Pro-Ject Phono Box RS2 phono preamplifier

Phono preamplifiers could be compared to children as viewed by a previous generation of adults: They are expected to be small in stature, and they should stay out of the way, seen but not heard and maybe not even seen. With the simpler models typically encountered at lower price points, there's little to do except "set it and forget it."

But a phono preamplifier such as the component under review—the Pro-Ject Phono Box RS2 ($1999)—could, with its many features, keep you up all night, playing. A component like the RS2 can increase your hands-on involvement with your vinyl playback, which can be a good thing: Vinyl lovers are typically hands-on; we like to be involved in our audio systems.

The RS2 is unusually full-featured, especially at its price. It's fully balanced, dual-mono, with all-discrete circuitry: no op-amps in the signal path. Unbalanced (RCA) and balanced (XLR) inputs and outputs are provided, and you can hook up both inputs at once, switching between them with a front-panel button. The RS2 offers—um—loads of flexibility. Gain settings range from 40dB to 70dB in eight steps: four each for MM and MC. Resistive loading for MC is continuously variable from 10 to 1000 ohms (plus, of course, there's 47k ohms for MM cartridges). The top of the continuous range—near 1000 ohms—is useful with certain moving iron cartridges, and it's missing on many phono preamps. Capacitive loading for MM cartridges is adjustable in 50pF increments from 50 to 400pF. A subsonic filter rolls off the lows below 20Hz at 18dB/octave unless you defeat it with its front-panel button.

Cartridges are the fine jewelry of audio: typically handmade by skilled artisans, often with materials found in jewelry stores. But they're not always perfect, and setup isn't always ideal, so the RS2 provides a balance control that enables adjustments up to 2dB to offset channel imbalances or to tweak the soundstage. Phono EQ is "split passive," which usually means that the different equalization tasks are handled in different gain stages. In addition to the standard RIAA curve, there's a second curve—Decca—that's intended for early Decca mono records.

All adjustments can be made "on the fly" via the front panel—no tiny DIP switches or optional loading resistors—which encourages experimentation. As you'll see, I experimented plenty.

I emailed questions to Jeff Coates, national sales and marketing director for Pro-Ject and Sumiko Analog, who, when necessary, brought in the Pro-Ject design folks in Mistelbach, Austria. He told me that the RS2 is not the result of a single designer's vision but, rather, a collective effort, with "input from our manufacturing and electrical engineering team in Slovakia, the design team in the Austria, and even feedback from the international distributors (such as the team here at Sumiko)."

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One of the most unusual features at the RS2's price is fully balanced operation. Coates described the advantages. "The Phono Box RS2 was designed to be a true differential balanced component," he said. "This exactly follows the balanced design of a moving coil phono cartridge, where the + and – audio signals are isolated from ground. The big advantage here is a near-complete reduction of background power supply noise and hum. The audio signal is completely isolated from any common-mode noise."

It makes sense to maintain a balanced signal for the output of an MC cartridge—the most delicate signal in any hi-fi system that uses one. But not everyone can benefit. "You need to make sure the tonearm output is balanced to enjoy the benefits of the differential balanced design. Any arm that features a five-pin DIN-style output connector (which features separate conductors for Left and Right +/– plus an isolated electrical ground) is preferred," Coates wrote.

Except on high-end tonearms, balanced phono cables are rare. Pro-Ject might be the world's largest manufacturer of turntables to offer balanced XLR connections ahead of phono preamplification—and even at Pro-Ject it's an option. Coates told me that any of Pro-Ject's turntables that have a detachable five-pin tonearm cable—several models from $3000 and up—can be ordered with a five-pin DIN-to-XLR cable instead of the standard DIN-to-RCA cable. Many turntable/tonearm manufacturers tie the chassis ground lug to the shield on the jackets, which renders the signal unbalanced, but all Pro-Ject turntables are fully balanced designs, with separate earth and signal grounds.

Balanced isn't an option with MM cartridges, which typically "tie at least one channel's signal to the chassis ground," as Coates put it. My tonearms have RCA cables, so, although I did try the balanced XLR inputs with adapters, I wasn't able to explore the Pro-Ject's "ideal" fully balanced operation (footnote 1). Most of the time, I connected my MC setup via the RCA inputs. "The Phono Box RS2 will separate the + and – signal paths and handle balanced from there," Coates said.

While it was here, the Phono Box RS2 served as an all-'rounder for my two phono rigs: an all-Clearaudio setup with a Performance DC Wood turntable, Tracer tonearm, and Talisman V2 MC cartridge, and the MoFi Electronics UltraDeck+ turntable with its own tonearm and StudioTracker MM cartridge. Two sets of inputs allow two turntables to be connected. The Input button enabled easy switching between them.

Listening and tweaking
Changing settings "on the fly" was satisfying. Instant gratification. I had fun and got some exercise; since there's no remote control, tweaking settings requires a trip to the equipment rack—all good. The only thing I minded, and only a little, was how small the labels are on the RS2's front panel. They were hard to read, especially in low light. That didn't significantly detract from my experience, though. I felt spoiled having all these options at my fingertips.

My methodology for this review was the furthest thing from "set it and forget it." I didn't just find the best settings for each cartridge and then evaluate its sound. I played with the RS2, fiddled with it, used it as a tone control, changing settings not just from record to record but even from track to track. I did this to explore the benefits of its versatility, aware that few people would ever actually use it this way.

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For the Clearaudio Talisman V2 MC, the specified output of which is 0.5mV, with a source impedance of 50 ohms, recommended loading is 400 ohms. I started with 63dB gain and loading set at 400 ohms, the recommended value for this cartridge. When using this same MC setup ahead of the VAC Sigma 170i integrated amplifier's phono stage, I found that 450 ohms loading yielded the best sonic results most of the time.

For the MoFi UltraTracker MM, which has output of 3.5mV and recommended loading of 100pF, I started with 46dB of gain and 150pF of capacitive loading. I did more critical listening with the MC setup than the MM.

First impressions: On the MC rig, the RS2 seemed neutral to slightly cool, detailed and lively. It sounded clean, almost pristine, on the lighter side in terms of body and heft.

As expected, the sound with the MM setup was more midrange-focused, with good detail and musicality. I heard what I was used to hearing on familiar recordings—just more of it. The RS2 helped reveal a lot of information the cartridges unearthed from the grooves.

Much of Andrew Bird's My Finest Work Yet (Loma Vista LVR005557) was recorded live in Stevie Wonder's old studio in Los Angeles. The opening cut, "Sisyphus," has some studio ambience. Starting with the MC setup, with gain at 63dB and the recommended 400 ohm loading, the group seemed to be positioned between and behind the speakers. Imaging, scale, and depth of field were how I'm used to hearing them, which wasn't surprising: Bird's vocals and violin—indeed all the instruments—sounded rich, full, and substantial, yet studio-natural without oversaturated colors. All sounded complete, of a piece.

When I moved the loading from 200 to 400 ohms, the degree of detail seemed to increase, as did realism and clarity. The musicians' placement seemed to grow more spacious and specific—the piano registered farther to the right, for instance. The whole ensemble "shifted back"—as if I were seated four to eight rows farther back in a venue.


Footnote 1: We, as reviewers, might be considered consumers by proxy.
COMPANY INFO
Pro-Ject Audio Systems
US distributor: Sumiko Audio
6655 Wedgwood Road N., Suite 115
Maple Grove, MN 5531
(510) 843-4500
ARTICLE CONTENTS

COMMENTS
Anton's picture

Thank you for reviewing it!

Julie Mullins's picture

Thanks for reading, Anton. It was my pleasure (as you might have guessed). Wish I still had it here. ;-)

Ortofan's picture

Are there any plans for reviewing it?

https://teac.jp/int/product/pe-505/top

https://www.lowbeats.de/test-teac-pe-505-symmetrische-phonovorstufe-fuer-mm-und-mc/

Jack L's picture

Hi

It is a real bargain:$1,999 for an Austrian built MM/MC fully in/output balanced dual-mono phono-preamp.

What impressed me most is the use of discrete active devices only & PASSIVE RIAA EQ !!!!. This shows the Austrian designer(s) knows music as much as the preamp design. Austria (ie: Vienna, classical music capital for the world for centuries, no wonder!".

Yes, passive RIAA EQ sounds so much better than the conventional NFB loop EQ used in most most commercial photostages available in the marketplace irrespective of selling price. Ny experience.

Only 'booboo' this preamp designer made, IMO, is the use of switching power supply BUILT-IN on the same circuit board ! To save manufacature cost, I guess.

IMO, NO repeat NO switching electronics should ideally ever be used in any phono-linestages. It will simply impair the sonic musicality.

Glad Pro-jet knows making it up with an outboard linear (non-switching) power supply with additional cost of $800.

Yes, power supply of a preamp is so so crucial for its sonic performance particularly when MC is involved.

FYI, my factory-matched headamp for my moving coil cartridge (both made in Japan) is a single-ended Classs-A fully symmmetric OTL push-pulll topology using discrete solidstate devices, powered by +/- D-size batteries. Only batttery power supply can assure no PS rippling noise & ground induced noise. Period. The sonic reward is: to say the least - very dark quiet music background.

Likewise, I've used a huge battery 'reservoir' to power the 6.3V heaters of the triodes used in my design/built phonostage+linestage.
Passive no-NFB-loop RIAA EQ for best sound, absolutely.

Listening is believing

Jack L

nidaje's picture

Doing a review of a truly balanced phono preamplifier like the Pro-Ject Phono Box RS2 I would expect that the reviewer at least is capable of meeting the criteria for that specific product and being able to supply the needed balanced phono signal, not just a single wired RCA signal path whatever that path might cost. The reviewer says: "My tonearms have RCA cables, so, although I did try the balanced XLR inputs with adapters, I wasn't able to explore the Pro-Ject's "ideal" fully balanced operation (footnote 1)."
Reviews are some times deepened by a "follow-up". Can You supply a "follow-up" with "fully balanced" contributions and with the Power Supply UNI 4.
Comprehensive is comprehensive.

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