Digital Processor Reviews

I've made some changes in my playback system since my last review—all of them for the better. Audio Research sent me their new LS5 line-stage preamplifier, a fully balanced, all-tube unit. As great as I thought the Audio Research LS2B was, the LS5 is clearly a notch higher in musical performance. I'll have a full report soon. Next, a Krell KSA-300S power amplifier was put to service driving the Thiel CS3.6 speakers. The big Krell has absolutely awesome bass control, seemingly unlimited dynamics, and a sense of slam that must be heard to be believed. The KSA-300s showed me what the Thiels can do with the right amplifier. I must commend the Thiel CS3.6es for keeping up with and revealing the improvements in electronics. They are not the weak link in the chain; the system's musical performance kept going up as better electronics were introduced. I did go back, however, to the LS2B and VTL 225W monoblocks just to check my findings. The comparison auditioning with other digital processors was performed with both sets of electronics.

Cables included the Expressive Technologies IC-1 (preamp to power amp) and AudioQuest Lapis, both in balanced configuration. Loudspeaker cables were AudioQuest Sterling.

I drove the SFD-2 with the PS Audio Lambda transport reviewed in October, and with the top-of-the-line Krell D-10 transport. Most of the auditioning was through the ST-type optical interconnect, although an Aural Symphonics Digital Standard coaxial cable saw some action.

After a brief introductory listen to the SFD-2 when it first arrived (I couldn't wait for the usual two-day warmup), I knew that I'd have to bring out the big digital processor guns to fully evaluate the SFD-2. The Mark Levinson No.30, Meitner IDAT, and a Theta DS Pro Gen.III took their places in the rack for the listening comparisons. The No.30 is the reference digital processor against which all others are measured. The Theta Gen.III sets standards for digital replay in the areas of bass control and depth, soundstage openness, transparency, and imaging. It is also priced very close to the SFD-2 ($5400 fully loaded with balanced outputs and ST-type optical input), making it a good point for comparison. The listening consisted of long-term listening to the SFD-2 on its own, and analytical comparisons with the other processors at matched levels (less than 0.1dB difference).—Robert Harley