Cambridge 840C as a DAC

My laptop isn't a Mac, but obviously my iPhone is. I'd rather be running out of the pc.

You need a new sound card, either internal or external with a digital output.

I use my 840C's DACs with a Squeezebox Classic and this is a huge improvement over the internal SB DAC. And because I use a wireless router at home I can listen to lossless uploaded CDs via iTunes through the SB into the 840C. This is an exceptional solution and works very well.

Face, When you say a 'Sound Card' is that something I can connect to my computer through a usb output that then has the appropriate digital connections for the 840?

Yes, check out http://www.newegg.com, they have a decent selection of USB sound cards. I've have good results with Creative and ASUS products.