Before I purchased my Esoteric K-01X I had borrowed the ARC CD9 to use for a few days. The CD9 replaced an Oppo BDP-105 so there were three different players I evaluated. I was then using the ARC Ref 5SE feeding Theta Prometheus monoblocks. The difference is primarily in the midrange region. The CD9 is warmer and more forgiving on older digital cd's. It also does have a great synergy with the ARC preamps. The K-01X is not as forward and warm in the midrange. It does have a wonderful midrange just not as "euphoric". Inner detail is with the Esoteric. I was hearing small details that were buried in the recording that I had not heard with the ARC CD9. Bass on both units was tight and extended. The K-01X has a faster attack on bass drums. With the CD9 you hear the fabric of the skin and mallet. With the K-01X, it was less organic sounding but with a tighter impact and longer decay. Almost similar to the SS versus tubes debate. It depends on what flavor you want. Both units I could live with. They both give wide soundstaging which helps with the right recording. I ended up choosing the K-01X. I had read from CD9 owners disappointment with the filter settings and downloading the windows driver IIRC? It takes some time for the Esoteric units to settle in and you have to experiment with the filter settings which is a smart choice to have with digital.
Esoteric K-01 vs ARC CD 9
Supposing both players had the same pre-amp, say an ARC Ref 6, which one would you prefer? The K-01 can also be played directly to amps--how would it do alone against the ARC combination, Redbook CD only?