What is the output power of a source unit that puts out 6 volts per channel into 4 ohms?

To determine the output power of a source unit that puts out 6 volts per channel into 4 ohms, you can use the power formula. The formula for electrical power (in watts) is:

[ P = \frac{V^2}{R} ]

where ( P ) is the power in watts, ( V ) is the voltage in volts, and ( R ) is the resistance in ohms.

In this case, the voltage output is 6 volts, and the speaker resistance is 4 ohms. Plugging these values into the formula gives:

[ P = \frac{6^2}{4} ]

[ P = \frac{36}{4} ]

[ P = 9 \text{ watts} ]

This calculation shows that the output power per channel is indeed 9 watts when the unit outputs 6 volts into a 4-ohm load. Therefore, the reasoning confirms that the correct choice is 9 watts per channel.