Just bought an ART DI/O here on Audiogon for a headphone system. It's headphone nirvana! I'm using it with a CAL Delta transport, an ASL MG OTL tube headphone amp, and a pair of Senn HD545s (which I like better in this setup than the HD600).
The other responses motivated me to give the ART a try in my speaker system (modded CAL Delta, Tact RCS 2.0, AES AE-3, AES SE-1, Merlin VSM-M, and Janis W3 sub). I was able to A/B the Tact DAC with the Tact/ART DAC by switching between inputs on the AE-3 preamp. I listened to solo classical guitar, solo cell, and solo piano. In all three cases the Tact was more three dimensional, harmonic structure of notes was more perceptable, the sound of fingernails on nylon strings was more obvious, the percussive quality of a hammer on piano strings seemed more accurate, and the sound of the bow moving across cello strings was more immediate. The ART was very round sounding both with a warmer tonal quality and with a slower attack on notes (less PRAT). I was surprised, however, by the fact that I seemed to have a more difficult time leaving the ART than I did leaving the Tact when doing comparisons (I guess you might call the ART seductive).
The bottom line is that the Tact is the right DAC for the speaker system, but when I want to have a truely mellow warm headphone experience, the ART DI/O is just the ticket.
The other responses motivated me to give the ART a try in my speaker system (modded CAL Delta, Tact RCS 2.0, AES AE-3, AES SE-1, Merlin VSM-M, and Janis W3 sub). I was able to A/B the Tact DAC with the Tact/ART DAC by switching between inputs on the AE-3 preamp. I listened to solo classical guitar, solo cell, and solo piano. In all three cases the Tact was more three dimensional, harmonic structure of notes was more perceptable, the sound of fingernails on nylon strings was more obvious, the percussive quality of a hammer on piano strings seemed more accurate, and the sound of the bow moving across cello strings was more immediate. The ART was very round sounding both with a warmer tonal quality and with a slower attack on notes (less PRAT). I was surprised, however, by the fact that I seemed to have a more difficult time leaving the ART than I did leaving the Tact when doing comparisons (I guess you might call the ART seductive).
The bottom line is that the Tact is the right DAC for the speaker system, but when I want to have a truely mellow warm headphone experience, the ART DI/O is just the ticket.