Ground Zero GZA 125.4-30A amplifier

4-channel amplifier, 4 x 125 W RMS (4 Ω) / 2 x 250 W RMS (2 Ω), class AB, BIAS adjustment, SQ components, Hi-Res, limited edition
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Zesilovač Ground Zero GZA 125.4-30A

A limited edition for Ground Zero's 30th anniversary presents the flagship four-channel amplifier GZA 125.4-30A, based on the EISA-awarded Ground Zero GZUA 4SQ. The manufacturer upgraded all key components, creating a true gem for sound lovers seeking absolute reproduction fidelity. The massive heatsink with a black piano-lacquer finish and gold details looks elegant and underlines the exclusivity of the edition. The real marvel, however, is inside — from premium components to a carefully engineered circuit concept. The amplifier is built on a proven Class A/B topology with adjustable BIAS, allowing behavior close to Class A. Ground Zero deliberately omitted all filters and minimized the number of active components in the signal path to achieve maximum purity and detail. The use of OPA2134 op-amps, premium MUNDORF® capacitors, and separate power rails for the preamp and power stages ensures not only excellent dynamics but also absolute silence in the background. The result is an amplifier that becomes both a collector’s item and an audiophile tool for the most demanding listening sessions.

Limitovaná edice k 30letému výročí Ground Zero

In 1995 Felix Lautner founded Ground Zero near Munich, and over three decades the brand has grown into one of the global leaders in car audio. To mark the 30th anniversary, a special edition was created as a symbolic thank-you to fans and collectors. This limited series includes three carefully selected products: the four-channel amplifier GZA 125.4-30A, the two-way component system GZC 165-30A and the subwoofer GZW 12-30A. Each offers unique technical features available only in this edition and is distinguished by an exclusive black-and-gold finish. Ground Zero focuses on quality and collectible value rather than mass production — that is why the most popular amplifier configuration, the widely used 165 mm speaker size and a 12" subwoofer were chosen, together forming a perfectly balanced core system. The edition sits in the higher price segment alongside the Hydrogen and Uranium series, but includes a range of exclusive improvements and details prepared specifically to celebrate this special anniversary.

Hlavní vlastnosti

Limited edition for Ground Zero's 30th anniversary.
Four-channel amplifier with Class A/B topology and adjustable BIAS.
Frequency range 5–70,000 Hz for high-resolution (Hi-Res) playback.
Filterless design for maximum fidelity and sonic purity.
OPA2134 op-amps with extremely low noise.
Premium audio capacitors MUNDORF® and high-quality output transistors.
Separate power rails for the preamp and power stage.
Optimized power-up with timed delay.
Gold-plated terminals for flawless signal transfer.
Massive heatsink in black piano lacquer with gold details.

O značce

Ground Zero Audio is a globally recognized car audio brand founded in 1995 in Germany. Since its inception it has built a strong market position thanks to cutting-edge technologies, precise engineering and a focus on sound quality. Ground Zero specializes in complete car audio solutions, from premium car speakers and powerful subwoofers to amplifiers designed for either SPL or SQ. Ground Zero products are known for their durability, high performance and faithful music reproduction, as confirmed by numerous awards from prestigious international competitions in Sound Quality (SQ) and Sound Pressure Level (SPL). The manufacturer uses state-of-the-art technologies in development, such as the KLIPPEL® measurement system and CEA 2006-A standards, to ensure maximum accuracy and reliability of each component. With the slogan "Respect The Music," Ground Zero Audio emphasizes its philosophy — to offer listeners an authentic musical experience that faithfully captures the emotion of every track. If you are looking for top-tier solutions, car speakers or subwoofers that excel not only in performance but also in build quality, Ground Zero Audio is the right choice for demanding customers worldwide. Ahifi is the exclusive importer of Ground Zero for the Czech and Slovak Republics.

Catalog number	GZA 125.4-30A
Brand	Ground Zero
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
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 125 W / 2 x 250 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 215 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.	5 - 70000 Hz
Harmonic Distortion (THD)Total harmonic distortion indicates how much the input signal is distorted in the amplifier. Distortions appear as overtones contained in the output signal. The proportion of originally absent parts of the signal is given as a percentage, typical values are between 0.001% and 0.5%. Distortion is measured in their power band. If it exceeds the limit of 0.7% from a certain power, it is the value of the output power of the given amplifier, from which it no longer plays without distortion and from which the distortion usually increases steeply, so that no further increase in power can be counted on. The lower the value, the better.	< 0.005 %
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.	110 dB
Input sensitivityIn order for the amplifier to perform its function correctly, it requires an input signal of a certain level, which is different for car radios. It is measured in "Volts" (e.g. 2 V, 4 V, etc.) The higher the value at the output of the pre-amplifier, or car radio, the less demands are placed on the power of the amplifier. However, the amplifier must allow this input sensitivity, and for that reason this value is also given for the amplifier.	0.8 – 6 V
Damping factorDF - Damping Factor . It is the ratio of the load (repro + cables, crossover, etc.) to the internal resistance of the amplifier. The bigger the DF, the more controlled the bass. Amplifiers with a lower DF tend to hum. Subwoofers with a higher Q in the bass reflex and sometimes in the enclosure will also cause humming.	> 800
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 40 A
High level inputsThe high-level input on the amplifier allows connection directly to the existing speakers in the car without additional purchase of an external high/low adapter. Important equipment in the case of installing an amplifier on an original car radio.	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.	Yes
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
Dimensions of the amplifier	195 x 53 x 360 mm