xV / xVM
What is the "Clock Monitor?
It is a part of schematic, intended to prevent USB driver from stuck if the external part (DAC) is not powered or not connected.
xV/xVM have own dual frequency clock oscillator, which provides the clock for XMOS:
During the normal operation, the system should be clocked from DAC's oscillator, which is external clock for xV/xVM. When it presents, detector switch XMOS' clock source from internal to external.
Both, internal and external oscillators are dual frequency, to clock 44x and 48x sample rates. This is switched by the "SCALE" signal.
We use 512*Fs oscillator's frequencies, i.e. - 22.5792/24.576 MHz.
XMOS based Isolated USB Interface.
xV (previously known as "xVeloci"):
Up to 384kHz PCM sample rate *.
DSD-64 and DSD-128 in DoP Mode
DSD-64, DSD-128 and DSD-256 in Native Mode.
Asynchronous USB Audio Class II Operation:
not required drivers for MacOS, Linux, Android.
required driver for Windows
Full galvanic isolation from USB source (PC, Tablet, etc.)
Slave I2S bus with Master MCLK.
External 512*Fs clock, switched by the "Scale" signal (44x/48x).
Scale signal polarity switch.
Clock monitor, which prevents stream interruption in case of external clock signal absence.
USB part is powered from USB bus, isolated part is powered from the external device (usually - DAC). However, external power for USB part can be used also (jumper selection).
External device must provide double frequency MCLK signal, power for isolated part and adopt the control signals: Scale (44x/48x), nMute and nDSD/PCM. Also sample rate indication signals are possible.
Very low nose, because only the linear regulators used.
I2S input is available, with the special firmware
Small size: 70x50mm.
* - 384 kHz is for output, input is limited to 192 kHz.
xVM - multi-channel USB Interface:
xVM provide complete solution for Home Cinema (up to 7.1) or multi-band stereo (4 bands in 2 channels) and other applications.
xVM adopt the most xV features with some difference:
8 channels slave output I2S bus (4 serial data lines).
2 channels input.
PCM sample rate is limited to 192kHz/24 or 32bit.
2ch DSD-64 in DoP Mode
2ch DSD-64 and DSD-128 Native Mode.
No external power connection (might be implemented in a future versions, if requested).
No sample rate indication signals.
xVM-10Ch - 10-channel version:
xVM-10Ch is the same as xVM, but modified PCB and different firmware.
xVM-6Ch - 5.1 Home Cinema/DVD-A/SACD version:
6Ch version for Home Cinema, DVD-Audio and SACD playback.There are 2 versions of firmware:
PCM up to 192/32
PCM up to 384/24
Both versions also supports 6 channel DSD-64 and DSD-128 playback (just in DSD Native Mode with ASIO)