(a) The power line voltage shall be 120 volts AC (230 volts when the equipment is made for foreign sale or use, unless a different nameplate rating is permanently affixed to the product by the manufacturer in which event the latter figure would control), RMS, using a sinusoidal wave containing less than 2 percent total harmonic content. In the case of equipment designed for battery operation only, tests shall be made with the battery power supply for which the particular equipment is designed and such test voltage must be disclosed under the required disclosures of § 432.2 of this part. If capable of both AC and DC battery operation, testing shall be with AC line operation;

(b) The AC power line frequency for domestic equipment shall be 60 Hz and 50 Hz for equipment made for foreign sale or use;

(c) The amplifier shall be preconditioned by simultaneously operating all channels at one-eighth of rated power output for one hour using a sinusoidal wave at a frequency of 1,000 Hz; provided, however, that for amplifiers utilized as a component in a self-powered subwoofer system, the sinusoidal wave used as a preconditioning signal may be any frequency within the amplifier's intended operating bandwidth that will allow the amplifier to be driven to one-eighth of rated power for one hour;

(d) The preconditioning and testing shall be in still air and an ambient temperature of at least 77 °F (25 °C);

(e) Rated power shall be obtainable at all frequencies within the rated power band without exceeding the rated maximum percentage of total harmonic distortion after input signals at said frequencies have been continuously applied at full rated power for not less than five (5) minutes at the amplifier's auxiliary input, or if not provided, at the phono input.

(f) At all times during warm-up and testing, tone loudness-contour and other controls shall be preset for the flattest response.