This design was published in Vacuum Tube Valley Magazine Number 17:

Click here if you want to read it:

Click here to see Line Stage schematic:

Click here to see Line Stage suggested PSU schematic:

Line_Stage.jpg (51353 bytes)

A transformer coupled balanced line-stage which accepts both balanced and unbalanced inputs.  The topology is a 6SN7 long-tailed-pair driving a Lundahl 1660 push-pull interstage transformer.  The power supply is an adapted surplus General Radio 1201-B.  The XLR inputs and outputs are hardwired using Canare star quad cable.

Sowter DAC.jpg (126295 bytes)

The XLR inputs are specifically provided to accept  balanced signals from Sowter 8347 DAC transformers (having mu-metal cores) which are an elegant and highly effective way to eliminate all silicon from the analogue path in a CD player having something like Burr-Brown PCM 1702/4 DAC chips.  Details of this modification are included in an inset on the schematic.