HIFIMAN EF400 Review: The Ultimate R2R DAC Amplifier for Audiophiles

Explore the exceptional sound performance and features of the HIFIMAN EF400 R2R DAC amplifier, a perfect choice for music lovers and audiophiles.

Introducing the HIFIMAN EF400: A Balanced R2R DAC Amplifier

The HIFIMAN EF400 is a balanced DAC/amplifier priced at approximately $650 USD, featuring an internal R2R DAC module that won the prestigious VGP Technology Award in Japan in 2022. This device boasts a fully balanced design for headphone output and competes with some of the best DAC/amplifiers reviewed on Audiophile-Heaven, including the Matrix Audio Element i, Pro-Ject DAC Box DS, Palab M1 Mini, Soundaware A1X PRO, Aune s6 PRO, SMSL DO200 Balanced DAC, and Keces S3.

HIFIMAN is a beloved brand among music enthusiasts and audiophiles alike. They offer an extensive range of products, from high-end digital-to-analog converters to amplifiers and headphones. Renowned for their excellent value for money, the company combines technological innovation with solid customer support, making them popular among both newcomers and seasoned audiophiles.

Design and Features of the HIFIMAN EF400

At the heart of the EF400 is the rare and sophisticated Himalaya R2R DAC module, developed under the guidance of Dr. Fan Bang. This analog-style DAC configuration is not only highly efficient but also delivers ultra-high resolution audio.

What sets this DAC apart is its fully balanced architecture: two separate DAC arrays process the left and right audio channels independently, followed by individual buffers and low-pass filters. The volume control is four-channel, managing each channel separately for precision sound control.

The headphone output features a dual two-channel design ensuring a completely balanced output. The amplifier operates in Class AB, combining the sonic advantages of Class A with lower power consumption and heat generation, ideal for extended listening sessions.

The front panel sports large, smooth analog rotary wheels—the main volume knob operates without steps or clicks, ensuring a seamless listening experience. There's also a selector wheel for gain settings and toggling between OS (Oversampling) and NOS (Non-Oversampling) filters.

For those new to NOS and OS filters: NOS mode disables oversampling filters, theoretically offering more accurate, pure signals, a feature mostly possible with R2R DACs. The OS mode enables oversampling filters, which deliver a more traditional sound character by shaping the impulse response.

Connectivity options include USB-B and USB-C inputs, balanced DAC output for desktop amplifiers or speakers, and RCA outputs. The device is powered via a standard IEC power connector with a fuse for protection. It’s recommended to use the balanced output for quieter, higher-quality sound compared to RCA outputs, which may introduce some noise.

Surprisingly, the EF400 includes four headphone outputs: two single-ended (6.35mm and 3.5mm) and two balanced (4.4mm and XLR). Each has distinct sound characteristics and power delivery, but balanced outputs are highly recommended for optimal performance.

In terms of specs, the EF400 boasts:

• Signal-to-noise ratio: 118 dB
• Total harmonic distortion + noise: 0.002% to 0.004%
• Maximum output power: 4.4W per channel, powerful enough for demanding headphones like the Audeze LCD-5.

The unit requires no drivers, connects instantly via USB-C, has zero latency making it perfect for music, gaming, or movies, and remains cool during prolonged use. A tiny LED indicator confirms operation. Its weight and size provide a professional feel while fitting neatly on a desktop.

Sound Quality of the HIFIMAN EF400

Testing was done with a diverse range of headphones and speakers, making the EF400 a versatile powerhouse. Headphones used included Dan Clark Aeon Flow Noire 2, HIFIMAN HE1000 V2, Audeze LCD-5, HIFIMAN Edition XS, AIAIAI TMA-2 Studio, and more. The amplifier was also paired with stereo amplifiers like Cyrus One Cast, SMSL AO200, and Burson Funk for speakers such as NHT C3, Buchardt S400, and KLH Model 5.

The EF400 even managed sensitive in-ear monitors (IEMs) like SeekReal Airship and Astrotec am850mk2 with impressive control—no hiss or background noise even at high output power.

Switching between NOS and OS filters reveals distinct sound signatures:

• OS mode: Produces a traditional, brighter, more detailed sound with pronounced bass and crisp highs.
• NOS mode: Delivers a warmer, smoother, and softer presentation with slightly less detail but greater listening comfort.

Gain settings also impact the sound. The low gain is the default sound level, while high gain offers a tonal boost akin to turning up the volume on a guitar amplifier, enriching detail, texture, and musical dynamics.

Bass

Deep, clean, and fast bass with natural balance. Increasing volume intensifies bass impact, addressing typical shortcomings in lesser devices.

Midrange

Clear, dynamic, and richly detailed mids with a neutral tone, slightly cooler in OS mode. NOS mode softens the mids for a gentler listening experience without fatigue.

Treble

The difference between NOS and OS is most noticeable here: NOS smooths and softens highs, while OS delivers bright, airy highs with excellent micro-detail retrieval.

High gain settings enrich mids and bass, making the sound more vivid and engaging.

Comparisons with Other DAC Amplifiers

HIFIMAN EF400 vs. Aune S6 PRO

The EF400 offers superior power and control, especially with heavy headphones. Its soundstage is deeper and more detailed, while S6 PRO boasts a wider but colder and more digital sound. EF400’s tone is warmer and more natural. Balanced 4.4mm output and filter selection on EF400 provide a distinct advantage.

HIFIMAN EF400 vs. Matrix Audio Element i

Element i acts as a streamer with headphone amplifier and DAC functions, while EF400 excels as a USB DAC with quieter headphone output and higher resolution. EF400’s R2R DAC offers a refined and natural sound distinct from Element i’s Delta-Sigma design.

HIFIMAN EF400 vs. Pro-Ject DAC Box DS

EF400 outperforms the DAC Box DS in resolution, clarity, and soundstage depth, showcasing years of development progress and delivering a more musical, clear, and clean sound.

HIFIMAN EF400 vs. Palab M1 Mini

Though M1 Mini is a portable DAC/amp with good depth and detail, EF400 offers much higher output power and better control with a fully balanced design, making it a superior desktop choice.

HIFIMAN EF400 vs. Soundaware A1X PRO

EF400 wins with better volume control, higher power, improved detail, and a more natural, less digital sound. A1X PRO feels slower and flatter in comparison.

HIFIMAN EF400 vs. SMSL DO200

EF400 offers richer bass, more air, and wider soundstage. DO200 sounds flatter with less dynamic range. EF400’s NOS/OS filter versatility makes it a better recommendation overall.

HIFIMAN EF400 vs. Keces S3

Despite the higher price of Keces S3, EF400 delivers a more natural tone, stronger power, superior headphone control, and lower background noise. It handles complex passages better, making EF400 a more valuable buy.

Value and Final Thoughts on the HIFIMAN EF400

The HIFIMAN EF400 is an exceptional value, arguably one of the best DAC/amplifiers available at its price. It surpasses most desktop competitors and requires no special cables or drivers, even working seamlessly with Windows 10 out of the box.

Its powerful output and R2R DAC technology have quickly earned it a place among the best DAC/amps ever created.

If you're after a top-tier R2R DAC and headphone amplifier, a sturdy device that outlasts headphones, and one that delivers sublime sound with fine-tuning capabilities, the EF400 is the best recommendation I can make right now—especially for its affordable price.

Technical Specifications

• THD+N (line output): 0.002% – 0.004%
• Channel separation: 125 ± 3 dB
• Signal-to-noise ratio: 118 ± 3 dB (A-weighted)
• Max output power: 4.4 W per channel
• Dimensions: 246.5 mm (L) × 228 mm (W) × 61 mm (H)
• Weight: 3.08 kg

HIFIMAN EF400 is one of the most musical, clear, and clean-sounding DAC/amplifiers I've ever experienced.

What are your thoughts on balanced R2R DACs vs. traditional Delta-Sigma models? Has the HIFIMAN EF400 caught your eye for your next audio upgrade?

Frequently Asked Questions

• Which headphones work best with the HIFIMAN EF400?
  The EF400 pairs excellently with demanding headphones like Audeze LCD-5, HIFIMAN HE1000 V2, and sensitive IEMs, offering enough power and control for a wide range.
• Can I use EF400 as a standalone DAC with my desktop amplifier?
  Absolutely. It has balanced DAC outputs optimized for integration with external amplifiers or speakers, providing superior sound quality.
• What is the difference between OS and NOS filters on the EF400?
  OS (oversampling) provides a brighter, more detailed sound; NOS (non-oversampling) offers a softer, warmer sound with less digital processing.
• Does the EF400 require special drivers?
  No, it is plug-and-play on Windows 10 and other platforms via USB-C without needing additional drivers.
• Is the EF400 portable?
  While not designed as a portable device, its size and weight make it ideal for desktop use, delivering high power and sound quality.

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