@Arnie,
A one off system designed by me is too time consuming especially when there are some good off the shelf modules available. Found two possible modules here:
http://www.esr.co.uk/cebek/index.htm (note add VAT to the prices).
Look at the ES3 and ES5 modules. In the technical information it shows how to connect up the unit.
@Akira
Have you re-wired your amplifier yet?