The SMSL DO400 is a fully balanced desktop DAC and headphone amp built on ESS's ES9039MSPRO, rated at 3,000mW per channel into 32Ω and decoding up to DSD512 over USB. It suits a one-box desk: balanced headphones, Bluetooth LDAC from a phone, and XLR or RCA line outputs for active speakers.
Who the SMSL DO400 is for
Balanced headphone owners: It has 4-pin XLR, 4.4mm and 6.35mm headphone jacks, and SMSL rates it at 3,000mW per channel into 32Ω and 700mW into 300Ω.
A one-box desk: A computer on USB, a phone on Bluetooth 5.1 with LDAC, and a TV or CD transport on optical, coaxial or AES/EBU can all connect to the same unit.
Active speakers now, a separate amp later: The XLR (5.2Vrms) and RCA (2.5Vrms) line outputs can run at variable volume like a preamp, or at a fixed level so the DO400 works as a plain DAC.
MQA and high-rate DSD libraries: It decodes MQA over USB, optical, coaxial and AES/EBU, plays MQA-CD from a CD transport's digital output, and takes DSD512 over USB.
Skip it if: you need an analog input to use it as an amp for another DAC: its inputs are all digital (USB, optical, coaxial, AES/EBU, I2S) plus Bluetooth.
SMSL DO400 key specs
DAC chip: ESS ES9039MSPRO
USB interface: XMOS XU316, USB 2.0 asynchronous
Formats: PCM up to 768kHz/32-bit and DSD512 over USB; up to 192kHz/24-bit over optical and coaxial; MQA and MQA-CD
vs FiiO K13 R2R: Built on FiiO's own R2R resistor-ladder DAC instead of an ESS chip, and its headphone jacks are 6.35mm and 4.4mm only; choose the DO400 if you need a 4-pin XLR headphone output.
vs FiiO K9 Pro ESS: Adds RCA and 4.4mm analog line inputs, so it can also amplify another DAC, but its USB input tops out at DSD256; choose the DO400 for DSD512 and AES/EBU or I2S sources.
Yes. Every unit we sell is genuine and brand-new, shipped in its original packaging, and backed by our 1-year TonePier warranty and 45-day returns.
Where does my order ship from, and how long does it take?
Every order ships from our warehouse in China, with full tracking, and most orders ship within 3 business days. Shipping is free on every order; most US orders arrive within 7–15 business days and most orders to other countries within 7–20 business days — see our shipping policy for details.
What if it isn't for me?
You get 45 days to decide. Keep the packaging, keep it in like-new condition, and send it back for a refund. Ear tips unsealed for hygiene reasons are fine — we expect you to actually listen.
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