Performance Continued

After testing the AKG K701s I moved on to the Sennheiser HD 580s, they are incredibly hard to drive and sound dull on a lot of amps where they suffer from insufficient amplification thus lacking impact and speed. With the Head-Direct EF1 they decided to come to life in a very nice way. The bass was big, powerful, and had a snappy impact along with a good depth. In combination with the Octavart the HD 580s sound OK, but lacked impact, speed, and precision. The power surplus of the Head-Direct EF1 really excels their performance and makes them a lot more enjoyable to listen to. Even the sound stage improved a lot with the EF1, becoming wider and deeper. The Sennheiser HD 580s do not have the same impressive sound stage as the AKG K701s, but with the Head-Direct EF1 it closes the gap due to a better match with the amp.

Normally tubes and low impedance headphones like the Grado SR-60s do not match well, but since this amplifier has a solid state amplification output stage it is able to drive the SR-60s well. What never ceased to amaze me was how versatile this amp is, powering everything from the low impedance Grados to high impedance headphones like the HD 580s is no easy feat. And the fact that it does it with amazing sound quality is just mind boggling. To round off my testing I curiously hooked up my Yuin OK1s which are a completely different beast than the other headphones and like with all the others this amp just elevated their performance.

The overall presentation with all my headphones was fast and highly transparent. Coloration wise this amp is quite warm which is great if you are into that, I find it highly enjoyable with all my records and headphones.

The vast differences in performance between the two tubes means that you probably will not be spending that much time with the Chinese manufactured one. It is not as smooth or retains as much detail as the RCA one. On top of that the frequency response is also altered for the worse for the new tube. The Chinese tube can of course be used as back up in case of the RCA one going bad.

Another thing you need to keep in mind is that even with the volume dial turned all the way down there will still be some output into the headphones. Not a problem in my case, but it is something you should be aware of. It is due to the fact that the amp uses AM active volume control, which sounds good, but cannot be turned all the way to off.

Durability

The aluminum box is very sturdy and all the components are fastened to the box and not just to the PCB. All the terminals on the back and the front are rock solid, you really have to try hard to break this little amp. The surface of the front panel will withstand some abuse like being poked with a 1/4” jack softly but if you pull it across it will most likely get a bit scratched. The tubes are of course going to get worn down over time. Head-Direct will eventually carry quite a few different brands of 12AU7 tubes so there is really no need to worry. The 12AU7 tubes are easy enough to get hold of so you will not have to worry about finding them once the one supplied with the amp breaks.