Digital Processor Reviews

Sidebar 2: Reference System

I auditioned the Krell Reference 64 as part of my usual system, and also in the context of an all-Krell system comprising the KRC preamplifier, KSA-300S power amplifier, and DT-10 CD transport (with the Time Sync connection).

Most of the auditioning was through an Audio Research LS5 preamp driving the KSA-300S via the Reference 64's balanced outputs. CD transports driving the Reference 64 included Krell's top-of-the-line DT-10 (reviewed elsewhere in this issue) and the Mark Levinson No.31. Digital interconnects included a Madrigal AES/EBU cable, Aural Symphonics Digital Standard coaxial, and AudioQuest Optical Pro II (ST-type). I listened to the Reference 64 on its own and in direct, matched-level comparisons with the Mark Levinson No.30 and the Sonic Frontiers SFD-2 ($4695, reviewed last issue). Loudspeakers were the Thiel CS3.6es, connected with 8' runs of AudioQuest Sterling.

I also had a unique opportunity to evaluate the Reference 64 when driven by an original 20-bit master recording played back on the new $26,500 Nagra D open-reel digital recorder. While the Reference 64 was under review, JA and I recorded pianist Robert Silverman performing Liszt with the 20-bit Nagra (and, of course, on our modified ½" Ampex ATR-100 analog machine) for future release in the Fall as a Stereophile CD and LP. After the sessions, I brought the Nagra and the master tapes home to drive the Reference 64, with the memory of the live microphone feed (and the piano in the hall) fresh in my mind. I'll report on this evaluation later (footnote 1).—Robert Harley

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Footnote 1: In my review of the Sonic Frontiers SFD-2 last month, I commented on how much more forward-sounding it was than the Mark Levinson No.30. After comparing the live microphone feed to the signal converted to digital by the Nagra's 20-bit A/D and decoded by the SFD-2, I must conclude that the SFD-2's forward perspective is less like the original signal than the No.30's more laid-back portrayal. In other words, the No.30 is more accurate in its overall perspective than the SFD-2.—Robert Harley