Home ProjectsWee DAC Wee DAC addons – XLR output and extra S/PDIF inputs

Wee DAC addons – XLR output and extra S/PDIF inputs

by nihtila

There are three addon boards for Wee DAC to expand feature set:

  • W-Output XLR – Balanced XLR output for W-DAC
  • W-Input+ Combo – Extra Coaxial and Toslink S/PDIF inputs for W-Input
  • W-Input+ Combo XLR – Extra AES/EBU XLR and Toslink S/PDIF inputs for W-Input

Wee DAC system with Balanced XLR output addon and AES/EBU+Toslink input addon

Design

All these boards are very simple as they are only addons to stack on W-Input or W-DAC. However, W-Output XLR can be used as a general purpose single-ended to balanced converter with slight modifications; therefore, it sort of replaces Addon BalOut board I have been offering before.

Below Wee DAC system level diagram shows how these boards are connected in the complete system.

W-Output XLR

Positive and negative (inverted) signals come from W-DAC and go to an identical differential amplifier stage as in W-DAC, followed by an inverting amplifier to generate the inverted output signal.

There is an option to leave inverting opamp out and just use ground as a negative signal. This works perfectly; balanced output is about impedance balance and using equal 47R resistor to ground, this condition is fulfilled. However, people usually just want to have the inverted signal as well, maybe due to not understanding that it’s not really necessary. Balanced output usually have 6 dB more gain than unbalanced so extra gain may be useful if only one opamp is used. Assembled board comes with two opamps though, as shown in the schematics.

W-Input+ Combo

This is just a simple board providing two extra inputs to W-Input. AK4115VQ receiver used in W-Input has four S/PDIF inputs so this uses the two free ones.

W-Input+ Combo XLR

Same as above but XLR is used instead of RCA for AES/EBU input.

PCBs

PCBs are 50 mm x 50 mm 2-layer boards as these are very simple.

Schematics and layout have been done with KiCad and components sourced from Mouser and Digikey. PCBs are from Elecrow.

W-Output XLR

W-Input+ Combo

W-Input+ Combo XLR

Measurements

These boards have been measured together with W-Input and W-DAC boards to ensure they have no impact on performance.

Regarding W-Output XLR, all W-DAC measurements apply to this board except output level is double at 4 V RMS or 12 dBV.

Current consumption

Typical current consumption from supplies:

W-Output XLR

  • +15 V: 26 mA
  • -15 V: 22 mA

W-Input+ Combo and W-Input+ Combo XLR

  • 5 VD: 6 mA

Files

Schematics are shown above and reference designators are on silkscreen, thus only BOMs are listed here.

References and additional information

Version history

Schematics / PCB version history and known errors and bugs

W-Output XLR

  • v1.2A First released version

W-Input+ Combo

  • v1.1A First released version

W-Input+ Combo XLR

  • v1.1A First released version

This page version history

  • 5.11.2019 Initial version

I may have missed something important here. If you have more questions about this board, please comment below or send an email.

Buy boards here.

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