Audio Research's DAC 9 is from their Foundations series which means it's voicing is a little more lush and tubey sounding compared to their reference CD9SE DAC. The DAC 9 also is a pure DAC and forgoes the CD player tray of the CD9SE.
If you are looking for a high performance dac that has a tube output stage and and extraordinary flexibility, the DAC 9 should be on your must audition list. The Audio Research tube amplification and output stage will give your system an organic, warm digital sound. In a way, putting a tubed digital front end on a system has a similar effect to adding tubed preamplifier to a solid stage amplifier to warm a system up, but perhaps even more-so. We've had customer's install a DAC 9 in a high end system with a solid state preamplifier and solid stage amplifier, and found the system took on a fair quantity of the spacial dimensionality and harmonically rich lifelike sound that tubes are known for.
The DAC9 digital-to-analog converter decodes most current formats with state-of-the-art vacuum tube technology. Five digital connections – USB, RCA, BNC, AES/EBU, and Toslink – provide connectivity to all of your digital sources. Quad DAC architecture provides a balanced digital signal, wide dynamic range, and decoding resolutions from red book CD up to 384 kHz and native DSD sampling rates. A pair of 6H30 vacuum tubes are the heart of the analog circuit. Both balanced and single-ended connectors are provided for output connectivity. Native-rate upsampling and selectable digital filters allow customization of the digital signal.