Xonar ST/STX mods...

[adamlau]

1. Which caps should be replaced if I only plan to use the digital coax out?
2. Has anyone replaced the digital out with a WBT 0210Ag?

[Coris]

Originally Posted by adamlau

1. Which caps should be replaced if I only plan to use the digital coax out?
2. Has anyone replaced the digital out with a WBT 0210Ag?

It is not necessary any modification if you intend to use only the digital out on this card. The mods about Xonar (ST/STX) are mainly meant about the analogue stage of this card, when is to use the analogue out (RCA outputs)...
But buying a such card to use only its digital in/out do not make much sense either...
Any type of sound card is very good if one only want to use its digital interface. The only problem is to find that card which can output a digital max samplings frequency (192Khz). If so, then are not so many which can do it. Xonar series can very well this... The case of mods is about the analogue stage and its digital to analogue converter used for have the best out of a such card.

[DJNUBZ]

I am not at the level I can do a lot of the SMD soldiering on this card but I would love to bring the quality of my up a bit. Could you tell me which 3 mods made the largest improvement for you?

[findingmyway4ever]

Originally Posted by Coris

It is not necessary any modification if you intend to use only the digital out on this card. The mods about Xonar (ST/STX) are mainly meant about the analogue stage of this card, when is to use the analogue out (RCA outputs)...
But buying a such card to use only its digital in/out do not make much sense either...
Any type of sound card is very good if one only want to use its digital interface. The only problem is to find that card which can output a digital max samplings frequency (192Khz). If so, then are not so many which can do it. Xonar series can very well this... The case of mods is about the analogue stage and its digital to analogue converter used for have the best out of a such card.

I have not tried any lower end (i.e. not so expensive) cards in the Xonar lineup, but from all that I have read, people can even hear a difference in the sound quality of the digital only between the ST and STX, with the ST having a better quality. Looking at it from outside of the computer, lets take cheap DVD players vs. very expensive standalone transports. How many would ever say the digital out is no different on a free to good home DVD player vs. some $50K transport known to be the very best transport out there. The primary thing that gets argued is jitter, and the ST with the CS2000 is supposed to take the jitter down over say, the STX, that probably has lower jitter somehow than the cheaper cards...same deal goes with transports...dvd and cheaper or even expensive cd players/transports can have terrible jitter specs while those raved about have the very lowest jitter specs.

I have no answer since I have limited experience with sources.

[Coris]

In the case of a digital output from ST/STX or other cards, is right that the jitter is or could be important. The jitter of one type card or another make the difference in the sound quality. This is right too.
The question(s) answered in that post refer to some capacitors in this digital stage which if changed, (supposable) will improve that digital out.
Changing the capacitors will not do so much improvement referring to a jitter problem/level. To improve the jitter level (lowered it) in such cases is about working with the oscillator on that card (changing it out or better regulator for it).
Personally, I just ignored the digital stage of my STX, and I`ve been focused in the improvements concerning the analogue stage (oscillator improvement it was included too in those mods, as to be seen here).

[findingmyway4ever]

Originally Posted by Coris

In the case of a digital output from ST/STX or other cards, is right that the jitter is or could be important. The jitter of one type card or another make the difference in the sound quality. This is right too.
The question(s) answered in that post refer to some capacitors in this digital stage which if changed, (supposable) will improve that digital out.
Changing the capacitors will not do so much improvement referring to a jitter problem/level. To improve the jitter level (lowered it) in such cases is about working with the oscillator on that card (changing it out or better regulator for it).
Personally, I just ignored the digital stage of my STX, and I`ve been focused in the improvements concerning the analogue stage (oscillator improvement it was included too in those mods, as to be seen here).

Thanks Coris. So changing the caps to something better or even larger values may help with the digital out, though that's basically up in the air as you put it. Makes me wonder just how these various sound cards sound with the digital out only and if there are real/true differences that can easily be heard or if it's more or less just a matter of preference. I have seen too much of the arguments going both ways about sound cards, usb converters, and so on as the source to an external dac, but I have used a number of USB converters, stock Xonar ST, and frankly, I honestly cannot put a finger on the differences. I don't consider my dac to be some great device that eliminates the jitter, but it's obviously something about the way the dac is designed that does the majority of what I am hearing. I use preamp+dac in one unit, so a 2" wire from analog line stage output to my digital dac chip's input inside one box. I REALLY question whether what people are hearing with the differences of the USB converters or a sound card (since some do prefer the sound card's digital out to even very expensive USB converters, much the same as my own experience with the ST vs. say, the Audiophilleo), but I don't hear such a difference where it's like, ahhh, name your adjectives, etc. etc. etc. So I'm thinking along the same lines as you are regarding the caps, and just thinking that the "majority" of this transport vs. that transport really is system dependent, where in my system, they are so mild in differences that I can essentially choose whichever one and stick to it. I just have never used a very cheap/inexpensive sound card. Just ST, and the more expensive USB converters shy of the most expensive ones of course like Empirical for $1300).

Maybe it also has a lot to do with the fact that a computer is not exactly a great source, and the primary thing that makes it a great source is all the software...in other words, hardware side of things is noise noise noise, but software side of things is something other devices just cannot do...well servers, but those are computers too...standalone, I can think of say a nice up converting standalone cdp, and tapping in my preamp section in place of the standalone cdp's analog section...then that could be competitive, perhaps even better? But the computer software side is so powerful that it really seems to eliminate all of these "noise" issues and make probably a super cheap sound card sound just fine as a digital source so long as you have a nice front end including the dac in the equation. Others will obviously disagree saying you need the fanciest transport device, but I'm still not convinced having heard up to $600 price range USB converters and Xonar ST should be darn good enough shy of the uber expensive "pro" sound cards.

[Coris]

The clue to using digital out of a sound card (or another source) is the posibility to carry the signal over quite long distances (meters...). But using the digital out of a source, mean too that the original signal have to suffer of many conversions, adding more jitter from the involved stages, and so on. Is not more reasonable to just take out the analogue signal from the output DAC on that source?
What mean using an external DAC? The I2S output from processor is converted to SPDIF standard and outputted so via Toslink or coax... Then SPDIF is converted again in the external DAC to get analogue out... What about jitter in all this process?
The audio card have already its local DAC, which produce an analogue out. Using an external DAC with SPDIF from an audio card is not a very big clue in my opinion. The best is using I2S output from the audio processor. But this is not possible over long distances (but only few cm). I just preffered to use the analogue out and the existing DAC (PCM179, which is a very good one) on the ST/STX.
The noises in the computer come essencially from the switching power and lot of high frequencies digital signals inside. What about to isolate the audio card power system from the computer switching power? And shield accordingly this sound card inside the computer? I just did like this on my STX. My sound card is now feed it from a completely different power system. I can now even switch to a battery to supply my STX with power, but is not big improvement in the sound doing so...
If one care a little bit more to improve the clock for the sound processor/DAC, then the jitter in the audio system is lowered quite much.
I can not say that a computer is a bead audio source. IS NOT! The only problem is (were for me) that the DAC on the sound card is not at last as performant as I wanted. Now is the ESS9018 which is the best! That because I intend to use the computer for tapping the I2S from the processor, and use this interface to a more performant DAC system. Another good solution is ExaU2I through USB and an external DAC. I work on this now... Else I can say that a computer is best as source and versatility (except the transport for CD/Blu Ray, etc)
The main improvements for the sound card (ST/STX) is the power system, and the oscillator/clock. There is not only to change the decoupling capacitors on it... This is only a part of the mods, but isolate the card from the computer power system is a must for a big improvement, and change the oscillator with a lowest as possible jitter one is a must too...
Is also essential to have a good amplifier/speaker system to hear the difference in between sound cards or improvements on an ST/STX card. I do not agree that the software in a computer lower the hardware jitter, but are some techniques to improve the clock system by software. Very important is a good motherboard, with a performant power system on it (mine have 48 parallel PSUs only dedicated to the CPU), and not at last, a performant processor (I have an i7 quad on mine).

[andreudze]

I have decided to swap the caps and resistors in I/U and LPF stages with the better types and new values. Does this look OK?

[andreudze]

Thinking of a new I/U and filter stage Ive come up with this one. It seems that it will burden the operational apms less.Am I right?

[Coris]

Is always positive to experiment... So just do it and her the result.
In my opinion, the less capacitors in the signal path is better, as the large as possible and good quality (no ESR/ESI) for decoupling/bypass to each of the opamps power pins.
I can see in your design quite much capacitors and quite high capacity values. I used in my I/V converter few pF and few pF in the final opamp stage. No any filter at all. If you will place a such 200pF or more in the I/V stage, you may have in mind that such cap will cut quite much of the high frequencies. Just use first that schematic as it is, try afterwords to lower the caps values, and hear the difference. Solder the resistors (SMD best) and caps right on the opamp pins and make the connections as short as possible, or just solder the opamps together using only theirs pins. This bring the best result. My I/V converter is not more than 20 mm long and almost the same bread... Take care of the GND connections and maybe an accordingly shielding may be taken in to consideration....
On the original ST/STX are many small caps on the signal path and some ferrite beads on the output lines. I will recommend to remove all those and output the signal directly as possible in to the amplifier. And keep also in mind: so long one keep the power in the right limits for the active components, is nothing to be wrong or to be burned out. The worst thing if is something wrong when experimenting in the signal path is only: no sound... This can easily be fixed.
I will say at last that personally, I did not find the right way from the beginning, or reading papers only. I`ve experimented a lot to find the best way. So, DIY!