The difference is that there is no sound card in the PC. You connect the speakers to a USB port instead of using the sound card.
Using this system, the sound signals are in digital form right coming from the harddisk or whereever, and they stay in this form when they are sent out on the USB channel and into the speakers:
With USB the noise sensitive digital/analog conversion will take place in the speaker, and this results in a superior quality. Both Philips and Altec Lansing produce USB speakers.
You find high fidelity loudspeakers with built-in amplifier and converter, which can receive pure digital signals (via USB). One could hope, that these speakers will be able to interpret data from hi-fi equipment, PC, TV/video and other sources. See the description of some of the finest speakers I ever have heard: A set ofPhilips USB speakers.
Also see: Module 7d - about digital music: MP3s, MODs etc.
Copyright (c) 1996-2005 by Michael B. Karbo. www.karbosguide.com.