x the sound is a lot better.

Do you know why this may be.

The m-dac won best dac under £1k for four years in a row in what hi-fi magazine, i thought hooking that up to the mobo's usb port and taking zeros and ones directly would give the best sound quality, but this has not turned out to be the case.

Is the mobo at fault, for some reason it is not passing the audio information to the dac very well.

Or is it the xonar doing something better than the mobo can do.

Many thanks. .

Hi. Thanks for the replies, much appreciated.

CharlieLaub I don't think it is a dirty power problem. The m-dac is mains powered and takes all its power from there.
The audio information is input to the m-dac via a usb connection. i don't think it actually takes any power from the usb hub, although i have read on some of the other forums people snipping away the usb power lines and experiencing better sound quality as within a usb cable the audio and power lines are close together and may be causing interference problems.

Jplesset Hmm, not sure how to answer. The audio from the usb sounds a little thinner and lacking in detail compared to the soundcard, the soundcard is more punchy and dynamic.
Is it perhaps the soundcard is specalised for sound duties so may be performing better because of that, or is the usb connection maybe more of a general purpose pathway and have have all kinds of other signals passing through it at the same time.

On a side note, what i want to do next is buy a motherboard as my present gigabyte one does not support gpt partitioning and my 3tb discs are not being recognised.
Are there any particular makes or models better suited for top end htpc duties, something good at passing usb signals to external dacs hopefully.
I have a quad 405-3 amp (£3k) and b&w natilus speakers (£6k) so need a really good board

Many thanks. John.

Maybe you just don't understand the digital (audio) world yet (either (ever heard term ABX)).

As you seem to prefer over priced audio gear ... just pick the most expensive mother board with features you think you could need in your "top end" HTPC. :D
 

goodguys

Member
2011-02-23 3:51 pm
Hi. Thanks for the replies, much appreciated.

abraxalito If the problem was a dirty switch would it cause audible noises to appear, such as pops, crackles, whistling sounds etc through the speakers.
I googled it and people are reporting that background sounds disappear when a usb isolator is employed.
Or would the dirty switch just cause an overall degradation of the sound without the background noises.

Also can you advise on the common mode choke, i noticed a few on digikey all with different current, resistance and impedance specs, is there anything particular i should be looking for.

Many thanks.
 
abraxalito If the problem was a dirty switch would it cause audible noises to appear, such as pops, crackles, whistling sounds etc through the speakers.

I see I've caused some confusion by using shorthand. A 'switcher' is engineer parlance for a switched mode power supply. Not a 'switch', no.

I googled it and people are reporting that background sounds disappear when a usb isolator is employed.

Isolation of full-speed USB (12Mbits) is fairly straightforward and a commodity item nowadays. There are very few isolators available for high-speed (480Mbits) USB and prices are considerably higher. What sample rates are you using with your DAC?

Also can you advise on the common mode choke, i noticed a few on digikey all with different current, resistance and impedance specs, is there anything particular i should be looking for.

You should choose a choke with the best rejection of frequencies from 40kHz and up. It should have the minimum current rating to do the job, too high a current rating and rejection suffers. You might try ordering a few and putting them in series until you get sufficient SQ.

I'd suggest starting off with something like Murata PLA10 series with sectional windings. I don't know how well kitted out your PC is (the best site for the choke) so can't suggest the appropriate current rating.
 

jiiteepee

Member
2007-03-22 3:43 pm
...

What sample rates are you using with your DAC?

...

M-DAC supports up to 24/96 through USB.

OP, if that quad amp takes analog signal in from the m-dac then, why not make the path simpler by removing the m-dac and stream directly through xonar converters? You might think this would degrade your audio system quality ... you would be totally wrong. :D

There's also the optical S/PDIF out port in your motherboard (mentioned earlier) ... why not use that path instead of coaxial/USB?
 

jiiteepee

Member
2007-03-22 3:43 pm
As you have not told much 'bout the computer system you connect the M-DAC to nor what all you have tried to solve your problem, before getting an isolator, I would suggest to check if the issue comes from software side. Assuming you run Windows system;
- if the M-DAC does not have a native USB audio driver but uses the generic system driver there's a change your system does not recognize the device properly. In many cases, which I have faced, the volume level is left quite low and/or can't be changed normally. You could check if the device is properly named (device manager) and that you be able to control it through system mixer etc.. Remember also check that the output level is set to 100% at system level (mixer / playback settings)
- you could try bypass the system mixer by using kernel level drivers (ASIO, WDM/KS or WASAPI in Exclusive mode). To make this type test easy, I'm running VB-Audio's Voicemeeter Banana as an output device for system and select the output 'method' through it's device selections. I guess asio4all can be used with m-dac.
- if m-dac isn't capable for auto samplerate/bit depth switching then check that the samplerate (and bit-depth as well) stays original through whole path starting from source file (device properties/m-dac settings)
- remember also disable all DSP features (system/software)
 

goodguys

Member
2011-02-23 3:51 pm
Hi. Thanks for the replies, much appreciated.

abraxalito I leave the sample rate unchanged as i find the sound is not so accurate if upsampled or downsampled, the instruments change and don't sound life like or realistic anymore.
My sample rates are 44.1khz for music mp3 mp4 mpeg etc, and 48khz for movies which are on bluray.
Have noticed a few isolaters on amazon for £30,
will give those a try - Many Thanks

jiiteepee I have actually done that, but the m-dac has a remote control for volume adjustments and other functions so i don't have to get up every few minutes, also it has multiple inputs so i can use it as a pre amp and plug all my other hardware in. I do appreciate what you are saying and you are right but the m-dac makes life a little easier.
Thanks for the pc configuration advice. I use jriver media player, the m-dac is recognised and used in wasapi mode

One last thing i wanted to ask, i am thinking of replacing my motherboard as it does not have gpt partitioning in the bios and some of my hard drives are not being recognised. Have tried to find a workaround for this but to no avail.
Do you know any motherboards which work well for htpc. I googled and am thinking of a gaming board as these tend to utilise higher quality components and generally have higher specs, better onboard audio and graphics.
Would any of this make a difference in terms of a/v quality for movies and music.

Many thanks. John.