Bose E4 manual Input gain setup sequence, Input gain controls

6.0 E4 System Setup

Input gain setup sequence

1.Set Opti-source®to Off. This allows you make the initial gain setting.

2.Select the source Type and determine if Mic Power +12V is needed. Set Mic Power to On if required. Leave it in the Off setting if you are using line inputs.

3.Start your input source and monitor its signal on the gain signal level meter. If the level is green, go to step 4. If the level is yellow, increase the input gain until the level is green. Likewise, if the level is red, reduce the input gain until the level is green.

Programmer’s Note: You may have to repeat step 3 a few times if the input source is a CD player. The output level of a CD player varies based on the program material.

4.Set Opti-sourceto On. If you are using a source that produces a varying output level due to program material, such as a CD player, Opti-source leveling will compensate for these variances. If your system will be switching among multiple sources, Opti-source leveling will compensate for variances among the different sources.

5.Repeat steps 1 to 4 for the remaining system inputs.

When you turn Opti-source on, you should only hear a small change in volume. If you hear a large increase, raise the input gain. Likewise, if you hear a large decrease, lower the input gain.

Input gain controls

Type – This setting determines the initial gain and amount of gain available for the input signal. The following table lists the choices for each input line.

Input Line	Input Type(s) Selection	Initial Gain
LINE 1	Line	0
LINE 2	Line	0
AUX MIC/	Line (default)	0
LINE 3	Mic	40
PAGE/MIC/	Line	0
LINE 4	Mic	40
	Line Page	0
	Mic Page (default)	40

Mic power +12V – This setting enables/disables +12V phantom power only for inputs 3 and 4, which are capable of accepting microphone signals. This power source is used for condenser type microphones.

Gain slider – Click and drag the gain slider up/down to set the input gain. Changes in the slider's position are continuously sent to the E4 hardware so you will hear the change in gain as it is applied and see the change in the signal level on the meter. The gain range is dependent on the Type setting: 80 dB for Mic; 70 dB for Line.

Programmer’s Note: When setting up the system, adjust the input gain slider until the meter is green. Occasional flashes of red are acceptable.

Input gain meter – The input gain meter indicates the average input signal level of the hardware. The meter is divided into three color segments:

Amber = Low signal level

Green = Good signal level

Red = High signal level

Signal present indicator – The signal present indicator tells you if a signal is being received by the hardware:

Inactive = No signal

Green = Good signal

Red = Signal clipping

Opti-source– This is the on/off control for this function. When on, Opti-source leveling automatically manages the input gain level so that the full output of the amplifier can be achieved. It does this by adjusting the input signal level to obtain the desired amplifier input signal level (+11 dBV). When setting the initial input gain level, check to make sure that Opti-source is Off. If you do not see this setting in the control pane, click on More to dis- play the Opti-source On/Off boxes.

Programmer’s Note: The Opti-source state cannot be changed when the Opti-voice®paging system is on.

The following chart shows how Opti-source leveling operates. For sources whose average input signal level is less than –20 dBV, Opti-source leveling will add 20 dB of gain. For sources whose average signal level is between –20 and 0 dBV, Opti- source leveling will add the necessary gain so that the average output of the Opti-source function is +11 dBV. Sources whose average level is greater than 0 dBV will have gain reduction applied so that they maintain an average of +11 dBV at the Opti- source leveling output.

25
17
9
Gain (dB)
-1
Compression (dB)
-7
-15
-30 -25 -20 -18 -15 -13 -10 -8	-5	-3	0	3	5	8	10 13 15 18

Input Signal Level (dBV)

Input signals from –20 to 0 dBV fall within the ideal operating range for the Opti-source leveling function. This is reflected in the color scale used for the input gain signal level meter. If your input signal level is within the green area of –20 to 0 dBV, Opti-source leveling will effectively manage the input source level.

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