Short answer: the Gustard X18. Both are rated 4.8/5 (#8 and #13 of 30 DACs), and the Gustard X18 costs $749 against $859.99 for the SMSL M400, with the ratings tied, the lower price decides it.
The case for the Gustard X18: Audio Science Review measured a SINAD of 122 dB, so its noise and distortion are inaudible. The tradeoff: The Topping D70 Pro SABRE matches its rating and measured slightly cleaner for less, and the SMSL D-6S matches its rating for a fraction of the price.
What the SMSL M400 does well: Audio Science Review measured 121 dB SINAD, so its noise and distortion are inaudible. Watch for: It is a DAC only, so you need a separate headphone amp or powered speakers.
Buy the Gustard X18. Both are rated the same, and it costs $110.99 less than the SMSL M400.
Want more options? Browse the full Headphone Amps and DACs rankings.
Specifications Side By Side
| Gustard X18 | SMSL M400 | |
|---|---|---|
| Price | $749.00 | $859.99 |
| Ranked | #8 of 30 in DACs | #13 of 30 in DACs |
| Device Type | DAC | DAC |
| SINAD | 122 dB (measured by Audio Science Review) | 121 dB (measured by Audio Science Review) |
| Balanced Output | Yes (XLR line out) | Yes (XLR line out) |
| Inputs | USB-B, I2S (HDMI), AES/EBU, coaxial, optical, Bluetooth | USB, optical, coaxial, I2S, Bluetooth |
| Outputs | RCA, XLR | RCA, XLR |
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, aptX LL, LDAC | UAT, LDAC, aptX HD, aptX, AAC, SBC |
| DAC Chip | ES9038PRO | AK4499EQ |
| Volume Control | Hardware knob | Digital (knob and remote), fixed or variable |
| Dimensions | 8.7” x 2” x 6.7” (220 x 50 x 170 mm) | 8.7” x 1.7” x 8.5” (220 x 43 x 215 mm) |
| Weight | - | 3.4 lbs (1,530 g) |
Related Amp and DAC Comparisons
More worthwhile head-to-heads for Gustard X18:
- Gustard X18 vs SMSL SU-10
- Gustard X18 vs SMSL RAW Pro-DAC1
- Gustard X18 vs SMSL VMV D1se2
- Gustard X18 vs Topping D70 Pro SABRE
- Gustard X18 vs Topping D90 III Sabre
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
Gustard X18: $749.00 Amazon eBay
Pros: Audio Science Review measured a SINAD of 122 dB, so its noise and distortion are inaudible. It has nearly every input you could want, including USB, I2S over HDMI, AES/EBU, coaxial, optical and Bluetooth with LDAC and aptX HD. It feeds an amp or powered speakers through RCA or balanced XLR outputs, with a volume knob for direct control.
Cons: The Topping D70 Pro SABRE matches its rating and measured slightly cleaner for less, and the SMSL D-6S matches its rating for a fraction of the price. Its full width chassis takes up more desk space than compact DACs.
Full Gustard X18 review and specifications →
| Released | Dec 2021 (4 years ago) |
|---|---|
| Balanced Output | Yes (XLR line out) |
| Bluetooth Codecs | SBC, AAC, aptX, aptX HD, aptX LL, LDAC |
| DAC Chip | ES9038PRO |
| Device Type | DAC |
| Dimensions | 8.7” x 2” x 6.7” (220 x 50 x 170 mm) |
| Inputs | USB-B, I2S (HDMI), AES/EBU, coaxial, optical, Bluetooth |
| Outputs | RCA, XLR |
| SINAD | 122 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
SMSL M400: $859.99 HiFiGo eBay
Pros: Audio Science Review measured 121 dB SINAD, so its noise and distortion are inaudible. It accepts USB, optical, coaxial, I2S and Bluetooth with UAT, LDAC, aptX HD, aptX, AAC and SBC, and drives amps or powered speakers through RCA or balanced XLR outputs. A volume knob and remote with fixed or variable output let it work as a preamp for active speakers.
Cons: It is a DAC only, so you need a separate headphone amp or powered speakers. Several rivals with the same rating measured slightly cleaner for less, including the Topping D70 Pro SABRE and the SMSL RAW Pro-DAC1.
Full SMSL M400 review and specifications →
| Balanced Output | Yes (XLR line out) |
|---|---|
| Bluetooth Codecs | UAT, LDAC, aptX HD, aptX, AAC, SBC |
| DAC Chip | AK4499EQ |
| Device Type | DAC |
| Dimensions | 8.7” x 1.7” x 8.5” (220 x 43 x 215 mm) |
| Inputs | USB, optical, coaxial, I2S, Bluetooth |
| Outputs | RCA, XLR |
| SINAD | 121 dB (measured by Audio Science Review) |
| Volume Control | Digital (knob and remote), fixed or variable |
| Weight | 3.4 lbs (1,530 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons