You can go from your computer to a Big Ben, You have to go from the computer to a converter that will convert USB to SPDiF. Edirol makes such a unit. Then take SPDiF from the Big Ben to the digital input in your DAC or Pre-Pro.
Computer -- USB -- USB/SPDiF Converter -- SPDiF -- Big Ben -- SPDiF -- DAC or Pre-Pro.
Computer -- USB -- USB/SPDiF Converter -- SPDiF -- Big Ben -- SPDiF -- DAC or Pre-Pro.