Yamaha CDX-530 Circuit Board   MONICA DAC This is the famous Monica non-oversampling DAC. I modified it for TOSLINK optical input. Replace C22 and C14 with 0.01uF capacitors as per the CS8414 datasheet. The TORX177 produces TTL output levels. Remove R16. Main Circuit Board Place the +5V/GND for the the TORX177 module into the holes for C3 TORX177 Module optical module showing +5V/GND (black and red) and signal wire (yellow)   MY RIG I do most of my listening using the Monica DAC along with the tube headphone amplifier. Audio is fed via TOSLINK interface from the PC running iTunes. I used to compress CDs using AAC at 256kbps, but switched to Apple lossless format recently. Tube Headphone amplifier Monica TDA1545 DAC, TOSLINK interface to PC Yamaha CDX-530 Sherwood - CD5090R Yamaha AX-350 Amplifier Cat (defective, only makes a rumbling noise when stroked)