Short answer: the D&A Alpha. Both are rated 4.9/5 (#2 and #1 of 43 DAC and headphone amp combos), and the D&A Alpha costs $399 against $499 for the SMSL DO400, so with nothing between them on measured performance, price settles it.
The case for the D&A Alpha: Audio Science Review measured 122 dB SINAD, so its noise and distortion are transparent. The tradeoff: It is a large, heavy desktop box at 3.6 lbs (1,650 g), so it is no fit for a cramped desk or travel.
The case for the SMSL DO400: Audio Science Review measured 123 dB SINAD, so its noise and distortion are transparent. The tradeoff: It costs more than the D&A Alpha and SMSL RAW-MDA1, which share its rating and also measure transparent.
Buy the D&A Alpha. Both are rated the same, and it costs $100 less than the SMSL DO400.
Want more options? Browse the full Headphone Amps and DACs rankings.
Specifications Side By Side
| D&A Alpha | SMSL DO400 | |
|---|---|---|
| Price | $399.00 | $499.00 |
| Ranked | #2 of 43 in DAC and Headphone Amp Combos | #1 of 43 in DAC and Headphone Amp Combos |
| Device Type | DAC and headphone amp | DAC and headphone amp |
| SINAD | 122 dB (measured by Audio Science Review) | 123 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 9,000 mW (manufacturer rated, balanced) | 3,000 mW (manufacturer rated) |
| Output Power (300 ohms) | 1,100 mW (manufacturer rated, balanced) | 700 mW (manufacturer rated) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced |
| Balanced Output | Yes (4.4 mm, XLR line out) | Yes (4.4 mm, 4-pin XLR, XLR line out) |
| Inputs | USB, optical, coaxial, Bluetooth | USB, optical, coaxial, AES/EBU, I2S, Bluetooth |
| Outputs | RCA, XLR | RCA, XLR |
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, LDAC | SBC, AAC, aptX, aptX HD, LDAC |
| DAC Chip | 2 x ES9039Q2M | ES9039MSPRO |
| Volume Control | Analog volume IC (NJU72315) | - |
| Dimensions | 7.7” x 2.2” x 8.2” (195 x 55 x 208 mm) | 9.6” x 1.7” x 7.3” (245 x 42 x 186 mm) |
| Weight | 3.6 lbs (1,650 g) | 3.2 lbs (1,450 g) |
Related Amp and DAC Comparisons
How SMSL DO400 compares with other leading options:
- SMSL DO400 vs Topping DX5 II
- D&A Alpha Pro vs SMSL DO400
- SMSL DO400 vs Topping G5
- SMSL DO400 vs JDS Labs Element IV
- SMSL DO400 vs Aune X1s GT
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
D&A Alpha: $399.00 Amazon eBay
Pros: Audio Science Review measured 122 dB SINAD, so its noise and distortion are transparent. A rated 9 W balanced into 32 ohms and 1.1 W into 300 ohms is enough for nearly any headphone, planar magnetics included, and it adds optical, coaxial and LDAC Bluetooth inputs with XLR line outputs for powered speakers. It matches the rating of the SMSL DO400 for less.
Cons: It is a large, heavy desktop box at 1,650 g, so it is no fit for a cramped desk or travel. The Topping DX5 II rates the same with similarly huge balanced power for less, and the 9 W figure applies only to the 4.4 mm balanced output.
Full D&A Alpha review and specifications →
| Released | Jan 2026 (9 months ago) |
|---|---|
| Balanced Output | Yes (4.4 mm, XLR line out) |
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, LDAC |
| DAC Chip | 2 x ES9039Q2M |
| Device Type | DAC and headphone amp |
| Dimensions | 7.7” x 2.2” x 8.2” (195 x 55 x 208 mm) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced |
| Inputs | USB, optical, coaxial, Bluetooth |
| Output Power (300 ohms) | 1,100 mW (manufacturer rated, balanced) |
| Output Power (32 ohms) | 9,000 mW (manufacturer rated, balanced) |
| Outputs | RCA, XLR |
| SINAD | 122 dB (measured by Audio Science Review) |
| Volume Control | Analog volume IC (NJU72315) |
| Weight | 3.6 lbs (1,650 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
SMSL DO400: $499.00 Amazon eBay
Pros: Audio Science Review measured 123 dB SINAD, so its noise and distortion are transparent. A rated 3 W into 32 ohms and 700 mW into 300 ohms drives nearly any headphone, through 6.35 mm, 4.4 mm or 4-pin XLR outputs. Inputs cover USB, optical, coaxial, AES/EBU, I2S and LDAC Bluetooth, with RCA and XLR outputs for powered speakers.
Cons: It costs more than the D&A Alpha and SMSL RAW-MDA1, which share its rating and also measure transparent. At 1,450 g it is a full size desktop unit.
Full SMSL DO400 review and specifications →
| Balanced Output | Yes (4.4 mm, 4-pin XLR, XLR line out) |
|---|---|
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, LDAC |
| DAC Chip | ES9039MSPRO |
| Device Type | DAC and headphone amp |
| Dimensions | 9.6” x 1.7” x 7.3” (245 x 42 x 186 mm) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced |
| Inputs | USB, optical, coaxial, AES/EBU, I2S, Bluetooth |
| Output Power (300 ohms) | 700 mW (manufacturer rated) |
| Output Power (32 ohms) | 3,000 mW (manufacturer rated) |
| Outputs | RCA, XLR |
| SINAD | 123 dB (measured by Audio Science Review) |
| Weight | 3.2 lbs (1,450 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons