Crown Audio MA-24X6, MA-36X12 operation manual AC Power Draw and Thermal Dissipation, page

Macro-Tech MA-24X6 & 36X12 Power Amplifiers

8 AC Power Draw and

Thermal Dissipation

This section provides detailed information about the amount of power and current drawn from the Macro-Tech 24X6 and 36X12 amplifiers and the amount of heat produced under various conditions. The calculations presented here are intended to provide a realistic and reliable depiction of the amplifiers. The following assumptions or approximations were made:

•The amplifier’s available channels are loaded, and full power is being delivered.

•The amplifier efficiency at standard 1 kHz power is estimated to be 65%.

•Quiescent power draw is 90 watts (an almost negligible amount for full-power calculations).

•Quiescent thermal dissipation equals 105 btu/hr at 90 watts.

•The estimated duty cycles take into account the typical crest factor for each type of source material.

•Duty cycle of pink noise is 50%.

•Duty cycle of highly compressed rock ‘n’ roll midrange is 40%.

•Duty cycle of rock ‘n’ roll is 30%.

•Duty cycle of background music is 20%.

•Duty cycle of continuous speech is 10%.

•Duty cycle of infrequent, short duration paging is 1%.

Here are the equations used to calculate the data presented in Figures

8.1 and 8.2:

The following equation converts power draw in watts to current draw in amperes:

The value used for Power Factor is 0.65. The Power Factor variable is needed to compensate for the difference in phase between the AC mains voltage and current.

The following equation is used to calculate thermal dissipation:

The value used for amplifier inefficiency is 0.35 (1.00-0.65). The factor 3.415 converts watts to btu/hr. Thermal dissipation in btu is divided by the constant 3.968 to get kcal.

If you plan to measure output power under real-world conditions, the following equation may also be helpful:

page 24 Operation Manual