ProJect Pre Box S2 Digital Review – Don’t Overlook This One

ProJect Pre Box S2 Digital on white

ProJect Pre Box S2 Digital

Tested at $499 / 350€

Sound quality (line-out)


Sound quality (headphone-out)









  • Mature sound signature
  • Soundstage depth
  • Versatility


  • Potential micro-USB and OLED issues

Project Pre Box S2 digital comes from the Austrian company probably best known for its turntables, which is the field I’m not particularly familiar with. My first encounter with the brand a few years ago was in a showroom where small project boxes (DAC, preamp, amp) were in charge of driving KEF floor-standers, Q750 if I remember correctly. This disproportionately sized combination sounded better than I expected, so the brand caught my attention. To cut this reminiscing short, I finally got the chance to try a piece of gear in my own system thanks to a kind loan from a friend.

Build and Connectivity

Project Pre Box S2 Digital comes in a really compact case but make no mistake, that didn’t prevent the company to go big on connectivity and features. Starting from the back panel, there are three digital inputs: USB, coaxial, and optical. Micro USB is reserved for supplying the unit with external power, but the unit can also be powered through the same USB cable that carries the signal. Lastly, a pair of RCA offers variable output, meaning you can use this small box as a very basic preamp too. On the front, we see a 6.35 mm headphone jack, a small but clear and readable OLED display, few control buttons, and a volume knob.

The OLED display is clear and easy to read but it doesn’t have any dimming or turn off functions. Navigation buttons are practical and easy to use. No complaints so far.

Features and Specs

When it comes to specs, Project Pre Box S2 Digital uses Sabre DAC chip ES9038Q2M, well, two of them actually as that formation supposedly provides better dynamics, channel separation, and so on. On the headphone side of things, there’s a fairly low-powered amplifier rated at 68 mW in 32 Ohm. On the other hand, file support is great with basically every possible PCM and DSD sample rate you could imagine. Yes, even the full hardware support for MQA file unfolding is supported (compression used for streaming hi-res music by some services that I’m not a big fan of, true and uncompressed hi-res files are always better).

A neat trick is that the unit remembers volume control for RCA pre-out and headphone-out separately. I firmly believe that every DAC/AMP combo should have this feature, otherwise, you’re bound to forget yourself sooner or later and put on your headphones with the volume cranked up, which is not a pleasant experience.

ProJect also lets you choose among several digital filters. I’ll not go too much into this as the difference is subtle anyway. I preferred minimum phase slow roll-off, but your preferences might differ.

Sound (RCA Out)

I started the testing process with S2 Digital in my room setup, hooked to my integrated amplifier Cyrus 8vs2 and KEF LS50 speakers. Volume is cranked to the maximum which is 0 dB, and that gives us ~ 2 V at RCA output which is the most common level for a DAC line-output. Little ProJect treated me with well-balanced sound. Bass-line goes deep but is also neat, hitting with precision and control. The midrange is clean but very smooth and free of any sort of edginess or harshness. The highest spectrum simply follows suit, providing plenty in terms of clarity and crisp micro details, without ever stepping into sounding bright or splashy.

The soundstage is reasonably wide but the star of the show here is the depth. ProJect Pre Box S2 Digital is definitely capable of creating more depth than I came to expect from the device in this price range. Layering is worth the praise too. Delivery is quick and snappy, but everything is presented in a slightly laid-back manner. If you want sharp edges thrown at your face, you’re not going to get that here.

Comparisons (RCA Out)

DragonFly Cobalt is more forward-sounding and might have some more slam to it too, but comes off as a somewhat blunt tool in direct comparison. It offers less control in the bass region and can’t match the soundstage depth and layering of S2 Digital.

Topping E30 sounded a touch wider but also with noticeably less depth and less capable layering. Some might prefer this forward and flatter presentation but I have to give this one to ProJect. There’s no shame here for E30 since it’s much more affordable too.

Schiit Modi Multibit puts up a much better fight with its full-bodied presentation and lusher vocals. ProJect strikes back with less bloom in upper bass and midrange, it sounds smoother too. Both offer quite three-dimensional imaging, but Multibit does it in a more forward manner, putting instruments right in front of you. S2 on the other hand creates a soundstage that starts farther away from the listener but also goes deeper behind the speakers, creating a spacier presentation. This is a tough call, but if pressed to choose, I’d rather keep ProJect in my system.

Sound (Headphone Out)

Everything said about the sound signature over RCA outputs, stands for the headphone out too, so I’m not going to repeat the same phrases. But I should go into the amount of power and drive integrated amplifier can offer. As mentioned in the Specs section, the power rating is rather low. I was using it mostly with Hifiman HE4XX that is an average load with its 93 dB/mW sensitivity rating. I was never left wanting more volume but came quite close to maxing it out if songs with low recording levels are used. Provided you’re not going to use a less sensitive set of cans, ProJect will treat you with fast and snappy sound, without any noticeable distortion all the way to the maximum level.

Comparisons (Headphone Out)

EarMen TR-Amp is another great and snappy device on its own but proved to be outmatched in direct comparison, sounding a touch softer and hazier, with a slightly splashier higher spectrum. TR-Amp does offer usefully more power and drive-through.

Topping E30/L30 stack is again more powerful with greater drive but sounds a bit brighter and sharper in comparison. Now, this is a slippery slope I’m threading on but I’ll do it anyway. If E30 and L30 are connected with a generic RCA interconnect, I feel that the ProJect offers a touch richer midrange and crisper micro details. However, if some effort is put into choosing the higher quality cable (for example this quite affordable but surprisingly good one), E30/L30 combo matches and in some areas such as slam and dynamics even surpasses ProJect. I know the whole cable story is a hard pill to swallow for many audiophiles, but I feel it needs to be taken into account when we’re talking about stacks. It’s an additional thing to think about and it can tip things one way or the other.

Living with it

Since this unit had been in use for some two-plus years by my friend already, I have a unique opportunity to mention some real-life issues that might occur with prolonged use.

The first one of them is that the OLED screen doesn’t possess any form of auto turn-off feature, and it also can’t be turned off by the user. This means that screen is slowly but steadily going through the wear and tear process. If you’re familiar with OLED technology, you might know that blue subpixels tend to age faster than red and green ones. This is obvious on my friend’s unit, since the area of the display where the white digit is displayed most often became almost yellow. This doesn’t affect functionality in any way and I personally don’t mind it as long as the info is clearly readable, but I know some of you are fuzzy about these kinds of things.

The second one is that the micro-USB connector used for the external power supply is of the surface mount variety and not so sturdy obviously. What happened to my friend, and few other owners we found online, is that the micro-USB broke off the board. Well, not actually broke as much as that soldering points got detached. It was annoying but fixable with 15 bucks at the local electronic service center, since it was out of the warranty at the time. I would be much happier if Project used a through-hole connector here or simply found a way to fortify this one better with hot glue or something similar. But as it stands, try to be gentle to this connector.

I don’t have any knowledge if ProJect addressed these issues in later revisions, but if they haven’t done that already, it’s certainly something they should pay attention to.


Don’t let the tiny size of ProJect Pre Box S2 Digital fool you, it’s a highly talented device brimming with features. If all in one DAC/Amp is what you need, and you don’t plan on using power-hungry headphones, this one should definitely be put into the consideration list.



Digital inputs: 1x USB (B), 1x Co-axial (RCA), 1x Optical (TOSLink)
D/A-converter: 2x ESS9038Q2M 32-bit
USB: up to DSD512 (DSD1024), PCM up to 32b/768kHz
Optical: PCM up to 24b/192kHz
Coaxial: PCM up to 24b/192kHz
Filter settings: 7 different selectable on the front
Analog outputs: 6.3mm Headphone (front), 1x Variable Out (RCA
Output voltage: 2.05 Veff
Minimal recommended headphone impedance: 8 Ohm
Headphone output power: 68 mW / 32 Ohm , 6.6 mW / 600 Ohm
THD: 0.0003% @ 0 dB, 2V RMS, 1 kHz
Dynamic range: 124 dBA
Outboard Power supply: 5V/1A DC (included)
Dimensions W x H x D: 103 x 37 x 122 mm (including knob and connectors)
Weight: 366 g (without power supply)

Official webpage

One thought on “ProJect Pre Box S2 Digital Review – Don’t Overlook This One

  1. Hello,
    Many thanks for the very good and detailed presentation. I own this DAC and am also very satisfied with it. However, I am toying with the idea of ​​purchasing a higher-quality device and have also subscribed to your YouTube channel. But it’s not easy for me to make a choice.

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