Pro-Ject Pre Box RS2 Digital - Balanced Preamplifier with DAC
Category: other
Tubes on Sunday, Transistors on Tuesday
The Pre Box RS2 Digital has a button most preamps do not. It switches the output stage between a solid-state path and a tube path running four current-production 6922EH valves. Same box, same source, two voicings, chosen from your chair.
The measurements show it is a real choice, not a gimmick. THD+N reads under 0.006% through the solid-state path and 0.017% through the tubes. That second figure is the tube character, deliberately left in, and the 6922EH is a plentiful Electro-Harmonix valve you can still buy new.
Conversion runs on two ESS ES9038Q2M chips in dual mono, playing PCM to 32-bit/768kHz and DSD512 over USB with full hardware MQA unfolding. All of it fits a box 206mm wide that weighs 1.7kg without its supply.
Connections Well Past Its Size
Digital inputs run deep for a small chassis: two optical, one coaxial, a balanced AES/EBU input, USB, and an I²S connection built for Pro-Ject's CD Box RS2 T transport. Bluetooth handles a phone, with SBC, AAC and aptX.
Analog is covered too. One balanced XLR pair and one RCA pair come in, and balanced XLR and RCA pre-outs go out to a power amp or a pair of active speakers. A 6.35mm headphone jack makes 245mW into 32 ohms, 90mW into 300 ohms.
With the CD Box RS2 T, the Pre Box RS2 Digital took the EISA Award for Best Digital Source, 2019-2020. A front display keeps volume and source visible, an aluminum remote handles the rest, and the finish is silver or black.
What Reviewers Are Saying
Gordon Brockhouse reviewed the Pre Box RS2 Digital for SoundStage! Simplifi on February 15, 2020, and put his verdict in four words: "I loved this component." One word summed it up for him — "gestalt" — because of how completely the parts cohered.
Jon Batiste's solo piano, he wrote, "had gobs of power but never sounded hard or glary." Pair it with a transport or streamer, he concluded, "and you have a fabulous, small-footprint digital front end."
One habit to know before it catches you out. Brockhouse notes "that it doesn't mute its main outputs when you plug in headphones" — so turn your power amplifier down, or off, before you switch to private listening.
Who Is This Preamp and DAC Best For?
- You cannot decide between tubes and transistors — the switchable output stage means you stop deciding, and pick per record instead of per purchase.
- Your shelf is small but your standards are not — dual-mono ES9038Q2M conversion, a balanced path and a real tube stage fit a chassis eight inches wide, so a desk or a bookcase stops limiting the system.
- You still play discs — the I²S input is built for Pro-Ject's CD Box RS2 T, and the pair won EISA's Best Digital Source award together, so the transport arrives ready rather than adapted.
- You listen on headphones too — 245mW into 32 ohms drives most headphones from the front panel, which saves buying a separate amplifier to sit beside it.
- You play records — this is a line and digital preamplifier, so a turntable needs a phono stage ahead of it. Choose one to suit your cartridge from our phono preamplifiers and run it into the RCA or XLR input.
How Does It Connect to Your System?
Run the balanced XLR or RCA outputs to your power amplifier, or straight to a pair of active speakers. Your computer joins by USB, a Pro-Ject transport by I²S, and other disc players by coaxial or optical. Broadcast gear uses AES/EBU.
Analog components take the XLR or RCA inputs, and a phone pairs over Bluetooth. Then pick your flavor, tube or solid-state, without getting up.
Pairs Well With
Building around the Pre Box RS2 Digital? Here are some great companions:
- CD Transport: The I²S input awaits Pro-Ject's CD Box RS2 T — see our CD Players & Transports.
- Headphones: The front-panel amp deserves a good pair — see our Headphones.
- Phono Stage: Bring a turntable into the system — see our Phono Preamplifiers.
- Interconnects: Quality XLR cables feed your power amp — see our Interconnect Cables.
Frequently Asked Questions
What does the tube and solid-state switch do?
It picks between two complete output stages: a solid-state path measuring under 0.006% THD+N, and a tube path with four 6922EH valves measuring 0.017%.
What DAC is inside?
Two ESS ES9038Q2M chips in dual mono, playing PCM to 32-bit/768kHz and DSD512, with full hardware MQA unfolding.
What is the I²S input for?
It is a direct digital link designed for Pro-Ject's CD Box RS2 T transport, keeping clock and data separate rather than combined.
Does it have analog inputs?
Yes, one balanced XLR pair and one RCA pair, so it works as the preamplifier for a whole system.
How much headphone power is there?
245mW into 32 ohms, 150mW into 8 ohms and 90mW into 300 ohms, from a 6.35mm front-panel jack.
What finishes are available?
Silver or black aluminum, matching the rest of Pro-Ject's RS2 series.
See It in Action
Steve Guttenberg reviews the Pre Box RS2 Digital alongside its CD Box RS2 T transport partner:
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