The output of the amplifier decreases for a given input voltage when the “Input Range” switch is placed in the “High” position. The output increases with the switch in the “Low” position. While this may sound counter- intuitive, it is correct as described.
CHANNEL CONTROL SECTIONS
To the left of the “General Setup” section on the Control Panel of the amplifer are three sets of controls: one for the “Rear Channel Controls” one for the “Front Channel Controls” and
one for the “Subwoofer Channel Controls”.
In each of these sections you will find a rotary control labeled “Input Sens.” (Input Sensitivity). These controls are designed to match the input sensitivity of each channel section of the HD900/5 to the specific signal source that
is feeding the amplifier. These controls must be adjusted, with care, following the procedures outlined in this manual. Failure to make correct adjustments can result in weak output, excessive distortion and/or undesirable noise in the audio output of the amplifier!
Note: The Channel Control sections also house
“Input Sens.” Controls
Once the appropriate “Input Voltage” range has been selected in the “General Setup” section of the amplifier, the “Input Sens.” controls are used to match the source unit’s output voltage to the input stage of each pair of amplifier channels
for maximum clean output. Rotating the control clockwise will result in higher sensitivity (louder for a given input voltage). Rotating the control
After using this procedure, you can then adjust the relative level of each channel pair by adjusting the input sensitivity downward on any of the channel sections, if they require attenuation to achieve the desired system balance.
Do not increase the “Input Sens.” setting for any amplifier or channel section in the system beyond the maximum level established during the procedure outlined in Appendix C (pages 18, 19). Doing so will result in audible distortion and possible speaker damage.
Be aware that all three “Input Sens.” adjustments will need to be made, regardless of how many input cables are feeding the amplifier. These controls will allow you to set the appropriate relative levels for the “Front” channels relative to the “Rear” channels and the “Sub” channel (and any other amplifier channels in the system).
CROSSOVER CONTROLS
Crossovers are groups of electronic filters designed to control the frequency ranges that each speaker in a system will be tasked with reproducing. Proper crossover setup is critical to sound quality and reliability.
The HD900/5 has three individually adjustable filter controls, one for the “Front” channels, one for the “Rear” channels and another for the “Sub” channel. The “Front” and “Rear” filters are
10 JL Audio - HD900/5 Owner’s Manual
