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Old 28th February 2012, 03:22 PM   #11
marce is offline marce  United Kingdom
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Again a lot (most) of the high frequency noise in a PC dose not come from the switchers, but from the digital circuitry switching, so is created by the circuitry itself.
Whetehr its powerewd of a battery (lap top) with a linear PSU or a SMPS, the noise and its spectral content dose not differ much.
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Old 28th February 2012, 03:22 PM   #12
Raj1 is offline Raj1  United Kingdom
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Originally Posted by 5th element View Post
Well actually the STX uses extensive CLC filtering to make sure that any high frequency switching noise from the PSU is reduced to a minimum.

The SNR ratio of the card is on a par with some of the best audio equipment too. Stereophile's measurements of the card speak for themselves really.
Is reduced not eliminated entirely. We are talking about if it could be improved or not, not whether it should be.
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Old 28th February 2012, 05:02 PM   #13
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Is reduced not eliminated entirely. We are talking about if it could be improved or not, not whether it should be.
Isn't that the same thing though? If something shouldn't be improved because there's no point in it, why would you bother? There is a lot of redundancy involved with DIYaudio with people doing things they really don't need to and in lots of cases often making things worse. Of course these degrading modifications always end up with the modifier singing some subjective praises about how it sounds way better, but in reality it probably does not.

The stereophile review pretty much speaks for itself however and I also have one of these cards and can attest to its performance. SnR greater then you will ever generally need with both its distortion and jitter performance representing some of the best. If the digital 'noise' is getting in, it certainly isn't doing so in any meaningful way. If Asus had really botched the design then it would show up on the FFT plots. If EMI is a problem then you generally do see it.

Where the card could be improved is with the power to the digital side of the card. This comes directly from the PCI bus and isn't filtered, but to sort this out would require some pretty hefty and largely, non reversible, modifications to the car. Is this worth it and are you prepared to sacrifice the card if something goes wrong? The Xonars PCB is quite fragile and isn't suited to trace cutting, I've been there and it isn't worth it and I'm all pro modifications where applicable.

For the money, the card represents amazing technical performance and ASUS have put in a lot of hard work to get it to perform in the way that it does. If using a sound card inside a 'noisy' computer is the sort of thing that will keep you up at night, then don't use a sound card. Use an external DAC of some sort.
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Old 28th February 2012, 05:28 PM   #14
Raj1 is offline Raj1  United Kingdom
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Isn't that the same thing though?
Nope, could and should are two different words with different meanings. One represents choice and the other requirement. It is well known that standard 3 pin regulators used on cards like these (yes, even the venerable STX) can be improved upon considerably with some of the discrete supplies often touted on this forum for digital and analogue use (they are often backed up by measurements, too). Outside noise, one can also take a look at such things as supply impedance.

Now whether or not one wants to try and go through the rigmarole is another question entirely.
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Old 28th February 2012, 06:52 PM   #15
marce is offline marce  United Kingdom
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Bravo, 5th Element, my vote for quote of the year.
With a card like this ASUS, how is a diyer going to compete, when the design has probably been done using a CAD system with signal integrity add on, a power delivery system add on similar to:
CADSTAR Power Integrity Advance | Zuken
Basic proffesional ECAD systems with all the necessary add ons for high speed digital design cost 10s of thousands of pounds, the average DIYer does not have that access to that level of tools. Modifying multilayer digital/analogue boards is not a good idea either, and adding on power supplies can bugger up EMC, with the harmonics of high speed digital even short wires can become antennas.
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Old 28th February 2012, 07:05 PM   #16
Drweird is offline Drweird  India
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Originally Posted by marce View Post
Start with the speakers, you'll get the best improvement.
Most of the noise in a PC is generated by the digital switching, not the power supply.
How can this be...you say... Simultaneous switching noise.
Having worked on a high reliability communications system running of battery power with a linear main supply (soon to be SMPS) the noise was there with both power supplies.
Interesting, never thought of it like that. So then modding the card's power section or changing its supply will yield a minimal improvement at best?
Yes I agree that changing out the speakers will be the best improvemnt, but I jus want to get the source outta the way first.

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Originally Posted by i2k92 View Post
why dont you get an external dac instead of gambling with external internal sound card idea ? there are many decent dac at that price point.
Well its exactly because there are many so dedicated DACs to choose from and their availability in India is iffy.
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Old 28th February 2012, 07:30 PM   #17
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Nope, could and should are two different words with different meanings. One represents choice and the other requirement.
Exactly and ASUS have obviously reached the requirement as is necessary for the performance the card can provide.

Quote:
It is well known that standard 3 pin regulators used on cards like these (yes, even the venerable STX) can be improved upon considerably with some of the discrete supplies often touted on this forum for digital and analogue use (they are often backed up by measurements, too).
Yes but the point remains, will these actually make any difference whatsoever? The measured performance of the card speaks for itself, there are no real areas where it is lacking. Noise is one area where I'd expect a better regulator to perhaps improve things over a lesser one, where the performance at higher frequencies deteriorates, both in terms of line regulation and the PSRR of the powered device. Power line filtering however will sort this out quite effectively.


Quote:
supply impedance.
This is one of those things that I feel is completely over rated. You may have a regulator with a very low output impedance, but add in power supply traces to multiple ICs and the benefit quickly goes away. It's a bit like a power amplifier with a listed damping factor in the thousands, add in the speaker cable and it ends up completely pointless as the cable dominates.

I can see where it might make an improvement if you're using remote sensing and you're only powering a single chip, but this isn't what the ASUS card is like.


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Originally Posted by marce View Post
Modifying multilayer digital/analogue boards is not a good idea either, and adding on power supplies can bugger up EMC, with the harmonics of high speed digital even short wires can become antennas.
Exactly. Several times I've seen people wanting to split power supplies across different signal domains without giving any thought to the loops that they could be creating. Nor do they really give it any thought as to if it will improve anything or what could it improve, it's just a case of 'I'm using a separate power supply for it, it must be better.'

As mentioned before though. If one wanted to attack an area that could very well be improved upon it would be the 3.3V power lines that power the digital side of all the on board ICs.
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Old 28th February 2012, 07:58 PM   #18
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People get obsessed with things that they feel can control. Changing power supplies is fairly simple, requires low level of skills and lots of DYI start there. of course they need some self validation of their work so they will start hearing improvements.
I wrote numerous times that in digital domain, power supply doesn't have that much influence (1%) as proper decoupling (99.9%)
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Old 28th February 2012, 08:04 PM   #19
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Originally Posted by Drweird View Post
Interesting, never thought of it like that. So then modding the card's power section or changing its supply will yield a minimal improvement at best?
The cards power section, even including the -12volts power inverter is absolutely fine. ASUS have taken adequate precautions to make sure that any external noise on the power lines is filtered out.

As marce says though the noise on power lines is mostly caused by the noise of things that you're powering and not the power supply itself. In the case of switching circuits you have to be very careful to make sure that the return currents flow close to the supply currents otherwise you end up creating very large loops that broadcast EMI all over the place. If done incorrectly your piece of electrical equipment will fail to meet specification and you won't be able to sell it. If designed correctly you can have very noisy systems next to sensitive circuitry without creating any issues, providing you consciously layout the components such that the return and supply currents of the two pieces of circuitry are kept separate.

This should happen inside the PC, the dirty current as pulled by the motherboard will flow out of the PSU around the circuits, then back (via it's layout) through a short return on the PCB and then back into the PSU. At no point should any of these currents be required to flow in and around any part of the sound card, except in the signal currents that communicate through the PCI bus, but these currents should flow back through the PCI bus return and not near the DAC/analogue circuitry.

High speed circuit design isn't trivial and is something that ASUS have years of experience with. Second guessing engineers is only something you can really do if you're in the position of knowing enough to realise why certain things have been specifically done. Then you'll know whether or not you can undo their work and know that you're not going to create a plethora of issues by doing so.

Another aspect of high speed signals is size. You stand a much better chance of reducing EMI and keeping signal integrity by keeping current paths and their returns small. Ergo, if you can use a short cable, do so, or do plug the sound card into the PCI socket and don't use an extension cable. By all means do place the sound card in the bottom most socket on the motherboard, or make sure that all your other cards, if possible, are placed before it.

DIYaudio is filled with people who want to second guess engineers who have no real clue as to what they are really doing. Or put another way there are areas where costs have obviously been cut, but the engineering is still sound. One can probably improve things by modifying the circuit and on the whole the mods will have some sort of success, but there are always other issues that crop up whenever you do something like this and the issues largely go unnoticed or are completely ignored due to ignorance. Now I have no trouble with someone wanting to do something/mod something for the sake of learning, this is after all how progress and understanding is made/come by, but you have to do it in the correct way and with the correct methodology if you want to correctly understand what it is you've done and be able to see if it actually made things better.

I've seen one persons modification of the xonar essence where almost every aspect of it's exemplary technical performance was destroyed. Is this really the kind of thing that we should be striving for?





Well its exactly because there are many so dedicated DACs to choose from and their availability in India is iffy.[/QUOTE]
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Old 29th February 2012, 04:59 AM   #20
Raj1 is offline Raj1  United Kingdom
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Originally Posted by 5th element View Post






This is one of those things that I feel is completely over rated. You may have a regulator with a very low output impedance, but add in power supply traces to multiple ICs and the benefit quickly goes away. It's a bit like a power amplifier with a listed damping factor in the thousands, add in the speaker cable and it ends up completely pointless as the cable dominates.




One should strive to keep leads short. There are some nice drop in replacements out there for 3 pins regs by a couple of very clued up power engineers that perform admirably when used properly. Supply impedance variance over the audible range for an analogue circuit can be quite noticeable.


I do agree that most mods shown on forums, breach a lot of the fundamental principles, however.

-Raja
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