[General Accessories] vectron:
This is a Review of HRT dSp USB DAC with OTG compatibility. http://www.hirestech.com/product/?pid=1675 .

High Resolution Technologies (HRT) is definitely not a new kid on the block. But one might ask, why a company with so many well known USB DAC products (including microStreamer and Music Streamer) decides to start KickStarter crowdfunding campaign for their latest dSp and i-dSp USB DAC products? In my opinion it's for the same reason Pebble had to crowdfund their latest smartwatch - extra publicity NEVER hurts! Based on some of the USB DAC reviews I shared with you over the last few months, you can see that competition is heating up with a lot of choices and sometimes it's hard to make a decision what is a best product for your particular needs. Luckily, most of the products in this category have a unique set of features that set them apart, and I will do my best to review dSp with a comparative summary to other USB DACs I recently covered in my reviews. So without further ado, let me share with you what I found after testing HRT dSp.

Unlike my other reviews, I'm not going to discuss here details of packaging since I received my review sample fresh off the grill after their KS campaign (btw, pretty impressive with almost 600 backers and close to $43k in raised funds), and it was only dSp module with included accessories rather than a final production packaging. This USB DAC comes in two flavors, dSp supporting USB interface (UAC - USB audio class) of Windows and MAC and USB OTG with Android, and i-dSp specific to iPhone, iPod Touch, and iPad supporting the latest lightning connector. Since my household is iDevice-free, naturally I went with dSp version.

Part of receiving a review sample inside of a small clear ziplock bag is the lack of anticipated surprise when you take it out of the box to reveal its actual size and finish. In line with some of the other similar USB-thumb drive devices, dSp is about 2.1" x 0.8" x 0.3" but with a remarkable weight of only 8 grams. This light weight is a result of all-plastic design, though I have to admit it felt rather sturdy and surprisingly with no flex or creaks. But I would be careful with dSp, making sure not to drop or step on it. Not sure about final packaging, but maybe some kind of a soft protective sleeve would be advisable when you pack it for traveling.

Along with dSp USB DAC, the two included accessory pieces I received were a short 6" usb to micro-usb cable to use with laptop/PC and 4" micro-usb OTG cable. Both cables were high quality with a thicker yet flexible jacket and a slim connector with a nice non-slippery grip. I was especially pleased with micro-usb connector of OTG cable since it was slim enough to work even with bulky Defender style smartphone cases. Also, this OTG cable didn't require any extra USB OTG adapters, assuming Pin 4 (sense) was internally grounded to Pin 5 (GND). Furthermore, convenience of 4" short cable was also great for a clean connection to a smartphone without any excessive cable slack.

There is nothing much to say about design, just a very small lightweight footprint with micro-usb connector on one side and 3.5mm headphone port on the other side. There is a pinhole opening next to micro-usb port, but doesn't look like it's intended for reset or led or anything like that. As I mentioned before, design is not exactly flimsy but it is plasticy and you have to be careful not to drop/step on it.

Design and accessories.

Connection to laptop/PC was flawless, and within minutes of installing drivers the dSp was recognized. Afterwards, it was a robust plug'n'play with instantaneous recognition from either USB2.0 or USB3.0 ports, and a typical instant recall of the last digital volume setting.

Another great feature of dSp is a robust support of Android OS. My Note 4 doesn't even has Lollipop installed, with a stock KitKat until Verizon rolls out official update. And still, connection was flawless with instant pair up and sound streaming (unlike delay recognition with other products). I especially liked how I was able to use any of my apps to play music, not just USB Audio Pro (lifesaver for some other usb dacs I tested). Plus considering very low power consumption of only 50mA, there shouldn't be too much worry about dSp draining your phone's battery.

Application.

So how about sound quality and improvement over my laptop/PC and smartphone audio output? The easiest one is of course a comparison to my ThinkPad stock sound. The difference is definitely very noticeable with a clean balanced sound, no more background hissing or any other glitches generated by noise coupled through internal D/A to headphone output. Processing analog portion of the audio signal outside of laptop has a definite advantage since you are moving away from a noisy power source and keeping it isolated from other computer components. Typically, small USB DAC devices are not equipped with heavy duty caps for filtering, but still there going to be higher level of noise attenuation in such external "soundcard". With my Note 4, sound improvement was less noticeable since my phone has a clean and detailed audio output to begin with, but dSp still provided higher power, less distortion at higher volume, and slightly more open soundstage. For other people with older phones, especially those who turn their smartphones into a wi-fi streaming DAPs, benefit from a sound improvement will be a lot more noticeable.

In more details, dSp has a nicely balanced sound with a good retrieval of details, and above average soundstage. Low end has a moderate sub-bass extension (not too deep), slightly boosted mid-bass, and in general a bass well controlled without spilling into lower mids. Mids are bright and clear, but a bit on a thin side lacking some body in lower mids. This probably perceived as a more revealing sound sig. Treble is crisp and nicely extended, just a bit hot but without crossing sibilance threshold. The sound signature of this DAC was actually quite good to pair up with all of my headphones, anything from darker v-shaped to brighter analytical sound signature.

I started my review with mentioning about competition "heating up", and that is true since in the past few months I had an opportunity to test a lot of other USB DACs such as E10k, FULLA, Astrapi, DragonFly, and now dSp. Overall, nothing really stands out as having out-of-this-world sound or a complete failure in comparison. Majority of big differences are still around the build/design, extra features and pricing, but if I have to partition them in terms of a sound quality - here is my humble opinion about it.

FULLA, Astrapi, dSp, AudioFly, E10k.

- E10k ($76) is warmer and smoother, it has a little less transparency and details, but compensates it with a lot of extra features like a handy volume pot, gain L/H, bass boost, LO and Coax Out, common micro-usb connection, and a solid build, though it's the largest one out of the bunch. Also, there is no easy connection to smartphone where you have to go through splitters with OTG adapters and external battery connection which bulks up your rig and makes no sense. In comparison, dSp is smaller and lighter, works seamless with a smartphone, and has a brighter and more revealing sound, though E10k warmer and smoother signature has a better organic tone.

Astrapi ($129)/DragonFly ($146)/dSp ($70) - all have decent transparency, good level of detail retrieval, and on a brighter side. In comparison between these three:

- DragonFly is a little warmer and smoother, has a better bass texture, good soundstage, a solid build quality and a cool sample rate dragonfly-led indicator, smartphone compatibility only using USB Audio Pro app and extra OTG adapter. In comparison, dSp is brighter and little bit thinner, has a little more details, has the same soundstage depth, but width is a bit narrower, flimsier construction but it cost 1/2 of DF price.

- Astrapi is a little brighter and a bit more detailed, a bit more power, wider 3D soundstage, solid build with aluminum alloy housing, and universal interoperation with Android/iOS/PC/MAC. In comparison, dSp compatible with both usb2.0 and usb3.0 while Astrapi only works with usb2.0. dSp audio pair-up is instantaneous while Astrapi has 5-10sec pair up delay. In terms of a sound, dSp is more neutral and a bit thinner, while Astrapi has a bit fuller body sound and slightly better bass definition. Astrapi is even smaller and has a clip, but it cost almost twice as much.

- FULLA ($79) definitely has a slight edge in sound quality over its competition with a more detailed and textured sound, better extension, fuller body, and soundstage above the average in width (similar to dSp, but not the same as Astrapi) and the same in depth as Astrapi, build is solid but not highest quality finish due to sharp edges, no smartphone support (wasn't able to get it to work even with OTG splitter and external battery and USB Audio Pro), and it uses mini-usb connector, but has a dedicated volume knob (though small and a bit slippery). In comparison to dSp, FULLA is a little more detailed, had a deeper bass, soundstage is slightly deeper, sound is more airy (better separation), and FULLA has more power. FULLA is definitely more appropriate for a desktop setup, while dSp is more flexible including a mobile setup.

Overall, based on the sound quality, small footprint, and flexibility of flawless integration with laptop/PC and smartphone (Android) - HRT dSp definitely has the best price/performance ratio when you put it against the competition. As I mentioned before, none of the USB DACs I recently tested standout as night'n'day against their competition. What sets them apart, beside an obvious price spread, is the build/design, set of extra features, and compatibility with smartphones. That is why you should first figure out your priorities of how you are planning to use USB DAC - it will help you narrow down your choices. Also, the 5 products I mentioned is just a tip of the iceberg with so many more dedicated USB DACs available out there, including so many portable DAPs you can use as USB DAC. Another option, if you are into hi-res audio with high sampling rates and DSD supported format, LH Labs GeekOut should be added to the list, and soon I will be reviewing their 450 and 100 models, but we are talking about PC/MAC only support (no smartphone due to a high power) and 3-4x price premium. Thus I'm still sticking to my original statement with dSp having the best price/performance ratio if you looking for a compact USB DAC solution to work with your laptop/PC/MAC and Android (or iPhone with i-dSp) smartphone.