Known examples of DAC’s requiring these settings are Burr Brown PCM1738 as well as Analog Devices AD1853. These types of DAC require the following jumper settings:
The input connections should follow the Scheme shown underneath:
All Ground connections must be made to the DAC’s Analogue Ground Pin. All Vcom connections from the Universal Tube Output Stage must be made to the “Reference Voltage (Vref)” or “Common Mode Voltage (Vcom)” Pin(s) on the DAC.