[bcschmerker4]

Upon reading the specification sheet for the TPA6120A2 from Texas Instruments®, I found my suspicions confirmed in terms of what sort of headset I need with the STX.  The TPA6120A2 is designed for loads ≥32Ω; with a 10.7Ω source impedance, however, it really needs headsets with ≥100Ω load impedance. 
 

 

[PelPix]

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Regardless, distortion != bloat, 
 
And have you ever rolled an opamp? No, it matters, ask anyone who has, particularly with AKGs, not so much with denons, but it matters enough. 
 
Your clearly looking at this from an engineering perspective and not an audio perspective, there are many places where the one does not correlate with the other. Sad truth, and I'm the white paper stats type, so I don't say this lightly.
 
You could roll a truck into the opamp slot of an STX and the odds are it will work, not well, but it will work. I have tried a fair few, and know what works from those.
 
 
elwappo99 I havent tried that opamp, I read somewhere it worked well as a buffer, which does not matter for the headphone jack, I would try LME49990, or THS4032 in IV section. Stay well away from the AD797 (oscillates, harsh, but o so clear) and any LM4562 derivative.
 
ALso if you are planning on using the STX with denons from the headphone port.... Don't

 
The type and form of distortion that the TI chip imparts presents directly as bass bloat.

 

[WiR3D]

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After reading too much that STX is not good for Denons to which I don't agree but after discovering I can get a couple of external DAC/AMPs locally and easily return them so got Audioengine D1 and Fiio E17and have 2 questions.Firstly where I can get misplaced optical to coax adapter which came with STX? I'm trying to use STX's optical out to send audio signal to D1's optical input and USB for power only. So after connecting them using optical cable I succesfully used before I chose Xonar STX SPIDF Pass- Thru as default device in Windows and than in Asus control panel I changed 'Headphones' to '2 speakers' put check mark to enable SPIDF and left default PCM as required by Audioengine. Then I set WASAPI : Xonar STX SPIDF Pass-Thru as output device in Foobar's preferences but when I start to play I hear nothing while program looks like song is playimg succesfully. Any suggestions? 

mmm the D1 also has a 10ohm output impedance, so your not avoiding the issue.... just substituting one for the other. The E17 will avoid the issue, but I doubt it will keep up with the STX for clarity. 
 
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What op-amps would you recommend for home audio 2-channel use?  The sound I hear with the stock op-amps is lacking in resolution-clarity-detail (details are a bit murky-not so clear)-and on bass "refinement".  Can op-amps really help get a sound that has a LOT more of the things I am looking for OR is it asking a bit much?

A big bump in clarity is asking a bit much, unless you go discrete and do bypass cap mods, a small bump, and better SS is possible. The bass refinement IME is what changes the most.
 
I'm only starting to play with that, the THS4032 still work nicely in IV, just trying to sort the buffer, the stock LM4562 has 0 midbass, and does some funny things with the rest of the bass, textures it in a bad way, almost distorting (Denon D7000 + Marantz 2270), although if I had to guess I'm willing to bet you could put 3x LME49990 in there and call it a day.  
 
 
 

The type and form of distortion that the TI chip imparts presents directly as bass bloat.

May be true, but it does not invalidate my other points

 

[PurpleAngel]

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After reading too much that STX is not good for Denons to which I don't agree but after discovering I can get a couple of external DAC/AMPs locally and easily return them so got Audioengine D1 and Fiio E17and have 2 questions.Firstly where I can get misplaced optical to coax adapter which came with STX? I'm trying to use STX's optical out to send audio signal to D1's optical input and USB for power only. So after connecting them using optical cable I succesfully used before I chose Xonar STX SPIDF Pass- Thru as default device in Windows and than in Asus control panel I changed 'Headphones' to '2 speakers' put check mark to enable SPIDF and left default PCM as required by Audioengine. Then I set WASAPI : Xonar STX SPIDF Pass-Thru as output device in Foobar's preferences but when I start to play I hear nothing while program looks like song is playimg succesfully. Any suggestions? 

When you set Windows (in 'Sound" playback tab) to Xonar STX S/PDIF pass-thru, it bypass all audio functions on the STX.
In the Windows>Sound> Playback tab, you need to set to "Speaker Asus Xonar Essence STX audio device".
and in the Xonar control panel, set analog output to "Headphone", S/PDIF enabled (checked) and set to PCM.
 
Try leaving foobar to "Primary Sound Driver", or Speaker (Asus Xonar Essence STX Audio Device).

 

[olegausany]

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When you set Windows (in 'Sound" playback tab) to Xonar STX S/PDIF pass-thru, it bypass all audio functions on the STX.
In the Windows>Sound> Playback tab, you need to set to "Speaker Asus Xonar Essence STX audio device".
and in the Xonar control panel, set analog output to "Headphone", S/PDIF enabled (checked) and set to PCM.
 
Try leaving foobar to "Primary Sound Driver", or Speaker (Asus Xonar Essence STX Audio Device).

Thanks for trying to help but it still don't work
E17 has no clarity of STX or D1 so it's going back, but there is noticeable improvement difference on D1 over STX but i hope optical to start working

 

[PurpleAngel]

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Thanks for trying to help but it still don't work
E17 has no clarity of STX or D1 so it's going back, but there is noticeable improvement difference on D1 over STX but I hope optical to start working

Is the motherboard's on-board audio disabled, in the bios?

 

[olegausany]

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Is the motherboard's on-board audio disabled, in the bios?

Yes

 

[bcschmerker4]

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There are two I/V opamps that serve as current/voltage converters. changing these will alter the signal of both the rca out and the amp. the third, buffer opamp takes the signal from the two converters and preamps them to be passed through the line out.
At any rate, I don't think you'll find much satisfaction in opamp swapping. the issues you are hearing are likely distortion from the TI dedicated headphone amp and swapping the opamps will not solve your problem.

The converters do not directly drive the headphone out--there is another dedicated chip that does this, and it is with this chip that you have issues.
That's the thing about the stx. The (already beautifully-designed and really unneeding of modification) line out can improve limitlessly, but the headphone out will never actually improve because it is bottlenecked by the ti chip that does the final headphone driving.

Speaking of the I-V, has anyone tested dual National Semiconductor®/Texas Instruments® LM6172IN's here (with any of the LM4562AN, LME49720NA, LME49860NA, or dual-LME49990MA DIP adapter in the Buffer)?  I ran across mention of this type in the linked Clinica article at TNT-Audio.com, where LM6172IN's were substituted for the stock JRC2114D's in a Marantz® CD-57/63/67-series Compact Disc deck.

 

[PelPix]

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Speaking of the I-V, has anyone tested dual National Semiconductor®/Texas Instruments® LM6172IN's here (with any of the LM4562AN, LME49720NA, LME49860NA, or dual-LME49990MA DIP adapter in the Buffer)?  I ran across mention of this type in the linked Clinica article at TNT-Audio.com, where LM6172IN's were substituted for the stock JRC2114D's in a Marantz® CD-57/63/67-series Compact Disc deck.

I wouldn't do it.  The slew rate is thousands of times faster than you need for audible frequencies and the THD isn't documented for audible frequencies, but for 50Mhz signals.
The LM6172 is for video, not audio.  Using it in an audio circuit is asking for trouble unless you very carefully design the circuit around it.  A bipolar opamp with a slew rate that high is not something you pop in to a circuit to replace another opamp.

 

[ROBSCIX]

I have heard of people using the LM6172 for audio but as was said it is not specifically for audio but that doesn't mean it can't be used for it.
However, with these high spec, fast chips you tend to usually run into stability issues.  If you do not have a scope or know how to figure out the current draw of the amp, just monitor the heat of the chip.
If it gets hot, the chip is oscillating and will need to be stabilized or replaced with another chip that is more stable.
I would do more research on the LM6172 before going forward.

 

[olegausany]

So problem is solved, it was optical cable but the correct settings in windows playback default device are Asus SPIDF Pass-Thru and in foobar output as well

 

[PelPix]

There are a lot of reasons I like the ST more than external DACs.  The biggest is no-hassle, properly-clocked, bit-perfect transport without upsampling.

 

[RushNerd]

It's a longshot, but does anyone have experience with this card and the HT Omega Claro Halo at all? Both are pretty darn similar and have the TPA6120A2 headphone amp onboard. I chose the Omega, obviously the Asus is the more popular choice, but are they really that different? 

 

[PurpleAngel]

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It's a longshot, but does anyone have experience with this card and the HT Omega Claro Halo at all? Both are pretty darn similar and have the TPA6120A2 headphone amp on-board. I chose the Omega, obviously the Asus is the more popular choice, but are they really that different? 

They both use the TPA6120A2 headphone amplifier
They both use the C-Media CMI8788 audio processor.

 

[PelPix]

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It's a longshot, but does anyone have experience with this card and the HT Omega Claro Halo at all? Both are pretty darn similar and have the TPA6120A2 headphone amp onboard. I chose the Omega, obviously the Asus is the more popular choice, but are they really that different? 

The ST has a low-jitter clock and the Claro Halo does not.  They otherwise perform identically.