Home Amps/DACS HIFIMAN EF400 Review: Exploring Innovation And Functionality

HIFIMAN EF400 Review: Exploring Innovation And Functionality

by Stuart Charles Black
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Greetings mate and Welcome aboard!

Stuart Charles here, HomeStudioBasics.com helping YOU make sound decisions, so…

HIFIMAN’s EF400 is another Amp/DAC you could use to break out of a psychiatric ward, coming in at an astonishing 6.5 lbs. or thereabouts. In other words, it’s built like a steel anvil.

But what about it, other than its gargantuan dummy THICC size, stands out from other Amps & DACS?

Like the EF600, the EF400 utilizes the HYMALAYA PRO R2R DAC Module.

This module incorporates an R2R (Resistor-to-Resistor) architecture, utilizing a network of resistors for digital-to-analog conversion.

This design represents an alternative approach to DAC technology, valued for its distinct features and performance attributes.

The 4-level function switch includes High Gain NOS, High Gain OS, Low Gain OS, and Low Gain NOS.

  • NOS (Non-Oversampling): NOS DACs bypass oversampling, maintaining a simpler signal path with minimal digital processing. This approach aims to preserve the original audio signal’s characteristics without additional interpolation.
  • OS (Oversampling): OS DACs utilize oversampling techniques to increase the digital audio signal’s sample rate before conversion to analog. These DACs typically employ digital filters to interpolate additional samples between the original data points, enhancing signal accuracy and reducing artifacts.

In terms of gain, NOS and OS DACs generally operate similarly in terms of gain control.

The difference lies primarily in their digital filter designs and processing methods, which can impact the overall performance of the DAC.

Oxygen Free Copper Wire

The EF400’s use of oxygen-free copper wire in the vicinity of a toroidal transformer helps minimize electromagnetic interference (EMI) and ensures optimal signal transmission.

Oxygen-free copper, with its superior conductivity due to reduced oxygen content, reduces resistance and signal loss, contributing to cleaner power delivery and enhanced audio quality.


Front Panel

HIFIMAN EF400 Review

The front contains the NOS/OS function switch, the 6.35mm (1/4″) single-ended headphone output, a 3.5mm single-ended headphone output, a 4.4mm balanced headphone output, an XLR 4-pin balanced headphone output, and the volume control.

Back Panel

HIFIMAN EF400 Review

Here we have a Balanced XLR output, single-ended RCA output, a USB Type-C and Type-B slot, and the AC Connector/Power Switch.

So you can use the unit as just a DAC into a separate amp or as a preamp into some speakers (Presonus Eris e3.5 as an example) or monitors (Yamaha HS7, etc.)

The EF400 pumps an admirable 4.4W per channel, which essentially means you can power a small country with it.

Jokes aside, there’s more than enough juice here for even the most demanding headphones; including but not limited to my AKG K240M (600 Ohm) and every other headphone I have here: Sennheiser HD600, HIFIMAN HE400se, Arya, OneOdio Monitor 60/80, Sony MDR-V6/7506/CD-900ST, HIFIMAN DEVA, Gold Planar GL2000, HarmonicDyne G200, Philips SHP9500, and more.


Now that we’re dancing around the subject, the EF400 was recommended to me by a reader of the blog who all but demanded I try it out.

He claimed the “sound” of the DAC was better than anything he’d ever heard, and me being extremely skeptical of DACS in general, I had to see what all the fuss was about. 

I tested the EF400 against a bunch of other stuff I have here, and this is what I came up with.

EF400 vs. JDS ATOM 2

JDS Labs ATOM 2 Review

The ATOM 2 is my benchmark for quality, and in short, there’s nothing about the EF400’s “sound” that makes me want to run out and buy it.

The ATOM 2 advertises a Signal-to-noise ratio of 123dB, arguably the most important metric to gauge the quality of an Amplifier/DAC.

The EF400 comes in at 118 dB.

Is there a difference in perceived quality? For me, not really. They both do an excellent job.

SINAD, an acronym for Signal-to-Noise and Distortion, measures the quality of a signal by comparing the strength of the desired signal to the combined influence of noise and distortion.

When SINAD is greater than 90dB, it indicates that the signal is significantly stronger than the noise and distortion present in the system, suggesting high fidelity and clarity in audio.

This level of SINAD is commonly sought after in audio equipment for optimal performance and minimal interference.

EF400 vs. Universal Audio Volt 2

The Volt 2 is a fantastic Audio Interface (also a DAC) and comes equipped with a 1/4″ headphone jack.

I never thought I’d say this, but after volume matching the DACS, I did hear a difference here; most notably in terms of overall resolution. Yes, the EF400 on NOS does seem to provide a bit more air and clarity. Interesting.

This was heard specifically on “Jazz Ballads & Black Coffee.” Things just seemed more open and spacious, but the distinction is rather subtle (but still noticeable to me).

Does it make sense to say that the song felt more lively? That’s the best way I can put it.

Her vocals seemed a bit more forward and engaging, and the background ambiance was more apparent. This continued with some other tracks I listened to.

EF400 vs. iFi Zen

iFi Zen DAC V2 Review

Didn’t hear much of a difference here.

EF400 vs. FiiO K7

FiiO K7 Review

Again, little to no difference.

Please keep in mind that these are my personal opinions and that your mileage may vary. Click here for my ethos.

Potential Caveats

It’s important to note that the EF400, depending on who you ask, does have some quirks.


3 reviewers mentioned that the unit produced crackling noises/static/distortion (one with an iPad Pro as the source and CD quality tracks), but engaging OS mode makes it go away. Both reviewers said NOS mode caused the issue.

The first person said another potential fix is to use Roon, turn on Sample Conversion, and set it to Max. Still, this is ultimately an inconvenience since you have to purchase something extra.

The 3rd reviewer chalked it up to low-quality caps but had the same general problems.

HIFIMAN EF400 Review

DAC not recognized/DAC cuts off

This is an issue I’ve personally had with the unit, but another reviewer on Amazon mentioned it as well. For me, the device would not show up in my audio settings – this after trying every cable I have here, using different ports, rebooting the unit, etc.

I’ve had no connection issues with the 70+ other Amps & DACS I’ve tried, so this was a bit of a disappointment.

That said, I’m on my second unit from HIFIMAN, and it finally decided to work after I almost returned it.

As a last-ditch effort, I again swapped cable types and tried USB-C (again). It’s been working fine as of now.

If something changes, I’ll update the article.

Click here for the Amazon review.

Final Verdict

HIFIMAN EF400 Review

The HIFIMAN EF400 is a fantastically priced Amp/DAC combo considering it uses technology reserved for much more expensive equipment.

That said, some of its shortcomings are a bit worrisome. In addition, the package contents are pretty sparse. You’re getting the unit and a power cable. For the money spent, I would have liked to see a lot more.

Because of that, I can’t recommend it today but I think it’s a pretty decent unit, all things considered.

If you’re looking for an end-game type of Amp/DAC, the K9 is only around $100 extra but miles more versatile. In addition, FiiO’s quality control is top-notch and you can purchase one worry-free. I’ve been using their products since 2018 and haven’t had a single issue.

Learn More:


Well, that’s about it for today my friend! I hope you’ve enjoyed this HIFIMAN EF400 Review.

Questions? Comments? Requests? Did I miss the mark on something? Let me know down below (please keep it civil) or Contact me!!

If you love what I do here and want to support the blog and channel in a more personal way, check me out on Patreon and discover all the value I have to offer you.

Is the EF400 worth a purchase in your mind? I would love to hear from you. Until next time…

All the best and God bless,





Can’t decide which headphones to purchase? Interested in a complete buyers guide outlining over 40 of the best options on the market? Click on over to the best audiophile headphones to learn more!!


  • THD+N (Line out): Between 0.002% and 0.004%
  • Channel Separation: 125+/-3dB
  • Signal to Noise Ratio: 118+/-3dB (A-Weighted)
  • Maximum Power Output: 4.4W per channel
  • Dimensions: 246.5mm(L) x 228mm(W) x 61mm(H)
  • Weight: 3.08kg

In The Box


Power Cable

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