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Zalman ZM300A-APF PSU

June 12, 2002 -- by Mike Chin

Product: Zalman ZM300A-APF
Manufacturer: Zalman
Tech Co. Ltd.
Supplier: Zalman
Tech Co. Ltd.

Zalman of Korea needs little introduction to quiet PC enthusiasts. They burst on the scene with their amazingly ingenious "flower" or "fan" style heatsink some 18 months ago and have steadily expanded their range of products for quiet computing. Much of Zalman's focus has been on heatsinks based on variations of the original "flower" concept, for which they been awarded an impressive total of 22 patents thus far.

When their ST300BLP 300W power supply came on the market, it was hailed by
many as a welcome addition to the growing range of quiet PC products. However,
the response was not unanimous; some reported that while quieter than most PSUs,
the ST300BLP was still not quiet enough.

Knowing that the ST300BLP has a thermistor-controlled fan, we suspected that
it might feature a quieter fan than other PSU, but perhaps it still spins too
quickly, too soon, like the vast majority of thermistor-controlled PSU fans.
Silicon Acoustics,
a great web retail shop for those seeking quiet PC products, kindly sent me
a sample of the Zalman ST300BLP power supply to review some weeks ago.

The ST300BLP PSU was a bit of a disappointment. It is quiet compared to many
PSU, but not quiet enough by Silent PC Review standards to truly justify being
branded as a quiet product. While trying to write an honest review that would
not discourage an innovative company that's making a difference in the noisy
PC world, we heard about a new and improved PSU from Zalman. Direct contact
with Zalman resulted in the prompt delivery of a review sample of their new
ZM300A-APF. (Whew! Saved by product development!)

ZM300A-APF: WHAT YOU GET

The suggested retail price of the ZM300A-APF is $74.95, the same
as the earlier ST300BLP.

What do you get for your money? Firstly, a nice retail display
box announcing their new slogan across the top: The Quiet Cooling Solution.
Inside, there is a nice fold-out manual, the ZM300A-APF PSU itself in bubblewrap,
and a handy little adapter that splits a Molex power connector into four 3-pin
fan connectors, two white ones for 5V, and two black ones for 12V. They call
it a Multi-Connector (ZM-MC1). It's a nice touch that will appeal to
quiet PC enthusiasts who like to run 12V fans at 5V for minimal noise. With
this handy little adapter, there's no need to hack around with wires and connectors
and soldering irons. There's hardly even a need for something like a fan bus.

A welcome change is the wire fan grill instead of the stamped-out
fan exhaust slots from the ST300BLP. Zalman presumably responded to market feedback,
something worthy of praise in itself. The new PSU has a cover that features
slots for air intake above the CPU area (in a tower case). This is a big change
from their original PSU, which has no vent openings on the cover.

One other obvious change is the absence of an AC input voltage
switch. This unit, like the Seasonic tested earlier, automatically adjusts for
any AC voltage from 100V to 240V. The manual attributes this feature to its
Active PFC circuitry. The original ST300BLP featured passive PFC.

POWER CORRECTION FACTOR

Increasingly, switched mode power supplies (SMPS) are being
designed with an active power factor correction (PFC) input stage. This
is mainly due to the introduction of regulations aimed at restricting
the harmonic content of the load current drawn from power lines. However,
both the user and the power company benefit from PFC, so it just makes
good sense.

Power Factor Correction (PFC) can be defined as the
reduction of the harmonic content, and/or the aligning of the phase angle
of incoming current so that it is in phase with the line voltage. Mathematically,
Power Factor (PF) is equal to Real Power/Apparent Power. The basic concept
behind PFC is to make the input look as much like a resistor as possible.
Resistors have a power factor of 1 (unity). This is ideal, because it
allows the power distribution system to operate at its maximum efficiency.

Non-PFC power supplies use a capacitive filter at
the AC input. This results in rectification of the AC line, causes high
peak currents at the crests of the AC voltage. These peak currents lead
to excessive voltage drops in the wiring and imbalance problems in the
three-phase power delivery system. This means that the full energy potential
of the AC line is not utilized. Nonlinear peak currents also distort output
voltage and create harmonic frequencies. There is now an international
standard for controlling harmonics (IEC100-3-2) and PFC is mandatory for
home appliances consuming 70W or more power in EU nations as of January,
2001 PFC circuits are classified into two types: active and passive.

Passive PFC uses passive elements such as a ferrite
core inductor on the input source to create a countering reactance. While
easily applied to the existing power circuitry without much modification,
the power factor is low (60 - 80%), the AC input must be chosen (115VAC
/ 230VAC), and the harmonics produced from the difference between the
capacitance and the inductance are hard to control. Significant electromagnetic
noise can result with an 115VAC input source

Active PFC uses switching regulator technology with
active elements such as IC, FET and diodes, to create a PFC circuit This
circuit has a theoretical power factor of over 95%, reduces total harmonics
noticeably, and automatically adjusts for AC input voltage. However, it
requires a complex EMI filter and an input source circuit, and is more
costly to build.

OK. You're probably asking, What is Active Power Factor
Correction?
The Seasonic PSU featured it, too, but it was never explained.
How does Active PFC differ from Passive? If these questions come
to mind, please read the sidebar on the right. This explanation is culled from Zalman
and Seasonic's literature, as well as this
PDF document
at General Semiconductor's web site. BTW, here's the short
and simple on PFC: The basic concept behind PFC is to make the input look
as much like a resistor as possible.
(A resistor is the simplest electrical
load.)

The fan used in the ZM300A-APF is model MGA8012HB by Protechnic
Electric, a brand I've not seen before. Judging by its 0.24A current rating,
it should be similar in RPM and CFM to the fans found in most PC power supplies.
I believe the B at the end of the model designation stands for ball bearing,
as opposed to sleeve. At startup, it is quiet.

A quick listen to the fan held in free air outside the PSU revealed
that it has a smooth quality when driven at 12V. As the voltage is dropped,
overall noise comes down steadily, with little of the bearing chatter that prevents
some fans from achieving quiet low speed performance.

Under the cover, the most notable aspect of this PSU are its two
large heatsinks. With a "L" cross-section, raised ridges and numerous
circular holes, these heatsinks are just about as large in surface area as any
I've seen in a computer power supply.

Note the black colored leads on the top of one of the heatsinks.
It leads to a thermistor hot-glued to the heatsink.

Yes, like the original Zalman ST300BLP, the Seasonic, the Enermax and numerous other PSUs, the Zalman ZM300A-APF fan speed is thermistor controlled.

THERMISTOR CONTROLLED FAN

As noted in the review of the Seasonic
SS300-FS
, most thermistor fan controlled PSUs usually start out fairly quiet,
but the fan(s) quickly speed(s) up to become quite noisy, even with a minimal
load and modest environmental temperature. The Seasonic was the first PSU I'd
seen that does not exhibit this behavior. The Zalman ZM300A-APF is the second.
True to the manufacturer's claims for its CNPS
(Computer Noise Prevention System)
products, this PSU runs very quietly.

Zalman states that its CNPS products cut traditional computer
system noise of 30dB or higher to 20dB or lower, which is below what a normal
user can usually notice.
However, no information about noise measurement
standards is given, so the description is of limited usefulness. For the ZM300A-APF,
a graph plotting the speed of the PSU fan and the temperature of its heatsinks
is provided in the manual. It was scanned and made prettier for this show-and-tell:

Don't be surprised if it looks familiar. Replace the horizontal
scale with Watts, and the vertical scale with Fan Voltage, and you'd get a graph
similar to that provided for the Seasonic PSU. The Zalman ZM300A-APF manual
states,

When the temperature inside the power supply is 55° C or less, the
cooling fan will operate in Quiet or Silent mode
.

Referring to the graph, it appears Zalman's definition of Silent
is when the fan is spinning at ~1350 RPM or less, while Quiet is when
the fan is spinning under 1500 RPM.

Regardless of semantics, this graph suggests that Zalman has struck
upon a similar approach to PSU cooling as Seasonic: Use a quiet fan that is
capable of fairly high airflow, run it at minimal speed through low and medium
loads, and allow it to speed up only when HS temperature reaches a certain minimum
level. According to the above graph, that minimum is about 42-43° C, very
similar to the Seasonic. For the vast majority of PC systems, the fan in this
PSU should run at minimal speed (and noise) under most conditions.

If this approach to PSU thermistor fan control is a trend, it's one quiet PC enthusiasts should be pleased to see!

SPECIFICATIONS

The published 75% efficiency at full power is noteworthy.
In response to a direct inquiry, Zalman stated that at 122W and 120VAC, the
efficiency is 72-73%
. The small drop is normal for switch mode power supplies;
they are most efficient at full power. These figures are impressively high,
as most PSU efficiency is specified to be 65% to 70% at full power.

The efficiency rating tells us how much energy is wasted as heat
by a PSU. At full power, the Zalman generates 100W of heat while delivering
300W of electrical power. A typical 65% efficiency PSU would generate 161.5W
of heat delivering 300W. That is a huge difference in the amount of heat for
a PC case. At the more realistic power level of 122W, the Zalman generates 50W
of heat. Assuming that the efficiency of a typical PSU drops to 62%, it would
generate 75W of heat. 25W is still a very significant amount of heat.

In practical terms, a less efficient PSU produces more heat, and
thus makes all components run hotter. To maintain safe component temperatures
with a less efficient PSU normally requires higher airflow in the case, which
means more fan noise. To state the obvious, conversely, a higher efficiency
PSU should allow for adequately cool components with lower airflow and lower
fan noise.

The DC output specifications are consistent with those
for most quality 300W PSU. (They are, in fact, identical to those for the Seasonic
SS300FS.)

DC Output
Regulation

Ripple & Noise

Output Load Current

Combined Power

min
max
peak
+3.3VDC
+,-5%

50mV

0.3A
28A
n/a
180W
280W
+5VDC
+,-5%

50mV

0.1A
30A
+12VDC
+,-5%

120mV

0A
15A
18A
n/a
-12VDC
+,-5%

100mV

0A
0.8A
n/a
20W
-5VDC
+,-10%

120mV

0A
0.3A
-5VSB
+,-10%

50mV

0A
2A

TESTING

Testing Platform

The Zalman ZM300A-APF was installed in the same system as that used in the
Seasonic PSU review. It is a stable, very quiet, low airflow PC running Windows
98SE, fully updated:

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 Both drives in cage at bottom of case, behind inflow case fan
Seagate Barracuda IV - 40 G
Seagate Barracuda IV - 20 G
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
Fans
1 Panaflo 80mm "L" @5V over stock Intel heatsink
1 Panaflo 80mm "L" @5V over video card / NB heatsink

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 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 27-29° C; ambient noise ~32-34 dBA

Motherboard
Monitor 5
enables monitoring of temperatures and voltages off motherboard
sensors. With the P4 diode, there is little question of inaccuracy here; 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 thermistor on the top of one of the heatsinks. The Heath is an ordinary
multimeter that has proven to be fairly accurate.

Kill-A-Watt
Power Meter is a new addition to our test bench that provides accurate power
draw in Watts for all kinds of AC powered devices. In direct comparison, the
readings from the DIY
super simple power meter
used before appear to be about 10% too low.

The Heath AD-1308 is a portable half-octave Real Time Spectrum
Analyzer with SPL meter 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 an uncontrolled reflective
environment. (Sorry, but we will not have access to that University of BC
anechoic chamber till September, at least.)

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 uncarpeted hardwood
floor, under a table on 4 legs that supports the monitors.

NOTE about Room Temperature: Sharp-eyed readers will notice that the
ambient room temperature in some of the tests was upwards of 29° C, compared to 20-23° C in previous reviews. Summer arrived
for a few days, and the lab does not have air conditioning. For comparisons against the data in our other PSU reviews, please remember to factor in this ambient temperature difference.

At Startup

The Zalman starts at a very quiet level. Subjectively, the noise it emits is
a bit smoother and seems quieter than the recently reviewed Seasonic, but the
difference is difficult to measure with the Heath AD-1308 analyzer. There is
a difference in the quality of the noises emitted by the Zalman and the Seasonic:
the latter has a bit more of a soft clicking (bearing noise), which makes it
sound slightly rougher. Aside from fan noise, there is also a small amount of
coil buzzing in the Zalman, not audible when the PSU is running inside a PC.
The Zalman is louder than our virtually inaudible reference power supplies,
which run Panaflo 80 mm fans at 5V or less.

The following table shows measurements taken over 16 minutes with the system
idle, from bootup.

Startup Log A: 28-29° C room ambient

Time (min)
0
2
4
6
8
10
12
14
16
CPU (° C)
40
42
44
44
44
44
44
44
44
PSU (° C)
31
33
34
35
36
37.5
38
39
39
System power (W)
78
79
79
81
78
78
78
78
78
Fan (VDC)
5.52
5.65
5.86
5.98
6.09
6.14
6.21
6.29
6.31
Noise dBA
39
39
40
41
41
42
42
43
43

Note that the PSU temperature continued climbing after the CPU temperature
stabilized at 44° C. In the current room temperature (28-29° C) with
the PC at idle, the PSU heatsink temperature seemed to stabilize at ~39°
C, and the PSU fan voltage at around 6.2-6.3V.

This data conflicts somewhat with Zalman's graph, which shows the fan speeding
up at 42-3° C.

The next morning, with the ambient room temperature several degrees lower at
about 26° C, the startup log was repeated.

Startup Log B: 26° C room ambient

Time (min)
0
2
4
6
8
10
12
14
16
CPU (° C)
37
38
39
40
41
42
42
42
42
PSU (° C)
27.6
28.7
30
30.9
32
32.2
32.5
33
33
System power (W)
78
78
78
79
78
78
78
78
78
Fan (VDC)
5.5
5.65
5.81
5.80
5.87
5.82
5.89
5.83
5.91
Noise dBA
39
39
40
40
40
40
40
40
41

With Hard Use

Photoshop 6.5 and Adobe Framemaker 6.0 were opened with large files in both.
For good measure, an e-mail program and MS Internet Explorer were also opened.
The game Command and Conquer: Red Alert 2 was opened and displayed
on the main monitor. On the secondary monitor, work on this article was done
in Macromedia Dreamweaver 4 while leaving all the other programs on, with occasional
jumps to the game. Here are the results after 30 minutes.

*
Start
30 minutes
Ambient
26° C
26° C
CPU temperature
42° C
53° C
PSU temperature
34° C
39° C
Fan voltage
5.8
6.4 V
System power
81W
78W to 98W
Noise
40 dBA (A)
43 dBA (A)

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. System power stayed at a constant 124W. The room ambient
as 26° C.

Time (min)
0
5
10
15
20
25
30
35
40
45
CPU (° C)
40
55
58
58
58
59
58
59
59
60
PSU (° C)
35
38.4
40.7
41.2
41.2
41.2
41.5
41.6
41.6
41.8
Fan (VDC)
5.84
6.18
6.87
7.02
7.07
7.1
7.14
7.15
7.14
7.19
Noise dBA
40
42
44
44
45
45
45
45
45
45

The measured noise difference between start and finish was about 5 decibels.
This is definitely an approximation, as environmental conditions were not ideal.
The subjective impression jibes with that number -- the fan did get louder,
and this difference was substantially louder than before. The sound level of
the PC at the end of this test is too high to be considered quiet by our standards.
However, running torture programs is not something the usual PC user is likely
to do often, and the noise was substantially less than with most other thermistor-controlled
fan PSUs.

Despite Zalman's charts to the contrary, the fan voltage varies closely with
heatsink temperature even when the latter is well under 40° C. The RPM and
sonic difference effected by a 0.1 to 0.2 Volt changed is subtle, however. Note
that the PSU temperatures did not rise much beyond 41° C, regardless of
continued load on the CPU, and the maximum CPU temperature reached was 60°
C.

Zalman vs Seasonic

The CPU Stability Test result is considerably different from that obtained
with the similar Seasonic SS300-APFC. Referring to the CPU Stability Test on
the Seasonic as reported here,
the following is a comparison of results at the end of the 45 minute CPU stress
test:

*
Zalman ZM300A-APF
Seasonic SS300-APFC
CPU (° C)
60
65
PSU (° C)
41.8
45.2
Fan (VDC)
7.19
4.84
Noise dBA
45
43
Ambient (° C)
26
23
Power (W)
124
114

A few things to note:

  • CPU temperatures, fan voltages and ambient temperatures are probably accurate
    to within 5%.
  • The PSU temperature only tells of the temperature seen by the probe in a
    specific spot one heatsink in each PSU. A small repositioning of the probe
    or tighter coupling to the heatsink could 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.
  • 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 tower case specification.
  • Although Zalman claims efficiency of 72-75% and Seasonic claims ~65%, the actual power measured was 10W higher for the Zalman. This suggests the Zalman sample is slightly lower in efficiency than the Seasonic sample.
  • These are single samples from production lines that produce thousands of
    units. It is not realistic to expect that every Zalman ZM300A-APF and every
    Seasonic SS300-APFC will behave exactly like the samples tested here. A 5%
    tolerance factor may be generous, but probably not unrealistic.

Keeping these factors in mind, the comparison suggests that

  • The Zalman PSU does a better job of keeping itself and the case cooler.
    Both CPU and PSU temperatures are significantly lower than with the Seasonic,
    suggesting better hot air exhaust and throughput due to its higher fan voltage.
    The large heatsinks in the Zalman may also contribute to the lower PSU temperature.
    All of this is likely related to the efficiency ratings of the two PSU: 75%
    for the Zalman vs. 65% for the Seasonic.
  • The ambient temperature was 3° C higher when the Zalman was tested;
    one can conjecture that at 23° C, the Zalman would have provided lower
    CPU and PSU temperatures and/or lower noise.
  • The tradeoff in the Zalman may be a slightly faster rate of fan noise increase
    under load. However, the slightly lower noise of the fan in the Zalman may
    offset its higher driving voltage.

CONCLUSION

The Zalman ZM300A-APF raises the stakes in the quiet PSU races. Impressively
constructed and designed for excellent cooling while maintaining low noise for
a wide range system loads, the new Zalman takes clear aim at the growing market
for quiet computer power supplies. The shot, while not quite dead center, is
close enough to make the ZM300A-APF a major contender.

PRO

CON

  • Quiet and cool
  • Not as quiet as our reference modded PSUs
  • Intelligent fan control
  • Price?
  • Stable
  • Excellent build quality, great heatsinks
  • Universal AC input; Active PFC
  • Multi-Connector almost like fan bus

Our thanks to Zalman for the review sample and their support. And thank you,
Silicon
Acoustics
, for getting us started with a Zalman PSU.

Zalman products are sold worldwide. Please check the Zalman
website
for dealers in your area. Silicon Acoustics sells Zalman products,
of course.

* * * * *

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