Xonar ST/STX mods...

[diyuser7572]

Hi everyone ! I need some troubleshooting advice. My Asus STX II 7.1 was working well, then the line in's gain turned miniscule (I need to up the volume on PC and desktop stereo to max in order to hear content streamed from android phone connected via cable to line-in feed). At the same time the gain of audio from PC more than doubled : I have to scale back the output level of the desktop stereo by about a half, and reduce the dial level of STX II to about 40%. Prior to the line-in problem, I would get the same volume with 80% STX II dial output and 1.5 times the level on mini stereo. In other words, the STX II's card gain increased for input from PC and became close to 0 for line in.
I have reinstalled the card and changed most, if not all, software configurations. Therefore, I wonder if it might be a hardware issue (stuck relay, etc).
I would like to revert the STX II card back to normal operating mode.
Any advice greatly appreciated.

[Coris]

Long time ago since my last work on Xonar boards. Coming back now with some recent STX2 improvements (very good results also).
I have to say that STX2 it is already an improved version by Asus itself, comparing with the first STX. However it still sounding moufed, even thought the good marketing/advertising...
This sound card it is also capable for high audio quality(after properly upgrading of the power system, clock system, as some other circuits).
My previous upgrade concept was based on adding of a full DAC system, with its own power system completely separated from the computer one, using only the digital interface tapped from the DAC digital inputs (also galvanically isolated). The result and the quality of the sound is indeed impressive. My last upgrade was realised on board, modifying the Assus design, and using the computer power system. Surprisingly, the audio quality level is similar for both these two upgrade approaches.

[Yaka]

Has anyone done a neat emi shield for the stx2 daughter board?
I have only just connected after using the stx 2 for years and i get crazy buzzing from the
Center and rear channels. This goes away if i leave the card dangling out side my pc case

[phofman]

I would check whether ground shells of the center and rear cinches do not touch the rear bracket which is grounded when in the PC and not grounded when outside. Just 2 cents...

[bchow]

Originally Posted by Yaka

Has anyone done a neat emi shield for the stx2 daughter board?
I have only just connected after using the stx 2 for years and i get crazy buzzing from the
Center and rear channels. This goes away if i leave the card dangling out side my pc case

I had a hum on my subwoofer channel and tried having the card dangling outside my PC case also which didn't fix the problem in my case. For me what turned out to fix it was by adding a cheater plug to my subwoofer.

I suspect your issue may also be ground-loop related.