Pros: Pairs well with most dynamic headphones. Dynamic, clear, and powerful sounding. Sounds amazing with the right tubes. Basically noise free.
Cons: Tubes must be rolled to achieve best sound, the DAC isn't that good, minor channel balance issues at lower volumes, some minor sibilance issues
Hifiman EF2A Review
This is my first headphone amp review and I'm just going to review the amp section of this headphone amp as the DAC is nothing special, a bit better than most computer or portable device DACs but is easily outclassed by any decent dedicated DAC or soundcard. I've had this amp for a while and I tried it with a variety of AKGs, Senns, Beyers, as well as a few other miscellaneous headphones. I fell in love with this amps sound from the get go and it was my first desktop amp. This is an amp I have owned twice, the first one died after a couple months of use but I later found it was a returned and defective unit and I was able to return it for a full refund with no shipping cost to me. I later got the Schiit Magni and I disliked how it sounded in comparison, the Magni was obviously a level below this amp and it became more obvious with a better DAC and headphones and this was confirmed when I got my second EF2A. I am using this headphone amp with the HRT Music Streamer II+ USB DAC set at 24/92 connected with Auric RCA interconnects. And the amp is mainly used with my AKG K712 Pro, AKG K612 Pro, and the Sennheiser HD 545. I have noticed there is a channel imbalance where the left become louder than the right at levels below my preferred listening level. This review is a bit of a work in progress, I'll add more later.
I did some experimentation with tube rolling. Much of how this amp sounds come from the tubes, so stating what tube I am reviewing based on and talking about the tubes traits in the amp is important for a review like this. I came to the conclusion the Radiotechnique(RTC) 5654RT tubes are the best sounding tubes I tried on the amp for most of the headphones I tried with the amp. The tubes generally run about $20 for a matched pair. The tubes have big and powerful dynamics, if you use a more intimate headphone like the AKG K240 MKII the dynamics may be too strong on some songs. There is a real sense of physical presence and tactility with the tubes, you don't just hear the sound/instrument, you feel and hear the sound/instrument with a life-like realism I haven't heard on any other tube or amp I have owned. There is a roundness, body, and depth to the sound that is something really special, especially in an amp this price. The tonal balance is also spot on but there some grain in the sibilants(I think this is more amp related than tube related). These tubes are clear and transparent with just a touch of pleasing warmth. These are incredibly musical and enjoyable tubes, especially with the AKGs I paired it with, the K712, K612, and K240 MKII. They also sounded good with the Sennheiser HD 545, Sennheiser HD 555, Sennheiser PX-100 ii, NVX XPT100, Beyerdynamic DT 990 Pro, but the AKGs are just something special with this tube/amp pairing. The Sennheiser HD 380 Pro with these tubes in the EF2A is a horrible match, excessively closed-in, collapsed soundstage, and bad dynamics and was the first and only bad pairing I experienced with this tube/amp combo. The K712 is the best pairing I have heard on this amp, it's simply beautiful sounding with big powerful dynamics, a strong physical presence, transparent sound with a black background. It doesn't seem underpowered or held back at all given the RTC tubes are used.
This is a great and versatile little amp given you are willing to invest in different tubes. It's a fun and musical sounding amp that doesn't lack power and pairs exceptionally well with some headphones. If you own AKGs similar to what is mentioned in the review and likely others this is probably one of the best amps out there for them under $200.