Hifiman EF-5 headphone amplifier
I do not consider myself as a headphone specialist partly because, although I might have found the headphone sound kind of pleasant, I've always failed to regard the sound natural. It's like listening to music in a Mercedes-Benz, in a vacuum with no background noise, the sound artificially surrounding the listener from an undefined direction, and always exhibiting too much bass no matter how much one would want to get rid of it.
But I do have tested a number of headphones over the years, and more frequently quite a many headphone amps since almost all external dacs nowadays feature an output stage for headphones.
Well, Hifiman EF-5 is not a dac integrated with a headphone amp: it's a stylish compact, analogue headphone amp for a desk next to a computer of a cigar box. The glass cover and the protruding tube make the EF-5 look luxurious and well-finished.
Hifiman has other more "professional" and more topical headphone amps to offer. I got a feeling that the EF-5 was designed to attract those who find traditional solid-state technology less appealing, and for whom good is good even if it is a couple of years old.
There's nothing dated in the techniques of the EF-5: Tianjin fullmusic 12AU7 welcomes the signal at the input and the OPA275 kicking at the output. The power supply, DY-1, is installed in a separate chassis.
According to the manufacturer, the amp has a wide frequency response (20Hz-30kHz), just a little distortion (THD+N <0,2%) and 95dB noise-ratio. The input impedance is 50 kilo-ohms, and what's the best: the amp is said to drive headphones from 2 ohms to 2 kilo-ohms, ie. practically all headphones. There's 2,5W power per channel or 15V per 32 ohm load.
Headphones with a 3,5mm plug will require a 1/4” adapter. For the source the EF-5 offer a pair of rca inputs. After switching on it will take a moment before the blue led lights and the amp is ready to play.
On what I heard
To my taste the background noise was fairly non-existant. The amount of noise and other not signal related sounds, if there's any, can be affected by repositioning the power supply. In practice there was hardly anything for ears to detect between the tracks.
Connected to my Mac mini the Hifiman EF-5 produced produced a much more spacious and better breathing (read: dynamic), not to say more picturesque sound, typically with music such as Haydn's Cello Concerto. But also more generally.
Reproduction of bass notes was clearly more lively and musically more convincing. Strong but not thick. Great! The EF-5 removed all listening fatigue causing coldness from the sound. The amp brought power to all kind of music, but it was not direct or mechanical power, but resilient, living with the rhythm of the music.
Although the EF-5 improved my Mac mini's performance to another quality level, I would rather see it together with a high-performance cd-player/dac. In this way it would be possible to take the maximum out its performance in addition to how it satisfies the eye. Even though I do not consider myself as a headphone specialist I dare to recommend the Hifiman EF-5 to everybody but the most serious headphone enthusiasts.