HiFiMAN Express have come up with this ridiculously inexpensive upgrade that will greatly improve the sound of headphones and desktop speakers. The HiFiMan Express HM-101 portable USB DAC is smaller than an old-school cigarette lighter. But it delivers big benefits to your digital music files. So buy this HiFiMAN HM-101 Audiophile USB DAC/Sound Card Was £29.99 Now £26.50.