Temperature, Ripple and Sound

We have a battery of tests lined up for these four power supplies, including thermal, sonic and electrical tests on the DC output of the power supply.  Our test bed consists of:

Gigabyte GA-7VRX

AMD Athlon XP 2100+

2x256 Kingston KV133

4x Maxtor 80GB 7200RPM

All tests will be conducted over a full load: all 4 drives will be spinning during each of our tests in order to maximize the drainage on the +12.0V rail.  Furthermore, our testbed will also be rendering a very large scene in 3D Studio Max 5 in order to stress the +3.3V and +5.0V rails.

Setting up

The ripple is the variation in voltage over a particular rail.  Like we mentioned on the previous page, too much fluxuation in voltage can lead to damaged hardware. A surprising fact we dug up during this review was that the majority of damaged RAM returned to memory manufacturers is destoryed by fluctuations in the voltage. For our first benchmark, we used an oscilloscope and a multimeter to measure the voltage and ripple within 10millivolts.  All three rails were tested directly on the motherboard to simulate real world results.  Remember, less ripple is better. These are the real world results, as opposed to the results printed on the boxes.  (Each unit we tested has a rating of +/-50mV, +/-50mV, and +/-120mV respectively.)

Scoping out the situation

Enlarged ripple capture

We see that Antec and Enermax provided the lowest amount of ripple, while keeping their average low and high voltages very tight.  Remember, these tight patterns are a necessity in order to keep processors and the entire system, stable.  Almost all of the power supplies had lower than advertised ripples with the exception of Vantec.  Interesting to see was the Vantec unit actually tipped a little bit over the advertised rating of 50mV (+/-1.0%) on the +5.0V rail.  We were slightly dissapointed to see this, especially considering the other units were for the most part under the advertised ripple rating.  Most notable was the Enermax unit which was well under the +12V rail ripple advertisement.  

Our thermal tests were conducted on a high load system inside a closed ThermalTake A6000B Xaser II Aluminum case.  All temperature is in degrees Celsius.  The temperature was taken from inside each of the units, just above the +3.3V transformer.

Vantec stayed the coolest of the four, but remember this power supply has three fans.  As we will see, the Vantec is able to stay a slight bit cooler, but unfortunately at a tradeoff with noise..  We previously pointed out that switching power supplies work inefficiently if they are not kept reasonable cool.  Each of these units operates well under 35C, but to put that figure into perspective, most portions of the inside of the case actually operate at a higher temperature.

The description of a quiet fan has almost always been a sort of oxymoron.  Of course, manufacturers like Vantec are already at a disadvantage with an additional fan.  A human whisper is roughly 30dBA while a typical conversation is held around 60dBA.  Keep in mind, the decibel scale is logarithmic.  Therefore, a device that is 8dBA louder than another is approximately twice as loud.  We performed our sound test outside of the case as to isolate the noise level of just the power supply.  Each measurement was taken from 12” away with the power supply outside of the case. 

Vantec seemed to be the noisiest supply in our batch, and a sound level meter only confirmed that.  Even though Vantec had a variable speed option in the rear, the fans are just too noisy.  For the most part, we can attribute this to the additional fan.  Since the Stealth Aluminum PSU has 2 80mm intakes and only 1 80mm exhaust, positive pressure exists inside the unit (assuming all 3 fans are running at the same rate).  In real world situations, the additional fan really did not improve the cooling performance significantly; the enormous increase in noise is not necessary.

Antec’s Truepower was on the opposite end of the spectrum.  At 31dBA, the unit is barely audible; certainly not able to be heard over typical case fans.  When inside a case, the supply is further muffled so that it is almost silent.  We also need to show respect to the Enermax unit which provides the Truepower with very solid competition in the noise category.