Efficient power for your music always set correctly
JBL's compact GTO-504EZ 4-channel amp will drive each of your front and rear speakers with 50 watts RMS, bringing exciting, visceral impact to the music in your car. Or, bridged in 2-channel mode, it can run a couple of subs with up to 150 watts each. This amp looks very cool with its "old-school" styling, and JBL includes a few innovations that really separate this amp from the others.

Simple Setup System for setting amp gain
One of the biggest problems with installing an amplifier is setting the gain properly. JBL has come up with a fool-proof method for getting it right, ensuring full-power performance and distortion-free play. Using test tones on the included setup CD, you adjust the gain knob until the yellow light or the red light goes off, and the green "Gain OK" light comes on — it's that simple. You'll never have to worry again about your amp "clipping" the signal, and possibly damaging your speakers or subs.

Plays well with factory radios
This GTO amp comes with screw-on bare wire-to-RCA adapters that let you hook up the amp, using your car's factory speaker wiring to supply the input signal. In some vehicles, the factory radio shuts down when you try to tap into the speaker wires, displaying a "no speakers are present" message. This amp features a special circuit that fools those factory radios by simulating a speaker load. The onboard crossovers and bass boost let you fine tune the system to perfection, and the large recessed knobs mean you don't need a tiny screwdriver to make your adjustments.

GTO-504EZ input panel

Product Highlights:

  • 4-channel car amplifier
  • 50 watts RMS x 4 at 4 ohms (75 watts RMS x 4 at 2 ohms)
  • 150 watts RMS x 2 bridged at 4 ohms (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • frequency response: 20-23,000 Hz
  • Class AB amp technology
  • variable low- and high pass filters (40-220 Hz, 12 dB/octave)
  • variable bass boost on rear channels (0-12 dB at 45 Hz)
  • Simple Setup System with test tone CD for perfect gain setting
  • routing switch for 2-channel sources
  • preamp outputs
  • preamp and speaker-level inputs (speaker wire-to-RCA adapters included)
  • switchable automatic signal-sensing turns on amp without need for remote lead
  • fuse rating: 20A x 2
  • 10-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 8-7/16"W x 2-5/8"H x 9-11/16"D
  • warranty: 1 year
  • Our 60-day money-back guarantee

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Two 20-amp ATO fuses (installed)
  • 4 Speaker wire to RCA adapters
  • Setup CD
  • Warranty information
  • Owner's manual (English/ German/ French/ Spanish/ Dutch/ Italian/ Swedish/ Danish/ Finnish/ Korean/ Japanese/ Chinese/ Russian/ Polish/ Portuguese/ Turkish/ Indonesian)

Product Research

Features
Controls
Connections

Features

Multi-Channel Design: The JBL GTO-504EZ is a 4-channel amplifier, basically two independent 2-channel amplifiers built into one chassis. Either half can be bridged so it can be used as a 4-channel, 3-channel, or 2-channel amplifier. The amplifier is stable to 2-ohms in stereo, and 4-ohms when bridged.

CEA 2006 Compliant: The power ratings are measured according to the Consumer Electronics Association CEA-2006 standards. These standards allow you to accurately compare the rated power output of all CEA 2006-compliant amplifiers, even different brands. Manufacturers who adhere to the standards can display the CEA 2006 logo on their products and packaging. The power output is measured from 20 Hz to 20 kHz, using a 14.4 volt power supply, and with no more than 1% THD+N:

  • 4-Channel (4-ohm): 50 watts x 4-channels into 4-ohms
  • 4-Channel (2-ohm): 75 watts x 4-channels into 2-ohms (2-ohms minimum)
  • 2-Channel (Bridged): 150 watts x 2-channels into 4-ohms (4-ohms minimum)

Setup Disc: The included setup CD is used to optimize the input gain. A test tone is output from the disc and the Gain LEDs on the amp (green, yellow, red) guide you through adjusting the gain controls.

Note: The instructions in the first version of the manual indicate the radio should be at full volume when playing the setup disc; this is wrong and JBL is in the process of correcting the manual. The volume should actually be as high as possible without distorting the signal; this will be different for every radio, but approximately 3/4 volume is typical.

Auto Turn-on: The GTO-504EZ has a signal sensing automatic turn-on circuit; it will turn on whenever an audio signal is present at any of the RCA inputs. The amplifier will automatically turn off approximately five minutes after the input signal ceases. If you prefer to use the radio's remote lead, the auto turn-on feature can be turned off.

Crossovers: There are independent crossovers for the front and rear channels built-in. Each crossover can be set to high-pass, low-pass, or full range (bypassed). The crossover points are continuously variable from 40 Hz to 220 Hz and adjusted independently. The slope of both crossovers is 12 dB/octave.

Audio Input: If your radio has no line-level outputs, use the included adapters to convert the speaker wires to RCA and plug them into the amplifier's inputs. The input level switch has a Hi2 position, used to present a speaker load to factory radios equipped with a circuit that turns the radio off when an amp is connected.

Line Level Output: The amplifier has a pair of RCA line level outputs to feed a full-range stereo signal to another amplifier. The GTO-504EZ's crossovers have no effect on the line output signal.

Routing Switch: The signal for the front and rear amplifier channels can be supplied from the separate front and rear inputs (two pair of stereo RCAs), or from just the front channel inputs (stereo RCAs). Set the switch to F&R (front and rear) or F (front).

Bass Boost: A bass boost circuit, centered at 45 Hz, can be applied to the rear channels. The boost is variable from zero to +12 dB. JBL recommends only using bass boost when the rear channels are bridged to power a subwoofer.

Controls

Top:

  • Front channels:
    • Crossover selector: three position switch; high-pass, full range, low-pass
    • Crossover Frequency: rotary knob; continuously variable from 40 Hz to 220 Hz
    • Input Gain: rotary knob (the gain LEDs are above the knob)
  • Rear channels:
    • Crossover selector: three position switch; high-pass, full range, low-pass
    • Crossover Frequency: rotary knob; continuously variable from 40 Hz to 220 Hz
    • Input Gain: rotary knob (the gain LEDs are above the knob)
    • Bass Boost: rotary knob; continuously variable from 0 to +12 dB; boost centered at 45 Hz

Right Side:

  • Input Level: three position switch; Low, Hi1, or Hi2 (used only with factory radios having a circuit that turns the radio off when it sees no speaker load)
  • Routing Switch: F (front)/F&R (front and rear)
  • Gain LEDs: on/off

Bottom:

  • Auto Turn-on: on/off

Connections

Left Side:

  • Power and Ground Terminals: set screw terminals; accept up to 4 gauge bare wire
    • Note: JBL recommends the power and ground cables be 10 gauge minimum. The recommended accessory list for the GTO-504EZ includes wiring kits with 10 gauge wire and either a 25 or 30 amp fuse, but the amp has two 20 amp fuses (40 amps total), so if one of these kits is used a replacement fuse must also be added (at least 40 amps). If an 8 gauge wiring kit is used no additional fuse is necessary.
  • Remote Turn-on Terminal: set screw terminal; accepts up to 8 gauge bare wire
  • Speaker terminal: four pair of set screw terminals (for front left, front right, rear left, and rear right); accept up to 8 gauge bare wire
  • Fuses: two ports for 20-amp ATO fuses (fuses are factory installed)

Right Side:

  • Audio Input: four female RCA jacks (front left, front right, rear left, and rear right); compatible with speaker level signals using the included adapters
  • Audio Output: two female RCA jacks (left and right)

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

JBL GTO-504EZ Reviews

Average Customer Review:

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JBL GTO-540 EZ

Written By Rich, McKinney, TX on Wednesday, September 17, 2014

I bought this amp for my jeep. Paired with OEM head unit, pair of JBL GTO 638 in sound bar, JBL GTO 608C components in the front & Sound Ordnance B-8PTD Powered 8" Subwoofer. System has incredible sound. Since I usually drive this Jeep on short trips & recently went on a 5 hour road trip when the amp went in to safe mode 30 minutes into the trip. Thinking that it was just overheated, I turned it off for about 30 minutes & tried it again. Well that got me about 45 seconds of music. 4.5 hours of no radio in a new jeep, with a new system. I have since checked out the install, with no issues. Called JBL and now have to send it back, on my dime, & wait until they send me a new one. I like the amp, when it works. Hopefully my new amp will arrive before winter. I called Crutchfield Tech Support and the tech was very professional and suggested a warranty replacement. The install was pretty straight forward. The speaker wire to RCA connectors are poorly designed like other reviews have noted. It helps if you can solder the speaker wire prior to using the adapters. Using the line out for the powered sub, I did have trouble with loosing the sub when fading from front to rear, (no bass) when all on front or all on rear. Tech could not figure that one out & I chalked it up as OEM head unit issues. As soon as my year of satellite radio is up, I'm getting a new head unit.

Pros: High/low input capable, great sound, low profile, cross over gain adjustments with CD, ability to turn off peak LEDs.

Cons: Safe Mode! Over sensitive. Heats up fast, and then shuts off.

Great Amp, Well designed

Written By Stubb, San Diego, CA on Friday, January 31, 2014

I think this is a really great piece of equipment. The size is compact and it is built solid. Connections are easy to make. Even though there are only RCA connectors on the side, the amp takes both Hi and Low level inputs and includes bare-wire to RCA adapters. There are two versions of the hi input, one that provides resistance for OEM systems that will shutoff with no speaker detected. It also has a wide range of input sensitivity, from 0.9 to 15V. I hooked it up both at speaker level after my stock amp and with a LOC that bypassed my OEM amp. Sound quality was much better bypassing the factory amp, but is was pretty good both ways so I would try it first before buying a converter. I didn't realize how much my OEM amp was probably clipping or distorting until I heard the clarity and detail from this. Amps make a difference so choose wisely. For setting crossovers, I used an RTA to set and check my setup and the markings were right on. Much better than others that only show the high and low, this amp has markings across the range so you can adjust with confidence. The layout makes it easy to set up and adjust as needed. The included CD is useful for setting the gains, but I must admit, it left the volume so high that I had to switch from Low to Hi (my inputs are 5V) to adjust so that I had a useable minimum volume. But then I needed only small adjustments for balance. I am using this in combination with the GTO3EZ for 6 speakers and a sub.

Pros: Great layout for adjustments Accurate and useful crossover markings Compact size and design Flexible Configuration

Nothing EZ About This Amp

Written By David, Atlanta, GA on Tuesday, November 19, 2013

I can't say that I would describe this amp as easy to install, unless you are using it with RCA inputs and a remote turn-on wire. First, the adapters for using speaker-level inputs are extremely tedious to attach to the speaker wire. If you strip 1/16" too much then the wire sticks out far enough that it could touch the other wire. 1/16" too little and the screw won't have a good hold on the wire. And the screws are INCREDIBLY easy to strip, even using the correct size detail Philips head screwdriver (not included). Second, the turn-on delay is surprisingly long. I have two pairs of speakers attached to the factory radio's leads, and they begin playing at least three seconds before the amplified woofers. When added to the factory stereo's initial signal delay, it takes over ten seconds before music plays when the car is turned on. That might not sound like too long on paper, but feels like an eternity when you experience it, and makes an otherwise quality stereo upgrade feel very cheap and aftermarket.

Third, there is an RCA output for sending a combined signal that does not decrease when the source is faded to the front or back, but this is a LINE-LEVEL output (not a passthrough of speaker-level inputs), so it will not trigger another amp's auto-sensing power on feature. Even worse, the remote lead also does not ouput a signal to turn on a second amp by remote wire as other amps do, so there is absolutely nothing easy about using this amp with a powered sub

Pros: Compact size, good power

Cons: Auto-on delay, quality of RCA adapters, lack of switched remote lead or speaker-level output.

Amazing

Written By Michael, Missoula, MT on Friday, December 14, 2012

I Bought this amp almost a year ago, and scene then had no problems or complaints with it. This amp has a bunch of clear punchy power. I had the amp hooked up to some Walmart Pioneer TS-G1643R 61/2"s in the front door but since then have upgraded to Sound Ordnance P-65C Component speakers, the rears are some Walmart Scosche 6x9 speakers that are in Sound Ordinance's Bass Bunker Boxes. The amp's power still continues to amaze me after all this time. As for the design of the amp, the install was easy, i did notice a delay when turning on, (remote wire) which causes the Sub (S.O. B-8P) to make a pop but it is not something to serious. you will want a good quality receiver (not stock) and preferably with a 7band EQ to really get the best sound out of the amp.

Pros: Easy install, looks good, hides wire connections nicely, Amazing power output, Great clear quality sound, Simple gain setup and well built internal cross overs.

Cons: -The EZ gain adjuster system is not perfected because it does not check if the deck is distorting, which makes it somewhat usless unless you only turn it up 3/4 volume as suggested by JBL. -Remote turn (via Remote wire) on is delayed

Great amp

Written By Jay, Florida on Thursday, March 15, 2012

Crutchfield Customer Review (What's this?)

This amp sounds great, clean and clear. easy hook up, simple set-up with screw-in hold connectors, compared to the other screw in connectors where u can loose the screws, good quality build. Great Idea for the uses of the knob design to tweak the sound, instead of the old school design where you need a mini flat head screw-driver . I would of gave this amp 5 stars but the automatic turn on by way of RCA had a delay and the amp would turn off if the music is to low which got annoying, but there is a setting to change the sensitivity, but I didnt bother so I hooked up the Lead wire(turn on). O yea and Great price $$$ worth every Dollar

Pros: clear and clean sound, simple to hook-up connectors. Prices

Cons: Automatic turn with RCA may has delay to turn on

Get everything you’ll need to enjoy your new JBL GTO-504EZ

Bring the music from your amp to your speakers.
Patch cables take the music from your stereo to the amplifier. Most amp wiring kits don't include them.
For multi-amp systems, you'll need a separate fuse holder.
Helps protect your car's charging system and improves power handling. Required power and ground wires not included with cap.
The right tools will make the installation easier.
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