JBL GTQ360, GTQ240 owner manual Adjusting the Gain, Typical Applications

To change the crossover frequency change the resistor network as follows:

1.Remove the screws from the bottom panel as shown below.

2.Select which resistor module, high pass or low pass, that you wish to change.

3.A chip puller, which can be obtained from any electronics store, is recom- mended to remove the resistor chip. Pull the resistor chip from the socket as shown in the figure below.

6. Adjusting the Gain

Before operating the GTQ amplifiers, recheck all wiring connections to make sure they are correct and secure. Be sure that a fuse (not included) is installed in the +12V line near the battery. Reconnect the negative ground (–) terminal of the bat- tery. Make sure that the mode switches, crossover switches, Group 2 Input switch- es, and crossover frequency modules are properly set.

• The setting of the gain controls on the

GTQ amplifiers is important to ensure

proper performance, low noise levels, and

maximum reliability in the system.

Using a high signal level from the source

and a low gain setting on the amplifier

will help keep background noise levels in

the system low.

7. Typical Applications

The following diagrams show the most common basic system configurations of the GTQ amps. One or more of these building blocks may be combined to form elaborate system designs.

The GTQ amps use the terminology “Group 1” and “Group 2” to indicate the two main signal paths within the amplifi- er. Each “group” may consist of a mono bridged signal or a stereo pair of L+R signals depending on the system configuration.

BEST-Vertical Mounting

AIR FLOW

GOOD-Horizontal Mounting

AIR FLOW

NEVER-Mount Upside Down

System 1

	.	CA
	NORTHRIDGE,JBLPC00108800REV
	JBLINC	GTS600	A
CROSSOVER	PASS
	LOW FILTERFREQUENCYSELECTIONMODULE
	C10
	C13
	PASS
	HIGH FILTERFREQUENCYSELECTIONMODULE

4. Place the new module in the socket

making sure all pins are lined up with the

socket holes. Press the module firmly into

• To adjust a system using a single GTQ

amplifier, start with both of the amplifier

gain controls fully counterclockwise. Set

all bass/treble or equalizer controls to

their centered or bypassed positions.

While listening carefully to the system

output, adjust the volume control of the

radio/tape deck to the point where you

first begin to hear audible distortion.

Use caution: excessive distortion can

damage loudspeakers. Reduce the level

just to the point where the distortion goes

Active 3-way using outboard tweeter amplifier

		Speaker	Preamp	Group
		Output	Output	2
	Mode	CrossoverCrossover		Input	X-over Frequency
GR 1	Stereo	Low	High	—	5k**
GR 2	Stereo	Low	High	GR 2	80Hz**

*A single (mono) subwoofer may be used by setting GR 2 mode to "L+R."

**The crossover frequencies listed are suggestions. Actual crossover points should be determined from loudspeaker requirements.

Input

Front

GR 1	GR 2	GR 2	GR 1
Pre Out	Input	Pre Out	Input

the socket.

5. Replace the bottom lid.

For further information on how to use the speaker output and preamp output crossovers for system building see the “Typical Applications” and “Add-On and

away. If this setting does not provide ade-

quate volume levels, gradually increase

(turn clockwise) the gain control for the

main (usually front) speaker groups on

the GTQ amplifier until the system plays

as loud as necessary or when the first

LOW-POWER

STEREO AMP

– +

L

+

R

–

GTQ AMP

GR 1 GR 2

–	+	–	+	+	–	+	–
L			R	L			R

Upgrade Steps” sections.

signs of distortion are heard.

Tweeters Midbass Subwoofers*

8