I t's about not using instrument cables like a guitar cable as speaker cable.  That would be very bad for your amp as it will mess with the output resistance.  Never use a guitar cable as a speaker cable.

Cheers,

Crusty

I know this is a somewhat old post -- but I thought I'd clear it up.

Class 2 wiring refers to the National Electircal Code class for wiring, which indicates to the installer what type of wiring practice is needed, and to the inspector as an indicator of the specifications of the equipment without having to contact the manufacturer for every single item.

This is aguideline for safety from shock and fire protection. For home use, it is really meaningless, unless you are installing the wire from room to room, or within the walls, on a high-power system or for

General guidelines for class 2 are that the voltage be under 30v and the total power under 100VA, For a speaker wire to an 8 ohm system, the voltage at 100W would be about 30V. Anything over 100W should trechniically be class 3, but for runs within a room, class 2 is fine.

More important to me that class are practical considerations, such as:

1. Don't use shielded cable (a guitar cord or phono cable) for more than 20 watts per channel and then only temporarily. As noted already, it can cause heating problems, and the capacitance can afect frequency response. It has other, less audible effects, but my 50+ ears can't tell.

2. Don't run wires acoss the floor, especialy under rugs. It is asking for damage, and shorting a speakler wire can be an expensive trip to the amplifier repair shop.

3. Instead of remote speakers from a central amp, think about powered speakers in a remote location -- more felxibility.

4. Buy bulk wire and make your own cables instead of name brands -- they use the same materials anyway. I challenge anyone to be able to spot the sound of different wires, unless the wire is defective, or something way out of bounds -- like using telephone wires for speakers.

5. Wires within walls should have a protective jacket ove the individual insulated wires, just in case something else is pulled through the same wall. It helps prevent costly damage later.

6.You don't have to have a professionsal installer for long runs or hidden wiring, but it can avoid simple mistakes. If you want to do it yourself, do some research. Not just online, go the library and get a book. Even old books on wiring for sound can prevent headaches. It might even make for a wise consumer if you hire an 'expert'.