Seasonic Platinum Fanless 520W PSU

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7. COOLING

The temperatures marked in the main test results table need some explanation. Normally, for a fan-cooled PSU, a thermal sensor is moved around a bit during warmup at ~200W load to find the "hot spot" on the exhaust grill where is attached using friction. This provides consistent enough readings of the exhaust air temperature. With a fanless PSU, there is no force airflow, so where should the sensor go? For the Seasonic Platinum 520W, it was placed on the grill atop what appeared to be one of the hotter spots in the PSU, directly over the large transformer. But this data is probably not very useful. To be honest, without an array of thermal sensors which can be placed at many spots all around the interior, monitoring the temperature of a fanless PSU is futile. In any case, the unit did not suffer any temperature overload shutdown during the testing.

As mentioned earlier, the Seasonic X-400 fanless PSU, with much smaller heatsinks, sailed unscathed through a 15-hour torture test at full load in a 53~57°C hot box two years ago. I did not run this sample in a test like that, but in normal use, the 520 Platinum should hold up fine even in hot weather.

8. NOISE, PART 1

There was some trace of tonal noise at level too low for it to be registered in the anechoic chamber with the microphone a meter away. It was more than a single frequency peak, there being a bit of lower frequency buzz, albeit very low in level, as well as higher frequency whine that was a bit more audible. The main source of noise was the 5V Standby line. Placing a 0.4A load on that line always provoked a 4.7 kHz tonal peak that proved to be audible from about 2' away in the anechoic chamber.

Outside the chamber, in a completely undamped and therefore reverberant quiet room (17~18 dBA), the audible distance was about the same; at a meter I could not hear it, but at 2' I could. Changing the 5Vsb load to 1A made the tone disappear altogether, but dropping it to 0.1A or 0.2A changed the frequency, to around 6 KHz; this was discovered using the mic at 1' distance with the spectrum analyzer.


The 4.7 kHz whine, traced to 0.4A load on the 5Vsb line. Note the close approximately one foot distance of the microphone from the PSU.

The question is whether this noise is...

Atypical or typical? This is one the hardest questions for any product reviewer to deal with: Whether the characteristic of the sample is analomous or normal. If the items are inexpensive, like fans, then getting even a dozen samples to check out is not difficult, and testing that many samples helps answer the question of consistency and what is likely to be typical. Mind you, when goods are mass produced in the thousands, 12 is still a paltry sampling (as any statistician would tell you). But when it's a high ticket item in short supply, even a dozen samples are impossible. I asked Seasonic to send me whatever other samples they can spare. They say they will try and get me one in the next 10 days or so.

Audible in a PC in normal use? I have assume that few users would use a fanless PSU in PC with lots of other noisy components. They'd use it in a quiet PC. So would this level of tonal noise be audible in a PC with broadband noise of less than 20 dBA@1m, in a relatively quiet room? My guess is... no for most users most of the time, but yes for some users, some of the time. This is assuming a fairly select, aurally sensitive group of users — which fanless PC components always attract. The frequency of the noise is not high enough to be affected by the age-related decline in high frequency perception, either.

There is no simple answer to these questions. I need to examine more samples, and hear back from end-users in the field. At time of writing, the first small shipment of Seasonic Platinum 520 PSUs were already sold out at Newegg. Some SPCR readers must be among them; please tell us about your experience on the discussion thread for this article.

Discussions with Seasonic

I discussed my findings with Seasonic, and they immediately arranged to have the sample flown back to their Taiwan headquarters overnight for their engineering team to examine. The acoustic phenomenon I described had not been enountered before. All the early samples for reviewers had been double-checked for normal operation before being shipped. They needed to find out what was different with this unit and if had changed, how and in what way. In the meanwhile, they asked me the favor of not publishing my review until they could at least get a handle on the problem. My review would probably have been the first out, and I appreciated that a negative one would have hurt, so I chose to be helpful. I wanted them to solve the problem anyway, it was certainly in the best interest of the Silent Computing Community. That was in early November.

9. NOISE, PART 2

Here we are a month later with sample #2 which just arrived late Friday. The feedback from Seasonic on the problem with my original sample was somewhat murky. It might be a language issue, as Seasonic's engineering team does not have much English, and I have no Mandarin. There seemed to be two primary messages:

  • First, the acoustic noise was caused mostly by new components used in achieving the higher efficiency, particularly for the <1W standby that's stipulated by the European Union ErP Directive (2009/125/EC) to reduce phantom power consumption. It's not clear whether Seasonic has developed a solution or whether my first sample was just particularly bad.
  • Secondly, they have a tough time measuring or hearing this noise because it is at such a low level, and Taipei is a noisy place. I did visit Seasonic headquarters in one of my trips to Computex, and while it is not a particularly noisy building, it is in Taipei, on the Northern side, and nowhere in Taipei is very quiet. There are no homes with the kind of quiet I have in my house, for example, except in Gigabyte's underground anechoic chamber. Hmmm... perhaps Seasonic should knock at Gigabyte's chamber door?

So in the end, the news from Seasonic engineering on the issue of the first sample noise is unclear and inconclusive. I will assume, for the time being, that it was an anomaly, Seasonic is aware there many be other samples with the same issue, and they are working on resolving the issue (if there is one which makes some samples noisier than others). At least I have another sample to consider.

So what of the second sample?

The first thing I did was to examine it physically. Check: No change from the previous sample, and no, it is not the same one.

Secondly, I hooked it up on the power load tester in the anechoic chamber and powered it up with a ~120W load, a mix of the various lines, including the 5Vsb, of course.

My intial observations, a foot away from the PSU:

  • No high pitched whine. Good!
  • But wait, there is a trace of a lower pitched tone. Not really a whine, that term suggests something higher pitched. This is more in the midband, more like a buzz. Move back a couple feet and it's gone. Move back close, and it's still there. Change the load settings, and there are some very subtle changes in pitch, affected most by the load on the 5Vsb line. Power up the acoustic measurements computer, calibrate the mic and take some quick measurements. From a meter, nothing registers above the normal ambient. Move the mic to 1' from the PSSU, and a sharp spike shows up in the spectrum. See it captured below.

There are two tonal peaks in the second Seasonc 520W Platinum sample: One at just under 500Hz, another smaller one at about 1.3kHz. Note the level of each -- about -7 dBA, and -10 dBA.
  • Some things to note about this spectrum capture:
    • The ambient noise was higher because it's been poring hard all day in Vancouver, and the drain pipes make a bit of a racket when it's raining this hard. No way to damp that out. Hence the blue line is higher than usual; the red ambient reference was captured on a quiet evening.
    • The two spikes are in the midband, which might make them more audible, but they are also much lower in level than the 4.7kHz tone of the original, which was at about +1 dBA with the mic at the same distance. These are -8 and -11 dB lower in level.
    • After an hour running at the same load setting, the noise did not change.
    • Outside the chamber, the audibility of the buzz was limited to perhaps 1.5', at least for me, in this environment (and yes, with the slightly higher ambient cause by the rain's pitter patter.)

In the end, I have to conclude that if this second sample is more representative, Seasonic doesn't really have a problem, although a small handful of highly sensitive people in the world might disagree. Do I think the first sample is an anomaly? Yes. It was much more readily audible and annoying than this one is, and no one in their right mind at Seasonic would have sent me or anyone related to SPCR a product with extraneous noise.

Spot checks of performance at various load points was done on the second sample, and the results were within 1W (or better than 1%) of the readings on the first; i.e., within my test equipment's margin or error. The amazing voltage regulation was the same.

COMPARISONS

The comparison table below shows the SPL versus Power Load data on PSUs tested in ambient room temperature, typically 20~24¬įC. By SPL at 1m, it tops the table; the question whether the tonal noise in my sample is typical.

PSU Noise (dBA@1m) vs. Power in Ambient Room Temperature
Model
90W
150W
200W
250W
300W
400W
500W
6-700W
850W
Seasonic 520 Platinums
<11
<11
<11
<11
<11
<11
<11
n/a
n/a
Kingwin Lazer Platinum LZP-550
<11*
<11
<11
<11
<11
<11
16
n/a
n/a
bequiet! DPP 10 550W
<11
<11
<11
<11
<11
12
15
n/a
n/a
Seasonic X-400 Fanless
<11*
<11
<11
<11
<11
<11
n/a
n/a
n/a
Enermax Platimax 60v0W
<11
<11
<11
<11
<11
12
18
24
n/a
Enermax Modu/Pro87+ 500
11
11
11
11
11
11
18
n/a
n/a
Corsair AX850
<11
<11
<11
11~13
12
13
17
24
35
Seasonic X-650
<11
<11
<11
<11
<11
16
27
32
n/a
Nexus NX-5000
11
11
12
12
12.5
14
19
n/a
n/a
Antec CP-850
12
12
12
12
12
14
20
24
40
Enermax Eco80+ 500W
<11
12
12
16
20
23
28
n/a
n/a
Antec TP-750
12
12
12
14
15
27
31
40
n/a
Seasonic G360
<13
<13
18
24
34
39
n/a
n/a
n/a
CoolerMaster Silent Pro M2 720W
15
15
15
15
15
16
22
31
n/a
Cougar GX-700
15
15
15
17
21
25
35
35
n/a

The comparison table below shows the SPL versus Power Load data on all the PSUs tested in the hotbox. It's difficult to rank them, as the measured SPL varies differently with power load. The units which are quietest at minimum load are not always the quietest at midload (100W~300W), which may make them louder in actual use. Then there's the noise level at 400W and up, which will determine the quietest PSUs for high power gaming rigs, during actual gaming. Again the Seasonic 520 Platinum tops the table.

PSU Noise (dBA@1m) vs. Power in Hotbox/Anechoic Chamber
Model
90W
150W
200W
250W
300W
400W
500W
6-700W
850W
Seasonic 520 Platinums
<11
<11
<11
<11
<11
<11
<11
n/a
n/a
Seasonic X-400 Fanless
<11*
<11
<11
<11
<11
<11
n/a
n/a
n/a
bequiet! DPP 10 550W
<11
<11
<11
<11
<11
13
22
n/a
n/a
Enermax Platimax 600W
<11
<11
<11
<11
12
16
21
24
n/a
Kingwin Lazer Platinum LZP-550
<11*
<11
<11
<11
<11
16
22
n/a
n/a
Enermax Modu/Pro87+ 500
11
11
11
11
14
20
23
n/a
n/a
Corsair AX850
<11
<11
12
15
18
25
35
38
39
Seasonic X-650
<11
<11
12
14
16
31
31
32
n/a
Nexus Value 430
11
11
16
18
18
19
n/a
n/a
n/a
Nexus NX-5000
11
11
12
14
22
24
25
n/a
n/a
Antec CP-850
12
12
12
14
14
26
40
44
45
Enermax Eco80+ 500W
<11
12
16
19
26
32
33
n/a
n/a
CoolerMaster Silent Pro M2 720W
15
15
15
15
16
21
25
32
n/a
Seasonic M12D 850W
14
14
14
14
14
24
37
42
42
Antec TP-750
12
12
14
14
18
33
40
40
n/a
Chill Innovation CP-700M
15
15
15
15
17
30
34
34
n/a
Antec Signature 650
15
15
15
18
18
28
36
47
n/a
Coolermaster M700W
14
14
18
21
25
27
34
34
n/a
Seasonic G360
<13
17
23
30
39
39
n/a
n/a
n/a
Cougar GX-700
15
15
18
20
25
32
35
36
n/a
SilverStone DA700
18
18
18
18
23
32
35
41
n/a
Nexus RX-8500
14
14
17
22
28
32
32
33
33
NesteQ ECS7001
22
22
22
21
23
25
36
37
n/a
PCPC Silencer 610
20
24
24
24
24
30
40
50
n/a

The green boxes are >30 dBA@1m SPL.
*<11 or 11= below the ambient of our anechoic chamber; immeasurably low @1m in any environment

Caution: Please keep in mind that the data in the above table is specific to the conditions of our test setup. Change the cooling configuration, the ambient temperature and any number of other factors, and you could change the point at which the fans start speeding up, as well as the rate of the rise in speed. The baseline SPL is accurate, however, probably to within 1 dBA.



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