Asus Xonar DX Mods!
Jun 28, 2008 at 12:50 PM Thread Starter Post #1 of 117


Headphoneus Supremus
May 4, 2008
I wasn't able to find a mods thread for this card anywhere and this card can be really nice with a few basic mods. So I've taken some time to figure out what is what on this card in terms of the stereo output stage.

Note: Everything on this card is surface mount and the board is very cheap. This requires some soldering skills if you want to be able to use the card again

I don't think this is good beginner project.

Final Modded Card:



Mod 1: Quality coupling caps

I chose to go with 22uF (same value as stock/CS4398 datasheet) 25V Nichicon Muse ES bypassed with 0.22uF Wima mkp.
[FYI All the stock electrolytic caps appear to be 10V.]

These are the left and right front coupling caps:


Apply heat to the edges of the solder pad and gently pull these off one side at a time (there are 2 solder pads).
I should say now, keep your soldering iron on low temp. I used 250C - this is as high as you should go.
Add a little solder to the pads.
Add the caps of your choice.
In the photo above these are the dark purple (black gate nx-hiq) caps.

Mod 2: Quality Low Pass Caps

this is a low pass filter. It is probably meant to remove high frequency noise. So this cap mod replaces the cap that is forming the low-pass filter
I used the same method to remove these caps as done in for mod 1. I used 220 uF (same value as stock) 25V Nichicon Muse KW (from Mouser). The replaced caps are the little gold and black ones closest to the purple black gates.

Mod 3:power supply decoupling caps

Also Nichicon ultra low esr HZ 1200uF caps decoupling the power supplies as seen in the second picture. Make sure to arrange the polarity as shown and use caps rated at at least 16V.

Mod 4: Upgrade Op-amp (yikes!)


Note: The opamp I have circled is definitely the cs4398 DAC opamp, but I haven't gone through the painstaking process of determining whether there is another opamp before the output. I don't think there is.

Now I also decided to replace the opamp. You should think twice about this if you're not familiar with how to do this. Basically you want to heat all pins on one side of the opamp and while the solder is liquid lift that side from the board. Then do the same with the other side. It's a little tricky to desolder these chips, so if you can practice on an old motherboard or something you should.
Have fun!
Jun 28, 2008 at 2:22 PM Post #2 of 117
Yeah, I was thinking of replacing the opamp on my line 6 guitarport. I am holding off for the time being since I have realized my soldering will improve more if I do a few other projects first.
Jun 28, 2008 at 3:54 PM Post #3 of 117
Let me provide a bit of info on the SMD SOIC (that's what they call the package of those SMD op-amps) desoldering that I've learned on my previous employment.

First of all, you put a large blob of solder on the more crowded side of op-amp's legs (for example, on the photo above, you'd be putting the solder down on the left first). After you made a large blob that covers all 4 legs of the op amp, you then proceed to do the same to the other side.

When you saturate the second side with solder, quickly move on to the previous "blob" and quickly melts it while the other blob is still liquid. when you find it melts, you flick it lightly and the whole thing, including most of the solder will fly off the board.

If it didn't work the first time, go back and heat up solder on the empty side (on the photo above, it would be the right side), then quickly go to the other side and flick it off toward the empty side when you melts the solder on the other side.

Of course, make sure you flick it in a direction where there's no components in the way, or you'd have quite a mess to clean up. And as always, practice it on stuff that you can afford to damage and destroy before moving on to the actual stuff.

After the removal, just use solder wick to quickly mop up the excess solder and you'd be ready to put a new op-amp in.

I usually use a 30W soldering iron for 63/37 leaded solder, and 40W soldering iron for the newer unleaded/RoHS/Green solder.

For anyone who just want the most important tip, BE QUICK. If you are good with this technique, it would actually be less stressful to the pads than desoldering it one pin at a time. (takes about 30 secs on average to do the whole process...)
Jun 30, 2008 at 7:08 AM Post #5 of 117
I've been trying to check which opamp was used for the front channels.
How did you manage to find out which op that was used?

Thanks alot, also, which opamp replacement did you use?
Jun 30, 2008 at 8:53 AM Post #6 of 117

How did you manage to find out which op that was used?

With a multimeter and the cs4398 datasheet.


Thanks alot, also, which opamp replacement did you use?

I first tried the ad8620, but found that the sound was too harsh. Now I'm using the opa2132, and it sounds good

But YMMV, it really depends on the rest of your system I guess.

EDIT: I'm back to the ad8620 and I'm liking it
Jun 30, 2008 at 11:04 PM Post #7 of 117
Thank you for figuring it out of me, I don't own an multimeter anymore so it was a hassle to borrow one. Was planning on doing what you did but never came to it. Thank you!

I have an LM4562 waiting to be put on the board, i also have some AD-amps i might try, and of course an 2134 as well.

I also have some Cerafine capacitors that might work?
Jul 3, 2008 at 12:35 AM Post #9 of 117
Changed the opamp in 10 mins, it was a no-brainer.
The way I did it with the cheap opamp on the card is a bit more crude.. I just cut the legs off and removed them from the pads with the soldertip. Then I just put the new LM4562 SO-8 in it's place and soldered it there.

Sounds.. different, more dynamics in the music, more silence yet the details are mostly preserved. Something happened to the vocals too, the music seems calmer and the bass has more definition.

Maybe time to play with the caps?
Jul 3, 2008 at 2:23 AM Post #10 of 117
Cool, it's good to hear back from someone else trying this.
Definitely try swapping out the coupling caps (Mod 1). It's easier than the opamp.

Another mod I found to be significant was adding more and better capacitance to the decoupling/power rail caps.
I'll add that in later. Also very simple.
Jul 3, 2008 at 5:42 AM Post #12 of 117
You know, you could have used Elna RVO for the coupling cap slot as those are an SMD type that is designed for audio applications. That airwiring job is rather precarious; I don't understand why you decided to invite all that inductance and make a giant antenna for RFI. Beware that the inductance of those long wires may interact with the supply bypassing and cause oscillation, among other sources of that problem (the op-amp may not like having its feedback loop configured that way, either).
Jul 3, 2008 at 6:14 AM Post #13 of 117
Thanks for the tip

While I wouldn't recommend wiring a dip socket to this board, the ground plane does shield the wires from RFI (the cards sits on the bottom of the mb with the socket facing the floor).
If you look at the part of the wire that will create inductance it's pretty short. Inductance could be lowered much further by moving the film caps so they are at right angles. In either case oscillation is very unlikely. Again this is not ideal - it is for trying different op-amps.

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