ZXti Amplifiers

ZXti400 SPECIFICATIONS:

Output Power:

4 ohm stereo @ 12/13.8 VDC	37/100 WRMS x 2
2 ohm stereo @ 13.8 VDC	200 WRMS x 2
4 ohm bridged @ 13.8 VDC	400 WRMS x 1
Crossover Frequencies	40Hz to 800Hz
Crossover Slopes	24dB per Octave

ZXti475 SPECIFICATIONS:

Output Power:

4 ohm stereo @ 12/13.8 VDC	18/75 WRMS x 4
2 ohm stereo @ 13.8 VDC	150 WRMS x 4
4 ohm bridged @ 13.8 VDC	250 WRMS x 2
Crossover Frequencies	40Hz to 8kHz
Crossover Slopes	24dB per Octave

ZXti600 SPECIFICATIONS:

Output Power:

4 ohm stereo @ 12/13.8 VDC	75/150 WRMS x 2
2 ohm stereo @ 13.8 VDC	300 WRMS x 2
4 ohm bridged @ 13.8 VDC	600 WRMS x 1
Crossover Frequencies	40Hz to 800Hz
Crossover Slopes	24dB per Octave

Frequency Response	+/-1dB from 20Hz to 20kHz
Signal to Noise Ratio	>100dB
Input Sensitivity	200 millivolts to 2 volts
Input Impedance	>10k ohms
Bass EQ	0 to + 12dB @ 45Hz
Input Voltage Range	10.5 volts to 15.0 volts
Typical current draw at idle	750 milliamps
Minimum Impedance	2 ohm bridged/1ohm stereo
Dimensions, ZXti400	11.75"L x 9.8"W x 2.25"H
Dimensions, ZXti450, ZXti600	16.0"L x 9.8"W x 2.25"H

What years where the ZXti series amplifiers produced?

1999 - Present

Why does the ZXti series amplifiers have such small output power at 12 volts compared to 14 volts?

The 12 volt rating is very conservative and used in most competition organizations.

How much power does my ZXti amplifier make at 2 ohms bridged?

When designing the ZXti amps we wanted a design that made its best power at normal loads. By that we mean 4 ohms bridged. Now we know that no matter what we say or how loud we say it people will still hook the amp up to lower impedances trying to get more power. So our number one goal is that the amp continue to operate at lower impedances. The only way to do that is to limit the power output of the amp when it's hooked up to lower impedances. But it really isn't that big of a deal. Here's why:

Wattage is equal to voltage times current. Running the amp at 2 ohms bridged means more output current. Current makes heat. We can't allow the amp to make more heat than the fan can deal with. The fan can deal with a bit more heat than what's generated from a 4 ohm bridged load. So there's some room for more power. Here's how we limit the power increase to what's manageable:

The ZXti amps have a circuit that detects the amount of current going out of the speaker terminals. If the current is high enough AND last long enough (longer than 50 milliseconds), the circuit limits the amount of voltage that the power supply can produce. This in turn limits the power output of the amp. So continuous power output remains about the same with the power composed of more current and less voltage.

But there is a bright side to all this. Remember I said that the excess current demand had to last longer than 50ms. The dynamic peaks in most music last less than 20ms. So the circuit never has a chance to effect the power supply voltage for musical peaks. All this means that the amp IS allowed to make more power with musical peaks while continuous power remains about the same. You could say that the "headroom" of the amp is increased.

If you want to run the amp 2 ohms bridged, go for it. Just understand that it will run slightly hotter and will pull more current from your car to make those musical peaks (add more capacitors and use thick gauge power/ground wire). I wouldn't recommend running it 1 ohm bridged. The amp will shut down (red LED) if the output current gets too high (looks like a shorted speaker).

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