Phono Box RS2
Fully balanced, fully discrete phono preamp of the highest class
Reference class phono preamplifier with unique impedance control
The Phono Box RS2 is the ultimate phono preamplifier of the highest class. It is fully balanced from the input to the output. Electronics are fully discrete, no op-amps are in use and it uses split passive RIAA and DECCA equalization.
A discrete circuit is composed of electronic components which are disparate, individual devices, also called discrete components. These can be “passive” components, like resistors, capacitors and inductors, as well as “active” components, which in our case are transistors. The opposite to this would be an integrated circuit, which uses operational amplifiers (Op-Amps) in the signal chain. Countless hours of listening tests and years of experience have shown us that even the very best Op-Amps do not tend to be so neutral, natural, dynamic or vivid. Standard phono pre-amplifiers with integrated circuits have a few tens or hundreds of components, but discrete designs will employ hundreds or thousands of components by comparison. That makes for an extended and more costly design process, but results in the best sound for your money.
The Phono Box RS2 employs a true fully balanced design principle. Balanced transmissions consist of a hot and a cold (also called + and -) signal. Both the + and – signal chains effectively carry the same musical information. A true balanced amplifier can now extract the final musical information out the +/- signals and subtract, remove, all noise that could potentially be added along the transmission. In a true, fully balanced amplifier, like the Phono Box RS2, the + and – sections of both the left and right channel are treated individually, which doubles the amplifier sections by 2 as a result.
Split passive EQ
The Phono Box RS2 uses split passive equalization for both of its RIAA and DECA curves. This is more costly to design and implement but ensures the most accurate representation of the ideal EQ curve. Split passive equalization allows for better impedance matching and lower deviation from the ideal RIAA or DECA curve.
Extreme cartridge loading options
No other phono-preamp in the world has such fine options of setting the gain like the Phono Box RS2. Very large ranges from 40dB (voltage amplification by 100x) up to 70dB (voltage amplification by 3690x) are possible.
Load impedance can be set continuously via potentiometer, a system invented by Pro-Ject Audio Systems. It allows you to seamlessly adjust the impedance during playback and immediately assess the impact of different loading options.
Cartridges, by nature, suffer from small imbalances between the left and right channels. To correct this the Phono Box RS2 introduces a new feature that is absolutely rare in this price category. A potentiometer allows you to adjust the exact center of the sound stage in ranges of 2dB to the left or right.
The Phono Box RS2 has a steel chassis which is covered by screwed aluminium panels. This construction brings very good rigidity and splendid isolation against interferences.
Power Box RS2 Phono – linear power supply upgrade
An outboard power supply with linear construction is even better, because it can offer much cleaner power. When you want to manufacture such clean and really high-end power supplies, you have to use a transformer with a very low core saturation and preferably with shielding between primary and secondary windings. Obviously, such a transformer becomes larger than one would expect. Also, much more expensive. That is why such a power supply requires a cabinet the size of the Phono Box RS2 itself. Our Power Box RS uni 1- & 4-way will be another step up for your Phono Box RS2 performance.
- MM & MC capable
- Fully balanced, true dual mono design
- Fully discrete hardware design - NO Op-amps!
- Fully passive RIAA & DECCA equalisation
- Balanced XLR & unbalanced RCA In & Outputs
- Unique continously variable input impedance loading and channel balance control to match every cartridge to 100% (adjustment even while playing)
- Superior low noise / low distortion
- Metal casing protects against vibration and interference
- Available in silver or black
|Input impedance||Fixed 47kohms, variable 10 - 1000 ohms|
|Load capacity switchable||50, 100, 150, 200, 250, 300, 350, 400 pF|
|Gain MM:||RCA: 40, 43, 46, 50 dB (+6dB using XLR)|
|Gain MC:||RCA: 60, 63, 66, 70 dB (+6dB using XLR)|
|Signal to noise ratio||MM (40dB): 89dB A-wt (10mV); MC (60dB): 79dB A-wt (1mV)|
|THD||< 0,0015% (MM 40dB, 1kHz); < 0,0024% (MC 60dB, 1kHz)|
|RIAA accuracy||within 0,4dB/20Hz - 20kHz|
|SubsonIc||at 20Hz with 18dB/octave|
|Inputs||RCA & XLR|
|Outputs||RCA & XLR|
|Power supply||20V/3A DC; 110 - 240V, 50/60Hz|
|Power consumption||350mA DC < 1 watt standby|
|Dimensions W x H x D (with sockets)||206 x 72 x 200 mm|
|Weight||1600 g without power supply|
“The Phono Box RS2 turned out to be an excellent product with exceptional functionality”
• The tested preamplifier showed how extremely energetic, explosive, strong, and aggressive the recording is.
• I got the impression that the Austrian preamp was able to attack quickly and cancel out the decay just as fast while retaining the energy in the sustain.
• The cymbals had an attack, drive, and impact on both records – everything that gets the music flowing when it needs emotional thickening.
• The component from the Austrian manufacturer also has a very deep soundstage.
• The scaling is good. The closer the sound source is to the stage, the higher the volume.
• The voice is also rounder than with the reference preamp.
• So we have a slightly warm presentation, excellent dynamics, good imaging, and very successful sound scaling.
• I think that the surprising mix of warmth, openness, suppleness, and dynamics of the preamplifier tested is rooted in the very high resolution.
• We will hear the “breath” of the music, it will flow, but it will also have energy.
• On the one hand, the preamp showed the depth of the sound, its smoothness, but did not erase the sibilants in the singer‘s voice, nor did it pull back the long reverbs, without which this album would be much poorer. It also showed deep and dense bass.
“The mix of features and musicality is great”
• The frequency response is so linear that you don‘t have to worry about distortion.
• Noise and hum are not an issue despite the maximum possible gain of 70 dB.
• The small box with the numerous customization options happily holds back with its own sonic input and at the same time manages to ensure that there is no lack of emotionality through a high degree of suppleness.
• We never had the impression that anything was lacking or that the phono box was adding .
• Even in projecting depth of space, the Pro-Ject Phono Box did not let down, and explored the dimensions of the room excellently.
• The Phono Box RS2 can claim the title of versatility-world-champion. It will become a permanent star in the analog heaven for music lovers and record listeners with an interest for experimentation.
• A technological and feature miracle in a compact package at a competitive price. Symmetrical circuitry, almost infinite customization options in combination with very good sound make it a price-performance heroine.[pdf]
The Phono Box RS2 has no equal
• The RS2’s contribution was to reveal her violin as a strongly embodied instrument, one with a feeling of weight and size, as well as tease out all the textural detail within its body and strings. I got to hear a large and fruity rendition.
• There was a sense of strong dynamic push to an orchestra comprising humans with instruments! The RS2 resolved the dynamics of this performance nicely, making for an engaging listen and my listening notes talk about “rich insight into strings”.
• Kick drum strikes were weighty and well resolved; I again got to hear the timbral properties of the instruments better than usual. It was a sophisticated sound.
• Vocals were just that: rich and full sized in front of me.
• The rolling drum work in a live recording moving our listening room nicely due to easily expressed dynamics, but there was also atmosphere from the studio microphones. The brass section blared out, individual instruments being discernible.
• Using the balanced XLR inputs, all the strengths of the RS2 were magnified. There was greater clarity and a sense of precision timing.
• The RS2 was able to resolve their massive bass power and pace, making for dynamite dynamics.
• For those interested in running a fully balanced turntable to eliminate hum and noise this is the one. Great sound quality and easy to use as well.[pdf]