There are many DIY USB audio projects floating around the web. However USB routing is not an easy task. There are some rules that the designer needs to follow in order to create a good PCB layout. The following document from Intel gives som basic and advanced guidelines on how to design a USB device and how to route the PCB. Though was it intended for a 4-layer design, many of the tips apply to 2-layer designs as well.
This document provides guidelines for integrating a discrete high speed USB host controller onto a four-layer desktop motherboard. The material covered can be broken into three main categories: Board design guidelines, EMI/ESD guidelines and front panel USB guidelines. Section 1.1 Background provides an explanation of the routing experiments and testing performed to validate the feasibility of 480 Megabits per second on an actual motherboard. Section 7 contains a design checklist that lists each design recommendation described in this document. High speed USB operation is described in the USB 2.0 Specification (http://www.usb.org/developers/docs.html).
High Speed USB Platform Design Guidelines – >>>[LINK]<<<