INSTALLATION AND SETUP

SETTING THE

CROSSOVER(S)

Determine your system plans and set the crossover mode switch accordingly. If you plan to use the GTO75.2 II or GTO75.4 II to drive full-range speakers, set the crossover mode to FLAT and skip to “Setting Input Sensitivity.”

Initially set the crossover frequency control midway. While listening to music, adjust the crossover for the least perceived distortion from the speakers, allowing them to reproduce as much bass as possible.

Systems using a separate subwoofer set the crossover mode to HP (high pass) for your full-range speakers. Adjust the crossover frequency to limit bass and provide increased system volume with less distortion.

For subwoofers, choose the highest frequency that removes vocal information from the sound of the subwoofer.

If using the GTO75.2 II or GTO75.4 II to drive a subwoofer(s), set the crossover mode to LP (low pass).

NOTE: The GTO301.1II, GTO601.1II, GTO1201.1II and the subwoofer output of the GTO755.6 II are low-pass only and do not have a crossover mode switch.

SETTING INPUT

SENSITIVITY

1.Initially turn the INPUT LEVEL control(s) to minimum (counter clockwise).

2.Reconnect the (–) negative lead to the vehicle’s battery. Apply power to the audio system and play a dynamic music track.

3.On the source unit, increase the volume control to 3/4 volume. Slowly increase the INPUT LEVEL control(s) toward three o’clock until you hear slight distortion in the music. Then reduce the INPUT LEVEL slightly until distortion is no longer heard.

NOTE: After the source unit is on, red LEDs (on the top panel) will light, indicating the amplifier is on. If not, check the wiring, especially the remote connection from the source unit. Also refer to “Troubleshooting” on the next page.

Figure 12. Control end panel.

REMOTE LEVEL CONTROL The GTO755.6 II and all three GTO subwoofer amplifiers have inputs for an optional remote level control (RLC). This will allow the amplifier’s input level to be adjusted from the listening position. Connect the optional remote level control using the RJ-11 jack on the side of the amplifier. Install the control module in the front of the vehicle within easy reach of the driver. Under the dash or in the center console are both suitable locations.

SETTING THE BASS BOOST The GTO755.6 II, GTO301.1II, GTO601.1II and GTO1201.1II are all equipped with a bass- boost control. This allows you to adjust the bass output of your system at 50Hz up to 12dB and enhance low frequency.

AUX OUTPUT

GTO amplifiers (except GTO755.6 II) are equipped with full-range outputs that can be used to connect additional amplifiers.

NOTE: When using the high-level inputs, the AUX outputs can be used to pass a line-level signal to another amplifier.

INSTALLING NEON TUBES (OPTIONAL)

1.Using a Phillips screwdriver, remove all screws on the amplifier’s output/power end panel and set them aside.

2.Using a 3 ⁄32-inch Allen wrench, remove only the screws on the amplifier’s (top) clear cover and set them aside.

3.Remove the end panel and slide the cover off. Set both parts aside.

4.Locate the enclosed hardware bag and remove the four clips. Each clip has a square end and a larger round end. Using a round end, press two clips onto each neon tube (e.g., Street Glow AN9 or equivalent), as shown in Figure 13.

5.For each tube, align both clips so the square ends slide onto an exposed extrusion edge, as shown in Figure 9. Do not cover any screw holes. When installed correctly, each neon tube will sit under an extrusion and not be visible when viewed from directly above.

6.Route each neon tube’s power cable through its respective NEON hole on the end panel (see Figure 13).

7.Slide the cover back into place and re- install its screws. Then, replace the end panel and reinstall its screws.

8.Finish the installation of the neon tubes as instructed in their owner’s manual.

GTO75.2 II

GTO75.4 II

GTO301.1II, GTO601.1II, GTO1201.1II

GTO75.6 II

6

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JBL gto755.6 II, gto75.2 II, gto75.4 II Installation and Setup, Setting Crossovers, Setting Input Sensitivity, AUX Output
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gto1201.1 II, gto301.1 II, gto75.4 II, gto75.2 II, gto755.6 II specifications

JBL, a brand synonymous with high-quality audio solutions, offers a range of amplifiers that cater to both casual listeners and audiophiles alike. Among their renowned products are the JBL GTO601.1 II, GTO75.4 II, GTO301.1 II, GTO75.2 II, and GTO755.6 II amplifiers. Each model embodies JBL's commitment to delivering powerful performance, refined sound quality, and advanced technologies.

The JBL GTO601.1 II is a mono subwoofer amplifier that boasts an impressive output of 600 watts RMS. This model features a unique Pulse Width Modulation (PWM) technology that provides high efficiency for maximum power delivery while promoting thermal stability. Ideal for driving large subwoofers, the GTO601.1 II is equipped with an adjustable low-pass filter, bass boost, and adjustable input sensitivity, allowing users to tailor the sound to their preferences.

The GTO75.4 II is a versatile 4-channel amplifier designed for both clarity and power. It outputs 75 watts RMS per channel at 4 ohms, enabling it to drive multiple speakers with ease. The High-Level Inputs with Auto Turn-On make installation straightforward, while the built-in crossover allows for precise control over the frequency ranges directed to each speaker. This model is ideal for those looking to upgrade their car’s audio system without sacrificing sound quality.

For those seeking a reliable and powerful mono amplifier, the GTO301.1 II offers a robust 300 watts RMS, perfect for driving subwoofers. Featuring a compact design, it blends seamlessly into varied setups while providing minimal distortion and maximum clarity thanks to its MOSFET power supply. The GTO301.1 II supports adjustable low-pass and bass boost features, ensuring every bass note is felt as much as heard.

In the 2-channel category, the GTO75.2 II stands out with its 75 watts RMS per channel output. This model combines lightweight design with high efficiency, making it suitable for powering speakers in both cars and boats. It features a built-in crossover and is engineered to minimize noise and distortion, delivering precise sound with rich overtones.

Finally, there's the GTO755.6 II, a 6-channel amplifier that provides flexibility and power, outputting 75 watts RMS per channel at 4 ohms. This model is perfect for larger audio systems requiring multiple speaker connections. Its Class D topology ensures high efficiency and low heat generation, making it a reliable choice for extended listening sessions. Additionally, the GTO755.6 II includes a variable high/low-pass crossover, allowing fine-tuning of sound for any setup.

Each of these amplifiers from JBL reflects the brand's dedication to quality and performance, ensuring that users can experience their music with the depth and intensity it deserves. Whether it's for daily listening or full-fledged audiophile setups, JBL's GTO series amplifiers set the standard in automotive audio.
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