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DACs — Pro-Ject Pre Box RS2 Digital
Description, images, technical data and specifications
Pro-Ject Pre Box RS2 Digital
Image source — © Pro-Ject
The Pre Box RS2 Digital combines a D/A converter, a line preamplifier and a headphone amplifier in a single enclosure from the Box Design family of Pro-Ject Audio Systems. Pro-Ject presents it as the bigger brother of the Pre Box S2 Digital, built on the same converter chips but with a wider feature set, and it carried an MSRP of EUR 2,199 including VAT. Its aluminium shell is offered in silver as well as black, and a full aluminium remote control is supplied.
Key specs that matter
Two ESS9038Q2M chips work in dual mono, one per channel, with separate signal paths for left and right. The USB 2.0 input accepts PCM up to 32-bit and 768 kHz plus DSD512 natively or through DoP. Further digital inputs are a coaxial S/PDIF socket, a pair of TOSlink optical ports, a balanced AES/EBU connector, each at 24-bit and 192 kHz, an I2S link over an HDMI connector and embedded Bluetooth 4.0 with SBC, AAC and aptX. Analogue sources connect through one XLR and one RCA pair with 15 kOhm input impedance. Outputs are XLR and RCA pre-outs plus a 6.35 mm headphone jack rated at 90 mW into 300 ohm, 245 mW into 33 ohm and 150 mW into 8 ohm. THD+N is below 0.006% in solid-state mode and 0.017% in tube mode at 2 V RMS and 1 kHz, with output impedance of 180 and 220 ohm respectively. The case measures 206 x 72 x 222 mm with sockets and weighs 1,710 g without its supply.
Engineering and use context
The output buffer is discrete and balanced, and the owner can switch between a solid-state path and one running four 6922EH tubes from the front menu or the remote. Eight digital filters are offered, one of them the optimal transient filter from the MQA developers, and MQA files are unfolded fully in hardware. A multi-core XMOS microcontroller handles USB, while an Altera MAX II CPLD performs re-clocking. Optional upsampling converts every digital input to 352.8 or 384 kHz. The headphone stage is DC coupled throughout with no coupling capacitors, and a fast DC servo keeps the output free of offset. Power arrives from a 20 V, 3 A DC adapter, with a maximum draw of 1.2 A and less than 0.5 W in standby, and 12 V trigger sockets let other Box Design units switch it on.
Pairing
The HDMI I2S socket is meant for the CD Box RS2 T transport, which receives its 16.9344 MHz master clock from this unit, and Pro-Ject suggests the Stream Box S2 Ultra as a network source. Balanced pre-outs suit active speakers or a power amplifier with XLR inputs.
Alternatives
The Pro-Ject Pre Box S2 Digital is the smaller converter and preamplifier built on the same ESS9038Q2M chips.
Key specs that matter
Two ESS9038Q2M chips work in dual mono, one per channel, with separate signal paths for left and right. The USB 2.0 input accepts PCM up to 32-bit and 768 kHz plus DSD512 natively or through DoP. Further digital inputs are a coaxial S/PDIF socket, a pair of TOSlink optical ports, a balanced AES/EBU connector, each at 24-bit and 192 kHz, an I2S link over an HDMI connector and embedded Bluetooth 4.0 with SBC, AAC and aptX. Analogue sources connect through one XLR and one RCA pair with 15 kOhm input impedance. Outputs are XLR and RCA pre-outs plus a 6.35 mm headphone jack rated at 90 mW into 300 ohm, 245 mW into 33 ohm and 150 mW into 8 ohm. THD+N is below 0.006% in solid-state mode and 0.017% in tube mode at 2 V RMS and 1 kHz, with output impedance of 180 and 220 ohm respectively. The case measures 206 x 72 x 222 mm with sockets and weighs 1,710 g without its supply.
Engineering and use context
The output buffer is discrete and balanced, and the owner can switch between a solid-state path and one running four 6922EH tubes from the front menu or the remote. Eight digital filters are offered, one of them the optimal transient filter from the MQA developers, and MQA files are unfolded fully in hardware. A multi-core XMOS microcontroller handles USB, while an Altera MAX II CPLD performs re-clocking. Optional upsampling converts every digital input to 352.8 or 384 kHz. The headphone stage is DC coupled throughout with no coupling capacitors, and a fast DC servo keeps the output free of offset. Power arrives from a 20 V, 3 A DC adapter, with a maximum draw of 1.2 A and less than 0.5 W in standby, and 12 V trigger sockets let other Box Design units switch it on.
Pairing
The HDMI I2S socket is meant for the CD Box RS2 T transport, which receives its 16.9344 MHz master clock from this unit, and Pro-Ject suggests the Stream Box S2 Ultra as a network source. Balanced pre-outs suit active speakers or a power amplifier with XLR inputs.
Alternatives
The Pro-Ject Pre Box S2 Digital is the smaller converter and preamplifier built on the same ESS9038Q2M chips.
Specifications
Model name
Pre Box RS2 Digital
Conversion type
N/A
Engine
ESS9038Q2M
DSD compatability
Yes
Parameters
up to 32bit/768kHz and DSD512
Frequency response low +/- 3dB (Hz)
N/A
Frequency response high +/- 3dB (Hz)
N/A
Gain (dBu)
N/A
Output Level (balanced) (V)
N/A
Output Level (single-ended) (V)
N/A
Input Impedance (balanced) (Ω)
15 000
Input Impedance (single-ended) (Ω)
15 000
Output Impedance (balanced) (Ω)
180 solid state, 220 tube
Output Impedance (single-ended) (Ω)
180 solid state, 220 tube
Analog outputs
N/A
Signal to Noise Ratio (dB)
N/A
Total Harmonic Distortion + Noise (% at 22 kHz)
< 0.006
Dimensions (mm)
206 x 72 x 222
Weight (kg)
1.71
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