The EF100 does not look like any of the older HiFiMAN amplifiers we have tested, which is both a good and a bad thing. The new design seems sturdier, and its aesthetics are more consequent.
One of the major things HiFiMAN resolved with the EF100's design is in the way its controls are placed. The volume-control knob is easily reachable without accidentally messing about with any of the other controls. The layout here is really simple, with most of the inputs on the back, the controls at the right part of the front's face, and the headphone-out to the left.
The EF100's volume control is pretty solid. There is a minimal volume mismatch at the very bottom of the range, but the range itself is huge.
The inputs on the back are plenty and of really good quality.
At the front is the headphone-out, a normal 1/4" jack of good quality.
The position of the mini-jack's input is a bit odd at first, but makes sense if you place your player near the device.
Like the older hybrid amplifiers from HiFiMAN, the EF100 uses a tube-driven input stage, which gives the sound that distinct tube-specific flavor.