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In search of a quiet PSU: Second Edition

The world of computer power supplies is a strange one. We have smart, knowledgeable reviewers like Aris Mpitziopoulos of Tom’s Hardware or Jeremy Schrag of JonnyGuru going into pornographic detail describing 1% differences in efficiency or voltage stability, even though such things never make a noticeable difference in real life (assuming you’ve bought a decent, brand-name PSU). Meanwhile, electrical noise (generally known as “coil whine”), which affects the user’s daily comfort in a very tangible way, barely gets mentioned.

I am not an EE nerd who salivates over ripple graphs. I’m just a guy who wants a solid PSU that doesn’t make noise, just like in the old days. The last time I was looking for a new PSU was in 2012 – the search ended in a resounding defeat. I spent dozens of hours testing five different power supplies. In the end, every single one had more electrical noise than my Corsair HX520 from 2007, though one of them (the entry-level Be Quiet! model) came close. In the end, I just decided to stick to my old Corsair. After 10 years of constant use, it’s working perfectly well, thanks for asking.

If I’m so happy with my HX520, why am I writing a new post about PSUs? Well, I recently bought a new video card (a GTX1070 from MSI). As every silent PC enthusiast knows, modern graphics cards generate tremendous amounts of coil whine, and my unit is no different. Tellingly, my HX520, which was dead silent with my previous card (an AMD HD7850), started making electrical noise – specifically, reproducing the coil whine of the video card. I know it isn’t just the noise of the card bouncing around, because I took the PSU out of the case and put my ear to it. This seems to suggest that maybe my beloved Corsair isn’t as spotless as I thought.

The second reason is that, when I was buying the GTX1070, I got into a conversation with the salesman about coil whine. He mentioned that he used to have a huge coil whine problem on his card, but that he managed to reduce the noise by getting a new PSU.

Finally, I was also curious to see if the acoustics of power supplies had improved over the past 5 years.

So I ordered three PSUs – all of them praised on the Internet for being particularly quiet: the Corsair RM650x, the Be Quiet! Pure Power 10 600W, and the BitFenix Whisper M 550W.

What’s your setup?

  • Motherboard: Asus P8Z77-V Pro
  • CPU: Intel i5 3570K (overclocked to 4.1 GHz)
  • Video card: nVidia GTX1070 (MSI Gaming X 8 GB)
  • 1 SSD drive and 1 very quiet mechanical hard drive (WD Red 2 TB)
  • Case: Fractal Design Define R4, all optional vents are closed
  • Case fan: 140 mm at 600-700 rpm (in the back of the case)
  • CPU fan: 120 mm at 600-700 rpm
  • GPU fan: I had the fan off while testing the PSU noise (of course not for long)

The computer is about 1 meter away, under a heavy desk. There’s a carpet on the floor.

How did you test for coil whine?

I ran a number of applications that place a high load on the GPU: the Unigine Valley benchmark, the Kombustor benchmark, Far Cry 4, The Witcher 2, Mass Effect 3, Grand Theft Auto IV, Dishonored 2, and Deus Ex: Mankind Divided. Some of these are older titles, because I wanted to generate high framerates (which are known to lead to coil whine). I tested each application with vsync off and on. Predictably, turning vsync on (with a 60 Hz monitor) eliminated coil whine or made it very faint.

Corsair RM650x

I’m a big fan of the Silent PC Review forums. The kind people over there truly care about computer silence, so if they say that some piece of hardware is silent, I know that’s the case. The only other site whose opinions on PSU noise are worth reading is Tom’s Hardware, because they publish the rpm graphs of PSU fans, rather than useless decibel measurements (I know that a 500 rpm fan is inaudible in my setup, but I don’t know what 18 dB means, especially that the sound pressure level depends on the distance at which you take the measurement.)

The Corsair RMx line is probably the most recommended PSU on SPCR. If you also consider my good experiences with the HX520, you see why the Corsair RM650x instantly landed at the top of my shortlist.

The RMx PSUs are semi-passive, which means that the fan in the PSU only turns on when the power drawn by the computer and/or the temperature inside the PSU exceeds a certain threshold. Under “average” conditions, the RM650x is supposed to run fanless up to 260 W, which is why I chose it over the RM550x, for which the threshold is 225 W. (As it turned out, that wasn’t the best decision.)

Now for the big question: is it quiet? Yes, it’s very quiet! To my genuine surprise, the overall electrical noise generated by the GTX1070 + RM650x duo was much lower than for the GTX1070 + HX520. This was true across all the tested apps. Essentially, what seemed to happen was that the PSU was now near-silent (save for some light buzzing that’s inaudible from more than 30 cm) – the only coil whine was coming out of the video card. As a result, the overall electrical noise was cut in half. The boys at SPCR didn’t lie. The Corsair RM650x is an excellent PSU for the silent PC enthusiast.

After an hour or two of testing, I couldn’t help but notice that the PSU case got quite hot – hot enough that I couldn’t touch it for more than a couple seconds (so probably > 40°C). This was despite the fact that I was working with an open case and the unit was supplying no more than 300 watts – and even that, only for brief periods. I am certain that the Japanese capacitors used by Corsair, which are rated for 105°C, will take the heat without breaking a sweat. That’s not the issue. The problem is that the PSU radiates heat into my case. I can, of course, remove the excess heat by cranking up my case fan. But then I would end up with noise because the case fan would cross the threshold of audibility. Suddenly, the “dead silent” PSU doesn’t seem so silent anymore.

Testing the RM650x made me realize that I am not a fan of semi-passive power supplies. I would much rather have a PSU with an always-on 500 rpm fan (which I won’t hear anyway) that will help expel hot air out of my case.

Here are some other thoughts about the Corsair RM650x:

  • The fans didn’t immediately switch on after maximizing the power draw with IntelBurnTest and Kombustor simultaneously (reaching total system power of 300 W). It took a few minutes for that to happen, which suggests that the fan speed depends not just on power, but also temperature or time. The fan also stayed on for at least 5 minutes after the test apps were closed. In the Tom’s Hardware review, the fan on the RM550x (the lower model) didn’t turn on below 275 W. (And, according to Corsair, the threshold is higher in the RM650x.)
  • The fan was very quiet once it switched on. I couldn’t hear it even with my head next to the case – the case and CPU fans in my system completely drowned it out. In fact, I had to look to make sure it was running. In the Tom’s Hardware review of the RM650x, the fan turned on at about 325W, slowly reaching 600 rpm at 375 W, then staying at 600 rpm until about 450 W. It’s risky to make statements about a subjective thing like noise, but 600 rpm in a fan located at the bottom of a case should be inaudible to almost everyone, even in the middle of the night. I would therefore expect this PSU to be practically silent in even the most high-powered single-GPU setups.
  • The fan seems to be of a high quality. Unlike with the other two review units, I couldn’t hear any clicking, even with my ear next to the fan.
  • The motherboard ATX connector is hard to plug in. I had to push so hard that it bent the motherboard PCB. Not cool.
  • When I first turned the PSU on, it blew out a fuse in my apartment. The capacitors fill up too quickly, which creates excessive current. I’ve seen reports of this problem with this specific PSU (not sure about the RM550x). If you’re one of the people who turn off their PSU (or the power strip connected to the PSU) at the end of the day, and you want to buy the RM650x, I suggest getting it from a store with a good return policy.
  • The PSU uses daisychained VGA cables, which is nice, because you can connect a card with two power inputs using just one cable.
  • The Corsair RM650x has a crazy 10-year warranty. Talk about having confidence in your product!

Be Quiet! Pure Power 10 600W

After the encouraging experience with the Corsair, it was time to hook up the Be Quiet. The Pure Power 10 is the successor of the Pure Power L8 model that almost won my last PSU comparison, so I was very interested to see if the current generation lives up to that.

The answer is yes! The Be Quiet! Pure Power 10 600W is a very quiet PSU. My electrical noise tests yielded results on par with the Corsair RM650x. Since I don’t have two identical PCs to do a side-by-side comparison, I had to rely on impressionistic notes to compare the PSUs (e.g. “when playing the Witcher 2 at 170 fps at 3 am, the coil noise is barely noticeable when the computer is under the desk”), but – as far as I can tell – these two models are equally quiet in terms of electrical noise.

The Pure Power 10 is not a semi-passive PSU, but the fan spins at a leisurely pace and, in practice, I wasn’t able to hear it over the sound of the rest of my system. In my stress tests, with a total load of 300–350 watts, I was unable to hear the fan spinning up, despite having the PSU just 30 cm away. According to this eTeknix review, the fan stays below 560 rpm up to about 80% load, which explains the excellent noise performance of this model. The active fan of this PSU has a clear advantage over Corsair’s semi-passive solution – the PSU stayed much cooler, even under a heavy load, while still staying inaudible. It seems there is a big difference between 0 rpm and 560 rpm in terms of cooling.

Some further observations about the Be Quiet! Pure Power 10:

  • The Pure Power 10 uses mediocre Chinese capacitors which are rated for 85°C, unlike most enthusiast PSUs nowadays, which use Japanese capacitors rated at 105°C. Heck, even my old Corsair HX520 is 100% Japanese 105°C (which might explain its longevity). Be Quiet clearly views the Pure Power 10 as a budget unit – which is kind of funny, because it only costs €20 less than the RM650x, at least here in Poland.
  • The fan (or something close to the fan) makes soft clicking noises at random intervals. This is only audible when the fan is pointing directly at your ear.
  • There is some doubt about the type of fan used on the Pure Power 10. The official spec says it’s a rifle-bearing fan, while Tom’s Hardware says (in their review of the Pure Power 9, which has the exact same fan model number: BQ QF1-12025-MS) “our sources indicate that the cooling fan has a sleeve bearing”.
  • The Pure Power 10 has a relatively short warranty of 3 years. This could indicate that Be Quiet does not expect the capacitors and/or the fan to last more than a few years.
  • The VGA cable is a little too short. An extra 5 cm would have made it possible to route it a bit better in my Fractal Define R4 case. As on the RM650x, it is daisychained, which allows you to connect two VGA power sockets with one cable.

BitFenix Whisper M 550W (BWG550M)

BitFenix is not normally considered one of the top PSU brands, but their latest Whisper M line has earned a recommendation from Tom’s Hardware and is based on the latest platform from CWT, the company that makes power supplies for Corsair.

The crucial difference between the Whisper and Corsair RMx is that the Whisper has an active fan, which keeps the PSU much cooler. The difference is quite dramatic and can be easily felt by touching the PSU chassis after playing a demanding game for 30 minutes. At the same time, BitFenix gave the fan a very quiet profile: in the Tom’s Hardware test, it stayed at 400 rpm up to 325 W, then slowly spun up to 600 rpm at 375 W – this is at ambient temperatures of 34–46 °C. The fan’s speed is temperature-dependent, so if the temperature inside your case is lower (it likely is), you will be able to reach higher wattage while staying below 600 rpm. In my tests, I was unable to make the fan audible over the rest of my system, despite stress testing my system rather vigorously, and sitting right next to the PSU.

What about the primary target of this comparison – coil whine? I’m happy to report that the BitFenix Whisper M 550W is every bit as coil-whine-free as the Be Quiet! and the Corsair.

Some more comments on the BitFenix:

  • The Whisper uses an FDB fan, which is theoretically very good, but – according to Tom’s Hardware – the model they used is only rated for 30,000 hours. At 12 hours a day, this is only 7 years, though one can hope that the slow rotational speed will extend the lifetime.
  • The fan has the same random clicking disease as the fan on the Be Quiet, except that the clicking happens more frequently. It’s inaudible unless the fan is facing you – the only problem is that it makes me worry about the long-term reliability of the fan.
  • The PSU uses a 135 mm fan. If you ever need to replace it, good luck finding a quality fan in that size.
  • The VGA power cable is not daisychained, which means that I need to route two separate cables from the PSU to my nVidia 1070 card.
  • On the other hand, the SATA power cables are super-long with 4 connectors each. This is the first PSU that has allowed me to connect my DVD-ROM and two hard drives with one cable.
  • The ATX cable is made up of 4 separate ribbons. I’m not sure what BitFenix was thinking here, but these cables take up more space than a standard sleeved round cable, and are more difficult to route behind your motherboard because you need to place them flat against the motherboard tray (at least my case wouldn’t close otherwise), which is very hard because they’ll twist around. In the end, I gave up and routed the ATX cable behind my hard drives, which is not ideal. Ribbons are a bad idea for huge cables!
  • The ATX plug is huge because it houses a bunch of capacitors to further reduce ripple (see here for photo). As far as I can tell, this accomplishes no useful goal, other than impressing the EE nerds who write PSU reviews. I love EE nerds, but that damn plug makes it harder to route the ATX cable and I daresay even blocks some airflow to the RAM sticks. At least the plug itself goes in and out easily, unlike on the Corsair RMx. It’s also a 24-pin plug, so there’s none of the 20+4 nonsense to deal with.
  • BitFenix backs the Whisper M with a 7-year warranty. Not as good as Corsair’s 10 years, but still very nice.
  • At the time of this writing, the BitFenix Whisper M 550 W is only €5 cheaper than Corsair RM550x.

Decisions, decisions

Well, what do you know – the quality of computer power supplies seems to have gone up over the past few years. Whereas five years ago I had to concede defeat in my quest to find a PSU to equal my almost ancient Corsair HX520, this time I have gotten my hands on no less than three PSUs that reduce the overall electrical noise in my system by about 50% when paired with my MSI Gaming X 1070 graphics card.

In a quiet room in the middle of the night, with a well-insulated case placed under a desk, I can just notice some coil whine (usually a kind of buzz) in demanding applications, especially with high framerates. I have to make a bit of an effort to hear it. If I put the computer on the desk, or had a less insulated case, it would of course be a different story. Is that a result I’m totally happy with? Heck no. I believe electrical devices should not be heard (unless they’re speakers). But until video card manufacturers start designing less noisy products, it’s a result I can live with.

With all the tested PSUs offering virtually identical performance in the noise department, I have to make a decision based on secondary considerations:

  • The Corsair RM650x is an excellent model with quality components and a crazy long warranty, but the semi-passive cooling means it runs quite hot, even without extreme load. I don’t want to deal with extra heat in my already hot case, so the Corsair was the first PSU that I eliminated. (The lower-rated brother, Corsair RM550x, turns on the fan a bit earlier, but the threshold is only 35W lower and it wouldn’t make much of a difference.)
  • The Be Quiet! Pure Power 10 600W runs much cooler than the Corsair, but the cheap Chinese capacitors and the relatively short warranty make me worried that it will not last more than a few years. (The higher-end Straight Power model also uses Chinese caps. Be Quiet! has announced a new generation of the Straight Power, to be released in the fall of 2017, which will have 100% Japanese caps.)
  • My personal winner? The BitFenix Whisper M 550W. It combines the cool operation of the Be Quiet! with the uncompromising component quality of the Corsair. The long-term reliability of the fan is a bit of an unknown in light of the unimpressive 30,000 h rating, and the non-typical fan size would make replacing it a challenge – if anything goes wrong, I will just have to use the 7-year warranty.

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4 Comments so far ↓

  • Alex

    Hey, thanks for the nice review. I am wondering why you chose to try the Pure Power. The Straight Power E10 would have been exactly what you were looking for. Its fan is spinning constantly and starts at around 200rpm. And it is one of the best and quietest fans there is.. a Silent Wing 3 with Fluid Dynamic Bearing.

    I myself am considering this or the Corsair RMx/RMi…

    Best wishes!

    • Tomasz P. Szynalski

      Alex– I chose the Pure Power because in my previous test, it had less electrical noise than the Straight Power. It may be a good idea to wait for the Straight Power 11, which is supposed to have 100% Japanese capacitors.

  • Andy

    Thanks for the great article. I have similar philosophy and goals of a quiet PC with less emphasis on performance. I hadn’t considered the downside of the Corsair semi-passive operation. Did you consider the Corsair RM650i which allows you to customize the fan profile via USB? You could then get all the Corsair goodness and put a floor on fan RPM. I was going to get an RM550x, but after reading your article am considering the RM650i, which is only a little more expensive.

    Thanks

    • Tomasz P. Szynalski

      Hi Andy. The answer is that I dislike the idea of running a sketchy background app all the time — if it were possible to set the fan profile once and have the PSU remember it forever in some kind of flash memory, I’d be interested. I’m a bit anal about that — just don’t like to have background apps eating up my RAM and CPU, and certainly an app for the PSU seems like overengineering to me. The Corsair app is not the best-written piece of software, either, judging by what the Internet says.

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