Rotel RC-850 preamplifier Review System

Sidebar 1: Review System

Putting my customary preamplifier, the Krell KRS-2, to one side, the references used for this review were the $635 Audio by Van Alstine Super PAS (reviewed in October 1998), and the $659 PS Audio 4.6 (reviewed in September 1988 by Tom Norton) used with its normal external power supply, not the $469 M-500 upgrade. For reference purpose, the RIAA response of the PS 4.6 is Flat through almost the entire audio band, with a well-extended bass response, though it starts to roll off at the top of the top audio octave.

Power amplification was provided either by a 1986-vintage Krell KSA-50 or by a pair of VTL 100W monos, these sitting on Mission Isoplats. Loudspeakers were the Celestion SL700s, used on their matching stands; source components included my stock Revox A77 for master tape replay, Marantz and Precision Audio CD players, and the fully loaded Linn LP player (Sondek/Ittok/Troika) sitting on a Sound Organisation table; interconnect was either Monster M1000 or Tiare solid-core silver; speaker cable was Monster M1, two runs being used to bi-wire the SL700s.

As well as being used as the main system preamplifier, bypass testing was carried out with the preamplifier set to unity gain at 1kHz and inserted in the tape loop of the PS Audio 4.6, used in its "Straightwire" mode so that no other active circuitry could impose its signature on the sound. I first used the Ben Duncan PAS-01 passive control unit for bypass testing, but changed to the PS because it will be more readily accessible to readers wanting to repeat these tests. (The high input sensitivity of the VTLs made it easy to achieve adequately high listening levels, despite the absence of any line-stage gain.)

A note on the auditioning of the preamps' phono inputs: not being familiar enough with the sound of any current MM pickup to be confident about using it as a reference, I decided to stick with the Linn moving-coil cartridge. I also conducted bypass tests on all three with the CD player driving the phono inputs via an Old Colony inverse-RIAA network. My comments on the sound of the preamplifier's phono input are based on an amalgam of this complete auditioning.

I need hardly add that the playback levels were matched for all the comparisons, removing volume discrepancies as a source of subjective differences. Audiophiles who don't practice such good housekeeping for their tests should be sentenced to a diet of Tiffany recordings until they learn to mend their ways.—John Atkinson

The Rotel Co. Ltd
Distributor: Rotel of America
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