Closer Examination

The HIFIMAN EF400 is a desktop class DAC/headphones amplifier all-in-one device that weighs a decent amount at 3.1 kg owing to the integrated power supply. Yet, at 246.5 x 228 x 61 mm, it feels solid in the hands and the mass is also well-distributed to where anyone judging quality of a DAC/amp purely by how it feels would be left content. It uses a stainless steel chassis given a black paint job in a semi-matte finish that can pick up fingerprints and smudges but is easily wiped clean. The form factor reminds me of a CD player from a few years ago and it fits nicely on a desk or under your PC monitor given the lower height profile. The front section is adorned by a thick CNC-machined aluminium alloy in native finish that works well with the two large knobs and the black-colored headphone outputs too. HIFIMAN branding is seen here in addition to the R2R DAC inside—notice it's spelled HYMALAYA here—and the product name itself is on the bottom right corner. The knob to the left has three steps that allow you to choose between any of four operating states of gain (Low/High) and OS/NOS (oversampling/non-oversampling modes) that are neat additions to the R2R DAC if executed well. The EF400 is also rich on headphones connectivity offering two types each of single-ended (3.5 mm and 6.35 mm) and balanced (4.4 mm and XLR) connections. Rounding off the front is the expected volume knob located on the right with a nice brushed finish and a marker that helps indicate the range between min and max as seen on the front fascia.


There isn't much of note on the sides with HIFIMAN having gone with a completely closed-off metal chassis rather than having any vents for cooling. Then we get to the back where things get interesting in the form of two separate line out options—balanced dual 3-pin XLR as well as single-ended RCA—allowing for the EF400 to be used with other amplifiers or active speakers should you only wish to use the DAC part of things. As such, we do get a decent assortment of outputs here although the input side is extremely sparse in the form of just USB. While it's not a deal breaker for TechPowerUp readers, and indeed I too generally use a DAC/amp with USB input, it's something to be aware of before forking out your cash for a source. HIFIMAN tries to sweeten the deal by giving you two USB inputs in the form of the traditional USB Type-B but also a Type-C input that makes it easier to use the EF400 with more mobile devices. Rounding off the tour here is the power input with integrated fuse and a dedicated on/off switch. The power supply is capable of taking in AC mains across 100-230 V, 50-60 Hz, and a max power draw of 45 W!


An examination of the bottom reveals four pre-installed large feet that have rubber pads to not only help lift the EF400 off the desk and add friction in use but also help prevent scratches to the chassis itself. These circular feet are plastic on the outside and are screwed in place to be easily replaceable if you wish to add in your own feet/support system, also making it possible to integrate the EF400 within a custom audio rack. Certification labels and the serial number is seen here too along with a voltage selector that is set to 220 V by default for me here in the UK. It's easy enough to change it to 110 V making it possible to take the EF400 with you should be move to a different country with 110 V AC mains.


Disassembly of the HIFIMAN EF400 was done after all testing was completed. I highly discourage you from doing so at all given the various electronic equipment inside that can result in a shocking experience—quite literally. The industrial design used here makes it simple with the use of six screws w/washers on the back that can be removed to then allow the steel chassis section to be slid out of place.


The interior of the EF400 is interesting in that the left side is dedicated to the power circuitry and the right side has DAC and amplifier modules in addition to the I/O stages. The integrated power supply is a toroidal transformer that uses oxygen-free copper wire winding that's heavy and bulky enough to assist with weight distribution too. The left knob handling the four operating states is associated with a Texas Instruments SN74HCS20-Q1 4-input NAND gate whereas the headphones outputs themselves seem to be HIFIMAN-branded! The USB decoder/controller isn't easily identifiable here given the hardware drivers are scrubbed clean of labels although we'll see shortly how the EF400 is using a ComTrue USB audio bridge for this purpose. Then we get to the DAC itself in the form of a separate HIFIMAN HIMALAYA/HYMALAYA R2R DAC module with two chips here. There is clearly room for HIFIMAN to pair the DAC with another amplifier, as it did with the HIMALAYA-based Bluetooth adapter DAC/amp for its Deva Pro, HE-R9, HE-R10 headphones, as well as potentially come up with higher end DAC modules to slot into the EF400 or a whole new product in the future. The amplifier section uses Class AB buffer and current + voltage amplification and there are a bunch of different audiophile-grade capacitors, including some large ones with 30,000 µF capacity! The hardware comes together to make for fairly impressive numbers given the R2R DAC topology used, be it the SNR of 118 +/-3 dB, THD+N of 0.002-0.004%, and crosstalk of 125 +/-3 dB. HIFIMAN doesn't specify what outputs these numbers are all for but thankfully L7 Labs has independently tested the EF400 for those who want to see more about how the unit performs and measures—not great, but also I wasn't expecting it to given this is not your typical solid-state amp paired with a delta-sigma DAC.