Asus Xonar St as bridge only...

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Hello, This is my first post here.

I have an Asus Xonar St in an Asus pc. It is only used as a s/pdif bridge to feed a Peachtree Dacit. The system works very well, but I would like to improve the input to the dac via the xonar. I bet you can exceed the performance of any converter using the xonar st.

I have read some of the posts here, and most of them are concerned with improving the st card performance as a whole. I'd just like to get the xonar to output an unmatched quality signal to my dac to improve it's performance. I read about picking off an I2P signal from the st, better voltage regulation, etc..

Any comments or help, or reference to a thread where this has already been done would be appreciated.

Jim
 
If you're using S/DIF then a lot of it is down to the DAC itself. Modern DACs often have jitter rejection circuits build into them so that even if the sender of said data is pretty poor it wont matter so much. If your DAC is excellent in this regard then it's not worth going to the extra trouble.

I mean, I've tapped into the I2S lines of the ST and transmit them over LVDS straight into my DSP, but all of that is home built. I wouldn't really want to go doing that to a consumer DAC as that presumably would have decent resale value and once modded, it'd have far less.

Looking at the DACit though, it isn't madly expensive so perhaps you would be less concerned. Either way Tapping the I2S off of the ST would probably be worthwhile but it isn't easy to do, you'll have the potential to break the card (I almost did and I'm experienced with soldering SMD parts etc, the PCB is fragile). Looking at the Stereophiles measurements of the DACit though, it's clear that the Xonars own internal analogue section is quite superior to that of the DACit's anyway, I'd just use the analogue out of the Xonar for now. If you want to upgrade you're going to need something expensive to beat it. If you want to DIY I'd recommend some of the Twisted Pear stuff.
 
Thanks for the responses.

The consensus here seems to be it's not worth messing with. I was concerned with several factors concerning trying to clean up 5 & 3.3 volts ps (I need only be concerned with the digital side of the card, and the creation of the PCM signal for transfer out of the s/pdif), where would I inject a cleaned up signal, and would doing this throw off settings on the card that take a dirty signal into account? If I used a new ps, then of course there is a question as to grounding. I don't really know how clean the filtering on the ST board gets the signal without intervention. The idea was a very clean signal <40 mv ripple has got to end with a better PCM signal to the Dac. In any event it appears that it is not worth the trouble.

As far as I2S (excuse the earlier misspelling), again the potential risks and difficulties seem to exceed any potential benefit. I had no idea it was so difficult to pick up the I2S from the ST, and that leaves the problem of where to introduce it into the Dacit, without a schematic.

Peachtree is coming out with an asynchronous usb to s/pdif converter for their dacs in 2-3 weeks. It is just functional, with no frills and will be $199 with a 30 day return policy.
I'll probably give it a try. Although it may be that the Asus Xonar ST gives such a quality PCM output that the Peachtree Converter is of no advantage.

As far as the performance of the stand alone ST as compared to it's use as a feed to the Dacit, the ST fails in a very big way to perform as well as the Dacit. Possibly with the mods discussed here it's performance would more closely approach the Peachtree Dacit. See review Peachtree Dacit;

Computer Audiophile - Peachtree Audio DAC•iT Review (AKA DACiT)

It is my experience that all of the reviewers comments are correct.

Possibly within the range of money spent, this system cannot be improved upon in a significant way. I will report back per this thread on the Peachtree Converter, and it's performance.

Thanks again,

Jim
 
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