RIGHT, FRONT LEFT, REAR RIGHT and REAR LEFT. The Gain Controls provide a wide adjustment range to accommodate output levels from any brand of source unit.
•Gain Controls - Seperate Front and Rear Gain Controls allow you to set the nominal operating level of the amplifier. The amplifier’s range, 250mV to 2.5V for RCA inputs or 500mV to 5V for speaker level inputs, can accommodate input levels from virtually any brand of source unit.
•Bass Boost Control - The amplifier also features a “high-Q” (i.e. narrow frequency band) Bass Boost circuit. It acts much like an equalizer, with adjustable gain (from 0 to +18dB) fixed at 45Hz. Use this feature 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 Bass Boost is undesired, set Bass Boost to 0dB.
High-pass/Low-pass Filter Controls
•Freq (Hz) Controls - The front crossover frequency is fully adjustable between 55Hz and 550Hz. The rear crossover frequency is fully adjustable between 55Hz and 5500Hz (via the Rear Crossover Frequency Multiplier) for a wide range of crossover points. Use this feature, along with your speaker manufacturer’s recommended crossover frequencies, to quickly design a more advanced system (see Applications on page 6.) NOTE: If either of the X-Over Mode Switches is set to OFF, varying the Freq (Hz) Control will produce no effect.
•Rear X-Over Frequency Multiplier Switch - When engaged, this switch increases the crossover frequency of the rear channels by a factor of 10. Example: If the Freq (Hz) dial is set for 240Hz, pushing in the multiplier Switch changes the setting to 2400Hz.
•X-Over Mode Switches - These switches are equipped with 12dB per octave electronic filters for precise frequency attenuation with minimal phase distortion. The steep crossover slopes keep midrange tones out of the subwoofer and thereby eliminating an unnatural “nasal” tone quality in the audio system. Each filter is activated by sliding the X-Over Mode Switch to either LP or HP.
•Input Mode Switches - These switches allow you to set the input mode for front and rear channels. Stereo input allows full left and right stereo operation. Right (bridged) input allows single channel input for bridged operation. This is especially useful in high-powered systems when using the APX400.4M as a bridged 2 channel amplifier. L + R (sum mono) allows a stereo input to be summed into a mono output.
