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Кстати, AKM4490Е










Fully supporting of high-resolution audio source: DAC, ADC and SRC

Up to 768kHz PCM and 11.2MHz in DSD are fully supported for premium digital playback / recording. In particular, our DAC has "DSD Direct Path" allowing the audio signal to bypass the ΔΣ modulator, to reproduce the original sound in DSD audio source. AK4137 converts the sampling rate of digital audio source from the range of 8kHz ~ 768kHz to 8kHz ~ 768kHz. In addition, equipped with a bidirectional PCM / DSD conversion function allows the system to support DSD/PCM data format perfectly.

Sound Color Digital Filter (SCDF): DAC/ADC/SRC

Focusing on the waveform in the time domain, the built-in 32-bit 8x digital filter controls the transient response of the signal. The 5 types of digital filters allow the music playback in a variety of sound quality settings by switching the filter type. http://www.akm.com/akm/en/product/featured/velvetsound/





REGISTER DEFINITION SUMMARY

(Updated with information from AKM support engineer)



Register address: 00 (Control 1)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| Reset chip without initializing registers
|_|_|_|_|x|x|x|_| Interface mode: 16bit, 24bit, 32bit, I2S, LJ... (1)
|_|_|x|_|_|_|_|_| External digital filter clock: 768KHz/384KHz
|_|x|_|_|_|_|_|_| Enable/disable external digital filter mode
|x|_|_|_|_|_|_|_| Master Clock frequency Setting: auto/manual (2)(3)

NOTES:
(1)- The only requirement for bitclock is >= 2x bit depth. Bitclock could be
32fs, 48fs or 64fs. Not limited to always be 64fs as in ESS DACs
(2)- Auto: detects master clock frequency and sampling frequency (44.1KHz,
96KHz, ...) automatically; sets oversampling rate (1x, 2x, 4x...) according to
input MCKL (this is kind of obvious).
Note: AKM calls sample rate "sampling speed" and assigns names to typical
sample rates: 44-48KHz="normal", 88-96KHz="double", 175-192KHz="quad"...
(3)- Manual: manually set the sampling rate (44.1KHz, 96KHz...) Use reg 01 and
reg 05 for sampling rate setting. This means, in its simplest form, manually
matching the sampling rate to the incoming data sample rate to use the highest
oversampling rate and best noise performance. This feature can also be used to
select a different sampling rate (from the maximum allowed by the master clock
frequency); for example, if selecting "normal" for 44.1KHz allows 8x over-
sampling (512fs), selecting "double" results in 4x oversampling (256fs). This
allows for experimentation with different oversampling rates.
AKM indicates in the datasheet that using a lower oversampling rate (512fs to
256fs) results in a decrease of S/N of 3dB.
Register address: 01 (Control 2)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| Mute/unmute
|_|_|_|_|_|x|x|_| De-emphasis: Off, 32KHz, 44.1KHz, 48KHz
|_|_|_|x|x|_|_|_| Manual setting of sampling speed: "normal", "double"... (1)
|_|_|x|_|_|_|_|_| Short Delay/Traditional filter (Minimum/Linear phase)
|_|x|_|_|_|_|_|_| Zero data detect mode: Separate channels or ANDed channels
|x|_|_|_|_|_|_|_| Zero data detect ON/OFF

NOTES:
(1)- Manual sampling speed setting uses 3 bits. The third bit is in reg 05.
See notes on register 00 for additional info on manual settings

Register address: 02 (Control 3)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| Filter cutoff slope: fast/slow
|_|_|_|_|_|_|x|_| MONO mode: left/right
|_|_|_|_|_|x|_|_| Invert output pin level on zero detect
|_|_|_|_|x|_|_|_| MONO/STEREO mode
|_|_|_|x|_|_|_|_| DSD Data on clock falling/rising edge
|_|x|_|_|_|_|_|_| DSD master clock frequency:512KHz/768KHz
|x|_|_|_|_|_|_|_| PCM/DSD mode

Register address: 03 (Left Channel Attenuation)
7 6 5 4 3 2 1 0
|x|x|x|x|x|x|x|x| Attenuation (1)
NOTES:
(1)- 256 levels, 0.5 dB each. 00=mute; ff=max volume

Register address: 04 (Right Channel Attenuation)
7 6 5 4 3 2 1 0
|x|x|x|x|x|x|x|x| Attenuation (1)
NOTES:
(1)- 256 levels, 0.5 dB each. 00= mute; ff= max volume

Register address: 05 (Control 4)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| Super Slow filter on/off
|_|_|_|_|_|_|x|_| Bit 3 of the manual sampling speed setting (see reg 01)
|_|x|_|_|_|_|_|_| Left channel phase invert ON/OFF
|x|_|_|_|_|_|_|_| Right channel phase invert ON/OFF

Register address: 06 (control 5)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| DSD bit 0 of sampling speed selection (bit 1 is in reg 9)(1)
|_|_|_|_|_|_|x|_| DSD Mode: Direct/Convert to PCM (2)
|_|_|_|_|x|_|_|_| DSD Automute release when Automute release is in "hold"
|_|_|_|x|_|_|_|_| Automute release: Auto/hold (3)
|_|_|x|_|_|_|_|_| Right Channel DSD flag when detecting full scale signal
|_|x|_|_|_|_|_|_| Left Channel DSD flag when detecting full scale signal
|x|_|_|_|_|_|_|_| DSD AutoMute: ON/OFF (4)

NOTES:
(1)- There is no facility for setting auto sample rate detection for DSD. The
use must detect the incoming DSD sample speed and match the sampling speed.
Will have to experiment to see what is the effect of sample speed mismatch.
(2)- In DSD direct mode, the volume control and delta-sigma modulator are
bypassed. In PCM mode, it converts to PCM and uses volume control block and
delta-sigma modulator. DSD direct with a combination of the internal filter
and simple output filter meets the filter specification of the SACD Scarlet
Book.
(3)- Automute condition disappears when data becomes under full scale
(4)- Automute condition is when data is full scale

Register address: 07 (Control 6)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| Synchronize ON/OFF (1)

NOTES:
(1) Synchronizes multiple DACs when used together in the same system. Read
data sheet for more information.

Register address: 08 (Control 7)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|x|x| Sound Quality Control Setting (1)

NOTES:
(1): Sound Control has 3 settings: "1", "2", "3". The AK4495 data sheet shows
additional settings "4" and "5". These setting refer to the 5 different filters
that are available in the DAC. They serve the same function as the filter
selection bits specified in the other registers. What is unclear is which
register takes precedence.

Register address: 09 (Control 8)
7 6 5 4 3 2 1 0
|_|_|_|_|_|_|_|x| DSD bit 1 of sample speed selection (see also reg 5)
|_|_|_|_|_|_|x|_| DSD filter selection when in DSD direct mode