JL Audio 505 12

APPENDIX B:

Input Sensitivity Level Setting

JL Audio amplifiers utilizing the Regulated Intelligent Power Supply (R.I.P.S.) allow delivery of their rated power when connected to any load impedance from 1.5 - 4Ω per channel (3 - 8Ω bridged) and when connected to a charging system with any voltage from 11 - 14.5V. This design is beneficial for many reasons. One of these reasons is ease of setup. Because each JL Audio amplifier will always deliver the same amount of power within its operational range of impedances and supply voltages, the maximum, unclipped output is very predictable.This makes setting the gain structure via the input sensitivity controls very simple. Following the directions below will allow the user to adjust the input sensitivity of the amplifier(s) simply and easily in just a few minutes using equipment which is commonly available in installation bays.

Necessary Equipment

•Digital AC Voltmeter

•CD with a sine-wave test tone recorded at 0 dB reference level in the frequency range to be amplified for that set of channels (50 Hz for subwoofer channels, 1 kHz for a midrange application). Do not use attenuated test tones (-10 dB, -20 dB, etc.).

The Nine-Step Procedure

(follow this procedure for each set of channels)

1)Disconnect the speaker(s) from the amplifier’s “Front”, “Rear” and “Subwoofer Output” connectors.

2)Turn “Off” all processing on the source unit and amplifier (bass/treble, loudness, EQ, etc.).

3)In all three input sections, switch the “Input Voltage” to “Low” and turn the “Input Sens.”

control all the way down (counterclockwise).

4)Set the source unit volume to 3/4 of full volume. If either set of channels is being driven by a source unit’s dedicated subwoofer output, also adjust the source unit’s subwoofer level control to 3/4 of maximum output.This will allow for reasonable gain overlap with moderate clipping at full volume.

5)Using the chart below, determine the target voltage for input sensitivity adjustment according to the nominal impedance of the speaker system connected to each set of outputs.

6)Verify that you have disconnected the speakers before proceeding. Play a track with an appropriate sine wave (within the frequency range to be amplified by the set of channels being adjusted) at 3/4 source unit volume.

7)Connect the AC voltmeter to the “Speaker Outputs” or “Subwoofer Output” connectors of the channel set that you are adjusting. For the stereo channels, it is only necessary to measure one channel. If bridged, make sure you test the voltage at the correct connectors (L+ and R–).

8)Increase the “Input Sens.” control until the target voltage is delivered for that set of channels. If excessive voltage is read on either set of channels with the control at minimum (full counterclockwise), switch the appropriate “Input Voltage” switch to

“High” and re-adjust.

9)Once you have adjusted each set of channels to its maximum unclipped output level, reconnect the speaker(s).The “Input Sens.”

controls can now be adjusted downward if any channels require attenuation to achieve the desired system balance.

! IMPORTANT

Do not increase any “Input Sens.” setting in the system beyond the maximum level established during this procedure. Doing so will result in audible distortion and possible speaker damage.

It will be necessary to re-adjust the “Input Sens.” for the affected channels if any equalizer boost is activated after setting the “Input Sens.”

	FRONT CH.			REAR CH.		SUB CH.
Nom. Imp.	Stereo	Bridged	Stereo		Bridged	Mono
8Ω	20.0 V	40.0 V	10.0 V		20.0 V	31.6 V
6Ω	20.0 V	34.6 V	10.0 V		17.4 V	31.6 V
4Ω	20.0 V	28.4 V	10.0 V		not recommended	31.6 V
3Ω	17.3 V	24.6 V	8.7 V		not recommended	27.4 V
2Ω	14.2 V	not recommended	not recommended		not recommended	22.4 V
1.5Ω	12.3 V	not recommended	not recommended		not recommended	19.4 V

with this procedure.This applies to any EQ boost circuit, including the amplifier’s “Bass EQ” and source unit tone controls or EQ circuits. EQ cuts will not require re-adjustment.

JL AUDIO 500/5