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Reviewer: David Kan
Financial Interests: click here
Source:Denon DP-59L/DL-302, Rega Planar 3/RB300/Elys, Ensemble PhonoMaster (Symphonic Line Audiobase, BIB Groov-Stat, Parastat MkIIA record cleaner- vinyl accessories), Marantz SA8260, Deltec PDM Two DAC, Restek Radiant, Assemblage D2D-1/DAC-3.1 Platinum, Philips DVP-9000S, Oppo BDP-83
Preamp/Integrated: Symphonic Line RG3 MkIII, NuForce P9, Restek Sector, Audio Zone PRE-T1, Dared MC-7P, Sim Audio Celeste W-4070 SE
Amplifier: NuForce Ref 9 V2, NuForce Ref 9 V2 SE, Sim Audio Celeste W-4070 SE, Thorens-Restek MMA-5, Symphonic Line RG4 MKIII
Speakers: Apogee Stage, Apogee Centaur Minor, Mark & Daniel Maximus-Monitor/Omni-Harmonizer, Klipsch Synergy F2, Yamaha YST-SW200, Yamaha YST-SW80, Infinity BU-1, Mark & Daniel Maximus-Subwoofer [in for review]
Cables: Clearaudio Silver Line interconnect, Deltec Black Slink interconnect, Luscombe LBR-35 interconnect, OCOS speaker cables by Dynaudio, Aural Symphonic Digital Standard digital cable, Aural Symphonic Missing Link, Ensemble Powerflux, Symphonic Line
Stands: Custom
Powerline conditioning: Tice Power Block IIIC, Belkin PureAV PF60, Monster Power HTS-3500 Mk II (modified by NuForce), Monster Power HTS-1000 Mk II
Room size:15’ x 13.5’ x 7’/8’ diagonal setup / 11’ x 18’ x 7’/8’ opens to 18’ x 19’ x 7’/8’, long wall setup, carpeted concrete slab floor, suspended ceiling and all walls finished with drywall (basement with small window on one side, concrete foundation wall with insulation) / 15’ x 15’ x 8’ / 12' x 24' x 9' opens to 12' x 17' x 9' L-shape, short wall setup / 13' x 28' 8" x 9' with openings on one side to hallway and staircase, short wall setup, suspended hardwood floor, suspended ceiling and all walls finished with drywall, external wall finished with insulation inside and concrete on the outside.
Review Component Retail: $1,550 (incl. MC/MM phonoboard), $1,300 (excl. MC/MM phonoboard)

“They say when there’s no clear option, the best thing is to do nothing.”
That was General Friedrich Fromm’s line from the Tom Cruise movie Valkyrie. Fortunately some people prefer the opposite: Do something and there’ll be a clear option. KingRex, the Taiwanese manufacturer of the T20/T20U Tripath amp and SLAP! battery supply, did just that. And to make sure the option is clear enough, they call it PREference. It is their new preamplifier with a phono stage—not only MM but also MC—and quite a departure from their PC audio lineage. The PREference is obviously not a replacement for the KingRex preamp. Anyone can see the huge price gap between $1,550 and $375. To justify the jump, KingRex gives us two chassis to separate the power supply. Both chassis have been upgraded from the standard KingRex aluminum front/hardened steel elsewhere scheme to all aluminum (same footprint but thicker). Amplification circuitry is still centered on a diamond buffer, high-quality OPA627 op-amp for the preamp stage and dedicated BUF634 current booster but with the following key upgrades:

1. A DC servo circuit has been implemented to avoid unwanted audio signal loss due to coupling capacitors.
2. A choice of 7, 14 or 20dB gain is selectable with a pair of jumpers on the PCB.
3. Volume control is an Alps RK27 Blue Velvet potentiometer.

It should be noted that the DC servo circuit op amps (similar for the preamp stage and current booster) are on 8-pin dip sockets. The preamp stock arrives with Burr Brown OPA177 but you could swap in OPA134, OPA604 or even OPA627 units to suit your own taste. Just make sure the pin assignment is the same. According to KingRex, “the result is accurate and perfect signal amplification free from coloration and yet highly adaptive, ideal for output to power amplifiers.” In addition, a separate power supply further guarantees optimal EMI/RFI rejection, critical for any phono stage. It houses a 16VA toroidal transformer and Panasonic FM electrolytic capacitors (praised by DIYers for their extremely low ESR) totaling 16,000uF to ensure ample reserves. The PSU connects to the amp through a 24” cable terminated with Neutrik connectors. Spec comparisons between both KingRex preamps at a glance:

  PREference - $1,550

Preamp - $375

Inputs RCA x 4 (selectable)

RCA x 2 (auto-select)

Outputs  RCA x 1   RCA x 1
Gain 7dB, 14dB, 20dB selectable 11dB fixed
Frequency response 20Hz-20kHz +0~-0.01dB, 5Hz-80kHz +0~-0.3 dB

20Hz-20kHz +0~-0.02dB, 5Hz-80kHz +0~-0.3dB

Max input level
9Vrms @ 0dB                           
6.5Vrms @ 0dB 
Max outputlLevel 9Vrms   6.5Vrms
S/N ratio Better than 126dB

Better than 114dB

THD+Noise ratio <0.0004% @ 1kHz <0.002% @ 1kHz
Crosstalk                -110dB at 1kHz, -91dBat 10kHz -104dB at 1kHz, -89dB at 10kHz
IMD Less than 0.0011% Less than 0.006%
Input Sensitivity
1.1V for 2.5V out @ 7 dB gain
510mV for 2.5V out @ 14 dB gain 
250mV for 2.5V out @ 20 dB gain
700mv for 2.5V out @11dB gain
Power use <10W <5W
Power transformer 16VA in separate power supply chassis 7.8VA buil into same chassis
Power capacitors 26000uF 9400uF
Op amp chips OPA627 + BUF634 + OPA177   OPA627 + BUF634 + OPA177
Phono MM/MC No

Mark the following for later: S/N ratio better than 126dB, THD+Noise less than 0.0004%@1k Hz. That’s respectable (more specs on the phono stage when we get there.) For those less specs conscious, there are other things to please the eye. The amp and PSU arrive in a gorgeous presentation box inside which the two chassis are snugly cradled in high-density black foam. KingRex has slightly increased the size of the Swedish Primare-style control knobs to complement the somewhat bigger all-aluminum chassis. To round out high-end ambitions, you get four isolation cones and discs for each black box. The cones and discs are made of aluminum and match the same pewter color of the control knobs. You only have to peel off the adhesive foam footers to locate the pre-drilled mounting screw holes and they fit right in. Each cone has a an adjustable tip for levelling and if desired, the unpeeled foam footers can be glued to the spike protectors by being the same size.

Turning point
: Input selection is performed with a Noble REB161 12-step rotary encoder. Unlike other selectors I’ve used, its rotary action is endlessly bi-directional. It turns in either direction without stops. (As I learned later, the proper technical term is 360° endless total rotational angle.) The four blue LEDs indicating input sources are arranged on an orbit circling the power LED and they follow the selector to light up in rotation clockwise or counter-clockwise. Isn’t that fun? The touch is tactile and smooth without clicking through the loudspeakers. My only complaint is that the LEDs are still blindingly bright. Fun aside, there is a hidden sonic benefit. Based on a CMOS circuit to perform the logic function, the rotary encoder is more accurate and reliable than a conventional switch. It is located close to the input terminals for the shortest possible signal path on the PCB and through a series of DC loop-controlled input relays, crosstalk between inputs is further minimized. While my Symphonic Line RG3 has audible crosstalk (I can faintly hear the unselected source with the volume turned up all the way), the PREference cuts off other sources completely. The Noble REB161 has a rotational life of 100,000 cycles compared to the 10,000 cycles of an industry standard like the Lorlin CK rotary switch.