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Signature 650 PSU: Antec's Challenge

Oct 30, 2008 by Mike Chin

Product
Antec Signature 650

650W computer power supply
Manufacturer
Antec Inc.
Market Price
~US$160

Antec is one of the longest estabilished brands for retail packaged power supplies. In the early days, the company's primary business was in retail PC cases, and they probably got into power supplies in order to provide a more complete package for their case buyers. Antec has since grown into the most successful case brand in the retail market, and they also do a booming trade in power supplies.

While the company does much of its own design, manufacturing is subcontracted to a number of partners. For power supplies, Antec used Channel-Well for a long time, then expanded their suppliers in the last few years to include Seasonic, FSP and Enhance. Now, they've partnered with Delta Electronics, possibly the world's biggest maker of electronic power supplies. Delta products in the US and Canada seem to be limited to fans and generic OEM power supplies, but the company is highly regarded in its industry, and it has the capability to design and make just about anything in power electronics. The Signature series models, the 650 and the 850, are the first fruits of the new partnership.

The selling prices suggested by Antec make it plain that these products are intended for the very high end market: $250 for a 650W PSU and $300 for 850W give these models the highest dollar-per-watt ratio of any computer PSU out there. Admittedly, the street prices have dropped substantially since the products were released a few months ago. At time of posting this article, Newegg in the U.S. currently sells the 650W model for $160, and the 850W model for $199. These prices are still on the high side for the power rating, but let's make a full assessment of what's being offered for the money.

PACKAGING & FEATURES

The elaborate packaging of the Antec Signature power supplies is reminiscent of other luxury consumer products, such as an expensive bottle of 30-year old single-malt Scotch or a jewel-studded chalice fit for a prince, not a PC component that will become invisible as soon as it is installed. We find such packaging wasteful and unecological, but we also know that it can sell more products and establish stronger brand image... and that's what the consumer trade is still all about.



A classy looking sleeve over a retail box that could fit a pair of small boots. The box itself is made of stiff, heavy cardboard that small children (and bigger, older ones) will immediately claim to store their favorite small playthings and keepsakes.



Aside from a handy manual and a signed individual QC report for the particular sample (with serial number), which are standard, a reviewer's guide was also provided, on paper and on a CD. The CD contents were a PDF copy of the guide plus a few glamour photos.



The box split in two, with detachable cables, AC cord and mounting screws below.


SIGNATURE 650 FEATURE HIGHLIGHTS (from the
product web page)
FEATURE & BRIEF Our comment
Voltage Regulator Modules for 3.3V and 5V lines

DC-to-DC conversion from the main 12VDC line eliminates the usual additional transformers for higher efficiency and transient response.
80mm Fan with Pulse Width Modulation (PWM) control PWM is more efficient, and in theory, allows the fan to run at very slow speed without risk of stalling, unlike straight voltage control. PWM often causes buzziness, however. The 80mm fan design is usually more efficient for cooling due to its straight-through airflow path compared to the right angle path 120mm fan PSUs.
Japanese made components Specifically, the fan and capacitors. Japan is upheld as a higher quality component producer.
Dual double PCB layout The circuit is spread out on two printed circuit boards. How? Later photos will show you. Should improve airflow and cooling. They claim the use of heavier components as well, though it's not clear exactly how that benefits... until after the unit is opened up and examined.
80 PLUS Bronze 82% or higher efficiency at 20%, 50%, and 100% load.
SLI Certification nVidia has checked and found it good for running two of its video cards in tandem. They specify limits, however: Cards no more powerful than 7900 GTX or Dual GeForce 7800 GTX 512MB
Hybrid Advanced Cable Management The mandatory cables are hardwired to reduce resistance, while the peripheral cables can be installed as needed... but this is the norm for modular cables, isn't it?
Safety: UL/CUL, TUV, CE, CB, CCC, FCC Class B, C-Tick Pretty standard.
Industrial grade protection circuitry prevents damage resulting from short circuits (SCP), over voltages (OVP), over power (OPP), over temperature (OTP), and over current (OCP) The more the merrier.
Universal Input, Active PFC Like just about every PSU
on the market.
MTBF: 100K Hours Min at Max. Load 230VAC, 25°C Ambient Conditions
Very good.
Antec's Quality 5 year warranty Very good!
Net Weight: 5.82 lbs

Gross Weight: 10.3 lbs

Size: 3.4"(H) x 5.9"(W) x 7.1"(D)
Good to know.

 

SPECIFICATIONS

The label on the PSU usually tells us most of what we need to know, but not all.



The product web page, surprisingly, did not appear to have complete specifications. The first table below is from the manual, which confirms the label; the second is from the reviewer's guide. The manual's power output details are more complete and correct: The total current for the 12V line
is given as 53A in the reviewer's guide and on the web site. This much current would be available on the 12V line
only if the other lines were delivering less than 14W (since
the maximum rating is 650W). The manual states more completely that 43A is available on the 12V line when the maximum total of 140W is drawn from the 3.3V and 5V lines. In an case, the reader should be aware that total 12V power capability
for any ATX12V PSU is not a fixed number, but can vary depending
on many conditions, including load on the other lines, and operating temperature.



Scanned from the manual.



From the reviewer's guide.

Three 12V lines: Note that three 12V lines are indicated. This usually means there are three separated paths for the 12VDC from the transformer/rectifier to the outputs. Each of these paths has a limiter on it to keep the current from exceeding the stated maximum. A user who seeks the maximum current from this PSU would want to know which outputs correspond to which 12V lines; this would allow the 12V load to be distributed evenly. Usually, this info is not provided, but Antec has done the smart thing and marked the modular output connectors as 12V1 or 12V3. However, whether all the attached cables are feeding off 12V2 (not likely) or a combination of the three 12V lines is not clear. Too bad that Antec didn't go all the way and tag or identify the 12V line for every output cable.

VISUAL TOUR

Along with Antec's NeoHE series (reviewed here three years ago), its Signature models are among the very few in-line 80mm fan power supplies on the market today. The overwhelming majority of retail PSUs use 120mm and larger fans in a configuration that requires a 90-degree turn of the airflow within the PSU. Often, this creates hot spots where airflow does not reach effectively. The more conscientious PSU makers often employ small vents next to the hot spots to help create some additional airflow, which then allow a bit of hot air to escape back into the PC. No such issues here with the Signature 650: The in and out vents are beautifully unrestricted, and there are no secondary airflow paths for hot to escape out into the PC case.



The 80mm fan harkens back to an earlier time, but the casing length suggests otherwise.



Matte black finish, modular three output connectors.



Great intake vents! Note 12V1 and 12V3 labels.

OUTPUT CABLES

Attached

1 - ATX connector (550mm) 20+4 pin

1 - 12V EPS connector (550mm) 4x2 (8-pin)

1 - Aux12V connector (550mm) 2x2 (4-pin)

1 - PCIe (550mm) 6/8-pin

1 - three 4-pin HDD connectors and 1 floppy drive connector (950mm)

1 - three SATA connectors (800mm)

Modular

1 - PCIe (550mm) 6-pin

2 - three 4-pin HDD connectors (850mm)

2 - three SATA connectors (800mm)

Note that only two of the modular HDD cables can be used simultaneously.

A LOOK INSIDE

Opening up the unit required the removal of six screws, not the usual four: Two on the bottom, two on top, and two on the back. This is not the usual clamshell design. It is quite simply the most impressive PSU I've ever examined. The execution is second to none, with mechanical fit and precision beyond reproach. The Signature exudes quality.



The PSU split into three parts.



There are two printed circuit boards, one mounted on the top, one on the bottom.

The two PCBs are mounted top and bottom, with the components filling the middle air space. All the heatsinks are arranged to present the smallest impedance to airflow, yet benefit from the airflow along their length. By using this arrangement, the 80mm fan is able to blow air around every component for maximum cooling with minimum turbulence, at least, as far as possible, given the large number of components. The only issue might be a bit of a dead zone just behind the AC socket. Still, you should be able to see that there are no components so tightly packed in that air cannot flow around it. This design should provide more thorough cooling than any standard single PCB design using either 80mm or 120mm fan. It has to cost more to implement than the standard single-PCB design. On the other hand, with such effective cooling airflow, it is probably possible to use larger components which cost less than similarly rated miniature ones. This makes clear the mention of large, heavy components in Antec's features summary.



The two beautifully executed PCBs communicate via two cable sets.



12V primary transformer on top right, two heatsinks strapped with copper plate, fan controller board on bottom edge.



The other board has most of the primary components, the rectifier circuit, the big caps (all caps are either Rubycon or Nippon Chemi-Con - high quality names), the Active PFC circuit.



The fan is a Nidec 80x25mm with a 4-pin PWM connector visible on top.

We're always interested in the details of the fan, the primary noise source. This is a Nidec D08A-12PS3 rated at 12VDC / 0.5A. After hunting through the more complete Japanese Nidec web site, I could not find any fan of this model number. Furthermore, I did not find a single fan with a current rating anywhere close to the 0.5A of this model. Implication? It's a custom-made speedster, guaranteed, probably capable of 4000+ RPM at some ungodly noise level. But with a good PWM controller, it could still be a very quiet performer.

TESTING

For a fuller understanding of ATX power supplies, please read
the reference article Power
Supply Fundamentals
. Those who seek source materials
can find Intel's various PSU design guides at Form
Factors
.

For a complete rundown of testing equipment and procedures, please
refer to SPCR's
PSU Test Platform V4.1
. The testing system is a close simulation of
a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

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 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.

The 120mm fan responsible for "case airflow" is deliberately
run at a steady low level (6~7V) when the system is run at "low"
loads. When the test loads become greater, the 120mm fan is turned up to a higher
speed, but one that doesn't affect the noise level of the overall system. Anyone
who is running a system that draws 400W or more would definitely want more than
20CFM of airflow through their case, and at this point, the noise level of the
exhaust fan is typically not the greatest concern.

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 too many
variables in PCs and 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 pretty good overall representation, but it is not quite the same as an extended
meeting in person.

REAL SYSTEM POWER NEEDS: While we test the PSU to full
output 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 40W and 300W, because it is the power range
where most systems will be working most of the time. To illustrate this point,
we
conducted system tests to measure the power draw of several actual systems
under idle and worst-case conditions.
Our most power-hungry overclocked
130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W
DC peak 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 very elaborate systems with the most power hungry dual
video cards today might draw as much as another 150~200W, but the total should
remain under 500W in extrapolations of our real world measurements.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.

When examining thermal data, the most important indicator of cooling
efficiency is the difference between intake and exhaust. Because
the heat generated in the PSU loader by the output of the PSU is always the
same for a given power level, the intake temperature should be roughly the same
between different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output
    level)
  • Efficiency of the PSU (how much heat it generates while producing the
    required output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the
only indicator we have about all of the above. This is why the intake temperature
is important: It represents the ambient temperature around the power supply
itself. Subtracting the intake temperature from the exhaust temperature gives
a reasonable gauge of the effectiveness of the power supply's cooling system.
This is the only temperature number that is comparable between different reviews,
as it is unaffected by the ambient temperature.

TEST RESULTS

Note that the test data shows just one 12V line/load for convenience's sake. Our PSU load tester has three separate 12V load circuits, and all three were used: One for the main ATX and drive power output cables, one for
the AUX12V connectors, and one for the PCIe 16X power connectors. The variations between the 12V lines were so small as to be insignificant, typically under 0.1V.

The ambient temperature was 22~24°, and the ambient noise level was 11
dBA.

OUTPUT, VR & EFFICIENCY: Antec Signature 650

DC Output Voltage (V) + Current (A)

Total DC Output

AC Input

Calculated Efficiency
+12V
+5V
+3.3V
-12V
+5VSB
12.16
0.92
5.06
0.99
3.40
0.97
0.1
0.1
21.5
38
55.4%
12.16
2.45
5.06
0.99
3.40
0.97
0.1
0.2
40.1
60
66.9%
12.16
3.48
5.06
1.96
3.40
1.86
0.1
0.2
63.3
87
72.7%
12.14
6.21
5.04
2.91
3.38
2.67
0.1
0.2
90.4
114
79.3%
12.14
9.32
5.04
4.55
3.37
5.44
0.2
0.6
150.8
184
82.0%
12.14
12.09
5.00
6.50
3.36
7.54
0.2
0.2
200.6
240
83.6%
12.08
15.56
4.98
9.00
3.34
8.48
0.2
0.3
251.4
294
85.5%
12.05
18.03
5.01
10.60
3.34
11.00
0.5
0.5
300.4
349
86.1%
12.01
24.67
4.98
13.60
3.32
14.89
0.6
0.6
402.0
472
85.2%
11.99
30.55
4.96
17.90
3.28
15.94
0.6
0.8
500.5
591
84.7%
11.95
40.57
4.94
19.50
3.25
19.60
0.8
1.0
649.2
796
81.6%
Crossload Test
12.00
40.59
5.00
1.90
3.3
1.89
0.8
1.0
517.2
656
85.1%
+12V Ripple (peak-to-peak): maximum of 18mV @ full power
+5V Ripple (peak-to-peak): maximum of 13mV @ full power
+3.3V Ripple (peak-to-peak): maximum of 16mV @ full power
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings of the DBS-2100
PS Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is <1W.


OTHER DATA SUMMARY: Antec Signature 650
DC Output (W)
21
40
63
90
151
201
251
300
402
500
649
Intake (°C)
21
21
23
25
28
33
31
30
35
35
47
Exhaust (°C)
25
26
28
30
34
39
37
36
42
44
55
Temp Rise (°C)
4
5
5
5
6
6
6
6
7
9
8
Fan RPM*
720
720
720
720
720
720
900
1220
1830
2700
4200
SPL - Anechoic
15
15
15
15
15
15
16
18
28
36
47
Power Factor
0.90
0.96
0.99
0.99
1.00
1.00
1.00
1.00
1.00
1.00
1.00

SPL: Sound Pressure Level measured in dBA at 1m

SPL at idle in 16 dBA live room:
19 dBA at 1m

AC Power in Standby:
0.7W / 0.1 PF

AC Power with No Load, PSU power On: 9.8W / 0.49 PF
*Fan RPM: With a PWM fan, the usual procedure of measuring the voltage to the fan is useless, it will always read 12V. Both of our tachometers (laser and strobe) were used to periodically monitor fan speed. This was not continuous, but rather done whenever a change in the sound was noted or seen on the the sound level meter. It may not be as accurate as our usual voltage reading, which is monitored continuously.

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


ANALYSIS

1. EFFICIENCY — This is a measure of AC-to-DC
conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency
or better at all output power loads. 80% efficiency
means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost
as heat within the PSU. Higher efficiency is preferred for reduced energy consumption
and cooler operation. It allows reduced cooling airflow, which translates
to lower noise.

At 20W load, efficiency was only 55.2%.
This is to be expected; 20W load it's a harsh efficiency test for a PSU rated
at 650W. Efficiency rose fairly quickly as the load was increased. 80% efficiency was reached around the 100W mark, and it kept climbing all the way to a high of 86.1% at 300W before sliding back down gradually to 81.6% at full power. The high efficiency plateau was 250W~500W, which is probably ideal for most system this PSU will power.

These are excellent results, expected of a PSU that's certified Bronze by 80 Plus. In our test, the sample just missed the 82% minimum efficiency mark at full power by 0.4W, but this is hardly a miss because of the thermal severity of our test. The 80 Plus testing is done at typical room temperature (20~25°C) while our test conditions feed the heat of the PSU output back into its operating ambient. To reach 81.6% efficiency at the maximum 650W output with intake air temperature of 47°C is excellent.

2. VOLTAGE REGULATION refers to how stable the output voltages
are under various load conditions. The ATX12V Power Supply Design Guide calls
for the +12, +5V and +3.3V lines to be maintain within ±5%. At all load
levels, voltages were right on target, and even at the
highest loads, the voltages barely budged off target. This is excellent
performance, matched by only a small handful of PSUs reviewed thus far.

3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It's usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines. Ripple at maximum power on the Signature 650 was as low as that measured on any PSU in the past, at any load. This is superlative performance.

4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating. Power
factor was very good for this model, running no lower than 0.96 at any point
during testing.

5. LOW LOAD TESTING revealed no problems starting at very
low loads. Our sample had no issue starting up with no load, either.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 400W load with 120VAC through the
hefty variac in the lab. The variac was then dialed 10V lower every 10 minutes.
This is to check the stability of the PSU under brownout conditions where the
AC line voltage drops from the 110~120V norm. The Signature 650 is rated for
operation 100VAC ~ 240VAC ±10%. Most power supplies achieve higher efficiency
with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, which
was used to check power supply efficiency for the benefit of those who live
in 240VAC mains regions.

Low VAC Test: Antec Signature 650 @ 500W Output
VAC
AC Power
Efficiency
244V
459W
87.2%
120V
472W
84.8%
90V
487W
82.1%


Efficiency improved around 3% with 244VAC input. The sample even passed the 90VAC test (less than the 100VAC minimum recommended) without any issues. Neither voltage regulation nor ripple changed appreciably
during the test.

7. TEMPERATURE & COOLING

Cooling was excellent, with the °C temperature
rise through the unit staying in single digits all the way up to maximum power. The low 8°C temperature
rise at full 650W power is unheard of in our test rig. Of course, this is at the expense of very high noise. It's interesting to note that while the temperature rise increased steadily as power was increased, the intake temperature actually dropped at bit at 200~300W. This is a reflection of the improved airflow and cooling as the fan began ramping up in speed.

8. FAN, FAN CONTROLLER and NOISE

The PSU fan stabilized at around 720 RPM shortly after being powered on. The fan
was just barely audible. From within a few inches, it was a bit of buzzing combined with some hiss. From farther away, it was quite soft and benign, as you'll hear in the MP3 recording. It's
one of the quietest PSUs we've tested, at least at idle. In the anechoic chamber it measured around 15 [email protected], while in the live room it was 18~19 [email protected] The latter was the only measurement taken in the old live test room.

The fan speed remained constant until somewhere past 250W, where it rose slightly to 900 RPM, and our sound meter registered a tiny 1 dB rise to 16 [email protected] After a few minutes at 300W, fan speed jumped to 1220 RPM and became far more audible, registering 18~19 [email protected] It climbed to 27~28 dBA at 400W, and somewhere a little above 400W output, the noise level passed the 30 [email protected] arbitrary demarcation line beyond we define as "too loud". As the fan speed and noise level increased, so did the overall perceived tone or frequency. At full power output, the PSU sounded like a 3" fan spinning at over 4,000 RPM. Lots of wind turbulence and a fair bit of whine. Hardly quiet.

The charts below from our SpectraPLUS audio spectrum analyzer should be self-explanatory. Note that the noise floor of the anechoic chamber is 11 dBA. The blue or green lower line is ambient level of the chamber without any noise sources.



The black line is the frequency spectrum with the Signature 650 running, up to ~250W.



The blue line is the frequency spectrum with the Signature 650 at 250~300W.



The blue line is the frequency spectrum with the Signature 650 at 400W.


Note: The scale of this graph has been shifted up 5 dB to fit the curve.

The sharp spikes at 1 kHz and 2 kHz are audible; they are part of the somewhat complex tonal signature of the fan. The >15 kHz peak in the top curve was not audible (to me, anyway). It may be real, but it's at too high a frequency and too low a level to be significant. The other curves don't display this peak.

COMPARISONS

How does this compare with the quietest PSUs that SPCR has reviewed? It's quite close to the best, the Enermax Modu82+ 625W, at least until the fan starts speeding up. The difference in measured SPL at low load between the Modu82+ and the Signature 650 is less than 3 [email protected], and they're both so quiet that unless you have a system of truly quiet components in a really quiet room, you may not appreciate the difference. But the Signature fan ramps up at a lower load point than the Enermax Modu82+ 625W, and several other competitive PSUs. Its 80mm fan gets louder both subjectively and by measured SPL, than the 120mm fans of the competition simply because it has to spin faster to move as much air.

Here's the comparative chart on the 12.74 [email protected] idle Enermax Modu82+ 425W in the anechoic chamber with the current audio test gear.

In the above chart, the area between the black and green traces represent the Enermax PSU's acoustic contribution. From a meter away, I have to strain to hear it. The peak at ~15 kHz is audible as a low level "hiss". You may be able to hear this in an MP3 recording on the next page.

In the comparison table below shows the SPL versus power load data on all the PSUs tested in the anechoic chamber thus far.

Comparison: Various PSUs Noise Vs. Power Output in Anechoic Chamber
Model
90W
150W
200W
250W
300W
400W
500W
6~700W


Enermax Modu82+ 625*

13
13
14
15
16
26
36
37

Antec Signature 650

15

15

15

18

18

28

36

47

SilverStone DA700
18
18
18
18
23
32
35
41

NesteQ ECS7001

22

22

22

21

23

25

36

37

PCPC Silencer 610
20
24
24
24
24
30
40
50
*Guesstimates based on the Modu82+ 425's idle in the chamber and the Modu82+ 625's load test.

The green colored blocks are 30 [email protected] or greater SPL readings. The PSU that stayed quiet (under 30 dBA) to the highest load is not in this table because it has not been tested in the anechoic chamber: The Zalman ZM1000, which stayed below 30 dBA to almost 600W load. It's idle noise may be low enough to match the Signature; its measured SPL in the live test room was 20 [email protected], compared to the Signature's 19 dBA.

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 or better.

MP3 SOUND RECORDINGS

These recordings were made as 24-bit / 88 kHz WAV files with a high
resolution, lab quality, digital recording system
inside SPCR's
own anechoic chamber
(11 dBA ambient), 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.

These recordings are intended to give you an idea of how the product 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!

Each recording starts with 6~10 seconds of room ambient, 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, then
don't change the volume setting again while comparing all the sound files.

Sound Recordings of PSU Comparatives
in the Anechoic Chamber

Older Recordings made with Sennheiser microphone in Live test room

Caution! It's important to understand that these recordings cannot be compared directly to the recordings made in the anechoic chamber. The live room in which they were made echoes and has a noise floor 4~8 dBA higher, the microphone has a much brighter sound quality and a different output level, and even the dBA measurements are wrong below ~25 dBA — they are higher by 2~8 dBA than they would be in the chamber with the new test gear. These recordings are here mostly for the record.

Ambient
acoustics of the anechoic chamber vs the live room
- Some of
you will be interested to hear this difference. The recording begins with
8 seconds in the anechoic chamber, then 8 seconds in the live room, followed
by a few seconds in the anechoic chamber. The SPL levels, as mentioned before,
were 11 dBA and 18 dBA respectively. It's interesting to note that the hiss
many SPCR forum members attributed to electronic noise is, in fact, not
so; it's part of the live ambient, due at least partly, to reflections at
higher frequencies in the room. This is obviously absent in the chamber.
(However, we did make a change to a new microphone which also has considerably
less noise than what we were using before the anechoic chamber, so some
of the hiss in past recordings was caused by microphone noise.)

CONCLUSIONS

The Antec Signature 650 performs better electrically in most areas than any other PSU that's been through the SPCR test bench. Voltage regulation, AC ripple, energy efficiency, power factor, cooling — not a single measured parameter was less than excellent. The build quality matches its electrical performance; we've never seen better. The technological advancements — such as the ingenuity of the physical / cooling design, the use of DC-to-DC conversion for the sub-12V lines, and PWM fan control — deserve to be lauded. This is no me-too product, but a declaration of innovation in a field rife with copycats.

Acoustic performance is also exceptional, at least up to 250W~300W load. The overall noise signature is good enough to rival the best of the best, as it could be quiet enough in some environments to be masked by either the natural ambient noise or the noise of other components in the PC. Beyond about 300W, however, the noise level rises quickly and its quality becomes less benign as the 80mm fan increases in pitch. For the silence lover, the trick is to keep the power demand below 300W or use the Signature 650 in a case with an isolated, independent PSU intake (like the P180 series, the Fusion and others, including systems that use a custom-made intake duct for the PSU). The latter option keeps heat from the rest of the components out of the PSU and pushes the fan ramp-up point to much higher power loads, making the internal cooling of the PSU the most significant factor in fan speed and noise. In such a setup, the high energy efficiency and the innovative cooling arrangement in the Signature should push the fan ramp-up point way up.

The Antec Signature 650 really is a statement, it's Antec's challenge to the overpopulated computer power supply world: Here's our best, go ahead and match that if you can. Whether the exacting performance lends any tangible benefits over a competitive product that's merely very good could be questioned, but there's no denying the engineering savvy and attractiveness of this power supply. This is just the beginning of Antec's partnership with Delta Electronics. We can all look forward to more interesting products in the future, and for some of this good technology to trickle down to more affordable levels. In the meanwhile, the $160 and $199 selling prices of these Signatures are looking pretty good after all.

Much thanks to Antec Inc. for this review sample.

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