JL Audio A2150 Input Section, Input Voltage Range, Input Sensitivity Control, Filter Controls

INPUT SECTION

The A2150’s input section allows you to send signal to the amplifier section through the use of two differential-balanced inputs, one for the left channel and one for the right channel. Connection is via RCA-type jacks.

Input Voltage Range:

A wide range of signal input voltages can be accommodated by the A2150’s input section (200mV – 8V). This wide range is split up into two sub-ranges, accessible via a switch located to the left of the Input Connectors.

The “Low” position on the “Input Voltage” switch selects an input sensitivity range between 200mV and 2V. This means that the “Input Sens.” rotary control will operate within that voltage window. If you are using an aftermarket source unit or an OEM interface processor with conventional preamp-level outputs, this is most likely the position that you will use.

The “High” position on the “Input Voltage” switch selects an input sensitivity range between 800mV and 8V. This is useful for certain high- output preamp level signals as well as speaker- level output from source units and

small amplifiers.

To use speaker-level sources, splice the speaker output wires of the source unit or small amplifier onto a pair of RCA plugs. No line output converter is needed in most cases.

The output of the amplifier will decrease for a given input voltage when the “Input Range” switch is placed in the “High” position.

Conversely, the output will be higher with the switch in the “Low” position. While this may sound counter-intuitive, it is consistent with the descriptions above.

INPUT SENSITIVITY CONTROL

Once the appropriate “Input Voltage” range has been selected, the control labeled “Input Sens.” located in the “Amplifier Controls” section can be used to match the source unit’s output voltage to the input stage of the amplifier for maximum clean output. Rotating the control clockwise will result in higher sensitivity (louder for a given input voltage). Rotating the control counter-clockwise will result in lower sensitivity (quieter for a given input voltage.)

To properly set the amplifier for maximum clean output, please refer to Appendix A (page

12)in this manual. After using this procedure, you can then adjust any or all “Input Sens.” levels downward if this is required to achieve the desired system balance.

Do not increase any “Input Sens.” setting for any channel(s) of any amplifier in the system beyond the maximum level established during the procedure outlined in Appendix A (page

12). Doing so will result in audible distortion and possible speaker damage.

FILTER CONTROLS

Most speakers are not designed to reproduce the full range of frequencies audible by the human ear. For this reason, most speaker systems are comprised of multiple speakers, each dedicated to reproducing a specific frequency range. Filters are used to select which frequency range is sent to each section of a speaker system. The division of frequency ranges to different speakers can be done with passive filters (coils and/or capacitors between the amplifier outputs and the speakers), which are acceptable and commonly used for filtering between mid- range speakers and tweeters. Filtering between subwoofer systems and satellite speaker systems is best done with active filters, which cut off frequency content at the input to the amplifier. Active filters are more stable than passive filters and do not introduce extraneous resistance, which can degrade subwoofer performance.

The active filter built into the A2150 can be used to eliminate potentially harmful and/or undesired frequencies from making their way through the amplifier sections to the speaker(s). This serves to improve tonal balance and to avoid distortion and possible speaker failure. Correct use of these filters can substantially increase the longevity and fidelity of your audio system.

1)“Filter Mode” Control: The A2150 employs a 12dB per octave filter which can be configured into one of two filter types or defeated completely by way of the three-position“Filter Mode” switch:

“Off”: Defeats the filter completely, allowing the full range of frequencies present at the inputs to feed the amplifier. This is useful

for systems utilizing outboard crossovers or requiring full-range reproduction from the A2150’s channels.

“LP” (Low-Pass):Configures the filter to attenuate frequencies above the selected filter frequency at a rate of 12dB per octave. This is useful for connection of subwoofer(s) to the A2150’s in a bi-amplified system.

“HP” (High-Pass):Configures the filter to attenuate frequencies below the selected filter frequency at a rate of 12dB per octave. This is useful for connection of component speakers to the A2150’s channels in a bi-amplified system.

2)“Filter Freq. (Hz)” The filter frequency markings surrounding this rotary control are for reference purposes and are generally accurate to within 1/3 octave or better. If you would like to select the filter cutoff frequency with a higher level of precision, consult the chart in Appendix B (page 13).

Tuning Hint: If you are using the A2150 to drive

asubwoofer system (“LP” mode), a component satellite speaker system (“HP” mode) or both, 80 Hz is a good baseline “Filter Freq. (Hz)” setting. After properly adjusting the “Input Sens.”, as outlined in Appendix A (page 12), you can fine tune the “Filter Freq. (Hz)” control to achieve the desired system frequency response.

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