Q: “What can I expect from USB 2.0 in terms of stability, speed and audio capabilities?”
A: The short answer is increased stability and multi-channel audio support. USB version 1.1 first appeared on PCs and audio and MIDI peripherals in about 1999. Its serial data transmission (one bit after the next, in one long stream, compared to SCSI or other parallel protocols that send packets of data down multiple wires simultaneously) allowed the USB port to use a much simpler cable and plugs. USB also allows you to plug and unplug external peripherals from the computer at will (usually called hot-swapping), although it’s generally not advisable to do this with sound devices without first quitting your music application.
Unfortunately, PC musicians experienced a wave of initial problems with USB audio peripherals, such as clicks, pops and high latency. These problems were largely due to the early USB controller chips in the PC and have mostly died out, but they left quite a few musicians mistrusting USB 1.1. Its 12Mb/second bandwidth is fine for MIDI and 16-bit stereo audio down to latencies of 3ms. USB 1.1 falters, however, when you try to record and play back stereo 24-bit/96kHz signals simultaneously. USB MIDI interfaces also used to suffer from higher timing “jitter” (timing inaccuracies) and latency than serial port or PCI-based interfaces. This was primarily the result of USB’s handling of asynchronous MIDI data in an otherwise isochronous stream, which caused MIDI data to lose its original timing reference as it was passed on to MIDI devices.
USB 2.0 ports are now found on nearly all current desktop and laptop computers (Windows and Mac). With a huge 480Mb/second bandwidth (40 times faster!) this new standard is far more suitable for multi-channel audio devices than the original USB. The world’s first multi-channel USB 2.0 device is Edirol’s UA 1000, a 10 in, 10 out interface with 24-bit/96kHz capacity.
You can plug USB 1.1 devices into USB 2.0 ports and they will operate as they always have (at 1.1 speeds). USB 2.0 also has significantly improved its handling of asynchronous MIDI data to reduce timing anomalies.