HRT has introduced two DAC devices designed to improve the sound of the music you're listening to from your smartphone. The i-dsp ($69.99) is designed to work with iOS devices that use a Lightning connector (iPhone 5/5s/6/6 Plus and any iPad less than 3 years old) and the dsp ($69.99) works with Android phones running 5.0 or later and any laptop with a USB port. I tested out the i-dsp with an iPhone 6.
Something that iPhone users have to keep in mind from the top. The i-dsp requires a lightning port adapter and use's Apple's Lightning to USB camera adapter, which sells for $29. If you don't already own one, that's going to make the i-dsp a $100 investment. That's still just about the least expensive DAC option out there for iPhone users but it's quite a hit versus the Android version. The dsp comes with a micro-USB cable for your computer and a micro-usb OTG cable for use with an Android phone, so it's an all-in purchase.
We've talked about this before, but here's the short recap: the worst thing about phones and laptop computers is the sound processing. Very few users care much about sound quality and manufacturers have figured out that it's easier just to cut that corner. The most expensive headphones in the world can't correct the signal processing problems with your phone's audio jack.
DAC (digital-t0-analog converters) devices bypass the phone or computer's converters and use a better chip that produces higher sound quality. Great DAC converters were the key to a quality CD player and they haven't been emphasized as much since we've made the move to mp3 players. The HRT devices can play back music that has up to a 96kHz sample rate and up to a 24 bit rate.
How does the i-dsp sound? It's an obvious and decided improvement over the converters in my iPhone 6. There's a lot more clarity in the midrange. The sound improvements aren't as dramatic as what you get with a device like the V-Moda Vamp Verza, but that device costs $600 and is a pain to lug around with your phone.
HRT has managed to deliver a good DAC device at a reasonable price, but some users might have an issue with the build quality: the plastic case feels a bit brittle, it's not tightly glued together and I don't think it would survive if you stepped on one. If you're in the habit of throwing electronics into a bag before travel, you should take extra care where you store the i-dsp.
Also note that you can't answer a phone call when you're plugged into the i-dsp. Apple only allows calls to be routed through the audio port in your phone. You'll have to unplug from the i-dsp and plug into the usual connection to answer your iPhone.
It's unlikely that Apple or Samsung or HTC is going to invest the $25-$50 it would take to improve their device sound anytime soon. HRT has made a good step to making improved audio a lot more affordable.