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Old 26th September 2011, 07:29 PM   #1
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Default Xonar STX Op-amp change

I have read that it is possible to easily change the op-amps of the Asus Xonar STX to "better" ones.

I have a pair of AKG K271 MKII headphones, will i be able to hear any difference?
If i understood right, you just pull the old op-amp from the socket and replace it with the new one? No soldering or permanent modifications needed?

What op-amps could i change to? Where can i find them? Is it worth the cost?
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Old 26th September 2011, 09:54 PM   #2
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Quote:
Originally Posted by Rullknufs View Post
I have read that it is possible to easily change the op-amps of the Asus Xonar STX to "better" ones.
Yes this is true. You can easily change the I/V converter opamps and the differential stage opamps.

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I have a pair of AKG K271 MKII headphones, will i be able to hear any difference?
Probably not and this isn't because your headphone aren't good enough.

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Originally Posted by Rullknufs View Post
If i understood right, you just pull the old op-amp from the socket and replace it with the new one? No soldering or permanent modifications needed?
This is correct.

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Originally Posted by Rullknufs View Post
What op-amps could i change to? Where can i find them? Is it worth the cost?
Opamps can cost quite a lot of money, but as the STX uses duals this removes some of the ridiculously priced singles from the equation.

The differential configured opamp already uses a high quality opamp from national semiconductor that has been designed specifically for high quality audio.

The I/V opamps use a version of the NE5532. This is quite an old opamp, but it gets the job done fine, it has been used in a lot of musical fidelities high end digital gear to do the same job as an I/V converter.

The output of the I/V opamps either feed into the headphone amplifier chip or the differential stage opamps. So if you're going to want to change something specifically for the headphones then all you need to change are the I/V opamps. Asus details which ones these are on their website under the downloads for the card.

You have to watch out what opamps you choose to use or change because some of them will not be happy driving a capacitive load, which is what the opamps in the STX are doing. The board layout is decent enough such that most opamps wont become unstable, but some, once again, require specific attention paid to guarantee proper operation. Usually the ones that aren't happy driving capacitive loads are the ones that are finicky about their implementation.

One thing that I find a surprise with the ST/STX is that Asus don't offer a list of opamps that are suitable for swapping in and out. You can't just go throwing any old opamp at the thing and expect it to work properly, even if the pins are of the right configuration.
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Old 27th September 2011, 06:24 AM   #3
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Thanks for detailed explanation. If i wont hear any difference, i think i'll skip this project
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Old 19th September 2014, 05:12 PM   #4
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Default STX & Opamps

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Originally Posted by Rullknufs View Post
Thanks for detailed explanation. If i wont hear any difference, i think i'll skip this project
I tried so far LM4562 with worse results than original (darker sound smaller soundstage), LM6172 (wide soundstage, balanced sq, better bass dynamics) and OPA2107AP which sound brighter and more detailed - depends on the headphones you're using. But the best mod was to add an 1uf MKT cap on the capacitor for VDD of the DAC. 1uf MKT added on the headphone amplifier caps sounds more open and dynamic as well.
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Old 20th September 2014, 06:32 PM   #5
Wungun is offline Wungun  Canada
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I just installed 3 of the newer, smaller Burson opams (using rca out)...mounted 0.01uf Solen caps to them.
Simply awesome (but not cheap!)
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Old 22nd September 2014, 04:07 PM   #6
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I just installed 3 of the newer, smaller Burson opams (using rca out)...mounted 0.01uf Solen caps to them.
Simply awesome (but not cheap!)
Could you show which ones you went for. I've heard good things about Burson. Does any of it involve soldering?
Thanks
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Old 23rd September 2014, 12:04 PM   #7
Wungun is offline Wungun  Canada
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They have the new ones on discount right now at Parts Connexion. The ones I bought... They recommend direct soldering (and they come with milled sockets) but I just plugged them into the Xonar sockets for now, until I can improve my soldering skills.
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Old 23rd September 2014, 03:05 PM   #8
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Thanks, in the UK so not sure about distributors over here.
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Old 23rd September 2014, 03:15 PM   #9
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Thanks, would this be the simplest way to bring about a big improvement. Is it just the opamps to replace or anything else in the same path
thanks
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Old 23rd September 2014, 03:18 PM   #10
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Is it just the one dual opamp or is it the pair on parts connexion
thanks again
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