MPA685 Owner’s Manual
3/2012
12
Attenuation / Gain Relative to Step Position "0"
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0
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Stepped Switch Position
R
e
la
ti
v
e
A
tt
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u
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n or
Ga
in (
d
B
)
Attenuation / Gain Relative to Step Position "0"
Gain Mode
Attn Mode
0dB = Reference
65dB Total
Adjustment
Range
Figure 1: Attenuation or Gain vs. Stepped Switch Position
6. Overload LED
The Overload LED is designed to illuminate at ~1% THD. The Overload detection
circuitry accurately tracks the 1% THD threshold to frequencies higher than 30kHz.
If the input stepped switch is adjusted one step below the setting that occasionally lights
the Overload LED, minimum 2dB of headroom before ~1% distortion occurs, and
dynamic range is maximized. If higher headroom is desired, the input stepped switch
may be adjusted lower.
The Overload circuit senses the audio before the High Pass Filter, so the High Pass
Filter setting has no effect on the distortion indication.
