The previous hybrid amplifier of the Austrian company Pro-Ject. The flagship among the previous amplifiers of the company.
Pro-Ject Pre Box RS is assembled according to a balanced circuit according to the principle of double mono. The Pro-Ject Pre Box RS circuit has high linearity and an extremely low level of inherent noise, works in class A and has no negative feedback. ECC88 (6922) selection tubes are installed in the output stages of the amplifier, and an Alps Blue motorized potentiometer is used to adjust the volume. Low ESR capacitors are installed in the audio circuits, and the printed circuit boards are optimized to reduce the audio signal path length. For source switching, precision signal relays are used, located in close proximity to the block of input connectors.
The preamplifier is equipped with three balanced and three unbalanced inputs, a balanced output for a power amplifier, and an RCA output for connecting a recording device. Unlike most similar devices, in which the balanced and unbalanced inputs for each signal source are alternate, the Pro-Ject Pre Box RS has a total of six independent inputs. All connectors on the back panel of the device have gold-plated contact surfaces. A remote control can be used to control the preamplifier.
The device is assembled in a solid metal case made of thick steel. It is equipped with a front aluminum panel. Pro-Ject Pre Box RS is equipped with an external power supply.

Features of the Pro-Ject Pre Box RS

Balanced inputs and outputs
Alps motorized volume control
Logging out
Inputs 6 linear (3 RCA + 3 XLR)
Tape outputs (RCA), Pre-Out (XLR)
Frequency range 20 Hz - 50 kHz (- 0.08 dB)
Gain 12 dB (18 dB when using XLR)
Input impedance 150 kΩ
Non-linear distortion less than 0.06%