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 several addon boards for Wee DAC to expand feature set:

  • W-Output XLR – Balanced XLR output for W-DAC
  • W-Output XLR Mute – Balanced XLR output with Mute relay 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
  • W-Input+ Combo BNC – Extra AES/EBU XLR and BNC S/PDIF inputs for W-Input

Updated 28.12.2020 to include W-Output XLR Mute and W-Input+ Combo BNC.

Wee DAC system with Balanced XLR output addon and AES/EBU+Toslink input addon
Wee DAC system using newer S-version boards and XLR/BNC 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-Output XLR Mute

Newer version to match W-DAC S which includes output mute relay – as does this addon. Output mute is controlled by Mute signal on J3 and it may be driven by W-Input S, W-DAC S, or external device such as host microcontroller. Without external control Mute can be tied to ground and it still monitors supplies and protects from startup and shutdown pops. This is very useful where the DAC is used as preamplifier and directly connected to power amplifier.

W-Output XLR Mute is available with one opamp version where cold lead is zero as explained above, and two opamp version where cold lead is usual inverted signal. One opamp version has very slightly better noise performance but two opamp version may be a safer option if input circuit of the connecting amplifier is unknown. Both have the same 6 dB gain.

W-Output XLR Mute can be used with non-S version of W-DAC as well; however, note that then mute relay is only at XLR output and not in RCA output of the DAC.

W-Output XLR boards can also be used with other circuits than Wee DAC but it is worth nothing that input impedance is rather low so the source must be up to the job.

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.

W-Input+ Combo BNC

Again the same as two boards above but with XLR and BNC.

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 (Mute)

  • +15 V: 26 mA
  • -15 V: 22 mA
  • Mute version needs additionally around 20 mA from 5 VD for the mute circuit

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

  • 5 VD: 6 mA

W-Input+ Combo BNC is completely passive circuit and does not need any supply.

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-Output XLR Mute

  • v1.0 First released version; A is single opamp version and B is dual opamp version

W-Input+ Combo

  • v1.1A First released version

W-Input+ Combo XLR

  • v1.1A First released version

W-Input+ Combo BNC

  • v1.0A First released version

This page version history

  • 5.11.2019 Initial version
  • 28.12.2020 Added W-Output XLR Mute and W-Input+ Combo BNC. Also reorganised some photos.

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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