Specifications

Operation Manual
Studio Reference I & II Professional Studio Amplifiers
page 32
This section provides detailed information about the amount of power
and current drawn from the AC mains by Studio Reference amplifiers
and the amount of heat produced under various conditions. The calcula-
tions presented here are intended to provide a realistic and reliable
depiction of the amplifiers. The following assumptions or approxima-
tions were made:
• The amplifier’s available channels are loaded, and full standard 1 kHz
power is being delivered.
• 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 307 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 estimated quiescent power draw of 90 watts is a maximum figure,
and assumes that the fan is running at high speed. The following equa-
tion converts power draw in watts to current draw in amperes:
The power factor of 0.83 is needed to compensate for the difference in
phase between the AC mains voltage and current. The following equa-
tion is used to calculate thermal dissipation:-
The constant 0.35 is inefficiency (1.00–0.65) and the factor 3.415 con-
verts watts to btu/hr. Thermal dissipation in btu is divided by the con-
stant 3.968 to get kcal. If you plan to measure output power under real-
world conditions, the following equation may also be helpful:
8 AC Power Draw and
Thermal Dissipation