Xonar ST/STX mods...

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hjam

Member
Joined 2012
lucpes,
Adding the 100nf Cap after the ferrite bead on the board was a very noticeable inprovement.
I also added another board in the adjacent PCI-e slot with some switches and several capacitors. This allowed me to put 0.1uf, 1uf, ... up to 470uf across the 3.3V of the bus. The improvements were less obvious, but noticeable. Surprisingly, on some recordings, the 470uf was too much. Male voices lost a bit of character and body. I'm probably liking some distortion that's not really in the recording.
I'm just using the spdif output of the STX II. Guessing some of this would help those using the analog outputs too.
Hugh
 
S

shakaraba

Member
Joined 2010
Hi,

I've done the next mods with great results to my Xonar Essence ST:

- External power supply for 5V, +15V, -15V directly soldered to the out pads of the 78xx regulators.

+-15V use two lm340 fixed and for the 5V I use lm317 plus a cascaded lt1963A.

- AD8599 opamps on all the three positions.

- Removed output capacitors and replaced them with wire.

With all the mods, the soundcard starts to sound a bit magical, but i want more.

What option do you thing is better for the next step?

a) Build 3.3V power supply with lt1963A. But I'm not sure where can I solder my 3.3V and where to cut the 3.3V line from PC.

b) Upgrade to a 5V clock so I don't have to build a new 3.3V power supply. I think that the on board clock is feed by the 3.3V line. Is this correct?

So a 5V crystal will improve things due to clean supply. What crystal do you recommend?

My PC power supply is a TP750C, it is not "bad" and the SQ is greatly improved.

The best mod for me is the power supply for 5V and +-15V. I think that simple lm317/lm337 boards feeded by its own transformers and rectifiers improve the soundcard the easy and cheap way. Don't use high current versions of LM317 board with transistors that ruin the noise/ripple...

Super regulators are nice, but hard to implement and expensive.
 
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lucpes

Member
Joined 2003
shakaraba said:
a) Build 3.3V power supply with lt1963A. But I'm not sure where can I solder my 3.3V and where to cut the 3.3V line from PC.

b) Upgrade to a 5V clock so I don't have to build a new 3.3V power supply. I think that the on board clock is feed by the 3.3V line. Is this correct?

So a 5V crystal will improve things due to clean supply. What crystal do you recommend?
Click to expand...

3.3V is on the back of the board right at the PCIex connector at least on the STX see ferrite marked in red. It's a shame that the processor and DAC digital 3.3V is powered via PCI/PCIex on these cards.

An externally hosted image should be here but it was not working when we last tested it.


Crystal on ST isn't powered. Only oscillators are powered. You have the clock conditioning on the ST CS2000 on board which ensures jitter stays low, so I wouldn't mess with the clock for PCI ST.

Post a back picture of your ST and someone may point to where to insert the 3.3V. COuld not find a back pic for the ST.
 
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oct81

Member
Joined 2015
Coris said:
Very sorry again about the missing pictures in thread. It were deleted by mistake of an moderator for a while ago...

I would like to repeat my opinion about a "silent" (low noise) computer.
A digital system, as the computer is, generate much electrical noises. There is the way a computer works, and is the way the digital systems behave. There is absolutely no reason to work to find low noise solutions, or expensive devices, which are stated as low noise ones, to power the entire computer, thinking it will help to get a better audio signal out of a sound card.
A low noise computer PSU is a great device, but will never replace a analogue PSU when about a analogue stage, as the sound card include. A low noise computer PSU is unusable for audio purposes anyway (to much noisy). Even more, one may know that on the mother board there are plenty of small switching PSUs to power the main processor as the other many chips on it. All those produce noises. These noises do not disturb the computer functionality, as there are filtered and rejected both hardware and software.
The computer noises disturb only the analogue stages of a sound card.
Another aspect is that a computer PSU have to deliver very high power. There is quite impossible to filter or find a so low noise power solution (to satisfy the analogue circuits) when heavy currents are involved.
The reasonable solutions are in this case two: heavy filtering of the power rails which goes only to the analogue stages, or replacing the build in PSUs for analogue circuits, with an external (analogue/low noise/audio suitable) PSU.

About Asus ST/STX cards I may say that basically are the only ones consumer cards which can 192Khz sampling (in/out), as I know. If somebody have another informations, please replay.
The weak part of these cards, are the power system for analogue stages, and the DAC circuit and post DAC processing of the audio signal. At least the most important parts of a sound card... Here is to be modded to get an exceptional quality sound card.

I work now to a more elegant/professional mod for an ST/STX card. There is about a completely new DAC design using the same PCM1792 chip, and also a new I/V and final stage. There will be also two solutions for powering the analogue stages: using the built in (moded) PSUs, or an external high end PSU. I will come out with some pictures in the near future
.
Click to expand...
First of all i would like to thank you for the tremendous tutorial. Helped me very much in my modifications. Even if the thread is quite old, i would like to ask something about the power circuit on 7812 regulator on asus essence st version 1.02. I changed the original one with a burson 7812 250mA. This suppose to power the three opams (burson as well). By mistake, checking in and out tensions on power regulator pins i touched the wires of in line and gnd. A short flame and led indicator of power regulator turned off. I control it applying the tension directly from molex and it works. My question is: what could happened on the rail that block the current to reach the power regulator. I hear the music, but the volume is very low. I am not able to figure out where is the problem. Thank u in advance.
 
Coris

Coris

Member
Joined 2009
Paid Member
As I understood from your description, shorting the output to ground it happened on your Burson regulator. It seems to me that this (7812 equivalent) Burson regulator have being damaged, and it can not deliver power when loaded. My first attempt to test the regulator, is to provide power to it (on bench), and check its outputs while loaded to 250mA.
You can also provide the right power on Molex input for your sound card, on bench, and measure the 12v rail on the card. With the card on bench, and power connected to the Molex inputs, you should find the right tensions for analogue stage on it, even it is not placed into the computer motherboard.
On the power lines of 12v (coming from Molex connector) are placed on the sound card some ferrite beads and some 3 ohm resistors. It may happened that some of these components have blow it up as consequence of that shorting...
 
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oct81

Member
Joined 2015
Coris said:
As I understood from your description, shorting the output to ground it happened on your Burson regulator. It seems to me that this (7812 equivalent) Burson regulator have being damaged, and it can not deliver power when loaded. My first attempt to test the regulator, is to provide power to it (on bench), and check its outputs while loaded to 250mA.
You can also provide the right power on Molex input for your sound card, on bench, and measure the 12v rail on the card. With the card on bench, and power connected to the Molex inputs, you should find the right tensions for analogue stage on it, even it is not placed into the computer motherboard.
On the power lines of 12v (coming from Molex connector) are placed on the sound card some ferrite beads and some 3 ohm resistors. It may happened that some of these components have blow it up as consequence of that shorting...
Click to expand...

I powered the regulator directly from the liner psu and the light indicator turned on. Maybe something on the line before could be interrupted. I checked the tension on the capacitors right behind the molex input, and the one on 12v rail indicates a vety low outputt voltage (like 0.7v). What i don't understand is how can i still have the music. Also, all op amps are regularly powered (around11,9v). I already changed 4burned capacitors after the short cut.
 
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oct81

Member
Joined 2015
sgrossklass said:
After seeing the measurements for the Burson reg from Linear Audio Vol. 4, I would also rather use a standard but good 78(M)12, like ON Semi's, or maybe squeeze in a low-noise LM317 setup.
Click to expand...
So you suggest to replace the burson regulator? It's not an easy choice since i paid them a quite high price. My main concern regards the power circuit on 12v rail. I can't figure out why the led power doesn't turn on anymore when the regulator is connected to the board. Tested the regulator separately and it's functional. I power the sound card with a linear regulated dual line power supplier (5and 12v) and an r-core transformer. I'll follow Coris advice and perform t he checks.
Thank you guys for your help.
 
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lucpes

Member
Joined 2003
Voltage on caps near the molex

I changed the caps (OSCON) near the molex for Rubycon ZLH and now when I connect power one shows 5V and the other is 0.6-0.7V... is that all right? If not I must have destroyed the trace and will connect the low voltage cap with a short wire to 5V?

You can measure the voltages with the card unplugged from the PCIex slot and just the molex on. No harm is done.
 
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LightMatic

Member
Joined 2010
Greetings to all participants of the forum,
This is my first post so please do not mind in my ignorance.
I own Asus Xonar ST sound card and I would like to bypass the entire analog part of the sound card (line out and headphone) means I'd take her only balanced outputs of the PCM1792. Please recommend what to use to be able to connect with balanced outputs PCM1792 to, for example, inputs (balanced or unbalanced) from Electrocompaniet EC 3 preamplifiers?

Thank you in advance

Best Regards
 
Coris

Coris

Member
Joined 2009
Paid Member
This is what you may need...
Fully balanced outputs, entirely redesigned DAC system, fully electrical isolated from the rest of the computer, direct connection to the I2S lines, and battery powered clock system (NDK oscillators).
High class DAC using the whole computer facilities. Ideal to use it on a music dedicated computer system.
Does not exist better solution than this.
 

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