The PSU’s cross-load characteristics are superb. A 2% deflection is exceeded at minimum and maximum loads only. The diagram for the +12V voltage is green (meaning that the voltage deflects by less than 1% from the nominal value) through the entire load range.
The output voltage ripple isn’t strong. It is about 25 millivolts on the +5V and +3.3V rails and within 60 millivolts on the +12V rail. This is about half the allowable maximum.
The PSU uses a Yate Loon D14BM-12 fan, too (it seems to have a rated speed of 1900rpm). Half of it is covered with a piece of celluloid film to drive the airflow to the back of the case. This film may rattle if fastened loosely.
And again, the fan speed is kept at 1000rpm until a load of 200W with something but grows up to the maximum during the next 200W. At loads from 450W to 600W its speed doesn’t change but the temperature began to grow up quickly. Moreover, I smelled overheat plastic at full load although the PSU went through the test unharmed.
The meaning of this regulation is still unclear to me. Perhaps the developer wanted to ensure an optimal thermal mode for the PSU in a load range from 300 to 400W as the most probable for a modern top-end system. This makes the PSU cool, but not quiet. Having a fan speed of over 1500rpm at a 350W load, it is only average in terms of noisiness.
The PSU has a good efficiency – up to 86% at the maximum with a smooth reduction to 83% towards higher loads.
Thus, Thermaltake’s Toughpower 600 AP and Purepower RX 550 AP are in fact twin products. They have almost identical specs, identical electronics, and very similar effective parameters. They differ in the amount of HDD power connectors, but this difference is insignificant for a majority of users. Moreover, the strange regulation of the fan that reaches its max speed at a load of 450-475W makes me think that the specified output power of the Toughpower 600 AP is somewhat overstated while that of the Purepower RX 550AP is closer to reality. Speaking in general, these PSUs are going to be interesting for owners of rather advanced gaming systems as they yield stable power at a reasonable level of noise.