Please don't ground the chassis of your Mac30 via a powercord. I found the original cord from my 240 and remembered why I ended up doing what I did. The Mac240 like the 30 has a non-polarized plug, and its 'ground' is tied to the chassis. A secondary groundpath along with 'non star ground' (a given for its age) virtually gurantees a ground loop and hum. If you use a shielded cable, do not connect either the ground wire or shield wire at the component end, and simply conncct them at the plug end yeiding whatever benefits there are from a Faraday shield around the cord.
If you're going for max sound and not looks or convenience, twist insulated 12ga solid core copper wire about 6 twists per foot, and hardwire to the component and terminate in a 2 prong plug. This construction yeilds an ugly unweildy cord. You could sheath it for cosmetic appeal, but its still an SOB to route. Good luck finding a heavy duty unpolarized 2 prong plug. I found a generic heavy duty 2 prong polarized plug at a hardware store, and filed the wider blade so I could endlessly obscess over which orientation sounds better
Alternatively, use the Canare starquad loudspeaker cable that will fit (or you're willing to fit) in the existing opening.
http://www.canare.com/index.cfm?objectid=ED0E00B5-3048-7098-AFCCB3149AB7ABB6The pages reference to 'twinned' wires refers to connecting the opposite wires together to yeild a pair from a starquad. This starquad configuration has increased noise rejection over a single twisted pair.
