This is a Review of Beyerdynamic A200p portable USB DAC/headphone amplifier. beyerdynamic A 200 p - Mobile amplifier with digital-to-analog converter (DAC) For anybody who is serious about sound quality and invested into audiophile headphones, you know that DAC and amplifier are among the essential pieces of your audio chain. Also, you would know how expensive this equipment cost and how much space it will occupy. So what are you supposed to do if you want to enjoy your 300 ohm headphones with your smartphone? Or maybe you want to stream Netflix on your laptop and surround yourself with hi-fi sound? There is a number of portable solutions available to help you with this task, but NONE of them will come even close to a small size of Beyerdynamic A200p portable USB DAC/amp. I just had an opportunity to test A200p, and here is what I found. Arrived in a very compact box, a size similar to Beyerdynamic in-ear headphones (MMX102ie and DX160ie) I recently reviewed, I actually expected this DAC to barely fit inside. There was plenty of info on the front and the back of the box, but no typical magnetic cover to reveal the actual product. I have a feeling Beyer guys did that intentionally to make a surprise even sweeter once you take A200p out of the box. When I say small, that wouldn't be even accurate. It's TINY, with a matchbox dimension of approximately 55mm x 55mm x 13mm and only 51g. It's hard to even believe that such a small footprint can host a powerful audiophile quality Wolfson WM8740 DAC (24bit/96kHz), an integrated rechargeable battery able to last up to 11hr, a capability to be connected to either Android or Apple smartphones or your laptop or computer, a set of Play/Pause and Skip song transport controls, a dedicated Power/Lock switch and a status LED indicator, and a large flush mounted volume control wheel covering the whole top of the device. In addition to the DAC/amp, a very generous selection of accessories was provided, including micro-usb and lightning adapters, full size USB adapter which also serves as a charging cable, a beautifully crafted leather case, and a quick-start guide. In addition, a set of 3 self-adhesive rubber pads was included to help with turning of the volume wheel. Though the end of the cables attached to A200p had a proprietary connector, these are all very high quality cables and this particular connection was very secure. As a matter of fact, everything about this product screams high quality and solid build, and there is a very good reason for that. Beyerdynamic teamed up with one of the top premium portable audio equipment manufacturers, Astell & Kern, to update their award winning AK10 DAC/amp to transform it into A200p. The operating principle of this device is very simple. You bypass internal DAC (digital to analog converter) which outputs internally to 3.5mm headphone jack on the phone or the laptop, and go straight with a digital data stream into A200p. In there, isolated from all the noisy components of your phones or computer, you convert to analog audio using one of the top quality audio DAC chips, and output to its own 3.5mm headphone jack where you plug in your headphones. The audio spec yielded some very impressive numbers with 0.008% of T.H.D. and 110dB signal to noise ratio, flat frequency response, and being able to support headphones with up to 600 ohm in impedance driven by an output level of up to 1.7 Vrms. With such an impressive spec and design, the next step of testing was to determine how this translates into audio performance. Let me just tell you that using it with my ThinkPad T430s laptop transformed a sound quality significantly! You can have the best set of headphones and use only FLAC files - that will not overcome bottleneck of low quality hardware. Switching headphones connected from laptop to A200p felt like someone lifted a veil off the sound. The soundstage really opened up, the bass felt more detailed and faster, the midrange became crystal clear especially in upper mids (benefiting vocals significantly), and treble got more sparkle. Of course YMMV depending on your laptop hardware, but I was impressed with a change I experienced on my laptop. I also enjoyed how I was able to Play/Pause Windows Media player using A200p built in controls. Now keep in mind, this was a comparison using laptop as an audio player. Testing it with my Note 2 didn't yield the same drastic changes, but those changes were still noticeable. It had a similar impact of opening up the sound and making it a little bit brighter and detailed. Also, benefit of being able to control song playback and skipping between tracks was priceless. The included leather case was also a nice touch, but I wish they would have thought of a better way to integrate it with some attachments for your smart phone. In my opinion, it can probably work if you use a rubber or wrist band around your smartphone and attach the flap of the leather case underneath of it on the back of the phone. Overall, I was very impressed with a design and a performance of this portable USB DAC/amp. If you have high impedance premium headphones, A200p probably going to be the smallest and very cost effective solution to connect these to your laptop or a smartphone. For a regular low impedance headphones, it's a lot easier to recommend A200p to anybody who wants to use it connected to your laptop since the sound improvement will be significant. For those with a smartphone and a typical low impedance headphones, it's all going to depend on the sound quality of your phone and being able to support digital audio output. Also, you will have to plan where/how are you going to place phone/DAC when using together. I would suggest for Beyerdynamic to include an optional longer micro-usb/lightning cable so you can keep your smartphone in the pocket with A200p clipped somewhere on your belt with headphones attached to it. But in general, this little device really deserves some consideration! Here are the pictures.