Pro-Ject Tube Box S2 phono preamplifier

After the undeniable success of its small Tube Box S phono preamp, the Austrian manufacturer offers an evolution of its best-seller.

PRO-JECT TUBE BOX S2: CHASSIS

At first glance, the Pro-Ject Tube Box S2 phono preamplifier does not seem very different from its predecessor.

But a keen eye will immediately notice that the chassis has changed. The previous version featured a brushed aluminum front panel (black or natural) mounted on a black steel chassis.

The Tube Box S2, however, has a chassis made of a sandwich of anodized aluminum and steel. Of course, this gives it a more "high-end" appearance, but it also provides better immunity against radio waves and various electromagnetic disturbances.

PRO-JECT TUBE BOX S2: FRONT PANEL AND SETTINGS

The front panel offers a power button and a button to engage the subsonic filter (20Hz with 12 dB/octave).

The big novelty compared to the old Tube Box S is the presence of two switches on the front panel that allow selecting the 6 gain values (40, 43, 50, 53, 60, 63dB). Part of the gain is achieved through ECC83/12AX7 tubes (one per channel). These tubes can be replaced with various models from different manufacturers to alter the preamplifier's sound signature to individual taste.

Its adjustable gains, load values, and capacitance values allow for a wide range of associations with MM and high-end MC cartridges. Indeed, the Tube Box S2 is fully compatible with all moving magnet (MM) cartridges and most moving coil (MC) cartridges. On its rear panel, we find the usual gold-plated RCA input/output connectors and a grounding connection knob.

PRO-JECT TUBE BOX S2: ELECTRONICS

The internal architecture is completely dual mono, allowing for highly precise stereo reproduction and sound staging. The RIAA correction is designed around a dual circuit. One part is active, and the other is entirely passive.

The Tube Box S2 is the first Pro-Ject phono preamp fully designed around discrete components. Pro-Ject did not use any integrated circuits (Op-Amps) here.

The input circuit relies on "Fet" transistors selected for their very low noise and distortion-free performance.

All capacitors are of polystyrene technology.

No chemical capacitors were used in the audio signal path.

PRO-JECT TUBE BOX S2: POWER SUPPLY

The Tube Box S2 is powered by an external power supply providing 18 V DC. This allows the device to exclude a rectification and filtering circuit. However, several regulated and stabilized voltages are handled internally for the different parts of the circuit.

PRO-JECT TUBE BOX S2: TEST AND LISTENING

The initial measurements are quite indicative of the performance of this Tube Box S2 phono preamp.

It retains the timbre quality and definition of its predecessor. But the overall transparency and soundstage precision have significantly improved.

On complex works, it shows authority with a lot of nuance and finesse when necessary.

There is no sense of frustration or aggressiveness, and there are no limits in the high spectrum.

The tubes perfectly fulfill their role in terms of timbre and harmonic richness, without adding coloration, as is often the case with this type of device.

PRO-JECT TUBE BOX S2: UNPACKING

Setting up and adjusting this phono stage is very simple and poses no problems, provided you have the specifications of the phono cartridge.

We advise waiting about ten minutes after turning on the device to fully appreciate its qualities.

Be careful not to be tempted to increase the gain more than necessary to try to achieve the same level as a digital source.

This would result in an aggressive sound and possibly some distortion. The Pro-Ject Tube Box S2 phono preamp is certainly the "best-seller" of the moment. In many respects, it performs as well as many devices costing twice its price.

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