JBL CONCERT A704 amplifier
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JBL CONCERT A704
The JBL Concert A704 amplifier is a powerful 4-channel Class AB amplifier that represents an ideal solution for a complete upgrade of a car audio system. It offers clean, dynamic and musical sound with better control over speakers than a typical car head unit, while maintaining compact dimensions and an affordable price.
Thanks to universal wiring options, the amplifier can be used to power front and rear speakers or bridged for subwoofer use, where it will deliver significantly higher output. The amplifier provides 70 W RMS per channel at 4 Ω, making it an ideal choice for most coaxial and component speakers.
Class AB technology combines the advantages of Class A and B, offering high-quality, natural sound with low distortion, which will be appreciated by more demanding listeners.
The amplifier is equipped with adjustable crossovers (HPF/LPF in the 40 - 400 Hz range), allowing precise tuning of frequencies according to the specific installation. RCA and high-level inputs are standard, as well as an auto turn-on function, making it easy to connect to factory head units without complicated modifications. The JBL Concert A704 is an ideal choice for anyone who wants a powerful and reliable amplifier for a complete audio system with an excellent price-to-performance ratio.
Hlavní vlastnosti
- Four-channel Class AB amplifier for high-quality, natural sound.
- Power 4 × 70 W RMS at 4 Ω for driving speakers.
- Bridgeable to 2 × 180 W RMS at 4 Ω for a subwoofer.
- Stable operation at 2 Ω impedance (up to 90 W RMS per channel).
- Adjustable high-pass and low-pass filters for precise system tuning.
- RCA and high-level inputs for easy connection.
- Automatic turn-on on signal detection (auto turn-on).
- Compact construction suitable even for smaller installation spaces.
- Ideal solution for a complete car audio system upgrade.
O značce
The JBL brand has long been one of the most significant names in audio, and its products are synonymous with quality sound, reliability and modern technology. In the car audio segment it offers a wide portfolio of speakers, subwoofers and amplifiers that stand out with a dynamic presentation, high sensitivity and the characteristic "JBL sound", making them an ideal factory audio upgrade for any driver. JBL also holds a strong position in the portable Bluetooth speaker category, combining compact dimensions, durable constructions (often with IP67 certification) and long battery life with surprisingly powerful sound. Whether you’re looking for a better car audio solution or a reliable travel companion, JBL offers products that combine innovation, quality and great listening in every situation.
| Catalog number | CONCERT A704 |
| Brand | JBL |
| Links | Official web presentation |
| Energy class of the amplifierAmplifiers are divided into two basic classes: analog and digital . Analog amplifiers (A/B) have higher consumption requirements, but usually have a more natural sound. Digital amplifiers (D) have significantly lower consumption and higher efficiency, but the sound may not be as faithful as with classic analog amplifiers. | AB |
| Number of amplifier channelsAmplifiers are divided into: - Monoblocks - 2-channel - 3-channel - 4-channel - 5-channel - 6-channel - multi-channel Each channel is used to power one speaker for the coaxial type, or one side if they are component speakers. Monoblock type amplifiers are mainly used for subwoofers. 2-channel are suitable for both subwoofers and, for example, the front pair of speakers in a car. 3-channel is used for front or rear speakers + subwoofer. 4-channel are used for front + rear speakers or 1 pair of speakers + subwoofer. 6 or 5-channel are used for 2 pairs of speakers + subwoofer, most often. Bridging means connecting the amplifier to a bridge, using the + pole from one channel and the - pole from the other channel. In most cases this is shown as "BRIDGED" on the amplifier. | 4/3/2 |
| RMS power into 4 ΩRMS power when loading speakers or subwoofer at 4 Ω. RMS power is the constant power of the amplifier and is one of the most important parameters when choosing an amplifier. | 4 x 70 W |
| RMS power into 2 ΩRMS power when loading speakers or subwoofer at 2 Ω. RMS power is the constant power of the amplifier and is one of the most important parameters when choosing an amplifier. | 4 x 90 / 2 x 180 W |
| Frequency rangeThe ability of the amplifier to reproduce the signal from the lowest frequency to the highest = faithfully reproduce the sound in a specific frequency band. Professionally: In the frequency range from 40 to 16,000 Hz, the vast majority of fundamental and overtones (harmonics) of all musical instruments are found. We are interested in the course of the radiated sound pressure in this range of frequencies when the loudspeaker system is supplied with constant power. We call this course the frequency characteristic, which tells us the level of radiated sound pressure in decibels (dB) depending on the frequency. The frequency characteristic of a speaker or speaker system can be expressed most succinctly with a graph. Mostly, however, the frequency characteristic is indicated by indicating the maximum tolerance of the sound pressure in the given frequency range, e.g. 50 to 15,000 Hz -+ 6 dB. Since the frequency characteristics of loudspeakers and systems in general are quite uneven, some manufacturers do not even specify this maximum tolerance of sound pressure in decibels in their catalogs for reasons of prestige. Data impoverished in this way is unfortunately worthless. What is valid is that the manufacturer offers a speaker system with a frequency range of 30 to 20,000 Hz, if he is worried about stating the maximum unevenness of the sound pressure in this range, because he can have a tolerance of, for example, +- 20 dB. The unevenness or undulation of the frequency curve in good speaker systems for high-quality music performance should not exceed +-3 dB in the 80 to 12,000 Hz band and +-6 dB in the 40 to 16,000 Hz band. Greater unevenness already depletes or emphasizes certain tonal areas, which can cause audible or even disturbing distortion. The proportion between fundamental tones and higher harmonics also changes, thereby changing the color of the sound, and individual musical instruments as well as the entire musical image sound unnatural. | 10 - 45,000 Hz |
| Signal-to-noise ratioThe signal-to-noise ratio means that the output signal always contains noise. The signal-to-noise ratio expresses how much of this noise is compared to the useful signal. The so-called A value is given, which does not take deep and very high frequencies into account. This corresponds to the characteristic of human hearing, which is not so sensitive to deep frequencies, especially below 1 kHz. The higher the value, the better the amplifier is. | 75 dB |
| SubsonicA subsonic filter is essentially a high-pass filter for very low frequencies, typically 45 Hz or lower. Anything below this setting is weakened. The point is that the subwoofer does not go below the subsonic filter setting and does not overload itself with very low frequencies. A useful function, if set correctly, the subwoofer is not overloaded. | No |
| Bass boostBass boost or bass enhancement. With this function, the bass itself can be emphasized, at a high level of bass boost, the speakers and the subwoofer can distort a lot and the sound will be worse than better. We therefore recommend using the "bass boost" function wisely. With maximum use of bass boost, there is a risk of damage to the speakers and thus to the subwoofer. | No |
| Phase shiftPhase shift is a linear electronic oscillator that produces a sinusoidal output. It consists of an inverting part of the amplifier such as a transistor. The feedback network "shifts" the phase at the output of the amplifier by 180 degrees to the oscillation frequency and gives positive feedback. The Phase shift filter produces a phase shift that increases with increasing frequency. This is usually used when the subwoofer sub-assembly is out with the magnet, or when two amplifiers are connected externally. Phase Shift is also used with active speaker wiring, where the time shift of the speakers is set. The point is that the subwoofer does not play the bass late, and for this reason better amplifiers offer this phase reversal option. | No |
| The value of the fuses on the amplifierFrom the value of the fuses on the amplifier, you can get a true picture of the real performance of the amplifier. | 2 x 30A |
| Automatic on and offThis function allows you to automatically switch on the amplifier. | No |
| Socket input terminalsFerrule terminals allow better wiring contact to the amplifier. It is also a more secure form of terminals. If you are tightening the sleeve terminals, we recommend retightening them after 1 day, as the connected cable gradually compresses. | No |
| Input for wired remote controlIf the amplifier has a remote control input. | No |
| Remote control included in the packageSome models of amplifiers also come with wired remote controls in the package, which on one side plug into the amplifier and on the other side you have a potentiometer that you can place anywhere in the cabin. A common place to place the remote control is under the steering wheel. The advantage is the regulation of power, and therefore volume, depending on driving conditions and the mood of the crew in the car. | No |
| Mass | 2.86 kg |