Essence STX II I/O
The Essence STX II features 2x RCA for stereo speakers, 6.3mm headphone, 6.3mm microphone/line in and S/PDIF/coaxial out.
As standard, we get a trio of Op-amps preinstalled all by MUSES, the low pass filter in use is a 8820 which is surrounded by four WIMA capacitors. The right/left I/V converters are using a MUSES 8920. Just south of the Op-amps is the Ti 6120A2 headphone amplifier which is a common choice on discrete soundcards.
ASUS AV100 audio processor
Under the AV100 audio processor is the crystal oscillator and to the left is the new 32bit asmedia PCIe controller. In the bottom left you can just make out the CS5381 120dB Analogue-to-Digital converter (ADC).
The Texas Instruments PCM1792A 132dB DAC
Just right of the Ti DAC you will see the TI TPS 7A4700 and 7A3301 LDO regulators.
The header to connect to the daughter board is one of the most noticeable differences in design layout over the original STX. There is also a front panel header, which can be an important feature for some, and for those PC enthusiasts who thought they were able to do away with those 4 pin molex cables, no such luck here. It is a shame that ASUS didn't choose to use a 6pin PCIe connector instead as they did with the ROG Phoebus.
The daughter board
The addition of the daughter board allows the STX II to expand to allow high quality 7.1 surround channels with each channel individually assigned their own RCA connection.
Replaceable Op-amp sockets galore, here we find good quality, albeit, more mainstream Op-amps rather than the acclaimed MUSES found on the stereo channels, though the use of sockets allow easy customisation and modification for those inclined that way.