Head-Direct recently launched a new product line dubbed HiFiMAN which currently includes only two products, the (PMP) and the all new EF2 USB headphone amplifier. The EF2 is a headphone amplifier with an integrated DAC which means that you can hook it up to your PC. Besides the DAC functionality the amplifier can also be hooked up to another source via a set of RCA-jacks on the back of the amplifier. Like its bigger brother the EF2 is a hybrid design that uses both op-amps and tubes as amplification stages. Where the EF1 is equipped with one 12AU7 tube the new EF2 uses two 6J1 mini-tubes. At the moment the EF2 is priced at a very reasonable $189 as opposed to the EF1 at $300.
The EF2 looks brilliant. The new polished front plated with the simple HiFiMAN graphics makes it look quite classy. Unlike the EF1 which is just an amplifier the EF2 has an integrated DAC, the chip it uses is a Burr-Brown PC2702 which has a good reputation, and is used in a large variety of performance DACs and amplifiers.
One of the things that impressed me the most about the EF2 is its size. Only a little wider than a CD and very shallow. The fact that it is so small makes it the perfect desktop amplifier. The small circuit board is densely populated by quality components. Most of the caps are made by Rubycon. The 6J1 tubes supplied with the amplifier are from an unknown Chinese manufacturer, but they sound good in this combination. They are definitely better sounding in this combination than the stock Chinese 12AU7 tube sounds in the EF1.
With the amplifier you also get an AC Adapter and a USB cable that you can use to hook it up to your computer. You have to buy an adapter if you live in Europe because the 220V version of the PSU has the wrong type of connector on.
The Chinese tubes just pop out of the top of the amplifiers acrylic top. The only problem I had with the amplifier was that I had to reseat the tubes in order to get a good connection between them and the sockets. Another minute issue is that the precut holes in the acrylic top do not align perfectly with the tubes making it an odd fit. This is most likely due to the fact that the tube pins are slightly bent.
The power switch is a little flip switch on the left side of the device. Right next to the on / off switch is the 1/4" headphone jack. The jack is of a really good quality and is attached to the front panel of the amplifier so that it does not put excess strain on the PCB.
The EF2 is aimed at use with a PC, but can also be used with another analogue source at the same time. The input selector switch is located at the front and lets you choose input type easily. The volume control is really nice and smooth. The range is likewise very good. It powers Ultrasone PRO900s to high volume levels at around 8 O' clock on the volume dial.