The test results
Efficiency
| Load | 10pc | 25pc | 50pc | 75pc | 100pc |
|---|---|---|---|---|---|
| Efficiency | 82.4pc | 88.4pc | 92.5pc | 90.8pc | 88.0pc |
PSU efficiency is a little higher with a 230/240V source than with a 115W source used over the pond, and this is because 230V supplies need less amperage - and, therefore less resistance and associated heat - to deliver the same load.
The efficiency figures, which examine DC power as a proportion of AC input, are pretty good across the board. The 25-50pc spread is crucial, as that's how the majority of users' systems load the supply under everyday conditions. Hovering around 90 per cent for this region is considered above average.
Regulation
In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line. We're changing the way we report the figures, now citing the exact voltage rather than percentage away from ideal. Any line that falls outside the prescribed ATX spec. is highlighted in red. Thus, the ATX spec. limits are 3.135V-3.465V; 4.750V-5.25V; 10.8V-13.2V for the three main lines, respectively.
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 3.28V | 5.04V | 12.10V |
| 50 per cent | 3.22V | 4.97V | 12.10V |
| 100 per cent | 3.20V | 4.88V | 12.04V |
The supplied voltage drops as the power is increased on all three lines. Of most import is the 12V rail - we can load all four up on our machine - and the be quiet! produces admirably solid voltages when under the hammer.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 48A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 15A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| Cross-load 12V focus | 3.24V | 5.00V | 11.88V |
| Cross-load 3.3V/5V focus | 3.21V | 4.80V | 12.30V |
It's interesting how the 12V buckles a little when crossloading it with just a sprinkling of load on the 3.3V and 5V lines. But we're being hyper-critical here; 11.88V is still very, very good.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 20mV | 15mV | 25mV |
| 50 per cent | 20mV | 20mV | 35mV |
| 100 per cent | 25mV | 35mV | 65mV |
The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.
We can describe the unit as 'quiet', with respect to ripple, at low loads. Crank it up to near the maximum and it becomes distinctly noisier on all three lines. The 12V's 65mV peak-to-peak figure is amongst the highest we've seen, though any criticism is tempered by the knowledge that the spec. allows for almost double this ripple. We'd only be concerned if the 12V ripple approached 100mV.
Temps
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 28°C | 33°C |
| 50 per cent | 29°C | 36°C |
| 100 per cent | 32°C | 44°C |
Again, good temps all round. You'd expect it to become warmer when loaded to 100 per cent for extended periods. We reckon the low-ish temperatures are a function of the relatively low power it has to push out and quality of the slow-spinning 135mm fan.
We'd also normally report the noise rating, but such is the din produced by the Chroma machine - ears are still ringing - that doing so would be completely pointless. That said, after the formal tests, we've now installed the PSU into one of our test-rigs, and at a 300W load - pertaining to an Intel Core i7 2700K CPU with over-volted HD 6970 graphics - the bulk of the noise is from the components, not the PSU.
