The PSU worked normally together with an APC SmartUPS SC 620 at loads up to 379W (from the mains) and 340W (from the batteries). It had no problems switching to the batteries.
The output voltage ripple is very low on the +12V rail even at full load. It is no higher than 40 milliseconds, which is only one third of the permissible maximum. The +5V rail meets the requirements too, but without any reserve, while the pulsation on the +3.3V rail exceeds the permissible limit even though by just a few millivolts. The cause of this problem is the pulsation of a mysterious origin at a frequency of about 1.5 kHz. Usually, there are only two types of pulsation in a PSU: at the frequency of the PWM-regulator (tens of kilohertz) and at the double frequency of the power mains (100Hz in our region).
The PSU boasts superb stability of the output voltages none of which violates the limits or even reaches a 4% deflection from the nominal value (a 5% deflection being the permissible limit). The +12V voltage, which is loaded the most in the modern PC, is ideal deflecting no more than 1% from the nominal value!
The PSU employs an 80x80x25mm ADDA AD0812UB-A70GL fan with a rated speed of 3400rpm (at 12V voltage).
The fan speed is constant at 1600rpm until a load of 500W. Then it starts to grow, reaching over 2500rpm at the maximum. So, the PSU is not really silent but it is quiet in comparison with the models I tested in my previous review whose 80mm fans would easily speed up to 3500rpm and more. Alas, the tradeoff for the quietness is high temperature: the difference between the air temperatures at the input and output amounts to 20°C, which is quite a lot.
You may wonder why the fan speed could not be set lower for loads of 200-300W to make the PSU truly silent? The problem is that PSUs still use fans whose speed is regulated by the supply voltage rather than by an independent signal (like in the new CPU coolers with a 4-pin connector). With this regulation, the speed can only be reduced to 50% of the rated one or the fan may not start up at all. You can expect a wider regulation range when fans with a separate speed-control contact appear in PSUs.
This model was developed to comply with the 80 Plus requirements and it is indeed 80% and more efficient through the load range from 20% (200W) to maximum. Of course, the efficiency is going to be lower in an 110V power grid, but the reserve is large enough for the PSU to exceed the 80% barrier then, too.
So, the Antec TruePower Quattro TPQ-1000 is a very high-quality and high-wattage power supply featuring superb stability of the output voltages through the entire load range and a relatively quiet operation. The latter thing is, however, accompanied with a high temperature at high loads. Moreover, this PSU is still obviously noisier than lower-wattage models like the Antec NeoHE, for example. If you want to have a really quiet PSU, you should realistically estimate the power needs of your PC and choose a quieter, perhaps lower-wattage, model. But if you are set upon buying a 1000W power source, the TruePower Quattro is going to be a good choice.