Introduction

The Amacrox Free Earth 88PLUS 600 W (AX600-88FE) is an 80 Plus Silver-certified unit, with the manufacturer promising 88% efficiency at typical load (i.e., 300 W). Let’s see if this unit is a good product.

Like other models from Amacrox, the reviewed product is manufactured by FSP.

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Figure 1: Amacrox Free Earth 88PLUS 600 W power supply

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Figure 2: Amacrox Free Earth 88PLUS 600 W power supply

The Amacrox Free Earth 88PLUS 600 W is only 5.5” (140 mm) deep, using a two-ball-bearing 120 mm fan on its bottom (Power Logic PLA12025B12M-2EP). Amacrox says this power supply uses a fluid dynamic bearing fan, but this information doesn’t match the sample we received.

This unit features active PFC, of course.

No modular cabling system is provided, and all cables have nylon sleevings that come from inside the power supply housing. The cables included are the following:

• Main motherboard cable with a 20/24-pin connector, 19.7” (50 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 19.7” (50 cm) long
• One cable with one ATX12V connector, 18.9" (48 cm) long
• Two cables with one six-pin and one six/eight-pin connector for video cards, each 20.5” (52 cm) to the first connector, 5.9” (15 cm) between connectors
• Two cables with three SATA power connectors, each 20.5” (52 cm) to the first connector, 4.7” (12 cm) between connectors
• One cable with three standard peripheral power connectors, 20.5” (52 cm) to the first connector, 4” (10 cm) between connectors
• One cable with two standard peripheral power connectors and one floppy disk drive power connector, 20.5” (52 cm) to the first connector, 4” (10 cm) between connectors

All wires are 18 AWG, which is the correct gauge to be used.

The cable configuration is perfect, and in fact, we rarely see 600 W power supplies with four video card auxiliary power connectors. Of course we prefer to see these connectors installed on separated cables. The additional ATX12V connector is clearly overkill.

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Figure 3: Cables

Now let’s take an in-depth look inside this power supply.

A Look Inside The Amacrox Free Earth 88PLUS 600 W

We decided to disassemble this power supply to see how it looks inside, what design is used, and what components are present. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

In this page, we will have an overall look, while in the next pages we will discuss the quality and ratings of the components used in detail.

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Figure 4: Overall look

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Figure 5: Overall look

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Figure 6: Overall look

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Figure 7: Printed circuit board

Transient Filtering Stage

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

Although this power supply has two more X capacitors and two more Y capacitors than the minimum required, it lacks an MOV, which is the component in charge of removing spikes coming from the power grid.

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Figure 8: Transient filtering stage (part 1)

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Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion of the components used in the Amacrox Free Earth 88PLUS 600 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Amacrox Free Earth 88PLUS 600 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses three GBU1006 rectifying bridges connected in parallel, each one supporting up to 10 A at 100º C. The bridges aren’t connected to a heatsink and the datasheet for the bridges doesn’t give the current limit for this piece. In theory, you would be able to pull up to 3,450 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning themselves. Talk about over-specification! Of course we are only talking about these components, and the real limit will depend on all the other components in the power supply.

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Figure 10: Rectifying bridges

The active PFC circuit uses two FCPF21N60NT MOSFETs, each one capable of delivering up to 20 A at 25º C, up to 12.5 A at 100º C in continuous mode (note the difference temperature makes), or up to 60 A in pulse mode at 25º C. These transistors present a 150 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

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Figure 11: Active PFC transistors and diode

The electrolytic capacitor used to filter the output of the active PFC circuit is Japanese, from Matsushita (Panasonic), and labeled at 105º C.

In the switching section, two IPI60R125CP power MOSFET transistors are used in the traditional two-transistor forward configuration, each one supporting up to 25 A at 25º C, up to 16 A at 100º C in continuous mode, or up to 82 A at 25º C in pulse mode, presenting an RDS(on) of 125 mΩ.

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Figure 12: Switching transistors

The primary is controlled by a CM6802 active PFC/PWM combo.

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Figure 13: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.

Secondary Analysis

This power supply has eight Schottky rectifiers attached to the secondary heatsink.

The maximum theoretical current each line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is generated using four SBR40S45CT Schottky rectifiers connected in parallel, each one having a current limit of 40 A (20 A per internal diode at 110º C, 0.55 V maximum voltage drop). This gives us a maximum theoretical current of 114 A or 1,371 W for the +12 V output.

The +5 V output is generated using two SBR30U30CT Schottky rectifiers connected in parallel, each one having a current limit of 30 A (15 A per internal diode at 150º C, 0.54 V maximum voltage drop). This gives us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output is generated using another two SBR30U30CT Schottky rectifiers connected in parallel. This gives us a maximum theoretical current of 43 A or 142 W for the +3.3 V output.

Of course these are all theoretical figures. The real current limits will depend on other components, especially on the coil used.

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Figure 14: +12 V, +5 V and, +3.3 V rectifiers

The outputs are monitored by a PS223 integrated circuit. This circuit supports over voltage (OVP), under voltage (UVP), over temperature (OTP), and over current (OCP) protections. This circuit offers four over current protection channels (one for +3.3 V, one for +5 V, and two for +12 V). A WT7518D integrated circuit is used to expand the number of +12 V over current protection channels to four, matching the number of +12 V rails advertised by the manufacturer.

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Figure 15: Monitoring circuit

Electrolytic capacitors found in the secondary are from Teapo and labeled at 105º C.

Power Distribution

In Figure 16, you can see the power supply label containing all the power specs.

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Figure 16: Power supply label

This power supply has four +12 V rails, and we can confirm that the over current protection (OCP) circuit supports four +12 V channels.

The available rails are distributed like this:

• +12V1 (yellow/black wire): Connectors for video cards labeled “PCI-E3” and “PCI-E4”
• +12V2 (yellow/blue wire): ATX12V/EPS12V connector (“CPU1”)
• +12V3 (yellow/white wire): ATX12V connector (“CPU2”) and connectors for video cards labeled “PCI-E1” and “PCI-E2”
• +12V4 (solid yellow wire): Main motherboard cable, SATA power connectors, and peripheral power connectors

This distribution is perfect, as separates the CPU and the video cards in individual rails.

The names of the rails as listed on the power supply label are different. We used the names on the power supply printed circuit board. But the presence of a list on the unit label and the labeling of the video card power connectors and ATX12V connectors is definitely handy for the user concerned about rail distribution.

Now let’s see if this power supply can really deliver 600 W.

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.  

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at 5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test the +12VA input was connected to the power supply's +12V3  and +12V4 rails, while the +12VB input was connected to the power supply's +12V2 rail (EPS12V connector).

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	4 A (48 W)	9 A (108 W)	13 A (156 W)	17.5 A (210 W)	22.5 A (270 W)
+12VB	4 A (48 W)	9 A (108 W)	13 A (156 W)	17.5 A (210 W)	22 A (264 W)
+5V	1 A (5 W)	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)
+3.3 V	1 A (3.3 W)	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4)
+5VSB	1 A (5 W)	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	3 A (15 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	113.3 W	238.4 W	350.1 W	472.2 W	599.4 W
% Max Load	18.9%	39.7%	58.4%	78.7%	99.9%
Room Temp.	46.3º C	45.2º C	45.3º C	46.6º C	45.8º C
PSU Temp.	49.0º C	49.3º C	49.9º C	50.9º C	52.0º C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	128.4 W	268.5 W	397.7 W	543.7 W	706.0 W
Efficiency	88.2%	88.8%	88.0%	86.8%	84.9%
AC Voltage	113.3 V	112.2 V	111.2 V	109.6 V	107.8 V
Power Factor	0.956	0.977	0.987	0.993	0.995
Final Result	Pass	Pass	Pass	Pass	Pass

The Amacrox Free Earth 88PLUS 600 W can really deliver its labeled wattage at high temperatures.

We were definitely impressed by the efficiency achieved by this unit: it presented efficiency above 88% (88.8% peak) when we pulled between 20% and 60% from its labeled load (i.e., between 120 W and 360 W). At 80% load (i.e., 480 W) efficiency was still high at almost 87%. And at full load (600 W) efficiency was at 84.9%. 80 Plus Silver certification is given to power supplies capable of achieving efficiency of at least 85% at light (20%) and full (100%) loads and at least 88% at typical (50%) load at a room temperature of 23º C. This unit from Amacrox could really deliver this performance level at higher temperatures (many power supplies can’t sustain their 80 Plus levels at higher temperatures, as efficiency decreases with temperature), and we were particularly impressed by the 88% efficiency at light load.

Voltages were always inside the allowed range.

Noise and ripple levels were always at very low levels. Below you can see the results for the power supply outputs during test number five. The maximums allowed are 120 mV for +12 V and -12 V, and 50 mV for +5 V and +3.3 V. All values are peak-to-peak figures.

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Figure 18: +12VA input from load tester during test five at 599.4 W (48.6 mV)

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Figure 19: +12VB input from load tester during test five at 599.4 W (36.2 mV)

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Figure 20: +5V rail during test five at 599.4 W (19.8 mV)

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Figure 21: +3.3 V rail during test five at 599.4 W (27.2 mV)

Let’s see if we can pull even more from the Amacrox Free Earth 88PLUS 600 W.

Overload Tests

Below you can see the maximum we could pull from this power supply. If we tried to increase one amp at any given output, the unit would shut down, showing that one of its protections kicked in, which is always the desired behavior.

Input	Overload Test
+12VA	33 A (396 W)
+12VB	33 A (396 W)
+5V	12 A (60 W)
+3.3 V	12 A (39.6 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	868.4 W
% Max Load	144.7%
Room Temp.	44.4º C
PSU Temp.	46.4º C
AC Power	1,090 W
Efficiency	79.7%
AC Voltage	101.2 V
Power Factor	0.997

Main Specifications

The Amacrox Free Earth 88PLUS 600 W power supply specs include:

• ATX12V 2.3
• EPS12V 2.92
• Nominal labeled power: 600 W
• Measured maximum power: 868.4 W at 44.4º C
• Labeled efficiency: 88% at typical load (i.e., 300 W), 80 Plus Silver certification
• Measured efficiency: Between 84.9% and 88.8% at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 20/24-pin connector, two ATX12V connectors that together form an EPS12V connector, and one ATX12V connector
• Video Card Power Connectors: One six-pin and one six/eight-pin connector on each of two cables
• SATA Power Connectors: Six on two cables
• Peripheral Power Connectors: Five on two cables
• Floppy Disk Drive Power Connectors: One
• Protections: Over voltage (OVP), over current (OCP), and short-circuit (SCP), with undervoltage protection (UVP) that is not listed by the manufacturer
• Warranty: Three years
• Real Manufacturer: FSP
• More Information: http://www.amacrox.com
• Average price in the US: This product isn’t sold in the USA

Conclusions

We were really impressed by the Amacrox Free Earth 88PLUS 600 W. It could keep its efficiency above 88% when we pulled between 20% and 60% from its labeled load (i.e., between 120 W and 360 W). At 80% load (i.e., 480 W), efficiency was still high, at almost 87%. And at full load (600 W), efficiency was at 84.9%. Unfortunately, we see lots of power supplies with 80 Plus Silver certification that can’t maintain 85% efficiency at full load at higher temperatures, which didn’t happen with this unit.

Voltages were always inside the expected ranges and electrical noise levels were always low.

The Amacrox Free Earth 88PLUS 600 W is certainly a nice option for the user looking for a high-performance, yet simple power supply. We hope this unit makes its way to the United States soon.