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APX2120/APX4240/APX1300 7
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4. OPERATIONS
Setting the operating level
The gain controls allow you to set the nominal operating level of the amplifier from
250mV to 2.5V for RCA inputs or 500mV to 5V for speaker level inputs. This wide
adjustment range accommodates virtually any source unit brand.
Improving bass sound
The amplifiers feature a narrow-frequency band bass boost circuit (known as “high-Q”).
The bass boost control acts much like an equalizer with switchable gain fixed at 45Hz.
Use this control to tune low-frequency audio response to compensate for a less than
ideal subwoofer enclosure design. The added boost produces rich, full bass tones that
are normally difficult to reproduce in the car audio environment.
Note:
If you don’t want to boost the bass frequencies, set this control to “OFF.”
Designing a more advanced system
Freq (Hz) controls
The crossover frequency is fully adjustable between 50Hz and 300Hz. Use the high-
pass/low-pass filter controls, along with your speaker manufacturer’s recommended
crossover frequencies, to quickly design a more advanced system.
Note:
If you set either of the X-Over mode switches “OFF,” varying the Freq (Hz)
control has no effect.
X-Over mode switches
These switches are equipped with 12dB per octave electronic filters for precise
frequency attenuation with minimal phase distortion. To activate each filter, slide the
X-Over mode switch to either HP or LP (APX4240 and APX2120 only).
Connecting a source unit without RCA outputs
The speaker level inputs provide connections for a high-level stereo source. Use them if
your source unit does not have RCA outputs.
AMPSOwnersManual.pmd 2005-12-13, 17:027