DIY power cable questions

sorry, but I totally disagree with millercarbon.  If you know what you're doing, a DIY cable can match or beat other manufactured power cables equal or even more expensive.

That being said, nobody really answered indyvw's question.  I see williewonka answered, but seems to have confusion between a C7 and a C17 connector.  The C7 is a 2-pole mini-plug that is found on many smaller devices, such as some bluray players among other things.  In this case, Furutech makes very good connectors.

The C17, on the other hand, is the same thing as a standard C13/C15, but without the ground conductor.  This is for equipment that has a floating ground circuit.  It is common in things such as receivers and sometimes bluray players and even amps.  The idea is to "float" the ground so that you don't have ground loop hum problems.  In this situation, you can just use a standard IEC connector.  Even if the power cord/connector uses all 3 conductors, the equipment it's plugged into will not use the ground conductor.  All is good.

well, the neutral wire is basically the same thing as ground.  At your main junction box or circuit breaker box, neutral is wired into the ground anyways (wired to a rod stuck into the earth).  The neutral wire is almost like a "drain" for the hot wire, since you need a return wire for A/C or even DC voltage.  You can actually get shocked if you touch a neutral wire that has current flowing through it (i.e. it's connected to a device that's using "HOT" current).   However, the third ground wire will never usually have current flowing through it (or at least a lot of current). 

When making a power cord for an equipment that doesn't use ground, you could just use two conductors if you wanted and everything will be fine.  Or you could build or use a true 3-conductor power cord.  In this situation, the ground conductor is not connected to anything in the equipment.  But the ground conductor is still connected to ground at the outlet.  If you do this, the ground wire can act as an additional shielding or EMI capture (since it allows any EMI or voltage to be shunted to ground.

There is no safety issue here.  You can safely use a 3-conductor power cord on a plate amp that only has 2-conductor floating ground circuit.

You might want to google "floating ground".  It can relate to the ground plane within an electronic equipment where all extraneous voltages are shared.  This includes the ground plan shared between equipment through the ground shield of interconnects.