Review: be quiet! Pure Power L8 500W

Running the numbers

Our testing procedures can be found at this link.

Efficiency

The 10pc figure equates to around 50W of load - it's not an exact figure as the various lines have to be loaded with particular amps/volts that may not exactly map out to the desired number.

It is important to look at low-load efficiency because a number of our test platforms idle at around 50W. In this case, the power supply needs an extra 10W, measured at the wall, to deliver the required DC load. Efficiency peaks at 50 per cent load (225W DC) but remains pretty nice right the way up to 100 per cent of the supply's continuous rating.

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.

The standard that most PSU-makers look towards when referencing line regulation is a +/- 3 per cent leeway. This £55 supply manages that on all lines, quite comfortably, which is to be commended for a budget PSU.

Regulation - cross-load

How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 35A 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 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely. As a final test and with Intel's Haswell CPU's zero load in mind, we set the 12V load to a miniscule 0.10V and ran the 3.3V and 5V rails at the same 12A.

Hammering one part of the PSU while using just a smidgen of the other can throw cheaper supplies of out kilter. The Pure Power 500W does well on the first two cross-load tests, but setting the 12V to practically nothing, imitating a C6/C7 state for a Haswell CPU, forces the 5V line to nosedive by just under five per cent, thus getting very close to the minimum limit mandated by the ATX specification. Bear in mind that this is the first PSU we've run with the Haswell cross-load test.

Ripple

The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.

PSUs convert AC power into DC, but doing so requires the AC waveform to be suppressed. be quiet! does a pretty good job here, and we must remember that this is a budget supply.

Temps

Fan performance

Temps are good but they mean little in isolation. Obtaining accurate noise readings is near-on impossible when the supply is connected to the Chroma test harness and dual-unit load-tester. We can test the manufacturer's quietness claims in a different way, by using an AMPROBE TMA10A anemometer placed directly over the centre of the PSU. The anemometer records the airflow being pushed/pulled from the PSU's fan. We can use a Voltcraft DT-10L RPM meter to measure the rotational speed of the fan, too.

We can then provide the fan RPM, airflow and, on a subjective level, the noise level of the PSU - undertaken rather (un)scientifically with the age-old ear-next-to-fan methodology.

The fan certainly spins up as load is increased, as you would expect, but to be quiet!'s credit it is practically inaudible at all times. We struggled to hear it at all, even at 100 per cent load, so the combination of high-quality fan assembly and the way in which the grille is structured means it's a very good fit for those looking to build quiet systems. Certainly living up to its name, the SilentWings fan performs better than expected.