After finally giving in and installing Windows, I discovered that this was caused by a motherboard fault. The fault is now cleared and sound works correctly (Hooray!).
So thanks for looking, and sorry for wasting anyone's time. -- Sound doesn't work on A8V-MX (VIA8233) https://launchpad.net/bugs/82021 -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
