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DAC and amp or Xonar STX

post #1 of 63
Thread Starter 

hello everybody

 

i'm going to upgrade the sound system here and i dont know what to buy

should i get an asus xonar STX, or a desktop DAC with AMP?

what is the main diference between theese two? does the essence audio processor makes it better than a desktop dac?

 

my budget is $170 

 

 

thanks

post #2 of 63

What headphones do you intend to use ? The DAC on the STX (and even some cheaper Xonar cards) is quite good, but the amplifier works best with higher impedance headphones.

post #3 of 63

Yep, as stv said.

But I wonder how good is the dedicated headphone amp on the Xonar Essence STX. They claim it can work upto 600 Ohms.

post #4 of 63
Quote:
Originally Posted by proton007 View Post

But I wonder how good is the dedicated headphone amp on the Xonar Essence STX. They claim it can work upto 600 Ohms.

 

It is generally similar to the E9, with about the same maximum output (~7 Vrms) into high impedance loads, and apparently lower best case (high frequency and/or high impedance) distortion. It has a fixed analog gain (slightly more than 10 dB relative to the line output), so the volume control and impedance setting are both simple digital attenuation, and have no effect on the absolute noise floor. See also the Stereophile review for some information.


Edited by stv014 - 5/12/12 at 1:58am
post #5 of 63
Quote:
Originally Posted by stv014 View Post

 

It is generally similar to the E9, with about the same maximum output (~7 Vrms) into high impedance loads, and apparently lower best case (high frequency and/or high impedance) distortion. It has a fixed analog gain (slightly more than 10 dB relative to the line output), so the volume control and impedance setting are both simple digital attenuation, and have no effect on the absolute noise floor. See also the Stereophile review for some information.

 

From what I read, the DAC  section seems to be pretty good, with a decent headphone amp. So would you suggest it over a USB DAC? 

post #6 of 63

The STX is REALLY good from my own hearing experience.

I do suggest you just go for it.

 

After all, it's a lot cheaper than any other options or combinations.

 

Trust me... ;-)

post #7 of 63
Quote:
Originally Posted by proton007 View Post

From what I read, the DAC  section seems to be pretty good, with a decent headphone amp. So would you suggest it over a USB DAC? 

 

The DAC is good, indeed (as shown in the Stereophile test linked above), although it also is on some lower priced models (D1/DX/D2/D2X), for those who intend to use an external amplifier only.

The TPA6120 amplifier is best suited for use with relatively high impedance headphones (e.g. DTxx0 250 and 600 Ohm, or HD6xx), so the card is best value for the money for those who have such headphones.

post #8 of 63
Quote:
Originally Posted by stv014 View Post

 

The DAC is good, indeed (as shown in the Stereophile test linked above), although it also is on some lower priced models (D1/DX/D2/D2X), for those who intend to use an external amplifier only.

The TPA6120 amplifier is best suited for use with relatively high impedance headphones (e.g. DTxx0 250 and 600 Ohm, or HD6xx), so the card is best value for the money for those who have such headphones.

Thanks for the clarification.

I'm building my PC, so this one's going in the list.

 

Quote:
Originally Posted by audionewbieyao View Post

The STX is REALLY good from my own hearing experience.

I do suggest you just go for it.

 

After all, it's a lot cheaper than any other options or combinations.

 

Trust me... ;-)

Haha Thanks! smile_phones.gif

 

And to the OP, sorry for hijacking you thread! redface.gif

post #9 of 63

Well, it seems the card does have a notable problem, which has also been found by others (see here). When using sample rates that are integer multiples of 44100 Hz instead of 48000, the noise level of the DAC is much worse, only about 110 dB SNR instead of the advertised 124. This, combined with the already mentioned fully digital volume and gain control on the headphone output, means that with sensitive low impedance headphones, the noise floor can be audible (higher than that of the FiiO E9). The problem does not occur when using 48000, 96000, or 192000 Hz sample rate, but unfortunately almost all available music is 44100 Hz (CD format). An external amplifier with a volume control fed from the line output fixes the issue, although at 44100 Hz the DAC is not better than the much cheaper Xonar D1. The D2/D2X allegedly also have the same problem, so maybe it affects Xonar cards that use a PCM179x DAC.

Perhaps this is a driver related issue, but the exact same effect can also be reproduced on Linux, so it could be a limitation of the hardware design.

 

Some comparisons (left: 44.1 kHz, right: 96 kHz):

Line output:

stxlo44k.png    stxlo96k.png

Headphone output:

stxhp44k.png    stxhp96k.png

 

I wonder if Stereophile tested the ST at 44100 Hz, and that is why it was so noisy ?


Edited by stv014 - 5/12/12 at 8:46am
post #10 of 63

@Stv014

I'll try to dig deeper into this.

For now it seems like this is either a design issue, or a driver issue. But it seems to be on the headphone out. Weird how its been over a year and still no fix.


Edited by proton007 - 5/12/12 at 9:02am
post #11 of 63
Quote:
Originally Posted by proton007 View Post
For now it seems like this is either a design issue, or a driver issue. But it seems to be on the headphone out. Weird how its been over a year and still no fix.

 

It also affects the line output, as you can see above, it is just not audible there, since for a line output a 110 dB SNR is still high enough. However, the problem is much worse (and audible with sensitive headphones) on the headphone output, as the noise is amplified by a fixed ~3.5x gain, and unlike with an external amplifier that has a real analog volume control, it is not reduced when the volume and/or gain is turned down to a realistic listening level.

 

By the way, changing the A/D sample rate to 44.1 kHz does not seem to have this effect, it only affects the DAC.


Edited by stv014 - 5/12/12 at 9:25am
post #12 of 63

@Stv014

Funny, the hiss seems to go away if using 24 bits mode, from what I read on some other thread.

Some are saying its because of the dither added to recordings, such that the quite portions are more audible. So why does up sampling reduce the noise? 


Edited by proton007 - 5/12/12 at 11:28pm
post #13 of 63
Quote:
Originally Posted by proton007 View Post

Funny, the hiss seems to go away if using 24 bits mode, from what I read on some other thread.

 

The above graphs were made using 24 bit input and output. That is why the -100 dBFS tone shown is even possible without significant distortion or dither noise.

 

Quote:
Originally Posted by proton007 View Post
Some are saying its because of the dither added to recordings, such that the quite portions are more audible. So why does up sampling reduce the noise? 

 

Of course, using 16-bit dithered output and software volume control makes the SNR even worse, dropping it from ~110 dB at 44100 Hz on the line output to only ~96 dB, and obviously significantly less on the headphone output at typical listening levels.

The reason why the 44100/88200/176400 Hz sample rates are noisier than 48000/96000/192000 Hz may be related to the fact that the card has a fixed clock frequency of 24.576 MHz, which is an integer multiple of 192000 Hz (128x), but not 176400.

post #14 of 63
Thread Starter 

thanks everybody for the infos and help

 

@stv014

i was reading some of the threads about this problem in the STX/ST series, and after this i am totaly sure i dont want to spend 160 bucks in a defective product

i'm thinking about an Xonar DX + desktop Amp

is it a good combo? i own a xonar dg right now, is it a good upgrade?

post #15 of 63
Quote:
Originally Posted by Tuny View Post
hello everybody

I'm going to upgrade the sound system here and I don't know what to buy

should i get an asus xonar STX, or a desktop DAC with AMP?

what is the main difference between these two? does the essence audio processor makes it better than a desktop DAC?

my budget is $170 

It might be helpful to know what you use your computer audio for?

Music?

Movies?

Gaming?

Also what headphones your currently using or planning on buying in the future?

(I am biased toward the STX myself).

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