Wisdom in mind,   enthusiasm at heart.

Even though the PCM1704 PDF declare the PCM1704 supports up to 96KHz / 24bit, highest word clock input is 768KHz.
In fact the PCM1704UK can support 192KHz / 24bit at 8X oversampling (USB or I2S model), the word clock input is 1.536MHz, as high as ESS9018.

Reference-10.32（USB applied USB-32）
Discrete  DAC + Headphone amplifier / Preamplifier

Built in DSP-1 data processor
32bit / 384K Asynchronous Transfer  USB-32 Chip
Built in 4 Pieces Hi-grade PCM1704UK Chips
OCC wires and TCXO built in

Price:  (With remote control)  USD1850
Included Accessories: Power cable and USB cable . Optical cable included per request when placing order.

Click to read    FAQ
USB-32 Introduce and drivers download
Audio-gd products had design and test based on the AP SYS-2722 (The top-drawer professional equipment in world)


Reviews:
http://www.tonepublications.com/macro/audio-gd-reference-10-2-dac-and-more/
http://www.head-fi.org/t/601259/audio-gd-reference-10/135#post_8543066
http://www.digitalaudioreview.net/2011/04/audio-gd-reference-71-dac-8-x-pcm1704uk/


DAC / Headphone amp / preamp all in one
Fully balanced design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS analog output stage .
Uses three R-core transformers (135W total), separate power supplies for the digital components, right and left channels.
More than 50,000uf audio grade NOVER capacitors are used to ensure ample and smooth power supply.
A total of 9 groups class A PSU's  are used to purify the power supply. To achieve a high S/N ratio, the control circuit is powered with separate regulators.
Uses high-grade parts and exactly matched transistors.
Four channel 99 steps digitally controlled relay-based volume control avoids channel imbalance and improves sound quality.
5 digital inputs:   AES / BNC+RCA coaxial / RCA coaxial / Optical / USB
3 analog preamp inputs:  XLR / RCA / RCA
Preamp / DAC output :   XLR / RCA / ACSS (variable)
Headphone output : 4 pins XLR / 6.3MM SE
Memorizes all settings and resumes the last setting when powered on (see user manual).

Modification guide on headphone jack for 4-pin balanced headphone output.
   Click here to read:   modification guide
Parts for the modification is USD30. (Includes one female 4-pin plug and one male 4-pin plug, some tape and WBT tin solder)