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Old 29th May 2012, 09:10 PM   #81
dhbiker is offline dhbiker  Slovenia
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just resolved the problem... tnx for that tip about PSU... one SMD resistor didnt have a contact... probably because of the heat... resoldered it back and works now... thanks again
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Old 31st August 2012, 10:33 PM   #82
Coris is offline Coris  Norway
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Is now quite long time since I did those Xonar STX modifications presented here. I thought it was finished... but in the last time I found out about a new oscillator from Crystek. My old Ebay 0,3ppm oscillator is now replaced with this last 24,576Mhz Crystek one. This oscillator is an 3,3v one. So I had to go down with the regulated tension from 5v to 3,3v, and I used an low noise dedicated 3,3v regulator. The new oscillator is now supplied from 3 regulation levels: 12vDC from Molex is down regulated to 7v, then to 5v, and at last to 3,3v (shunt and voltage regulations).
It seems that the signal output level from this 3,3v supplied Crystek is enough to well run the clock of CMedia processor.

For those who can buy a such last edition Crystek oscillator I strongly recommend to do it so and use it for the ST/STX board. It cost 26$ at Digikey. The result is fantastic. I just was not aware about how high fidelity can come out from an PCM1792 DAC with this last high quality oscillator (and the rest of my modifications on STX card).

Last edited by Coris; 31st August 2012 at 10:40 PM.
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Old 4th September 2012, 10:00 AM   #83
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26$ + $5 S/H + time/effort/risk (5v --> 3.3V mod) ... beautiful, unflushable tips for the constipated.
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Old 6th September 2012, 05:48 PM   #84
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do you know if this board has phantom power for a microphone to do mesurements with rew ?
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Old 6th September 2012, 06:08 PM   #85
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The xonar st does provide phantom power but only 5 volts as is per standard in PCs. The input is switchable via relays, in line in mode you get what you'd expect, when you swap to the mic, via the software, the relays click in and turn the input into signal, phantom power and common ground. I don't think the mic input goes through the same ADC as the line input though.
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Old 6th September 2012, 07:10 PM   #86
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thanks 5th element
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Old 7th September 2012, 09:03 AM   #87
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does anyone know a microphone that works with 5volt phantom power i can use with this board for mesurements ?
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Old 8th September 2012, 02:33 PM   #88
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no one ?
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Old 8th September 2012, 03:57 PM   #89
Coris is offline Coris  Norway
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You can try Google... I you write there "microphone", "5 volt phantom", you get for sure some results...
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Old 17th January 2013, 06:23 PM   #90
Corvus5 is offline Corvus5  Poland
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Hi, I'm modding and trying to improve Xonar Essence ST since a few months. I use it mostly as an DAC and headphone amp for various DIY headphones. I tried a lot with amp power decoupling using amp socket. Also tried a lot of different opamps with different feedbacks. Headphone driver, cables and plugs made also change to how the card works.

However no changes were made to the original card. I noticed the I/V amps have electrolytic capacitors near them and I may try to utilize them as they may cause some resonanses with all the setups. Low ESR cap inserted into the RCA output amp can change how the I/V amp work even if I use headphone amp as output. That's why I may try to bypass existing caps and change them as they may interfere.

Here I'm asking if I should desolder these Nichicon Muse FG caps or cut their legs and use them to solder different one? There are always 2 caps near important chip. Do they utilize ground and use +12V/GND/-12V or the ground is not used? When I decouple using amp socket I cannot access ground plane and use at least 35V caps. 25V tantal cap put here was blown away in a few seconds after computer start.

Also this could let get better access to the TPA amp power.

Proper power decoupling is very important for these opamp as they can behave very unstable and their settling time can be very large. Different cables and plugs causes a lot of changes in the settling time and feedback delay. Large headphone amp feedback with very good cables and plugs can give very good results but increases the power quality requirements. When it lacks power, op-amp can behave very strange causing oscillations depending on the components used in headphones or just saying "I'm off, I'll be slower". The option is lowering feedback and putting 1kohm serial resistor into the output but that decreases the resolution but makes op-amps more stable.
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