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Coping with resistance: At first glance, the two MC resistive load settings (100 ohms and 220 ohms) on the PREference seem somewhat restrictive. But is that really so? The output impedance of MC cartridges is so low that a discrepancy in the phono stage’s resistive load setting has little audible effect as long as you keep to no lower than what’s specified. A wise vinyl man once told me that in general an LP after more than 20 times play—and a needle after 1,000 hours—will start to show a gradual ultrasonic dip where a higher resistive load could help. Although the bulk of my vinyl collection averages 30 years of age, I doubt any of it was played more than 20 times since I had the habit of dubbing my favorite titles to metal cassette tapes with my three-head Nakamichi deck, which still works like new. But still, my Denon DL-302 sounds good with the 47-ohm output impedance matched to the 100-ohm resistive load on the PREference and excellent with 100ohm+100pF. Resistance myth solved.


Matching capacitance: Capacitance. P is for picofarad (pF). 1pF is 0.000001uF. How could that possibly affect a phono cartridge? Selectable capacitance settings are not entirely common for phono stages. Most MM and MC cartridges don’t even bother listing capacitance. If I remember correctly, the cartridge that suddenly got the world’s attention on cartridge capacitance was the Shure V15. In a V15 Type IV user manual on the Internet, I was able to read: “Optimum load: 47,000 ohms resistance in parallel with 200 to 300 picofarads capacitance per channel. Load resistance can be up to 70,000 ohms with almost no audible change in frequency response. Total capacitance includes both the tone arm wiring and amplifier input circuit. Most amplifiers, tone arms and cables meet this requirement.”

What Shure brought to our attention was how inductance and capacitance that exist or build up along the long journey from cartridge through tone arm and interconnect cables to phono circuit do affect high-frequency performance as much as the resistive load. Compounded by the mechanical resonance of the tone arm, the phasing of certain high frequencies may be altered (peaks diminished or shifted forward) to affect the coherence of the overall audible bandwidth. Adjusting capacitance is an effective control measure. In the past, some preamps with phono input paid even more attention to capacitance than resistance settings. The Proton AP-1000 in the 1980’s for instance had a switch for 100P, 200P and 320P but MM or MC was just a straightforward push-button affair.


Is selectable capacitance coming back? Is there a need? Restek has been a firm believer. My 20-year old Sector preamp with MM/MC phono stage in addition to the four resistive loads of 10, 30, 47 and 100 ohms has four capacitance settings of 47, 100, 200 and 470pF. The new Restek MRIA/MRIA+ phono preamp has the finest calibrated settings to almost the point of excess: 47Kohm for MM, 50 to 680 ohms in 10-ohm increments for MC plus 100 to 600pF in 50pF increments. The British Origin Live Ultra phono stage has five settings for resistance from 10-ohm to 47K and five settings for capacitance from 0 to 4.7nF, the highest value I known of. Here the PREference offers only 100pF and I can hear the difference readily. The Ensemble PhonoMaster, like any other outboard phono stage, requires one extra run of interconnects. Does it have any capacitance compensation? Do you begin to see the advantage of onboard phono stages? When I told James Lee, chief designer at KingRex, of my findings with the 100pF setting, he explained: “Although capacitance compensation is an effective high frequency noise filter, it might lose some high frequency details. Most phono stages would build that into the circuit but we decided to give users the option.” 


Gaining control: One very obvious advantage the PREference phono stage has over the Ensemble PhonoMaster is extremely low noise. I could tell that the Ensemble was much noisier right from the start. The MM circuit of the PREference is almost as quiet as CD if I set both phono gain and preamp gain to low. With volume open and needle out of the groove, all I hear is a very low hiss with my ear to the speaker driver. But I also have to dial up the volume to max when playing music and still get somewhat compromised bass and punch. My personal preference is setting phono gain to high and preamp gain to low to get a perfect balance of SPL and sonic integrity. With that setting, the volume knob only needs to be dialled to 11:00 long before noise sets in.


MC is more sensitive to noise and the variable gain control of the PREference becomes handy when matching MC output. Based on the Denon DL-302, I have conducted a simple research into comparing the noise/gain performance of PREference versus Ensemble. Though nowhere near sound lab accuracy, it still serves some general guideline. The ideal is to keep listening level below noise level:
  Noise begins Comfort listening level
Ensemble + PREference preamp gain low 11:00 12:00
Ensemble + PREference preamp gain medium 10:00 11:00
Ensemble + PREference preamp gain high 9:00 10:00
PREference phono gain LOW + preamp gain low   Not enough gain
PREference phono gain LOW + preamp gain medium   Not enough gain
PREference phono gain LOW + preamp gain high   Not enough gain
PREference phono gain HIGH + preamp gain low          
2:00 3:00
PREference phono gain HIGH + preamp gain medium 1:00 1:30
PREference phono gain HIGH + preamp gain high 12:00 12:30

Obviously, the last two settings would be my preference for the Denon DL-302 cartridge. It gives the best balance of SPL and sonic integrity at the lowest THD+N. Oops, did I just mentioned that horrible spec jargon? Well, it’s about time to reveal the phono stage specs of the PREference:


Signal to Noise Ratio: MM: 112dB/95dB (Low gain/High gain), MC: 104dB/88dB (Low gain/High gain)
THD+N Ratio @1kHz/1vrms output: 0.0006% (MM-Low gain), 0.004% (MC-Low gain), 0.004% (MM-high gain), 0.03% (MC-high gain)
THD+N Ratio @1kHz/2.5vrms output: 0.0005% (MM-Low gain), 0.0018% (MC-Low gain), 0.004% (MM-high gain), 0.01% (MC-high gain)
Crosstalk (at 1kHZ): -94dB MM low gain, -79dB MC low gain
Crosstalk (at 10kHz): -100dB MM low gain, -86dB MC low gain
Gain (at 1kHz): 24dB MM low gain, 43dB MC low gain, add 20dB for high gain
Max Input Level: 19mV MM, 6.6mV MC high gain; 218mV MM, 72mV MC low gain
Output Impedance: <100 ohms
Input Impedance: 100 ohms, 220 ohms, 47k, switchable
Input Capacitance: 0P, 100P, switchable.


KingRex published only one set of THD+N figure on their website: 0.0006% (MM low gain) and 0.01% (MC low gain) without a specific reference level for those measurements. To make sure I compared apple to apple, I asked James to provide me with all the THD+N lab tests and he sent me eight lab reports in PDF whose figures I tabulated above. When I compare that with the specs of the Ensemble PhonoMaster, it becomes evident that my audition findings weren’t imaginary. If phono stage design is about balancing noise and gain, KingRex has done an excellent job. The THD+N figures are exceptional by any standard, not to mention compared to Ensemble’s <0.29% for MM and <0.24% for MC @1kHz/1vrms output.