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Old 23rd January 2013, 04:31 PM   #111
Coris is offline Coris  Norway
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Originally Posted by Corvus5 View Post
Coris, thank you for out pointing 5v filter caps, DAC 5v decoupling and 3,3v filter caps on your previous images. It's much easier now

I modify the TPA power. I noticed the sound got faster, higher tones are slightly louder now and precise enough to provide some details. The echo reverberation is also better defined and easier to hear: I can not only hear the echo but also the reverberation given to it. All higher frequencies and now controlled better.

Is there any power supply design you can recommend?
There is not any very special design for such PSU. A double PSU and I`ve used some standard complementary regulators. Is important to make one of those +/- 15v rails variable so that at last the opamps will get the most equal tensions as possible on both + and - rails. For 5 v I used the 12v rail from computer PSU. This tension it have to follow the designers ways, because the processor take some informations from this rail and use those internally. You may review my precedent descriptions about this.
I used first an 8v regulator to lower the tension with lowest dissipation from 12v, then an 5v low noise regulator to give power to analogue stage of the DAC chip and clock. The same 5v is then regulated to 3,3v and used on this rail for all the board (cut it that rail which come from computer PSU). Large decoupling capacities on every input point for power for DAC. I used the original board cover as heat sink for my regulators. This use to be a god enough shield as well, so it may be in its place anyway. As you see in the pictures, on other side of the board is a quite solid steel plate for sustain the toroid and as shield in the same time. The toroid is quite heavy, so you may find a solution to sustain this without create mechanical tensions in the PCI connector in the motherboard. An relay will start your double PSU when power start for computer. Your external PSU`s GND have to be connected very short to the board, in that point where the final opamps have theirs common GND. You may connect this external PSU directly to wall, The toroid will so be all the time connected to 220v (do not forget an fuse), and only low voltage power will be ON/OFF synchronized with the computer. Do not use the relay on 220v. Good large capacities as filter for your PSU, and that`s all.
The way to have a DC coupling it have to work at last for you too, but try this later after another mods are in place. Maybe just at last.

Else, you will realize that doing those mods (carefully and doing right), one after another it will come better and better sound out of the board, for your satisfaction...

Last edited by Coris; 23rd January 2013 at 04:36 PM.
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Old 23rd January 2013, 05:49 PM   #112
Corvus5 is offline Corvus5  Poland
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I've got the PSU from my previous amp design but I've been the design I use is very bad. Tuned to +/-11,5V, caps are 10.000uF.

I added 10uF in parallel to the existing DAC 5V analogue decoupling. Are there 2 caps? +/-5V? This 10uF should be enough to hear difference in the highest part. These caps have to burn in. First I didn't notice any change. Then I noticed the tone colour didn't change but the space and sound freedom improved. It's more natural. The impuls settling time futher improved but just stlightly. The sound imaging could have improved. It may sound too smooth. Not just analogue. Smooth and little slow. It's good the difference can be heard
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Old 23rd January 2013, 07:50 PM   #113
Corvus5 is offline Corvus5  Poland
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Since I started soldering these caps, I solder additional for the DAC 3.3V. First I didn't notice the change and started listening to songs I know. Then I forgot I was listening and the song played. The transitions are so smooth. The synthesized music fits so well with the rest. Reverberation is much better, the imaging is better. It's so natural sounding. It's so natural to hear it. I thought I will have to switch to LM6172 or even JRC2114 or increase gain on the I/V amp. Now it's so natural. There's nothing distracting in the sound. I can forget the music is playing yet it seems to be still very detailed and fast. The sound system is so harshness free.

There are still 5V filter caps and more I didn't change which seems to be in parallel like 47uF and 100uF where I added to the 100uF only. Then I'll remove existing one or play with different ones.
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Old 23rd January 2013, 08:49 PM   #114
Coris is offline Coris  Norway
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Originally Posted by Corvus5 View Post
I've got the PSU from my previous amp design but I've been the design I use is very bad. Tuned to +/-11,5V, caps are 10.000uF.

I added 10uF in parallel to the existing DAC 5V analogue decoupling. Are there 2 caps? +/-5V? This 10uF should be enough to hear difference in the highest part. These caps have to burn in. First I didn't notice any change. Then I noticed the tone colour didn't change but the space and sound freedom improved. It's more natural. The impuls settling time futher improved but just stlightly. The sound imaging could have improved. It may sound too smooth. Not just analogue. Smooth and little slow. It's good the difference can be heard
There are 2 decoupling caps on DAC analogue for the its 2 channels L/R. There is no any +/-5 v Only +5v for both separate L/R channels.
It may be enough +/-11,5v for the opamp you use. You may read in the opamps datasheet the right power to use for it. You may look for the right power for the max slew rate for the opamp you use/chose. There is important to get the max slew rate the chip can, and that is happen at the specified +/- voltage. You may try to chose the highest slew rate you can find for the opamps you want to use. This is quite important... Many types opamps are rated (specified parameters) for +/-15v or/and +/-5v. In your case is to chose +/-15v, and power it at that level. If you will chose an +/-12v opamp, then of course power it accordingly... I use LM6172 with 15v
If you will decide to make a stable/dedicated PSU for those final opamps, you may build that PSU which is adequate for that job... Not at least a small as possible one...

You may not increase the gain of the I/V stage. That it may be 1, but 1,2 - 1,5 it work very well. But not more. You may fix the gain in the final stage. You will not have to have very much gain anyway. With the right PSU you will get anyway 25Vpp on output on LM6172. I will suggest that you get out on cables with this voltage, and use adequate potentiometer or resistors to lower this level in amplifier (input). This way you will have a very good rate S/N over cables (not long cables anyway)

Last edited by Coris; 23rd January 2013 at 08:57 PM.
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Old 24th January 2013, 08:37 AM   #115
Corvus5 is offline Corvus5  Poland
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I started desoldering existing caps. With the 3.3V dec. cap half of the leg sitting in the hole was removed.

After a day I've got the feeling the caps in the analogue 5V stage stopped helping, the sound got little distorted. It may be due to low capacitance to overcome the existing one: (maybe 47uF FG) + 100uF FG + (added) 10uF elna silmic II. I start to lack in higher capacities.

Even with not too good 5V line, I could hear the difference with different 3.3V decoupling options. Do the 5V and 12V filter caps work when using external PSU?

About the getting little hot capacitor. It's only one of two os-con sitting near the molex: the one closer to the center. It's probably working very hard. Why only one?
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Old 24th January 2013, 10:38 AM   #116
Coris is offline Coris  Norway
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There is very wrong when caps get hot... You may measure what is there. You do not have to have distortions because of decoupling. It is happen something quite wrong somewhere with the signal/signal path.
The external PSU it may deliver power to the board as it were designed. It is quite difficult to change something on the board (it have also internal layers too), when about power traces. Few may be cut it, but only few. That because one may do a research to cut where is to be cut it the traces, and connect right the external PSU`s outputs.
I will suggest you to do the mods step by step. If you go back to change something in many places, it will be quite difficult for you to do it right, and faults may occur...
So, change something test it, work on that until you will be satisfied and then go further to the next mod. Repeat this procedure until you have the board modded as you wish.
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Old 24th January 2013, 04:33 PM   #117
Corvus5 is offline Corvus5  Poland
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I can't solder anything in the place of broken cap. I've go to use back of the card.

I find the LM6172 to be still worse than OPA627 and much more worse than AD797B. The sound is not enough dynamic and sharp and the resolution is gone when using LM6172.
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Old 24th January 2013, 06:00 PM   #118
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what opamp do you recomend ?
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Old 24th January 2013, 08:04 PM   #119
Coris is offline Coris  Norway
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Originally Posted by Corvus5 View Post
I can't solder anything in the place of broken cap. I've go to use back of the card.

I find the LM6172 to be still worse than OPA627 and much more worse than AD797B. The sound is not enough dynamic and sharp and the resolution is gone when using LM6172.
Just try to scrap well around the rests of the cap legs. The legs which are inside the holes it may come up a little bit. So use that top to initiate the soldering. You have to have enough power on your soldering iron to succeed on the ground plane. There is a quite big dissipation there. But be carefully to not exfoliate the traces. This is a delicate operation but will work at last.

Else, opamps are a mater of taste at last... For me is OK the LM6172. How the sound is out of it it depends of quite many parameters in the system... The mods it have at last a logic and a kind of succession for the operations. It may be first a good power supply, then the decoupling system, then the clock, and at last the opamps. If one may begin with the opamp, what about all the rest, bad PSU, bad decoupling, an low quality oscillator...? How to appreciate the quality of the resulting sound of an opamp if all the rest is bad quality?
If one live the board as it is and do the mod to connect a better (external) PSU, then the result in quality is immediate and very audible. The same for the rest of the mods. The quality of the system will increase and every step will bring very obviously the improvement out in the resulting sound.

Last edited by Coris; 24th January 2013 at 08:17 PM.
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Old 24th January 2013, 08:04 PM   #120
Corvus5 is offline Corvus5  Poland
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There's probably no lead, I had to deal with it in order to solder properly

I tried different settings. I can properly guess in which place the sound lacks the most. I also added 2x1000uF caps to the input os-con caps near molex, near the one which is a little hotter. The caps were Elna RJH. The higher audible frequencies are mediocre while mid and lower are better. This time I added them here, not at the I/V amps as some time before. The higher tones went lower, but the mid-freqs are beautiful: voices, pianos.... The lower tones are also present in very fine way. My current driver lacks very low frequencies compared to the older which could play very low tones pretty easily: 40Hz or 30Hz wasn't a problem. This one is problematic. These 1000uF caps placed there made the whole sound perfectly controlled in the bass part. It's not only present in quantity like in older driver, but the quality went much higher. The bass parts can always be heard no matter the rest. It's there and you can easily listen to it playing.

Right now I'm using OPA627AU, the AD797B are usually better. Fitting opamps into stock card is diffucult: you can't guess how will it sound. It depends a lot on what you will plug into the cards. Stock Xonar ST/STX doesn't control the sound pretty well. It may behave unpredictably.
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