Short answer: the SMSL DO400. Both are rated 4.9/5 (#1 and #5 of 43 DAC and headphone amp combos), and the SMSL DO400 costs $499 against $699 for the D&A Alpha Pro, with the ratings tied, the lower price decides it.
What the D&A Alpha Pro does well: Audio Science Review measured a SINAD of 121 dB, so its noise and distortion are inaudible. The catch: It costs far more than the Topping DX1 II, which rates the same and measures the same 121 dB SINAD.
What the SMSL DO400 does well: 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 SMSL DO400. Both are rated the same, and it costs $200 less than the D&A Alpha Pro.
Want more options? Browse the full Headphone Amps and DACs rankings.
Specifications Side By Side
| D&A Alpha Pro | SMSL DO400 | |
|---|---|---|
| Price | $699.00 | $499.00 |
| Ranked | #5 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 | 121 dB (measured by Audio Science Review) | 123 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 6,000 mW (manufacturer rated) | 3,000 mW (manufacturer rated) |
| Output Power (300 ohms) | 700 mW (manufacturer rated) | 700 mW (manufacturer rated) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced |
| Balanced Output | Yes (4.4 mm, 4-pin XLR, XLR line out) | Yes (4.4 mm, 4-pin XLR, XLR line out) |
| Inputs | USB, optical, coaxial, Bluetooth, RCA | 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 | ES9039MSPRO | ES9039MSPRO |
| Volume Control | Hardware knob | - |
| Dimensions | 8.9” x 2.2” x 7.8” (225 x 55 x 199.3 mm) | 9.6” x 1.7” x 7.3” (245 x 42 x 186 mm) |
| Weight | 3.9 lbs (1,760 g) | 3.2 lbs (1,450 g) |
Related Amp and DAC Comparisons
How SMSL DO400 compares with other leading options:
- D&A Alpha vs SMSL DO400
- SMSL DO400 vs Topping DX5 II
- 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 Pro: $699.00 Amazon eBay
Pros: Audio Science Review measured a SINAD of 121 dB, so its noise and distortion are inaudible. A rated 6,000 mW into 32 ohms and 700 mW into 300 ohms will drive nearly any headphone, including demanding planars, through 6.35 mm, 4.4 mm balanced or 4-pin XLR outputs. It doubles as a full desktop hub with USB, optical, coaxial, RCA and Bluetooth inputs (LDAC, aptX HD, AAC) plus RCA and XLR outputs.
Cons: It costs far more than the Topping DX1 II, which rates the same and measures the same 121 dB SINAD. The SMSL DO400 also matches its rating for less while measuring slightly cleaner. At 1,760 g and 225 mm wide, it needs real desk space.
Full D&A Alpha Pro review and specifications →
| Released | May 2025 (1 year ago) |
|---|---|
| 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 | 8.9” x 2.2” x 7.8” (225 x 55 x 199.3 mm) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced |
| Inputs | USB, optical, coaxial, Bluetooth, RCA |
| Output Power (300 ohms) | 700 mW (manufacturer rated) |
| Output Power (32 ohms) | 6,000 mW (manufacturer rated) |
| Outputs | RCA, XLR |
| SINAD | 121 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob |
| Weight | 3.9 lbs (1,760 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