Quick summary on things that you should know about the current state of USB sound cards.
First I have to say that there are many differrent cheap usb sound cards. Some have the same internals, but different cases. Some have same cases, but different internals. Some have coupling capacitors... There is no foolproof way to find out by looking at a picture whether the sound card is the same as another one, unless there is a picture of the internals. Some cheap USB sound card are missing the needed coupling capacitors in the headphone output. That can break headphones and the sound card due the constant power draw caused by huge DC offset voltage. Leaving those capacitors out will cut the cost little bit, but it will have dramatic efffect on sound quality and reliability of the sound card. For some reason manufacturer left those capacitors out and replaced them with traces, that way both AC and DC can go from the IC inside the epoxy blob to the headphone jack. You can see the various different designs in the pictures below. you may also see them listed as USB Audio Cards, External Sound Cards, 3D sound cards, 7.1 Channel Sound |
Interesting • Mod/Fix for the "3D USB Sound" to prevent damage to headphones and improve audio quality. And another description of the mod • Make an Osciloscope using a $1 usb sound card • USB DAC using the PCM2704 is an excellent budget solution. Link |