July 09, 2016

This article was written by Tristan Jacquel and originally published in Son-Video.com:blog here


The HiFiMAN EF2C headphone amplifier is a hybrid model with a USB DAC which features two 6N1 power tubes for preamplification and classic transistors for the amplification section. This type of system is ideal to enjoy the famous melodic tube sound with a reasonably sized device and without spending too much. Just connect the amplifier to the USB port of any computer to listen to music. This model replaces the very popular HiFiMAN EF2A and integrates a new DAC as well a new volume potentiometer.

Two inputs are available, one RCA line input (to connect a portable player or any audio player with a stereo output) and one USB (type B) input. The integrated DAC is compatible with PCM stereo stream up to 16 bits and 48 kHz. The headphone amplifier can deliver up to 2×320 mW at 32 Ohms, this powerful amp can thus easily power medium to high sensitivity headphones (150 Ohms for example).



HiFiMAN EF2C- the benefit of using power tubes

As a quick reminder, the power tube is the ancestor of the transistor. In spite of its low power and efficiency, this electronic component is still widely used in hi-fi and monitoring. Many electric guitar amplifiers use power tubes to obtain a warm sound as well as a certain distortion. The two small 6N1 tubes of the EF2C headphone amplifier serve a similar purpose. They give warmth and life to the audio signal before it is amplified by the transistors. Although a tube preamp paired up with a solid state amplification section might not be the best configuration possible, as it doesn’t quite reach the quality of an all tube model, it gives a flavour to the sound which no other transistor headphone amplifier can offer, regardless of its price.



HiFiMAN EF2C- installation

We tested the HiFiMAN EF2C headphone amplifier with a Raspberry Pi2 (Raspbian/VLC) and our usual FLAC and DSD files hosted on a Synology NAS. We used an Audioquest Carbon USB cable and a pair of Sennheiser PX-100 headphones.

We had to be patient with the HiFiMAN EF2C as the first listening impressions were honestly disappointing. The sound was stifled, both bass and treble extensions were non-existent… a real let down! Especially considering that the last tube headphone amplifier we listened to, the Aune T1, gave us a completely different impression from the very first notes. We gave the HiFiMAN EF2C a two week break-in period before we wrote this review. Once the electronics are broken-in, it is a completely different story. The sound is clearly vintage and melodic.

Note that after breaking it in, the HiFiMAN EF2C is a completely different creature, offering a clearly vintage and melodic sound.

We noticed that we couldn’t turn up the volume of our USB source beyond 50 % without creating an obvious dynamic compression (pumping effect). This was not caused by the Raspberry Pi2 we used as it happens with any USB source. It is possible that the DAC is too energetic for the tubes, although it doesn’t affect the quality of the musical restitution.


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HiFiMAN EF2C- sound signature

Low range: high-bass is very present, even puffed up during the first 200 hours of use, then gets back to an enjoyable level. The infra-bass is a little short but transients are very good, which is a rather rare quality. Bass lines and guitares are very satisfactory.

Medium range: rich and warm, very convincing in the low-mediums with a very good restitution of human voices.

High range: smooth but slightly in the background. In other words, treble is really well handled as too much high frequencies can have a negative impact on the depth of the sound stage and make it too tight. This is not the case here. Here is a headphone amplifier that will work well with many treble oriented earphones and headphones.

After a break-in period of about 200 hours (2 weeks of daily listening sessions with the power permanently switched on), the HiFiMAN EF2C then stabilizes.

First observation: at low volume (or even at very low volume), the sound is well balanced. As we turn up the volume, the overall balance is preserved without any excessive dynamic compression. Globally, it is easier to hear when the notes start and fade than with solid its state competitors (in this price range and above). The HiFiMAN EF2C often offers more details as well as a richer sound texture. It is especially obvious with strings and percussion. The frequency response is not as wide as with other traditional DACs. It might be a drawback for some people at first, but the coherence as well as the overall balance of the sound are much superior to what more expensive DAC amplifiers have to offer.


          The push button on the right is used to switch between the USB and line input

HiFiMAN EF2C- listening impressions

New Kid in Town, The Eagles, DSD 2.8 MHz -> PCM 16/44
The Eagles lost Glenn Frey this past Monday, the wonderful composer and singer of New Kid in Town. This small amp reproduces the voice of the artist and all its melancholy very accurately. We would have liked a slightly more energetic cymbal sound but the overall listening experience is coherent and touching with absolutely no harshness.

Hurricane, Bob Dylan, DSD 2.8 MHz -> PCM 16/44
Always a difficult test to pass, this song can turn into a real nightmare if the percussions and the violin are not well under control. Nothing is simple with Hurricane, Dylan is almost screaming throughout the song, the drummer hits as hard as he possibly can and the acoustic guitar can have a hard time cutting through the mix. The same thing applies to the backing vocals. The HiFiMAN EF2C handles the track really well, although we would have liked a slightly more spacious sound stage. Nevertheless, both vocals and instruments fall into place and suffer no harshness.

My home is in the Delta, Muddy Waters, DSD 2.8 MHz -> PCM 16/44
A different register here. The soundstage is very wide and the dynamic range is outstanding, but the amplifier remains undaunted. Muddy Waters’ guitar resonates wonderfully.

Muddy Waters

The Police, Message in a bottle, DSD 2.8 MHz -> PCM 16/44
Let’s go straight to the point, the EF2C has an obvious sense of rhythm. Sting’s vocals are well extracted and are perfectly intelligible, the bass guitar has a nice full sound and the drums are very appealing. We can hear many details and macro-dynamics which make it a pleasure for the ears.

I’ve got you under my skin (version mono), Frank Sinatra, FLAC 16/44
The crooner’s vocals are well delivered. The violins and the brass section are solid and easily find their place in the tight sound stage (mono).

Karmacoma, Massive Attack, FLAC 16/44
The amplifier unravels the recording very well, the wind instruments and the synthesizers are floating around the voices and bass guitar. The rhythm is very enticing and we rediscover this track.

Protection, Massive Attack, FLAC 16/44
Bass and drums are well articulated (this track is a very difficult test regarding the rhythm section). The bass is neither short-winded nor overwhelming but well balanced. The sound of the rain at the end of the song is very intense.


Street Life, Randy Crawford (Deezer)
A very “vintage” restitution. What rhythm! Instruments are not pushy and the female vocals are at the fore from beginning to end. It lacks treble and bass but the result is nonetheless catchy. Let’s not forget that this is an MP3 version.

Requiem pour un con, Serge Gainsbourg (FLAC 16/44)
In this restored version, the requiem is wonderful. The width of the sound is impressive, Gainsbourg’s vocals are right in the centre, as if protected by an air bubble.

Breathe me (live, Lady Croissant), Sia, FLAC 16/44
The reverb on the piano can be clearly heard, which lets the listener truly appreciate the sound of the instrument. Once again, the bass guitar is well placed and offers great rhythm.

HiFiMAN EF2C- conclusions

What we liked: the smoothness and swiftness provided by the power tubes, the opening of the sound stage, the capacity to explore the medium range and the volume notch potentiometer.

What we would have liked:more expressive treble and deeper bass, a better management of the preamplification volume and a Euro power supply plug.

The listening experience is always warm and enjoyable. Average recordings can be completely rediscovered, even the “barely relevant” recordings become interesting to the listener. Do you want to clearly hear the artist’s vocals? Do you want to constantly keep track of the bass? Maybe you want to avoid a downpour of high frequencies. For all these reasons, the HiFiMAN EF2C is a very interesting device.

PS. The featured power supply (16 V, 1.2 A) is a model with non-European connectors. An adapter is supplied but due to the weight of the block, it is recommended to avoid plugging it into a wall socket. We used a multi-socket block placed on the floor for this test.



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