Zalman ZM1000-HP: Quiet KiloWatt PSU

Power
Viewing page 5 of 5 pages. Previous 1 2 3 4 5

7. TEMPERATURE & COOLING

Our sample ran quite cool, with the temperature rise through the unit staying below 10°C till past 300W output. The exhaust air temperature exeeded 50°C at 400W, and it rose steadily to 70°C after 15 minutes at continuous full load. Considering the amount of power passing through the unit, the temperature rise seems well controlled.

8. FAN, FAN CONTROLLER and NOISE

The PSU fan stabilized at 4.6V within a minute after turn on. The Sound Pressure Level (SPL) reading on the test day was 20 dBA@1m, audible at 1m, but quiet and smooth. It would have measured lower had the ambient in the lab been lower, but it was 19 dBA that day.

There was no audible buzzing from a meter away. There was none at this distance above the fan noise at any load. When the fan was stopped with a plastic wire tie jammed into the blades, a bit of buzzing could be heard from a foot away, but this was about at the same level as fanless PSUs we've tested. When the Standby Noise Reduction switch was turned on, even this buzzing disappeared. In other words, audible buzzing or humming was not an issue.

The fan noise and voltage remained essentially unchanged during testing all the way to over 400W output load. This is extremely quiet performance, the very best we've encountered in any PSU.

Beyond 400W, the fan speed and noise climbed quickly, as expected. The quality of the fan noise was quite decent, despite our anticipation of nastiness given its 2-ball bearing design. Surprisingly, 40 dBA@1m was the loudest the unit ever reached. Again, for a kilowatt PSU, this is quite amazing.

In the comparison table below, the >30 dBA@1m readings are highlighted in light green.

Comparison: Various PSUs Noise Vs. Power Output
Model
90W
150W
200W
250W
300W
400W
500W
600W
800W
1000W
Zalman ZM1000-HP
20
20
20
20
20
20
26
37
40
40
Enermax Modu82+ 625
19
19
20
21
22
26
36
37
n/a
n/a
Corsair HX520/620
22
22
22
22
22
29
40
40
n/a
n/a
Corsair TX650W
21
21
21
21
23
38
43
44
n/a
n/a
Corsair VX450W
21
21
21
22
26
44
50
n/a
n/a
n/a
Seasonic S12 E+ 650
20
20
20
21
26
38
40
40
n/a
n/a
Seasonic S12II-380
21
21
21
25
31
39
n/a
n/a
n/a
n/a
Antec EW 430
22
22
24
29
37
41
43
43
n/a
n/a
Zalman ZM600
25
27
29
30
31
36
40
40
n/a
n/a

The above comparison table should not be taken as absolute. It shows sound pressure levels recorded on SPCR's test platform. The ambient temperature varies a bit, in a range of 20~23°C, and some of the PSUs may have the small advantage of lower ambient temperature during testing. This can help lower the overall noise curve, and more importantly, increase the power level at which the fan starts getting seriously louder. Still, at higher power levels, the temperature in the test box is determined mostly by the load. There is also some variance in ambient noise. When it's quieter in the lab, the quietest PSUs actually measure lower at idle. The Zalman ZM1000-HP was measured as low as 19 dBA@1m... but not on the day of load testing.

The top two-thirds of the models in the table above represent the quietest PSUs SPCR has tested. The ZM1000-HP clearly stays quieter to a higher output load and temperature than any other PSU. It is a completely different animal than the ZM600, the last Zalman we tested. It can be fairly described as a truly quiet PSU for power hungry gaming systems.

MP3 SOUND RECORDINGS

These recordings were made with a high resolution, studio quality, digital recording system, then converted to LAME 128kbps encoded MP3s. We've listened long and hard to ensure there is no audible degradation from the original WAV files to these MP3s. They represent a quick snapshot of what we heard during the review. Two recordings of each noise level are made in some cases, one from a distance of one meter, and another from one foot away. More details about how we make these recordings can be found in our short article: Audio Recording Methods Revised.

The one meter recordings are intended to give you an idea of how the subject of this review sounds in actual use — one meter is a reasonable typical distance between a computer or computer component and your ear. The recording contains stretches of ambient noise that you can use to judge the relative loudness of the subject. Be aware that very quiet subjects may not be audible — if we couldn't hear it from one meter, chances are we couldn't record it either!

The one foot recordings are designed to bring out the fine details of the noise. Use this recording with caution! Although more detailed, it may not represent how the subject sounds in actual use. It is best to listen to this recording after you have listened to the one meter recording.

Each recording starts with 6~10 seconds of room ambience, followed by 10 seconds of the product's noise. For the most realistic results, set the volume so that the starting ambient level is just barely audible.

  • Zalman ZM1000-HP at up to 400W, 19 dBA@1m: One meter (This recoding is marked 19 dBA because it was recorded on a different day than the rest of the testing. The ambient on the day of this recording was 18 dBA, and the PSU measured 19 dBA@1m. But the sound that the PSU makes obviously does not change when the abient changes.)
  • Zalman ZM1000-HP at 500W, 26 dBA@1m: One meter

    The higher level noises were not recorded; you can rest assured they are simply too loud.

Sound Recordings of PSU Comparatives

CONCLUSIONS

The Zalman ZM1000-HP is really irritating. We don't want to like or recommend it because it's a gargantuan power supply of the type we have mixed feelings about... at best. No one needs a 1000W PSU. But...

This PSU is not just quiet, it is incrementally quieter than any other PSU we've tested. Perhaps that phrase doesn't have much impact because we say it often. In our work, a PSU that stays at minimum noise at an output level 100W higher than the best one we tested is significant. That's what this PSU does. At the same time, at the minimum level, it may be just as quiet as the quietest Seasonics, Corsairs and Enermaxes that have come before. Without doing very close A/B comparison listening in the same quiet room at the same time, we can only go by memory — and imperfect recordings and measurements.

Its electrical performance is impeccable in almost every way: The highest measured efficiency, extremely tight voltage regulation, etc. This Zalman is really at the cutting edge of PSU performance. The Enermax Galaxy 1000W PSU mentioned earlier shows its age in comparison; the past year has seen a lot of progress in PSU design and performance. The single fly in the ointment is the higher-than-normal AC ripple. As pointed out earlier, however, we don't really think it's that significant because the out-of-spec ripple is in the less important 3.3V line, and it occurs at such a high output.

Then there's the close attention to details like the label which identifies the 12V line distribution (which has never been done in any PSU we've encountered before!) and the clever 5V Standby No Noise switch. Maybe the heatpipes and thin aluminum fins are more than just gimmicks, too. Maybe it's another example of high attention to detail that helps the PSU's overall overformance. All this from a company that's gone so mainstream in recent years instead of staying at the unwashed edge where it was so likable. It's not easy for an iconoclastic reviewer to deal with!

Despite these positives, we can't recommend the ZM1000-HP without qualifications. Except in the most extreme of systems, many of the other PSUs in the noise comparison table above would actually provide the same acoustic performance; ie, the extra headroom of the ZM1000-HP would not necessarily translate to lower noise. You have to be something of a crazy gamer to want a kilowatt PSU. We've already said many times that no real-world DIY desktop computer needs this kind of power. But maybe you're totally obsessive-compulsive and you feel you should have at least 100% headroom even for the shortest pulse peak. Maybe you're that much of a dedicated gamer and you're going to use a quad-core dual-video card setup with a dual CPU board along with peltier cooling and a mini beer fridge built into the PC. Whatever. If uber power is your thing, this Zalman will do you right.

At over $250 from the lowest priced online discounters, it's a steep price to pay for a macho symbol most people will never even see or understand, but at least you can also brag that it's as quiet as your eco-loving, highly-sensitive cousin's 300W fan-tweaked Seasonic. (The 850W version was deemed the only super powerful PSU quiet enough for the EndPCNoise SPCR-designed Extreme Gamer PC.)

Much thanks to Zalman for this review sample.

* * *

SPCR Articles of Related Interest:
Power Supply Fundamentals
Recommended Power Supplies
Power Distribution within Six PCs
SPCR PSU Test Rig V.4
Enermax Modu82+ 600W
Enermax Galaxy: A KiloWatt power supply
Seasonic S12 Energy Plus 550 and 660
Zalman ZM600 heatpipe-cooled modular PSU
Seasonic M12-700
Corsair HX520 & HX620

* * *

Discuss this article in the SPCR Forums.



Previous 1 2 3 4 5

Power - Article Index
Help support this site, buy the Zalman ZM1000-HP Power Supply from one of our affiliate retailers!