http://www.head-fi.org/forum/thread/504037/mini-review-digizoid-zo-portable-subwoofer   That's my whole review. In summary:   The zo is an interesting product. It seems like it would be just marketing fluff, but it actually does work like they claim. I was able to get (seemingly) hard hitting bass out of some headphones that had never been able to produce anything like that before. As a portable amp, the zo is a bit better than most cheaper amps you would find, such as the various cmoy based designs on ebay. But the real star of this show is...

http://www.head-fi.org/forum/thread/484235/review-audinst-hud-mx1-usb-dac-amp   That's my full detailed review. In summary:   The Audinst is still one of my most often recommended pieces of gear, especially for people just getting into this hobby. As a DAC it is detailed and transparent with no specific weak points. As a headphone amp it is very poweful but of course has it's limits (could use more refinement but what do you expect for the price?). The overall package is very well done, with lots of nice features like an optical out for...

http://www.head-fi.org/forum/thread/494832/review-fournier-hta-1-hybrid-tube-amp-excellent-budget-amp   That's a link to my full review. In summary:   The Fournier HTA-1 is a small hybrid tube amp. It is made by an enthusiast who sells on eBay under the name "Linear Designs". He designs and hand builds each amp he sells, and is very knowledgable about this hobby.   The sound is fairly "tubey", with an excellent soundstage. Mids are the prominent focus in the spectrum, although lows and highs are quite nice as well, and transients are...

Skylab already linked to my review, so I'll just summarize here:   I find the Yulong amp to be very neutral and transparent sounding. I've owned various models in the $1,000+ range including Benchmark DAC1, Grace Design M902, and Lavry DA10. This Yulong competes well with those units and is even superior to some of them in certain aspects. The headphone amp, while not quite on the level of the DAC section, is still quite good, and you'd need to spend a significant amount of money on a standalone amp to get much improvement.   Bottom line: if...

http://www.head-fi.org/forum/thread/508076/review-leckerton-audio-uha-6s-portable-amp-dac   That's a link to my full review. In summary:   the Leckerton UHA-6S is one of the best portables amps I've used (and I've used a lot). It has a very high end sound, both as an amp and a DAC. The battery life is very good, it charges via a simple USB cable, it works with almost any headphone thanks to dual gain settings, and it even has socketed opamps inside for people who are inclined to tweak. It is built by a small audio company in the USA who...

http://www.head-fi.org/forum/thread/513019/review-maverick-audio-tubemagic-a1-integrated-amp-pre-amp-headphone-amp   That's my detailed review. In summary:   The Maverick A1 is an excellent tube headphone amp for the price, period. The fact that it is also a good tube pre-amp and hybrid amp for full sized speakers is just a bonus. The sound is ultra smooth and warm, with a great low end.   The amp section is powerful enough to work with lots of speakers provided they are reasonably efficient. You get surprising volume in small to medium...

http://www.head-fi.org/forum/thread/515068/review-hot-audio-dac-extasy-usb-dac   That's a link to my full review.   In summary, the Hot Audio DAC Extasy is a hand-built USB only DAC with a great warm sound. It uses a Wolfson WM8501 DAC chip which has a somewhat unique feature: direct line driver capability. This simplifies the design because the output comes directly off the DAC chip itself, with no post processing required. It also allows for a direct headphone connection; it isn't a traditional headphone amp, but works quite well.   The...

http://www.head-fi.org/forum/thread/516993/review-matrix-cube-dac   That's a link to my extensive review.   In summary, the Matrix Cube is a cross between the Cambridge DacMagic and the Musical Fidelity V-DAC. It matches the detail of the DacMagic with the smoothness and musicality of the V-DAC, all for a lower price. And don't forget the built in headphone amp, which is very much on par with the Musical Fidelity V-CAN/V-PSU combo. In my humble opinion this is a best buy right now in the $300 range, and would make a very solid foundation for...

http://www.head-fi.org/forum/thread/475618/matrix-m-stage-amp-review-simple-cheap-and-excellent   That's a link to my full review, which has become a very long thread.   In summary: The M-Stage is a clone of the Lehmann Audio Black Cube Linear, which is a high end headphone amp selling for around $1k. The M-Stage matches or exceeds the real thing in every aspect. It features a socketed opamp in the output stage so you can upgrade or try different things yourself (the Lehmann does not allow this). It is built like a tank, perhaps not the...

http://www.head-fi.org/forum/thread/510802/review-unique-melody-aero-custom-triple-driver-iem   That's a link to my extensive review. In summary:   The Aero has the Unique Melody house sound, which will appeal to some but not all. Lovers of AKG K701, Etymotic ER4S, Sennheiser HD800, AKG K1000, or Electrostatic headphones in general will likely find these to be almost perfect. Fans of Denon D2000/5000/7000, Beyerdynamic DT-770/DT-990, Sennheiser HD650/IE8, or other bass oriented headphones should probably look elsewhere. For the price, they...