The old Meitner designs were special, and still hold their own today. I don't know about the Bitsteam DAC, but the IDAT series used a novel digital filter algorithm that automatically calibrated itself and would apply a normal SINC filter for optimally flat frequency response if required, or would change to a linear interpolation filter if the source material is rich in transients. The result: a time-resolute filter with no ringing on transients (giving you the benefits of a non-OS design), but with no high frequency roll-off, aliasing distortion, or stair-step "jaggies" on sine waves (thus avoiding the weaknesses of non-OS designs). It really was a DAC ahead of its time, and apparently the IDAT algorithm became the basis for Meitner's design for DSD.