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Antec Phantom 500

May 8, 2005 by Mike Chin
and
Devon Cooke

  • POSTSCRIPT added Oct. 22, 2005
Product
Antec Phantom 500

ATX
2.01 Hybrid Power Supply
Manufacturer
Antec
MSRP
US$200

The Antec Phantom 500 is a new, more powerful power supply based on
the fanless Phantom 350 that we reviewed last September
. Antec's 350W fanless PSU
recorded the highest peak efficiency we've ever seen, a whopping 88%.
The most visible difference between the two models appears to be the addition of
a fan in the 500 that turns on only at higher wattages to provide the extra capacity
required to support 500W output. Antec describes this as a Hybrid Fan technology.

Is the Phantom 500 a fanless PSU with an auxiliary fan for cooling at high power or is it a fan-cooled fan whose fan stops when the load is low? It's not a semantic question, and it is one of several questions we'll be asking in this review:

  • Under what conditions does the Phantom 500 run fanlessly?
  • Under what conditions does the Phantom 500 fan come on?
  • Does the Phantom 500 operate fanlessly up to 350W? This is the maximum rated power of the fanless Phantom 350.
  • When the fan comes on, how can its behavior be characterized — in terms of speed vs. noise vs. cooling?
  • When the fan comes on, how does its noise / power curve compare to quiet conventional fan-cooled PSUs?

We start this review with the usual photo of the retail box.



The Phantom is shipped in a large cardboard box.

The Phantom ships in one of the largest boxes we've ever seen for a power supply.
Part of the reason for this is the additional length that the cooling fan adds
to the chassis, but the main reason is to accommodate the substantial packing
materials that it is shipped in. Obviously, Antec is taking no chances when
it comes to shipping damage. Because the primarily fanless design requires hard-mounting
heavy heatsinks directly to the internal electrical components, the extra precautions
against damage are probably a good idea.



Care is taken to ensure the unit doesn't break during shipping; its surrounded
by an inch of soft foam on all sides.



Manual, mounting screws, optional support hardware, 24-pin to 20-pin adapter, AC cord and the PSU are the contents.

The manual for the Phantom is quite complete. It is in five languages and covers 21 pages, with
far more detail than the typical four page pamphlet.
It provides full electrical specifications.
Much of the information is highly technical, and often not publicly
available for many consumer PSU brands.

FEATURE HIGHLIGHTS

This information comes from the Antec web site product page and the manual.

FEATURE & BRIEF COMMENT

ATX12V version 2.01 compliant

The latest version of the spec.

24-and-20-pin adapter connector with detachable 4-pin section
for 20-pin for backward compatibility with older motherboards

Our sample came with a 24-pin connector with a 24-to-20 pin adapter. We're told this production run might have missed this change, which was also applied to the Phantom 350.
Dual +12V lines,
with dedicated circuits to isolate the CPU power line from peripherals
Standard for ATX12V 2.x.
Hybrid fan
design
Why a hybrid
PSU? Higher power capacity from a mostly fanless design.

Exceptional power efficiency up to 86% (US version) at
full load

If the older Phantom 350 is any indication, the Phantom 500 should
live up to this claim.

4 Serial ATA power connectors

Fairly standard for a quality modern PSU of this capacity.
PCI-E
graphic card power connector
For VGA cards
that draw >75W.
Fanless operation
for absolutely silent computing. Three user selectable fan kick-in points
for quiet computing under higher loads
The kick-in
point will be crucial for quiet computing. We'll be examining this closely.
Specially designed
internal heatsinks and chassis heatsink for maximum heat dissipation
This design
makes fanless operation possible.
Power Factor
value greater than 90% (EU only)
PF
correction is required in the EU, and it reduces efficiency.
Safety Approval: TUV, UL, CUL, CE, CB, FCC The more the merrier.

Gold plated connector for superior conductivity

Actually, both male and female connectors must be of the same metal in order to avoid long term chemical reaction and resulting increased contact resistance.

SPECIFICATIONS

Comparing the specifications of the two Phantom models is quite instructive.
Voltage rail capacities are almost identical. The +3.3V gets a 2A
boost and one of the +12V lines gains 1A. The large increase in capacity
comes from a higher combined wattage, not an increase
on any individual line. This suggests that the circuit design of the two models
is basically the same. The higher capacity of the 500W model is probably made
possible by the addition of the fan, not any special electrical engineering.

ANTEC PHANTOM 500 SPECIFICATIONS
AC Input
90~135VAC @ 9A, 47~63 Hz or 180~265VAC @ 5A,
47~63 Hz
DC Line
+3.3V
+5V
+12V1
+12V2
-12V
+5Vsb
Max Output
30A
30A
17A
18A
0.8A
2A
Min Load
0.3A
0.3A
0.3A
0.3A
0A
0A
Regulation
±5%
±5%
±5%
±5%
±5%
±5%
Ripple & Noise
50mV
50mV
120mV
120mV
120mV
50mV
Max Power
99W
150W
204W
216W
10W
10W
484W
500W

OTHER DETAILS

Unit Size

5.9"(W) x 7.2"(D) x 3.4"(H)

15cm(W) x 18.3 cm(D) x 8.6 cm(H)

Net Weight

7.5lbs / 3.4kg

Operating Temp.

10 ºC to 50 ºC

Power Efficiency

82% (with PFC) at full loads, 115V/230Vac 60/50Hz; this is for the EU version.

86%
w/ no PFC -- US version

PHYSICAL DETAILS

The sheer size and weight of the Phantom 500 is impressive. At 3.4 kg and 18.3cm depth, it is the biggest, heaviest PSU we've encountered. The casing is manufactured from extruded aluminum
and acts as a heatsink to move heat out of the unit. There is also a plastic module
on one end that contains the fan. This increases the total length of the unit,
making it about an inch and a half longer than a standard power supply. The extra length
may make it difficult or impossible to install the Phantom in some cases, although
it should fit most cases without any problems.



The fan is mounted on the inner end of the power supply in a plastic
module.



The rear end looks identical to the 350W model.

Some extra hardware to provide non-standard support at the back of the unit is provided; this requires some mechanical expertise. We'd recommend some kind of additional back support. The standard four screws that normally secure a PSU to a case will hold this Phantom, but the cantilever force on the back panel will be high. The back panel of lighter weight steel or aluminum panel cases would certainly flex with this much weight hanging off it. We'd ship a PC with this PSU installed only with additional back support; the manual has a caution to this effect.

The aluminum casing of the Phantom 500 appears to be identical to the 350W
version. Only the plastic module for the fan is different. We did not remove the casing entirely to compare the internal circuitry of the two models. Simply opening up the unit may affect the close coupling of internal components for heat conduction to the external casing.



There is a small air vent along the right side of the unit.



The grill on the rear panel is quite unrestricted, but it's easy to see that the airflow path through the unit is pretty obstructed.

FAN DETAILS



An unusual fan grill prevents the output wires from getting tangled in the fan.

The fan can be set to turn on at one of three preset thermal thresholds.
A small switch on the fan module allows the user to choose between "1",
"2", or "3". It is necessary to refer to the manual to discover
what these numbers mean.

According to the manual, the "1" setting sets the fan
to turn on when an internal temperature reaches 40°C. We do not know where this internal temperature
is measured. The "2" and "3" settings set the thermal threshold
to 47.5°C and 55°C, respectively. The switch came set to "1"; most silence-seekers will want to bump the setting
up to "3" right away.



The user can select one of three temperature thresholds for the fan.

Is this feature really necessary? Anybody who buys a Phantom will have low noise as their main goal, and if Antec
feels that it can perform at the "3" setting, why should they include
the more conservative settings? The manual has some instructions about this.

"How to set the fan operating mode

"....Before you set this switch, take a moment to think about how you usually use your computer.

"Position 1: "High Performance" mode.... We recommend this mode if you're a gamer or high-performance-oriented user, and you care more about ultra-fast performance than the noise level generated by your computer.

"Position 2: "Quiet Computing" mode.... We recommend this mode if you'd prefer a balance between high-performance computing and quiet computing.

"Position 2: "Quiet Computing" mode.... We recommend this mode if you're determined to have the quietest power supply possible. (Obviously, we don't recommend this setting for overclockers or gamers.)"

The obvious implication is that in a high thermal and power draw environment, it is safer to run the Phantom 500 at the most aggressive fan setting. But does this mean the PSU will not cool itself adequately when used at the "3" setting in a high power rig (that still draws less than 500W, of course)?

The cover of the plastic fan module
can be removed to access the fan, although this procedure requires some care. The fan measures 80x15mm. It is thinner and blows less air than most other power supply fans. The interior of the Phantom is densely packed with heatsinks, which limits
the amount of airflow that can be pushed through it. The restriction may require greater than usual air pressure from the fan to push the same amount of air. The shallow 15mm depth of this fan actually means it produces less pressure than standard 25mm depth fans.



The grill can be popped off revealing a thin 80 x 15mm fan.

Keep in mind that the Phantom was originally designed for fanless use;
in theory, the fan should not be required often in ordinary
use. The low-airflow fan and the airflow restrictions many be less important here
than for other power supplies. When the fan does turn on under heavy load,
with its much larger heatsinks, the Phantom should be able to use the minimal airflow more efficiently
than an ordinary power supply.

The manual also notes that "your chassis must be well-ventilated... make sure the exhaust fans installed in your PC chassis can cool the whole system without the help of a power supply fan."

CABLES AND CONNECTORS

The Phantom 500 has a total of seven cable sets:

  • 19" sleeved cable for 24-pin ATX connector
  • 24" cable with a standard 4-pin AUX12V
    power connector and an 8-pin 4x12V connector for EPS12V (dual CPU) - The latter feature is not in the Phantom 350.
  • 38" cable with three 4-pin IDE drive connectors and
    one floppy drive power connector
  • 30" cable with two 4-pin IDE drive connectors and
    one floppy drive power connector
  • 2 x 25" cables with two SATA drive connectors each
  • 19" 6-pin auxiliary power connector for PCI Express

For a power supply of this wattage, the Phantom 500 has surprisingly few cables.
This is a good thing: "surprisingly few" is still far more than most
ordinary systems require, and fewer wires to
impede case airflow. Even dual-processor servers should not be missing any connectors.



Cable sets are entangled as they leave the casing.

On minor issue that we encountered was the way the wires were tangled as they
leave the casing. The tangle of wires effectively shortens the total length
of the connectors, especially if two cable sets need to be pulled in opposite
directions. This is not an uncommon criticism of power supplies, but we expected
a higher level of workmanship.

ON THE TEST BENCH

For a fuller understanding of ATX power supplies, please read our article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides, closely followed by PSU manufacturers, at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to
the article
SPCR's Revised PSU Testing System
. It is a close simulation of a
moderate airflow mid-tower PC
optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with
its output load, which is exactly the way it is in a real PC
environment. But there is the added benefit of a precise high power load tester
which allows incremental load testing all the way to full power for any
non-industrial PC power supply. Both fan noise and voltage are measured at
various standard loads. It is, in general, a very demanding test, as the operating
ambient temperature of the PSU often reaches >40°C at full power.
This is impossible to achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are far too many variables in
PCs and far too many possible combinations of components for any single test
environment to provide infallible results. And there is always the bugaboo of
sample variance. These results are akin to a resume, a few detailed photographs,
and some short sound bites of someone you've never met. You'll probably get
a reasonable overall representation of that person, but it is not quite the
same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: One very important point is that the while
our testing loads the PSU to full output (even >600W!) in order to verify
the manufacturer's claims, real desktop PCs simply do not require anywhere near
this level of power. The most pertinent range of DC output power is between
about 65W and 250W, because it is the power range where most systems will be
working most of the time. To illustrate this point, we
recently conducted system tests to measure the maximum power draw that an actual
system
can draw under worst-case conditions.
Our most powerful P4-3.2
Gaming rig drew ~180W DC from the power supply under full load — well within
the capabilities of any modern power supply. Please follow the link provided
above to see the details. It is true that elaborate systems with SLI could
draw as much as another 150W, but the total still remains well under 400W in
extrapolations of our real world measurements.



The extra length of the Phantom 500 is obvious; it doesn't fit properly
on our test bench.

Ambient conditions during testing were 21°C and 20 dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet. This is slightly warmer and louder than is typical in the lab. All testing was done with the Phantom 500 fan controller
switch at "3", the least aggressive setting for fan cooling .

TEST RESULTS

ANTEC PHANTOM 500 TEST RESULTS
DC Output (W)
65
90
150
200
250
300
400
500
AC Input (W)
83
111
177
227
278
337
452
566
Efficiency
78%
81%
85%
88%
90%
89%
88%
88%
Intake Temp (°C)
26
28
32
35
37
39
43
44
PSU Exhaust (°C)
40
40
44
46
46
48
52
56
Fan Noise (dBA/1m)
n/a
n/a
n/a
24
29-32
35
36
37
Power Factor
0.57
0.58
0.60
0.62
0.63
0.65
0.67
0.68

NOTE: The ambient room temperature during testing
varies a few degrees from review to review. Please take this into account
when comparing PSU test data.

Please note -- you may need to refer back to the article, SPCR's Revised PSU Testing System, to understand the following discussion fully.

1. VOLTAGE REGULATION was well within the ±5% claimed. Throughout
the range of test power output levels, the range was as follows:

  • +12V: 11.9 ~ 12.1 V
  • +5V: 4.8 ~ 5.0 V
  • +3.3V: 3.1 ~ 3.3 V

2. AC-to-DC CONVERSION EFFICIENCY

As mentioned, the Phantom 350 peaked at a record 88% efficiency
at 300W when we tested it last September. We were expecting the Phantom 500 to perform
at least as well, and we were not disappointed. The Phantom 500 surpassed its
smaller brother and peaked at 90% efficiency: A new record! Even better, this
peak was reached at 250W output instead of 300W, meaning that the Phantom
500 will likely provide more benefit to real systems in real applications (at lower power) from its high-efficiency design than the original
version.

One thing that we noticed was the wide variation in
the efficiency of the 350W version, which ranged from 72% at 65W to 88% at 300W. The Phantom 500 is much better in this regard, starting with a high 78% at the 65W mark. It has a much flatter efficiency curve. At 90W output and higher, the Phantom always ran well above 80% efficiency, an impressive
achievement unmatched by any other power supply we've tested so far. Above 200W output (where the internal heat production of a power supply
is signficantly higher) efficiency never dropped below 88%. (Note that these figures apply to the more efficient non-PFC North American version.)

3. POWER FACTOR

Our review sample was the North American version, which does not feature PFC.
Power factor ranged from 0.57-0.68, which is typical of
non-PFC power supplies. The European and UK versions of Phantom both feature
active PFC that is rated for >0.95 power factor. Antec states that
these models are 4% less efficient than the North American version.

4. TEMPERATURE

The exhaust temp sensor was placed in one of the exhaust vent holes on the back panel of the PSU. The intake temp sensor was left where it has been for all the PSU reviews going back at least a year: One inch below and behind the PSU, inside the thermal test box.

Unlike all of the other power supplies we've tested, the difference between the intake
and exhaust temperatures was greatest at low output levels. This result reflects
the hybrid design of the Phantom 500. When the fan is not spinning, all the
heat generated by the power conversion process is only removed by condution and convection, so the unit gets fairly warm. At higher output levels, the temperature climbs higher and the
fan begins to spin, thus exhausting the heat more efficiently and keeping the unit
cooler.

Even at its full 500W output, the Phantom stayed surprisingly cool. The exhaust
temperature never rose above 60°C, a level that is occasionally broken even
by units with much larger, more powerful fans. The fan ramps up quickly enough that past 35°C intake temperature (200~250W load in our test setup and conditions), the temperature difference between exhaust and intake stayed at ~10°C, which is similar to that seen in high efficiency conventional fan-cooled PSUs.

It is interesting to note that the Phantom 350 is specified for safe operation up to 65°C, wherever this temperature is actually measured. In contrast, the Phantom 500 is rated for an operating temperature up to 50°C. Why should this be so?

Here's one hypothesis: The Phantom 500 is essentially a Phantom 350 with a fan. It is because the fan keeps temperature lower that the Phantom 500 can be allowed to run at higher output. In other words, if active airflow cooling was applied to the Phantom 350, and its overload protection settings changed, it could also safely produce 500W.

5. FAN, FAN CONTROLLER & ACOUSTICS (TEST RESULTS, continued)

At the "3"
setting where all the tests were conducted, the fan is supposed to turn on when the internal temperature reaches
55°C. We didn't have access to the internal thermistor; our standard temperature probes were used to determine
the trigger temperature.

In our test setup, the fan turned on when the intake or internal case temperature
reached ~33°C. The fan stayed running until the intake temp dropped to 32°C. The 33°C temperature
was reached after running the power supply at 150W output for more than
half an hour, in a 24°C ambient room.

This is surprising, given that the fanless Phantom 350 runs without a fan all the way to 350W output. It was questionable enough that we contacted Antec to find out whether this was normal fan controller behavior in this unit.

Antec's answer was that the Phantom 500's fan is set to turn on at the "3" setting when the load reaches ~200W. This calibration is imprecise, because it is an estimate based on temperature. In other words, the internal thermal sensor reaches 55° at ~200W load in a system with a level of airflow deemed suitable by Antec engineers. They could not tell me what "intake" temperature this correlates to.

The fan began spinning at a low level, putting out a quiet-but-not-silent
24 dBA/1m. The noise is a fairly pure tone that is higher in pitch than most
quiet 80mm fans, but at 24 dBA/1m, it is easy to ignore. As the temperature rose (in responsed to increased output), the fan ramped up fairly quickly. By 35°C intake temperature, the 30 dBA/1m noise level, which we consider the upper limit of "quiet", was breached.

It was difficult not to notice that slight variances in temperature and airflow
caused the fan controller to go up or down almost immediately. All airflow through the
test rig can be stopped by turning off the fans. This reduces the flow of hot air from the loaded resistors in the PSU tester, causing a temporary reduction in the air temperature at the PSU intake. It caused the fan controller to audibly ramp the
fan speed down within a second or two. Turning the test system fans back on
immediately caused the PSU fan to ramp up again.

This observed behavior suggests that the fan controller has two states:

  • Below the trigger temperature, the voltage fed to the fan does not vary with temperature; it is fixed at 0V.
  • Above the trigger temperature, the relationship between fan speed and temperature is linear, and there is very little hystersis. In other words, every change in temperature results in an immediate proportional change in fan voltage (along with its speed and noise).



Phantom 500 fan speed/temp curve




Other PSU fan speed/temp curve

The basic shape of the curve in the above right chart should be familiar to regular SPCR visitors. It is the same one used in many PSU fan controllers. The starting / default fan voltage is usually somewhere between 4 and 5 volts, and the fan spins at a slow, quiet rate. At the trigger temperature, the fan begins to ramp up, often in a linear fashion. The best fan controllers have a some of hysteresis in the latter portion of the fan controller's curve so that small changes in temperature do not lead to instant and rapid changes in fan speed and noise.

The chart on the left illustrates how the Phantom 500 fan controller works. The main difference here is that instead of 4~5V as the starting voltage for the fan, the Phantom 500 starts at 0V. Hysteresis is non-existent in the linear (sloped) portion of the fan controller's operation.

The irregular nature of the fan controller was most pronounced at lower fan
speeds; on our test system this was at about 200W output. In fact, the effect
made it impossible to make reliable measurements of the noise level. Even more
than usual, the above SPL measurements should be considered approximations of
what we heard.

Here is a recording of the noise we refer to. It was difficult to capture because of higher than usual ambient noise in the neighborhood, and because the thermals in the test box had to be varied a bit to cause the fan variances. You may have trouble hearing it. The SPL was not monitored during this recording, as we were also busy quietly turning the test box fan on/off. Our guesstimate is 24~26 dBA/1m. The load was 200W.

MP3: Antec Phantom 500 - variable fan noise at 200W load, with small changes in operating ambient temperature.

Finally, there was a small amount of buzzing that could be heard at times from under two feet disatance, directly behind the back panel. This buzzing did not appear to be directly related to load.

Sound Recordings of PSU Comparatives

Seasonic S12-430 @ 200W (22 dBA/1m)

Nexus NX4090 at 200W (30 dBA/1m)

Enermax Noisetaker
600W (2.0) @ 200W (30 dBA/1m)

Nexus 92mm case fan @ 5V (17 dBA/1m)
Reference

HOW TO LISTEN & COMPARE

These recordings were made with a high
resolution studio quality digital recording system. The microphone was 3" from
the edge of the fan frame at a 45° angle, facing the intake side of the fan to
avoid direct wind noise. The ambient noise during most recordings was 18 dBA or
lower.

To set the volume to a realistic level (similar to the original), try playing the Nexus 92 fan reference recording and setting the volume so that it is barely audible. Then don't reset the volume and play the other sound files. Of course, tone controls or other effects should all be turned off or set to neutral. For full details on how to calibrate your sound system to get the most
valid listening comparison, please see the yellow text box entitled Listen to
the Fans
on page four of the article
SPCR's Test / Sound Lab: A Short Tour.

ACOUSTICS VS. COMPETITORS

It would be instructive to compare the noise of the Phantom 500 against similar power competitors tested by SPCR in recent months. The ambient temp for every PSU test on this table was 21°C, except for the FSP Blue Storm, which was tested at 20°C.


NOISE AT VARIOUS POWER STATES COMPARED (SPL in dBA @ 1m)
DC Output (W)
65
90
150
200
250
300
400
500
Antec Phantom 500
n/a
n/a
n/a
24
29-31
35
36
37
FSP Blue Storm AX500
26
26
29
36
42
43
45
45
Enermax Noisetaker EG701AX-VE 2.0
23
23
27
30
n/a
35
42
45
Seasonic S12-430
18
18
19
22
26
31
32

n/a
Nexus 4090
21
21
24
30
n/a
38
38

n/a

Please note that although this data is accurate, it is within the context of SPCR test rig setup, which simulates a typical low-noise, low-airflow setup of the kind we most often espouse. Results will definitely vary based on case airflow, system components, applications and ambient temperatures. The audibility of the sound levels will also vary depending on your hearing sensitivity as well as ambient noise.

SYSTEM TEST

An informal test was run on a Phantom 500 in a system that was built by Mike at the time of testing. The
following components were used:

Altogether, this setup drew ~160W AC when running CPUBurn. This equates to about 135W DC output. The system was burned in for a day running Prime95 continuously. CPUBurn was also run on the machine for about two hours. The room ambient varied from 22°C to 25°C. During
this time, the PSU fan never turned on, meaning that the Phantom 500 was effectively
fanless. At no time during this load testing did the system exhibit any instability. The measured SPL during CPUBurn was measured at ~27 dBA at 1m from the front, top or sides. The acoustic character was predominantly the benign broadband wind noise of the smooth, slowly spinning fans. When the hard drives moved into seek, the SPL jumped 2~3 dBA, but in idle, the Raptor HDDs were amazingly quiet. The buzzing reported during the testing was occasionally present, but it could only be heard when directly behind the PSU and a foot way; practically speaking, it was a non-issue.

The system was not built with ultimate quiet as a target, but rather, high performance, stability and reliability at up to 30°C ambient room temperature — and very low noise. The original PSU choice was a Seasonic S12-430, but its main ATX cable was stretched a little too tight for comfort due to the positioning of the PSU so far from the motherboard. The Phantom 350 was a possible choice, but for higher reliability, the fan and the higher power capacity of the Phantom 500 seemed a better match for this system. After a couple hours of being turned on, especially when running CPUBurn, the top and back case panels near the PSU became somewhat warm to touch. The PSU back panel was a bit warmer, of course, but not at all uncomfortable to touch. Unfortunately, temperatures were not taken, but if I had to guess, I'd say the back of the PSU was not much higher than 40°C.

The configuration and mods for this case would have been the same with the S12. The additional 80mm fan under the PSU just seemed wise, given the hot running tendency of the 10K Raptor HDD positioned below it. (Even with the S12-430, airflow for the HDD was pretty modest because the 120mm fan in the S12 runs at such low speed.) Subjectively, from the user's point of hearing with the PC on the floor by or under a desk, the extra 80mm fan does not add to the overall noise. The two biggest noise challenges of this system were two small fans: One on the video card, and especially the one on the motherboard northbridge chip. Allowing the latter to ramp up easily destroyed the silencing work on all the other components; its high pitched, loud whiny whooshing at full speed was difficult to tolerate for more than a minute or two. It's only the fan controller in the BIOS that saved this DFI NF4 board from being summarily rejected.

CONCLUSIONS

The Phantom 500's extremely
high efficiency is noteworthy. We find ourselves crowning a Phantom as efficiency
champion once again. There must have been tweaks and production improvements to the circuit design of the original Phantom 350 to improve
the efficiency at lower output levels, and to maintain efficiency
above 80% throughout most of the output range. It may be possible that current production Phantom 350 samples also exhibit improved efficiency.

Its $200 recommended retail price is the same as the Phantom 350. At time of writing, the Phantom 350 can be found for as low as $130 from discount online stores, so the 500 can probably be expected to be available for a similar price as availability expands. The pricing suggests that the 500 is positioned alongside the 350 as an alternative, not as a higher rank model.

If the Phantom 500 had been equipped with a smoother fan and its controller configured so that the fan would start at say ~300W and ramp up without the quick variations in speed that causes annoyance, then there would be no need for the Phantom 350 at all. As it is, the two represent a somewhat complex choice with overlaps in suitability; neither quite replaces the other.

It is important to remember that neither the 350 nor the 500 are intended to be used in a fanless system. The Phantom 500 manual notes, "your chassis must be well-ventilated... make sure the exhaust fans installed in your PC chassis can cool the whole system without the help of a power supply fan." This advice is pertinent to every fanless ATX PSU on the market.

For the silent PC seeker, our general recommendation is to keep the overall system power as low as possible so that there is a minimal amouint of heat to content with. Our test system above is a good example of a powerful system that still does not even reach 150W DC maximum output. In this system, it would make no difference which of the two Phantoms was used, because the the 500's fan would probably not turn on unless ambient temperature soared, perhaps to >30°C. Some would say the 500 is a better choice for this system because it will be just as quiet as the 350, yet protect itself in a thermal emergency. Others would say they'd prefer to know that there is no fan to ever turn on and keep the thermal management in their own hands. The bottom line is that if the temperature at the PSU "intake" can be kept below ~33°C all the time, the 500 will be just as silent as the fanless 350. The fan trigger point is affected by ambient temperature, and it can also be controlled by adjusting the case airflow, especially in the vicinity of the PSU.

There is a stronger case for the Phantom 500 for the inveterate, power-hungry gamer who seeks a quiet PC. There are lots of such folks floating at SPCR these days; yes, even gamers are starting to hear the call of the silence siren. These PC users still want to run a thermally extreme system -- something like dual >75W VGA cards in a loaded high power system with a CPU that draws >100W. Or perhaps a dual-CPU system (since the Phantom 500 has an 8-pin EPS12V connector). Such a system could push the fanless 350 to its output limits and challenge its ability to keep itself cool. The Phantom 500's built in fan would certainly keep it cooler, and it would provide the necessary power. At the same time, when the system is in idle, reduced power consumption would likely bring the temperatures in a well-designed system down to the point where the Phantom 500 fan would turn off.

In this kind of application, the Phantom 500 has to compete with more conventional but still very quiet fan-cooled PSUs, such as the Seasonic S12-430 (or the slightly less quiet S12-500). Even though its maximum power is lower than the Phantom 500, 430W is probably still enough power for all but the most extreme gaming PCs. The main advantage of the Phantom 500 is that at lower power levels, it is silent, while the more conventional quiet PSU runs very quietly. But then there is price to consider, and whether or not the rest of the system components are quiet enough to make that PSU noise difference audible.

The Phantom 500 is also a good choice for silencing newbies with deep pockets. The
cooling fan is good insurance against burning the power supply in a system with
inadequate airflow. The user-selectible options on the fan controller let the
end-user determine their own level of thermal tolerance, although most newbies
will probably just set it to "3" and forget about it.

Adding a fan to a "fanless" power supply seems counterintuitive,
but it does provide a fail-safe option that is not present in the Phantom 350.
In most circumstances, the Phantom 500 will function well as a fanless
power supply so long as airflow through the case is well managed.

* * *

Much thanks to Antec
Inc.
for this Phantom 500 sample.

POSTCRIPT: Efficiency Correction

October 22, 2005

Recently, we discovered that our power supply testing equipment and methodology were providing erroneously high efficiency results. In general, the biggest errors occurred at higher
output load points above 300W. At lower output levels, the efficiency error
was often no more than one or two percentage points. No other tested parameters were significantly affected.

Through a fairly arduous process of discovery, analysis and old fashioned problem solving, we modified our testing equipment and methodology to improve the accuracy of the efficiency results and described it all in the article SPCR's PSU Test Platform V.3. As part of this revision, we re-tested most of the power supplies on our Recommended PSU List. In most cases, the same sample was used in the second test.

The corrected and original efficiency results for all the re-tested PSUs are shown in in the article, Corrected Efficiency Results for Recommended Power Supplies. The relative efficiency of the tested power supplies has not changed.
If the tested PSUs are ranked by efficiency, the rankings remain the same whether we use the original results or the new results.

This
data is also being added to relevant reviews as postscripts like this one.


CORRECTED EFFICIENCY: Antec Phantom 500

Target Output

65W

90W

150W

200W

250W

300W

400W

500W

Actual Output
67.2W
92.8W
152.2W
198.8W
251.9W
299.1W
398.9W
499.9W

Efficiency

Corrected
74.7%
77.3%
81.0%
82.1%
82.6%
81.9%
81.4%
78.1%

Original
78%
81%
85%
88%
90%
89%
88%
88%

In this case, our original efficiency calculations were way off across the board. It's not clear why they were so far off, as most other test results were reasonably close at lower power output points. The extreme high efficiency results we obtained originally have dropped mostly into the low 80s and high 70s — still very good results, and bettered only by the Fortron Zen among fanless PSUs.

Discuss this article in the SPCR Forums.

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