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Pro-Ject Pre Box S2 Digital

Micro-sized digital stereo preamp with built-in headphone amp (Black)

6 Reviews

Item # 252PBS2DB

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Our take on the Pro-Ject Pre Box S2 Digital

Use this little gem for high-fidelity sound with your digital audio sources, including high-res audio tracks. The Pro-Ject Pre Box S2 Digital measures barely over four inches wide, but it's big on flexibility. Use its stereo RCA outputs to feed pristine audio signals to a pair of powered desktop speakers or a power amp. Or connect your favorite set of headphones to the front-panel 1/4" jack.

Pint-sized audio precision

Use this little gem for high-fidelity sound with your digital audio sources, including high-res audio tracks. The Pro-Ject Pre Box S2 Digital measures barely over four inches wide, but it's big on flexibility. Use its stereo RCA outputs to feed pristine audio signals to a pair of powered desktop speakers or a power amp. Or connect your favorite set of headphones to the front-panel 1/4" jack.

Built to impress

The Pre Box S2 Digital sports a dual mono configuration, with two high-performance DACs (digital-to-analog converters) onboard. It can play just about any high-res audio track you send its way, including super-high-res DSD files. There's built-in hardware support for MQA (Master Quality Authenticated) files, such as those available through TIDAL's streaming audio service. Jitter — digital timing errors that can smear musical details — is reduced to vanishingly low levels. It all adds up to surprisingly robust sound, given the Pre Box S2's small size and reasonable price tag.

Praise for the Pro-Ject Pre Box S2 Digital from The Absolute Sound

"The Pro-Ject Pre Box S2 Digital offers audiophiles a very high-value DAC/digital preamp at an almost ridiculously low price. Not only does it include a plethora of important features, but it sounds good, has an elegantly designed control surface, and is expandable."

— From Steven Stone's January, 2019 review in The Absolute Sound Read the full review

Product Highlights:

  • dual mono circuitry with two high-performance ESS Sabre DACs (ESS9038Q2M)
  • high-res audio playback, including PCM-based files up to 32-bit/768kHz and DSD512
  • full hardware-based MQA support
  • selectable digital filters
  • vanishingly low jitter (as low as 100 Femtoseconds)
  • frequency response: 20-20,000 Hz
  • total harmonic distortion: 0.0003%
  • headphone output power: 68 mW (32 ohms)
  • 1 coaxial digital
  • 1 optical digital (Toslink)
  • 1 USB Type-B for connection to a computer
  • RCA stereo output (rear-panel)
  • 1 front-panel 1/4" full-sized headphone output
Dimensions & Warranty:

What's in the Box:

  • Micro preamplifier
  • AC adapter with attached 45" DC output cord and Micro-B USB plug (DC output: 5.0V 1.0A)
  • 3 AC plug adapters (US / EU / UK)
  • Wireless remote control (12-button)
  • CR2032 Coin cell battery (for remote)
  • CD with USB driver
  • Instructions for Use (English)
  • Instructions for Use (German)

Wonderful unit used to convert my optical 4k TV audio feed to my Bryston integrated. Sound is great!

Dave, NY


Pro-Ject Pre Box S2 Digital Reviews

Average Customer Review(s):

(6 Reviews)

More Stone-Cold (dead) than Steve Austin

Shane from Atlanta, GA on 1/9/2019

Crutchfield Customer Review (What's this?)

Well, right out of the box it was DOA. Terrible quality control from Pro-Ject. I'll see if the second one is any better. To be continued!


Cons: DOA our of the box

Pro-Ject Pre Box S2 Digital

padmakumar from Peachtree City, GA on 12/7/2018

Crutchfield Customer Review (What's this?)

I will say the best DAC you can buy not just on its price but even with twice or thrice its price even. Dual mono design with Sabre 9038 is unmatched quality. I sold my Yamaha CXA5100 after experiencing MQA streams from Tidal. The remote that comes with this is the game changer. You can change the track even the Tidal player in PC playing MQA files. Anyone need to experience MQA and or high-resolution audio this is the ultimate unless you have a super high budget. I tried with Parasound JC5, Mcintosh MC152, Emotiva XPADR2, and every amp sounded fantastic with this preamp. To me for ultimate 2 channel experience, all you need is Pro-Ject PreBox S2 Digital, PC/streamer, good AMP and a good speaker. Enjoy music



Impossibly beautiful!

Drummer from mountains of northwest nj on 10/21/2018

Crutchfield Customer Review (What's this?)

Impossibly beautiful! What a great time to be an audiophile. I am going to use two terms I have read in hi fi reviews for years but never really experienced for myself. Weight and presence. Had to do it. These describe the startling (to me) experience I am enjoying. Openness, transparency, oh man, I am sounding like the reviews I like to read but you know what? These are the words that really do best describe the sound of the S2. I am a 2 channel guy. Connected gear: MacBook Pro (late 2012) > Tidal Hi Fi subscription (16 bit and MQA files) > the great Audirvana App (connects to Tidal replaces audio path in Mac) > Audioquest Carbon USB ($ but try it) . Listening on my trusty old (but still strong) Grado SR 80 headphones. I sincerely hope my enthusiasm for this product might inspire you to give it a listen. And Crutchfield's continued excellent customer support is exemplary. (PS- I have read that upgrading the power supply yields a bit of improvement. Hard to imagine, but worth mentioning)

Pros: Sound, build quality, value. professional reviews cite EISA awards and say the device compares to previous generations of DACs costing significantly more.

Cons: I'd appreciate documentation about the filter types the device offers. I am relatively technically aware, and would like to learn more about this aspect of the DAC. Again, not a flaw on the device, but a preference for the documentation.

Pro-Ject Pre Box S2 Digital

Bill from Vancouver, WA on 7/29/2018

Crutchfield Customer Review (What's this?)

I purchased this recently and am on the third unit, which each one having issues - I am glad Crutchfield has such great customer service. On this third unit, I have reached out to Project to see what they have to say about the problems. The problems are always with the higher data rates - the PCM at 768k periodically looses sync and comes out as loud garbled noise - the DSD at all data rates (worst at 256 and 512) have significant dropouts - the third unit seemed to be O.K. when I received it for a few days, then it began experiencing the same problems - I am using this on a 64bit Win7 system, but tried it on a Win10 system to see if the problem went away (and it was still there) - I have not tried the MQA function, but everything else works great and it sounds wonderful - I looked around to see if I could find anyone else experiencing the same problem and there was nothing I cold find online - I wondered if this was similar to other products implementing the same chipset, but again, I found nothing online - hopefully the vendor can help, otherwise, I will be returning this unit in the next week or so. :( All settings are set to the most conservative to minimize any latency and dpc latency shows the PC is working perfectly. The ASIO control panel shows the output latency is greater than the input latency in all PCM modes and the other way around on all DSD modes???!!! Hopefully they have updated drivers or firmware that will address this problem.

Pros: sounds great (in most modes)

Cons: fast modes have issues

TV audio option

Dave from NY on 4/30/2018

Crutchfield Customer Review (What's this?)

Wonderful unit used to convert my optical 4k TV audio feed to my Bryston integrated. Sound is great!

Pros: Conversion and build quality.

Cons: none

had to buy.

roberto from longmont, co. on 4/26/2018

needed money for my car n sold my AYRE cd player, thought i could live with my tascam recorder , no way, so i took some of the money from the sale n bought open box s2, wow that really helped. not as good but no cd player is like the AYRE. at this price it should be a killer. this came with a remote n saber dacs. very happy over all.

Pros: great sound for the price. remote. filters to chose from.

Cons: little shy on bass. needs real power cord.


Hands-on research

Product Research


Overview: The Pro-Ject Pre Box S2 Digital is a high-quality digital micro preamplifier with dual D/A converters built in. This tiny package has USB, optical, and coaxial digital inputs, RCA analog outputs on the back, and 1/4" headphone output on the front. The Pre Box S2 Digital is available in black and silver, and comes with a 12-button remote control. Dimensions: Width 4.057", Height 1.457", Depth 4.783", Weight 13.3 ounces (w/o AC adapter).

Construction: The Pre Box S2 Digital features a dual mono configuration with two high-performance ESS Sabre digital-to-analog converters (ESS9038Q2M), capable of high resolution audio up to 32-bit 768kHz PCM and DSD512. Its proprietary clock circuitry delivers jitter rates down to 100 Femtoseconds. The Pre Box S2 Digital supports MQA decoding, which enables hi-res audio streaming. It also has a high-quality ESS9602 headphone amplifier. All of this technology is housed in an extruded aluminum casing.

Connections: The Pro-Ject Pre Box S2 Digital offers three digital inputs. The USB input is for connecting the unit to your computer. A USB driver is supplied on the included CD, if needed. The Optical and Coaxial digital inputs allow you to connect to components, such as CD players, DVD players, TVs, Audio Streaming devices, etc. You can select the input from the front panel, and the selected input will be shown on the 1" OLED display. The Pre Box S2 Digital has a stereo RCA output on the back panel and a 1/4" (6.3mm) headphone output on the front. When headphones are connected to the unit, the rear output is muted.

Sampling Frequencies: The Pre Box S2 Digital supports 32-bit PCM, DSD, and full MQA unfolding. The USB input is capable of the following sampling rates: 32, 44.1, 48, 88.2, 96, 176.2, 192, 352.8, 384, and 768kHz. It also supports DSD64, DSD128, DSD256, and DSD512. The Optical and Coaxial Digital inputs will support PCM up to 24-bit/192kHz.

Power Requirements: The Pre Box S2 Digital provides two options for powering the unit. If you are not going to use the USB input, you can power the unit via the included 5V AC adapter. If you plan to use the USB input, you can power the unit directly from your computer via the USB input. In this case, you should unplug the AC adapter to avoid interference between the two power supplies.

Digital Filters: The Pre Box S2 Digital has eight selectable digital filters, including Pro-Ject's proprietary Optimum Transient Digital Filter. Other available filters includes: Fast Roll Off (Linear Phase), Slow Roll Off (Linear Phase), Minimum Phase Fast, Minimum Phase Slow, Linear Apodizing, Hybrid Filter, and Brickwall Filter. These filters can be accessed from the front panel or remote to let you shape the audio precisely to your liking.

Front Panel Controls: The unit has a rotary volume control with a range of -80dB to 0dB. Pressing the volume control instantly mutes the audio. There are separate volume settings stored for the headphone output and the RCA output. Two buttons let you select the input (USB, OPT, or COAX), while a single button is for cycling through the available digital filters. The Menu button gives you access to settings for Distortion Compensation and Audio Quality, and displays the software (SW) Version. You can change the values for the audio settings by turning the volume knob while in the menu.

Remote Control: The included credit card-sized remote control gives you basic playback control of your digital music files, including play/pause, forward, and reverse. You can also raise or lower the volume, mute/unmute, cycle through the Digital Filter selections, control the balance, and access the menu. The remote is 1.58"W x 3.4"H x 0.29"D, and powered by a CR2032 coin cell battery (included).


  • Frequency Response: 20Hz to 20kHz
  • Output Voltage: 2.05 V (effective)
  • Headphone Output Power: 68mW (at 32 ohms)
  • Total Harmonic Distortion: 0.0003%
  • Dynamic Range: 124 dBA
  • Power Consumption: 5V, less than 1 watt

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Good Reviews, MQA support, latest ESS DAC chipset. [ DiMora  Jan 07, 2019 ]
Seems to be what I need for my desktop audio setup. I need volume control for my powered speakers which have volume control on back which is not convenient for speaker location. Dac is top of line which is positive. I know if I have setup problems, Crutchfield will help me. [ ROY  Dec 07, 2018 ]
Reviews Mqa decoding build quality internal components [ matthew  Nov 21, 2018 ]
MQA support is the reason I chose to purchase this DAC. I use Audioquest Dragonfly RED at this time. Need a DAC for my Cambridge CXC transport so I think it is worth auditioning a DAC to cover both requirements. Solid reviews around the forums regarding this DAC. We will hear. [ O  Oct 16, 2018 ]

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