Short answer: the Pro-Ject Pre Box S2 Digital, though neither ranks well in its class. It ranks #38 of 43 DAC and headphone amp combos by measured performance, rated 2.9/5, at $399. The xDuoo DM-01 ranks #41, rated 2.4/5, at $279, $120 cheaper, which does not close the gap in measured performance. Both are rated below 3.0/5 among the 43 DAC and headphone amp combos, so if measured performance matters, consider the D&A Alpha instead, ranked #2 at $399.
The Pro-Ject Pre Box S2 Digital is the better-sounding pick. It accepts USB, optical and coaxial inputs and also works as a preamp with a variable RCA output, all in a compact box about the size of a paperback. The catch: Pro-Ject rates it at only 68 mW into 32 ohms, which suits in-ear monitors and easy headphones but not demanding full-size models.
What the xDuoo DM-01 does well: It supports a long list of Bluetooth codecs, including LDAC, aptX Adaptive and LC3, alongside USB-C. Watch for: Audio Science Review measured just 38 dB SINAD, a severe and audible level of noise and distortion.
Buy the Pro-Ject Pre Box S2 Digital. It is rated higher, and the $120 you would save on the xDuoo DM-01 does not close the gap.
Looking for alternatives? See the complete Headphone Amps and DACs rankings.
Specifications Side By Side
| Pro-Ject Pre Box S2 Digital | xDuoo DM-01 | |
|---|---|---|
| Price | $399.00 | $279.00 |
| Ranked | #38 of 43 in DAC and Headphone Amp Combos | #41 of 43 in DAC and Headphone Amp Combos |
| Device Type | DAC and headphone amp | DAC and headphone amp |
| SINAD | 100 dB (measured by Audio Science Review) | 38 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 68 mW (manufacturer rated) | 1,500 mW (manufacturer rated) |
| Headphone Outputs | 6.35 mm | 6.35 mm |
| Balanced Output | No | No |
| Inputs | USB-B, optical, coaxial | USB-C, Bluetooth |
| Outputs | RCA (variable) | AUX line out |
| DAC Chip | 2 x ES9038Q2M | CS43131 |
| Volume Control | Hardware knob | - |
| Dimensions | 4.1” x 1.5” x 4.8” (103 x 37 x 122 mm) | 6.9” x 3.4” x 2.4” (175 x 86 x 60 mm) |
| Weight | 0.8 lbs (366 g) | 1.6 lbs (730 g) |
| Bluetooth Codecs | - | SBC, AAC, aptX, aptX HD, aptX Adaptive, LDAC, LC3 |
Related Amp and DAC Comparisons
More worthwhile head-to-heads for Pro-Ject Pre Box S2 Digital:
- Chord Mojo 2 vs Pro-Ject Pre Box S2 Digital
- xDuoo XA-10 vs Pro-Ject Pre Box S2 Digital
- SMSL M10 vs Pro-Ject Pre Box S2 Digital
- Essence HDACC II-4K vs Pro-Ject Pre Box S2 Digital
- Pro-Ject Pre Box S2 Digital vs Leckerton Audio UHA-6S.MKII
Prices on this page were last checked October 11, 2026 at 4:59 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Amps and DACs In Full
Pro-Ject Pre Box S2 Digital: $399.00 Amazon eBay
Pros: It accepts USB, optical and coaxial inputs and also works as a preamp with a variable RCA output, all in a compact box about the size of a paperback. Audio Science Review measured a SINAD of 100 dB, which is fine for most headphones.
Cons: Pro-Ject rates it at only 68 mW into 32 ohms, which suits in-ear monitors and easy headphones but not demanding full-size models. At 100 dB SINAD, sensitive in-ears may reveal some hiss, it has no balanced outputs, and the Neutron HiFi DAC V1 rates higher and measured cleaner for less.
Full Pro-Ject Pre Box S2 Digital review and specifications →
| Released | 2017 (9 years ago) |
|---|---|
| Balanced Output | No |
| DAC Chip | 2 x ES9038Q2M |
| Device Type | DAC and headphone amp |
| Dimensions | 4.1” x 1.5” x 4.8” (103 x 37 x 122 mm) |
| Headphone Outputs | 6.35 mm |
| Inputs | USB-B, optical, coaxial |
| Output Power (32 ohms) | 68 mW (manufacturer rated) |
| Outputs | RCA (variable) |
| SINAD | 100 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob |
| Weight | 0.8 lbs (366 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
xDuoo DM-01: $279.00 Amazon eBay
Pros: It supports a long list of Bluetooth codecs, including LDAC, aptX Adaptive and LC3, alongside USB-C. A rated 1.5 W into 32 ohms is enough power on paper for most planar magnetic headphones.
Cons: Audio Science Review measured just 38 dB SINAD, a severe and audible level of noise and distortion. There is only a single unbalanced 6.35 mm output, and the Loxjie D30 rates far higher and measures transparent for much less.
Full xDuoo DM-01 review and specifications →
| Released | Mar 2025 (1 year ago) |
|---|---|
| Balanced Output | No |
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, aptX Adaptive, LDAC, LC3 |
| DAC Chip | CS43131 |
| Device Type | DAC and headphone amp |
| Dimensions | 6.9” x 3.4” x 2.4” (175 x 86 x 60 mm) |
| Headphone Outputs | 6.35 mm |
| Inputs | USB-C, Bluetooth |
| Output Power (32 ohms) | 1,500 mW (manufacturer rated) |
| Outputs | AUX line out |
| SINAD | 38 dB (measured by Audio Science Review) |
| Weight | 1.6 lbs (730 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons