[Mosaic FAQ] Serial Connection issues between Vivaldi DAC and Upsampler

dCS Mosaic offers a number of features that allow for intelligent management and control in a multi-box Vivaldi setup. In order for these features to be available the RS232 cable included with the Vivaldi Upsampler must be installed properly. When properly connected the following features are available:

Mosaic Control

  • Control of DAC volume and mute state
  • Selection of DAC input
  • Standby / Wake function applies to DAC and Upsampler
  • Management of all DAC settings and configuration options
  • Display of DAC status information
  • Display of DAC software version information


  • Control of DAC volume and mute state
  • Standby / Wake function applies to DAC and Upsampler
  • Display of MQA rendering status for DAC in signal path
  • Custom sync offsets for Roon grouped playback that take into account buffer setting

Airplay & Spotify

  • Control of DAC volume and mute state

If the functions listed above are not available (or only partially available) then this indicates that the RS232 serial connection between the Upsampler and DAC is not setup properly. Please consult the Vivaldi Upsampler manual for information and keep the following in mind:

  • The RS232 Y-Cable is labeled and you must pay close attention to connection. The end with two cables attached should be installed on the Upsampler (labeled UPSAMPLER). The end labeled DAC should be connected to the DAC.
  • Make sure the cable is fully seated.
  • Both the Upsampler and DAC must have their RS232/ Serial modes set to BINARY. This configuration is available via the front panel menus.
  • The Mosaic Processor determines whether or not the DAC is connected during its boot process. If you resolve a connection or configuration issue then you should fully power cycle the Upsampler.

The communication mechanism between the DAC and upsampler is complex and relies on both the RS232 cable as well as the dual AES connection. Some functions will work partially if the RS232 cable is not connected properly so it’s important to make sure that changes on the DAC are being properly reflected in Mosaic Control.

The easiest way to do this is to make a volume adjustment in Mosaic Control to a specific level (say -20dB) then adjust the volume using the knob on the Vivaldi DAC. If the volume level in Mosaic Control does not reflect this change (it stays at -20dB) then you have an issue with the RS232 connection.