Pros: Excellent price, solid build quality, sound quality is clean and pure, 3 band passive EQ
Cons: Minor interference (EMI/RFI) due to no shielded case, but easy to avoid/fix
This is a wonderful little tube amplifier for the price. I paid only $59 for the amp and it was in perfect condition with a new Electro-Harmonix 6922 tube. The tube itself runs about $15, so the actual cost of the item was only roughly $45 (minus the tube). For that price, it is a well made, extremely well priced amp, and the value you get is superb.
Initial impressions - the amplifier is a more "DIY" open design, with no shielded case. This is fine considering the price. The actual build quality is great: solid soldering, and good quality parts. The gain potentiometer, for example, is an ALPS pot which are known to be high quality. For the price, this thing is built to a great standard. Doesn't come with very much extra: the power supply, amp, and the tube. Simple but efficient packaging. Two LED lights (blue and red, one signifies power - the red - and the blue is for the tube attachment, which draws voltage from the capacitor and can stay on for a few seconds after the tube is unplugged due to the capacitor holding some charge).
I've driven higher and lower impedance headphones. Most of my cans are low impedance, and this amplifier worked wonderfully for anything I threw at it. It states an output range of 20-600 Ohm, so that is pretty flexible with regards to driving cans. I don't have a pair of high impedance (600) cans to test with, however it should work fairly well for most cans on the market.
Sound quality is warm yet clean with no distortion or any real noise, which is something I would expect from a tube amplifier that is fully Class A driven. The amplifier comes with a 3 band graphic EQ, which is passive. This is pretty cool and adds some character and optimization potential to the amplifier for sure. Putting the settings all the way to max is basically the "0" setting since it is a passive switch; there's no "added" frequency adjustment, simply subtraction (not allowing certain frequencies through). Similar to a passive volume attenuator. So unlike a more traditional, non-passive EQ switch where the lowest setting is the default, the maximum up setting for the EQ is the technical default and lowering the switches simply attenuates the frequencies without distortion. This is a nice feature. Works well because you can adjust to your desire, and it's very flexible.
Amp can get a little hot, but this is expected, especially because this is an open case design. The heatsinks are what really get hot, which hold the rectifiers, which are power MOSFET's so they have a bit of heat. Nothing unexpected, just gets a little hot but nothing too crazy. I can still touch the EQ sliders just fine, but obvious caution should be applied as it is an open amplifier chassis. The tube itself is only somewhat hot; it is the heatsinks of the rectifiers that really bear the most heat load!
Since this is an open case, there is some EMI/RFI (electromagnetic/radio-frequency interference). This is solved by keeping things like cellular devices a few feet away from the amp, putting the amp in a solid, EMI shielded case (such as one made of solid aluminum or related materials), or placing it on a shielded surface. By doing this I easily get rid of the EMI/RFI. Part of the EMI/RFI is also due to the power cord, which is not grounded, but this is easily minimized to a significant degree with the methods I just mentioned as well.
Overall, I give this amplifier a 5/5. For the price to quality ratio, this thing certainly performs with flying colors. An excellent starting tube amplifier that gives the warm, crisp Class-A driven sound quality expected from a tube at a very accessible price point. Some photos below (click to see higher resolution).