QSC Audio ISA 500T - Manual (Page 24)

CONNECTIONS:
POWER SHARING BETWEEN HIGH & LOW IMPEDANCE OUTPUTS
The ISA 300T, ISA 500T and ISA 800T models are equipped
with autotransformer-coupled, high impedance (High-Z)
outputs. They are also equipped with low impedance (Low-
Z) “direct” outputs. The high impedance outputs are not
isolated.
The unique feature of the “T” model outputs is that you can
connect loads to the high impedance AND low impedance
outputs for maximum system flexibility. If the total output
power of a channel’s high impedance connections does not
exceed 20% of maximum rated power, then any of the rated
low impedance load values can be connected at the low
impedance terminals. For applications where the high
impedance output power is 20-50%, then 8 or 16 ohm
loads on the low impedance output is OK. If the high
impedance output power is 50 to 80% of rated power, then
16 ohm loads are OK. If the total output of a channel’s high
impedance connections exceeds 80% of that channel’s
maximum rated power, then DO NOT USE the low imped-
ance outputs. The following chart is a useful guideline:
Power sharing between “Direct” (Lo-Z) and “Distributed” (Hi-Z)
Outputs: Acceptable Low-Z loads as a function of High-Z output
power. NOTE! “Caution” advisory means that this load impedance
may be suitable for low power or low duty cycle applications.
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