Following is additional information on using Kaamos W-DAC XLR board. Please also see the product description. If something is still unclear, please contact us. We will try to update the information based on feedback.
Power supply
The DAC board requires 5V for digital (VD, max 5.5V), 6V for analog references (VA), and +/-12…15V (VP/VN) for output stage. If you don’t have 6V references supply, you can solder an onboard ferrite or 0R resistor to take the reference supply from the VP (+12…15V), or just connect VP to VA outside the board; however be careful if using other Kaamos boards in the system as VP-VA connection may not be allowed in all boards.
See current consumption per supply on product page.
If you use a Kaamos power supply, all four supplies are provided in one 6-pin Molex Micro-Fit connector. If not, you can solder your own power supply wires in the Molex footprint or order a power cable, cut one end and connect it to your power supply.
PWR led indicates power is on.
PCM/I2S signal inputs
W-DAC XLR has PCM digital serial input consisting of following four signals:
- MCLK – Master Clock
- BCLK – Bit Clock
- WCLK – Word Clock (sometimes also referred as LRCK)
- DATA
MCLK must be in sync with BCLK and WCLK.
All these are inputs and provided with U.FL connectors. Signal level is 3.3V and there is no termination. The same connectors are used in DSD mode; see below.
For information on using U.FL cables with headers, please see this post.
Other signals
Signal names on silkscreen around power supply connector and edge headers:
- G = ground
- VD = 5V digital supply
- VA = 6V analog reference supply (can be taken from VP if not available)
- VP = +12…15V output stage supply
- VN = -12…15V output stage supply
- EMUTE = External active-high mute input; the input is low (no mute) when not connected
- SDA = I2C data (I2C variant only)
- SCL = I2C clock (I2C variant only)
- nIRQ = IRQ from TCA9554 (I2C variant only), not used unless you connect your own inputs to TCA9554
Filter selection
Most DAC and ADC ICs offer selectable digital filters to fine-tune the response and sonic features. The impact of these filters on sound quality is minimal and not everyone can hear the difference. Feel free to try. The default option by the chip manufacturer is Sharp. A bit more on digital filters can be found on nihtila.com posts about PCM1794A filters and Audiolab M-DAC filters.
In HW-variant the filter selection is done by “DAC Filter Sel” jumper link or you can use a rotary switch to add the filter selection on the front panel. In I2C-variant the selection must be done via register.
Mute
W-DAC XLR has automatic mute circuit that hard-mutes the output if supplies are not up.
In addition, there is an external input (EMUTE) to this mute circuit that mutes the output when the signal is high (3.3V). When unconnected, it remains low.
OUTP led indicates mute is off (output on).
I2C variant information
Following information only applies to I2C variant of W-DAC XLR.
HW and I2C variants are the same PCB but use slightly different BOM. It is possible to convert the board between the two variants but it requires soldering/desoldering components, including ICs.
There are two ICs onboard that needs to be programmed to use the DAC, otherwise it will not do anything. Complete firmware is not provided but example register settings are provided below. It is simple to set up the board if you are familiar with I2C-devices.
SDA and SCL needs to be connected for I2C. They have 10k pull-ups on W-DAC board but you may want to have stronger pull-ups close to Host – albeit this works fine at least with slower I2C speeds.
I2C address
The address formats and default 7-bit addresses for the two ICs are:
- AK4493: 0010 0 A1 A0 RW (0x13)
- TCA9554: 0100 A2 A1 A0 RW (0x23)
A2, A1 and A0 are configurable by bottom-side resistors. By default these resistors are unpopulated, and in this default state A2=0, A1=1, A0=1. Soldering the resistors invert the bits. RW bit is 0 for write and 1 for read as always in I2C.
Note that different AKM ICs use the same address format so if you have a DAC, ADC, and S/PDIF to I2S in the same I2C bus, make sure all boards use unique addresses.
Register programming
For details of the register settings see TCA9554 and AK4493S datasheets. However, a few code examples are provided below. Writing the following sequence configures the board to stream I2S-audio.
var adExp = 0x23; // TCA9554
var adDac = 0x13; // AK4493S
// Set up IO Expander
Write(adExp, 0x01, 0x01); // Mute high, attenuation low, nPDN low (all still inputs)
Write(adExp, 0x03, 0xCE); // Direction port; PDN, attenuation and Mute outputs
wait(1)
Write(adExp, 0x01, 0x20); // Active, mute off
//Write(adExp, 0x01, 0x21); // Active, mute on
wait(2) // Note that there is a long RC delay for nPDN
Write(adDac, 0x00, 0x8F); // auto MCLK, 32-bit I2S, reset off
// Volume
var vol = 0; // in dB
vol = 0xFF + 2*vol;
Write(adDac, 0x03, vol);
Write(adDac, 0x04, vol);As seen, AK4493S only needs one register write to work with default settings. In addition, you can change volume, digital filter, and lots of other settings.
TCA9554 offers option to engage the output mute relay. It also used to control attenuation relays but they were removed from W-DAC XLR.
There is also nIRQ output from the TCA9554 but it is not used in the W-DAC XLR as there are no inputs to the TCA9554. There are unused pins though so you can use it for your own external control signals.
DSD operation
DSD operation is only supported in I2C mode. This is a limitation of the DAC IC. Please see AK4493S datasheet for setting up DSD. Signal names are on silkscreen and use the same connectors as I2S:
- MCLK – Master Clock
- DCLK – DSD/Bit Clock
- DSDL – Left Data
- DSDR – Right Data
More information
See a post on connecting DAR 18 and W-DAC and W-DAC XLR product page.