Yes, this is probing on the "line in" the signal from the card output, in my case through headphone out. The output is practically not shorted, however you may thing the ground plane is shorted, but it's the same card and the output uses the same +12V/gnd/-12V as the line in. I thing the ground loop may not be the problem. Maybe the PSU fault.
In comparison the line out without final stage opamp, so it's comming through the probably 500-1000ohm + 100ohm. Large voltate dropout (can be 30dB) when supplying headphones. The noise and the THD. Noise floor is -146dB. Wow! The 50Hz and its odd harmonics is still present. The THD has a lot of harmonics but is shouldn't matter here.
By measuring the noise I found the required capacitance in the given filter. Too small made the lower frequencies noisy and introduced some peaks in the spectrum. This is also audible: it changes the sound resolution. Using too high capacitance and far away causes the higher freq to not be filtered properly.
The Vanguard should arrive today. I removed all electrolytic caps from the xonar supply output at the 5V and +/- 12V stages. Used relatively small MLCC caps. Seems more transperent, unnatural and requires all analog stage to use MLCC otherwise the sound is slowed down somewhere. I heard MLCC give high THD at low frequencies.
Joel, the bad power supply for the xonar may lower the sound quality. I think noone has taken any xonar essence measurements for different PC PSUs.
Take a look at the first image: the headphone out noise. The only change is added filtering near the molex line. The noise goes down. The PC PSU is not able to handle it. It's not the cheapest psu available, it's the OCX modxstream 500W as seen on my previous image.
The second is the THD. Third and fourth is the the noise and THD one the line out without buffer opamp.
I have 2 different Xonar stx in 2 different computers. One with internal smps and one with external and picopsu connected to the mainboard.
Only looking at det spectrum from the line in the one with external PSU seems a bit better but that might just be small differences in the cards themself.
I also have a Xonar essence one (havent testet it yet) and will buy Creatives newest ZXR which looks very promising. Especially the ADC part.
Will maybe change the psu in one of the computers to this
http://www.techpowerup.com/reviews/Seasonic/SS-520FL/9.html
Seasonic platinium s-520.
Fanless (I like it silent
)
Only looking at det spectrum from the line in the one with external PSU seems a bit better but that might just be small differences in the cards themself.
I also have a Xonar essence one (havent testet it yet) and will buy Creatives newest ZXR which looks very promising. Especially the ADC part.
Will maybe change the psu in one of the computers to this
http://www.techpowerup.com/reviews/Seasonic/SS-520FL/9.html
Seasonic platinium s-520.
Fanless (I like it silent
)
By taking a look at the Xonar Essence drivers source code, I see that in my case the main chip controls the CS2000 and then the CS2000 clock ouput is given to the PCM1792. In the case of first release of STX the AV100 has the direct control the the DAC clock and internally does the clock multiplication. Also the CS2000 clock aux output is available on the third top pin on the large pin connector.
The AV100 uses I2C to control CS2000. Other inputs are: CLK_IN, XTO and XTI/REF_CLK. I guess the CLK_IN comes from the AV100 and XTI/XTO are connected to the quartz as in application note. I wonder how it works.
There's a delta-sigma fractional-n frequency synthesizer and Hybrid analog-digital phase locked loop.
The AV100 uses I2C to control CS2000. Other inputs are: CLK_IN, XTO and XTI/REF_CLK. I guess the CLK_IN comes from the AV100 and XTI/XTO are connected to the quartz as in application note. I wonder how it works.
There's a delta-sigma fractional-n frequency synthesizer and Hybrid analog-digital phase locked loop.
I think I get it. the CLK_IN is used as a base, but the PLL uses the clock or quartz for better resolution and stability. I will connect REF_CLK to the oscillation ouput and leave the XTO as it was.
Almost everything is fixed. First, the card wasn't recognized. The device ID was ok. Then the card device ID switched to the universal CMI8788 driver. No sound, the sound and movies were slowed down to 60%. I ran the eeprom fix utility which recognized the card as Xonar Essence ST. I selected to rewrite the eeprom anyway. After reboot the was recognized by the Windows as a Xonar Essence ST and sound was playing The only problem is with the slowown. Everything is slow. Recently I moved the ground for the oscillator to the ground of the 7805.
The only problem is with the slowown. Everything is slow. Recently I moved the ground for the oscillator to the ground of the 7805.
You may have a wrong measurement method.... Of course is not possible to have 28v at the output of an oscillator powered at 5v... The output level should be a little bit under 5v.
Or you got something else in the box of an Vanguard oscillator...
Almost everything is fixed. First, the card wasn't recognized. The device ID was ok. Then the card device ID switched to the universal CMI8788 driver. No sound, the sound and movies were slowed down to 60%. I ran the eeprom fix utility which recognized the card as Xonar Essence ST. I selected to rewrite the eeprom anyway. After reboot the was recognized by the Windows as a Xonar Essence ST and sound was playing
Something got wrong with your mod... At least you have wrong frequency out from that oscillator, or very wrong level of the clock signal. If you`ve got problem with the identification of the board in your computer, then it may happen something with the main processor of the board, or it is not working as it should... or its clock is very bad.
Power the board out of your computer (12v/5v on Molex), on your bench, and do some measurements on the oscillator power, frequency out, or so...
At least you may not trust very much what to be bought on ebay... Just do some measurements on that oscillator, and be sure that is working as it should, before connecting it to the STX processor.