Q-Technology QT-02300 Power Supply

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TESTING

Testing Platform

The Q-Technology QT-02300 was installed in the same system used for other PSU reviews. It is a stable, (normally) very quiet, low airflow PC running Windows 98SE:

Case Landmark ATX-202 18" tower
CPU Pentium 4 - 1.6A (overclocked to 2.0 GHz)
Motherboard Gigabyte GA-81RXP
RAM 512 MB 2100 PC DDRRAM
Video Card Matrox G400 Max (dual mode, driving two 18" monitors)
Hard Drives

Seagate Barracuda IV - 20 G; Barracuda IV - 40 G Both drives in cage at bottom of case, behind inflow case fan.

Floppy Drive Generic
DVD Drive Toshiba SD-M1502
CD-Writer Creative RW121032E
Network Card Intel Pro/100VE - Built into motherboard
Sound Card Creative SB PCI128 - Built into motherboard
Fan - CPU 1 Panaflo 80mm "L" @5V over stock Intel heatsink
Fan - VGA 1 Panaflo 80mm "L" @5V over video card / NB heatsink
Fan - Case 1 Panaflo 80mm "L" @4V lower front case fan

Test Instrumentation and Environmental Conditions

CPU temperature
Motherboard Monitor 5 reading CPU diode
PSU temperature
Veriteq Spectrum 1000 with probe lodged in large PSU heatsink
Fan voltage
Heath / Zenith SM-2320 Multimeter across fan terminals
System power
Measured with Kill-A-Watt Power Meter
Noise*
Heath AD-1308 Real Time Spectrum Analyzer
Room 23-25° C; ambient noise ~32-34 dBA

Motherboard Monitor 5 enables monitoring of temperatures and voltages off motherboard sensors. With the P4 diode, it is usually accurate within 1° C. The Veriteq Spectrum 1000 will be familiar to anyone who has read other articles on this site: it is a highly accurate data logger that samples temperatures via its probe. For all PSU temperature measurements, the probe was lodged next to the the larger heatsink. The voltage to the fan was monitored using the Heath, an ordinary multimeter that has proven to be fairly accurate. Kill-A-Watt Power Meter was used to measure total system power consumption in Watts.

The Heath AD-1308 is a portable half-octave Real Time Spectrum Analyzer with sound level meter (SLM) functions. Below 40 dBA, its accuracy is limited to 3 dB increments, down to 23 dBA. Some 15 years old, this LED-based unit has long since been displaced by digital devices with better interfaces to PCs. (Shown on page 3 of the Seasonic PSU review.) The "A" weighting was used, as recommended by numerous acousticians; it most closely approximates the frequency response characteristics of human hearing.

The microphone on the sound meter was positioned about an inch to the side of the PSU fan exhaust to avoid fan turbulence in the microphone itself. The dBA obtained here cannot be compared to any other measurements due to the lack of adherence to a repeatable standard and the uncontrolled reflective environment.

No effort was made to change acoustics in the lab, which is a small room measuring 12 by 10 feet, with an 8 foot ceiling. The PC sits on the bare hardwood floor, under a table on 4 legs that supports the monitors.

NOTE about Room Temperature: For comparisons against the data in our other PSU reviews, please remember to factor in any ambient temperature differences. The test environment is not air-conditioned.

At Startup

The QT-02300 starts at a very quiet level. The noise is smooth, consistent and has little high pitched content. It is ever so slightly quieter than the Zalman or Seasonic competitors reviewed here. This noise difference could not be confirmed with the SLM which lacks the necessary resolution; it is probably 1-2 dB or less, even from less than a foot away. The QT-02300 is louder than our virtually inaudible reference power supply, which run Panaflo 80mm "L" fans at ~4.5V.

Aside from fan noise, there is also a small amount of coil whine, which varies from inaudible to plainly audible with the test platform PC on the floor under the desk, several feet away from my ears. The whine does not seem related to load, and may be result of some type of conflict between the video card or motherboard and the PSU. The whine was considerably subdued on an AMD XP test platform.

The following table shows measurements from boot to 60 minutes, with the system idle, .

Startup Log A: 25-26° C room ambient

Time (min)
0
10
20
30
40
50
60
CPU (° C)
36
38
41
43
44
45
45
PSU (° C)
29
35
39
41
42
43
43
System power (W)
83
83
84
83
83
84
83
Fan (VDC)
5.62
5.65
5.71
5.75
5.75
5.75
5.75
Noise dBA
39
39
39
39
40
40
40

The system power of 83W is 5W higher than the Zalman at idle in the same system, and 11W higher than the Seasonic. It suggests lower efficiency. The PSU temperature also is a little higher than with either Zalman or Seasonic.

With CPU Stability Test

CPU Stability Test by Jouni Vuorio is a useful tool to stress systems. Here are the results over 45 minutes of CPU stress testing, begun after the system was turned off, allowed to cool to ambient, then restarted. System power stayed at a constant 128W. The room ambient was 26° C.

Time (min)
0
5
10
15
20
25
30
35
40
45
CPU (° C)
37
55
61
63
64
65
65
66
66
66
PSU (° C)
32
39
45
48
50
52
52
53
53
53
Fan (VDC)
5.6
5.6
5.7
5.7
5.7
5.8
5.8
5.8
5.8
5.8
Noise dBA
39
39
39
39
39
40
40
40
40
40

The measured noise difference between start and finish was 1 dBA. This is an approximation, as +/- 1 dB is the resolution of the SLM. Subjectively, the sound level of the PC at the end of this test was not higher than at the beginning.

Q-Technology vs Zalman vs Seasonic

The CPU Stability Test results are considerably different from that obtained with the Zalman ZM300A-APF and the Seasonic SS300-APFC. Referring to the CPU Stability Tests on the other PSUs, the following is a comparison of results at the end of the 45 minute CPU stress test:

45-min CPU Stress Test
Q-Technology QT-02300
Zalman ZM300A-APF
Seasonic SS300-APFC
CPU (° C)
66
60
65
PSU (° C)
53
41.8
45.2
Fan (VDC)*
5.6 / 5.8 - 3.5%
5.8 / 7.2 - 24%
4.3 / 4.8 - 12%
Noise dBA*
39 / 40
40 / 45
39 / 43
Ambient (° C)
26
26
23
Power (W)
127
124
114

*The first figure is the measurement at the start of the stress test; the second is at the end; the third figure is the percentage gain between start and finish.

Notes on the comparison:

  • CPU temperatures, fan voltages and ambient temperatures are probably accurate to within 5%.
  • The PSU temperature only tells of the temperature at a specific spot on one heatsink in each PSU. A small repositioning of the probe or tighter coupling to the heatsink will result in different temperature readings.
  • The noise measurement is most subject to error, due to the limitations of the measuring SPL meter and variations in background noise.
  • The measured fan voltage cannot be regarded independently of the fan that each PSU is equipped with. The QT-02300 fan has the lowest current rating (0.15A); the Zalman and Seasonic fans are rated at 0.24A and 0.25A, respectively. Lower AMP rating does mean lower speed and lower noise. It is more instructive, therefore, to consider the % difference between start and finish.
  • CPU, PSU and case temperatures are all affected by the airflow provided by the PSU fan, as it is a primary hot air exhaust "driver". This is a basic cooling concept built into the ATX case specification.
  • Although QT-02300 efficiency is specified at 65%, the same as Seasonic, its actual power measured was 13W higher. The data suggests the Q-Technology sample is lower in efficiency than the Seasonic or Zalman samples.
  • These are single samples from production lines that produce thousands of units. It is not realistic to expect that every Q-Technology, Zalman and Seasonic unit will behave exactly like the samples tested here. A 5% tolerance factor is probably not unrealistic.

Keeping these factors in mind, the comparison suggests that

  • The Q-Technology PSU keeps itself quieter by using a high quality, lower noise fan, and by keeping the speed of that fan low at all times.
  • The tradeoff in the Q-Technology is higher temperature within the PSU itself, and to some degree, in the CPU and the case as well. Because the exhaust airflow provided by its fan is lower than the other PSUs, the QT-02300 may tend to increase temperatures somewhat in other components in the PC.
  • The ambient temperature was 3° C higher than when the Seasonic was tested; at 23° C, the Q-Technology would probably have provided lower than the measured CPU and PSU temperatures.

CONCLUSION

The Q-Technology QT-02300 sports the quietest fan we've encountered in a PSU so far, by a small margin. This may be the key to the original Q-Technology's quiet mystique. No doubt this aspect of its performance will please whoever seeks it out in search of a quiet PSU.

The coil whine exhibited may be unique to this sample or to the combination of the components in the test platform. This test platform did cause excessive coil whine in Antec PSU samples as well. In future, the sample will be tried on another system, and results will be reported here as a postscript.

The unresponsiveness of the PSU fan control circuit to a fairly high level of heat is a bit worrisome. Given that the total power draw was only 127W, we simply don't know what the fan control circuit will do closer to the maximum capability of the PSU. (This is a shortcoming of the PSU review setup we are working to correct.)

The concerns about heat are somewhat allayed by the promise on the manufacturer's website of "100,000 hours MTBF (mean time between failure) at 75% of maximum continuous output loading at 25° C ambient conditions." (Of course, the statement begs the question of which ambient conditions -- in the room or in the case?) To the question of heat, Michael van der Jagt of Q-Technology's distributor, CG Consultant BV, responded:

The critical components such as semiconductors and transformer can withstand about 120° C. A temperature of 55° C inside is no problem for the power supply.

PRO

CON

  • Quietest fan in a PSU by a small margin
  • Gets quite hot; small air intake vents
  • Stable
  • Case air exhaust stays low at higher loads
  • Good build quality
  • Coil whine sometimes audible
  • Universal AC input; Active PFC
  • Price?
  • Proper wire grill for fan

Our thanks to CG Consultant BV for the review sample and their support. And thank you, QuietPC.ca for delivering the review sample to us.

* * * * *



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