Aug 14: Note that these are the last two boards, then 4490 version will be retired and only 4493 remains.

Features:

• Proven high performance: -108 dB THD+N, 119 dBA SNR
• Unbalanced RCA output (optional balanced XLR available)
• I2S input, supports up to 32 bits and 768 kHz sample rate
• 5 digital filters selectable with jumper links
• AK4490EQ DAC, LM4562 opamps
• Compact size at 70 mm x 50 mm
• Can be used with any compatible I2S output or with W-Input board

W-DAC 4490 is part of modular Wee DAC system offering several boards to build a DAC with required features.

Specifications (typical):

• THD+N ratio: -108 dB (1 kHz -5 dBFS)
• THD ratio: -115 dB (1 kHz, -10 dBFS)
• Dynamic range / SNR: 119 dBA
• Crosstalk: -125 dB, 10 kHz
• Output level: 2 Vrms / 6 dBV

What's included?

W-DAC board with all SMD components assembled. Connectors can be soldered or unsoldered depending on option (both options may not be available at all times, for example in the beginning all boards are fully soldered). All boards have been individually tested.

Full measurement results, schematics, and BOM available at nihtila.com

What else is needed?

I2S signals

This DAC has I2S input and you should be familiar with the format prior to buying. You can get I2S signal either from USB to I2S modules or S/PDIF to I2S modules (such as my W-Input board). Up to 32 bits and 768 kHz sample rate is supported by the DAC. I2S source must provide master clock (MCLK) as well.

I2S consists of:

• Data
• Bit clock (BCLK)
• Frame/word clock (LRCK or WCLK)
• Master clock (MCLK)

Supplies

Following supply voltages and currents are required:

• VAP: +15 V, 37 mA
• VAN: -15 VA, 32 mA
• VA: 7.2 V, 22 mA
• VD: 5 V, 9 mA

±15 VA are used for opamps so they are not very strict. I wouldn’t go higher due to excess power consumption but it can be lower. 7.2 V is the value for VA in Wee DAC baseboards but it can be something like 6-9 V; if going higher it’s worth checking tiny LP2992 regulators can take the extra heat.

VD cannot be higher than 5.5 V.

Note that there is no protection against over-voltage or reverse voltage; if you are unsure connecting please use a dedicated Wee DAC baseboard.

You can wire supplies directly to pinheaders or use one of the baseboards offered. There are both simple breakout boards and baseboards with all supply regulators in place.

Other information

Connections

External connections are marked below. These connections are made automatically when using other Wee DAC boards but with help of the diagram the board can be used in other systems.

Digital filter selection

Really the only setting for user is digital filter, provided by pinheader J2. There are 5 digital filters in AK4490, named in the datasheet as follows:

• Sharp
• Slow
• Short Delay Sharp (SD Sharp)
• Short Delay Slow (SD Slow)
• Super Slow

Filters are selected by closing jumper links F0-F2, marked on PCB. Default filter is SD Sharp which is selected if no jumper link is placed on J2.

For tech-minded I have carried out extensive measurements of these digital filters.

LEDs

There is one LED to show DAC is on and another indicating if mute is on.

Output pop

A few words’ disclaimer on output pops and clicks, meaning unwanted glitches when turning power on or off.

W-DAC does not have an output mute circuit!

DAC with an external output circuit without external mute will always generate some unwanted pops. This is not a complete product so it is always end user’s responsibility to protect their speakers, headphones, and ears from potentially harmful pops and clicks.

A circuit that delays power-on but is fast at power-off is typically enough; usually power amplifiers have this. For example, I have an extension cord with switch that powers my whole system at once, including headphone amplifier, subwoofer power amplifier, and active speakers – there are no pops at all in any of these.

AK4490 DAC used here creates a pop when I2S signals are applied. Therefore, I2S input signals should be continuous to prevent pops.

PCB

This is a 4-layer 70mm x 50mm PCB. Dimensions and distances between connectors are shown below.

Optional balanced XLR output

This is an addon board (50 x 50 mm) W-Output XLR that stacks on W-DAC adding balanced outputs.

All other specifications remain identical except output level is doubled at 4 V RMS or 12 dBV.

W-Output XLR requires extra current:

• +15 V: 26 mA
• -15 V: 22 mA

Wee DAC system

Please see my store for full range of Wee DAC system boards.

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