Corsair TX550M vs. OCZ ZT550W 550W

In this review we will compare two almost identical products from OCZ and Corsair. Even so, there are still crucial differences between the offerings. With 550W both PSUs deliver more than enough power for most current systems. On the following pages we'll find out which handle overload situations the best, who has the highest efficiency, and which PSU provides the best voltage regulation.

The ZT models from OCZ are based on a Great Wall design with some modifications in the details. Interesting features include the fully modular cable management and a silent fan control. Today we will review the smallest version with 550W. Here's a complete rundown of the features.

• Available in 550W, 650W, 750W
• Single +12V rail
• Fully Modular Cabling System
• Dimensions: 150 x 86 x 175mm (W x L x H)
• 80-Plus Bronze Certified
• MTBF: 100,000 hours
• 5-year warranty
• 140mm ball-bearing fan
• Active PFC
• ATX 12V 2.2 Compliant

The second unit we test today is a Corsair TX produced by CWT. "Enthusiast Series is designed for reliable operation in high-performance PCs where clean, stable power is important." It's able to deliver the full output power at an ambient temperature of up to 50° Celsius. Like OCZ Corsair uses a double ball-bearing fan. Except the cables with mainboard connectors all cables are modular. In addition the fan grille looks unusual.

• Available in 550W, 650W, 750W, 850W
• Single +12V rail
• Modular Cabling System
• Dimensions:150 x 86 x 160mm (W x L x H)
• 80-Plus Bronze Certified
• MTBF: 100,000 hours
• 5-year warranty
• 140mm ball-bearing fan
• Active PFC
• ATX 12V 2.31 Compliant

Corsair TX550M Overview

In the package we find a large number of modular cables in a plastic packaging, an accompanying document with warranty agreements, one Corsair sticker (for your case), some cable ties, four screws, and one power cord. In short, Corsair provides plenty of extras to keep the customers satisfied.

Corsair believes in powerful single rails. On +12V this PSU can deliver nearly the full power since step-down-converters are included for the smaller rails. +3.3V as well as +5V are rated at 140W and/or 25A maximum load. At 3A, 5VSB is relatively powerful as well.

The PSU has a black finish and honeycombed ventilation holes. There is no typical fan grill but a solution be quiet! (Listan) used before. At 160mm, the case is moderately long. As usual these days, there is a power switch next to the mains plug. Modular cables can be mounted on the connector panel at the rear side, and as usual Corsair's overall build quality is very good.

The 24-pin cable is relatively long with 60cm. The long CPU cable is very good as well, particularly for cases where the PSU is mounted on the bottom. The 24-pin, the CPU, and two peripheral cables are fixed. Note that there are FDD adapters. Corsair included the adapters in the packaging, though, "just in case". Moreover all removable cables consist of black wires only. Some of them are flat as well.

Corsair TX550M Internal Design and Fan

Corsair uses a 140mm fan from Ong Hua with a ball bearing. The product number is HA1425H12B-Z and it takes 0.50A. A Sanyo Denki fan would be better but the price could be a problem and Sanyo Denki is still a reason to buy the more expensive Corsair AX. Opening the unit clearly reveals that Channel Well is the ODM. Transient filtering starts behind the AC inlet and continues on the mainboard. Like nearly all modern PSUs, the TX550M has active PFC. All transistors have very common ratings so there is nothing special needed to reach 80 Plus Bronze.Most capacitors come from Nippon Chemi-Con and there are some all solid ones in the secondary circuit, but the KY models are a usual choice for high-end PSUs. It would be nice to see some other brands or types; however, all parts are high-quality. The only point of criticism is that the fan connector could be glued down, but that's a minor issue at best.

Voltage Regulation

Noise Levels

Efficiency and PFC

All the rails fall clearly within ATX specifications. They start slightly over the target voltage and end with results close to 0%. +3.3V and +5V show the best regulation, and will have no trouble with higher voltages. -0.60% at overload is one of the best results we have seen so far. 0.824-0.990 PFC is very good and most users will find 86-87% efficiency more than sufficient. While it doesn't quite make 80% efficiency at 10% load (115V), it is a good 80 Plus Bronze PSU for sure. Both smaller rails have less than 20mV ripple and noise, making this PSU a good choice.

OCZ ZT550W Overview

The OCZ ZT550W comes with the usual assortment of parts: you get an extensive user manual, a US/UK/Europe power cord (depending on your location), and the necessary mounting screws. In addition, the power supply has cable management, so some modular cables with a common sleeving are placed in the package as well.

Rated at up to 540W, the +12V rail can deliver nearly the full power of the PSU. +3.3V and +5V are rated at a maximum capacity of 24A each, with a combined output of 140W. Compared with most modern high-efficiency power supplies (like Corsair), OCZ has no DC-to-DC converters inside. In fact they use mag amp regulators for the smaller outputs which is a suitable solution too.

The whole housing is coated with a black finish. The fan grille with a OCZ logo in the middle is black too, and both sides of the case have an OCZ logo.  As usual the ventilation holes are honeycombed and a large power switch is located next to the AC input. On the front are modular cable connectors, color coded for PCIe (grey) and peripherals (black). The depth of the device is 17,5cm, which is quite much for a 550W power supply.

Again the 24-pin and CPU cables are relatively long with 55-60cm. Both 6/8-pin cables are 5cm shorter than the ones Corsair used. The cable sleeving somewhat better but they still use different colors for all wires and no flat cables. The FDD connector is a separate adapter that splits off a Molex connector if needed; there are six Molex connectors available. The peripheral cables have exactly the same lengths like the ones from Corsair, what a coincidence!

OCZ ZT550W Internal Design and Fan

OCZ uses a 140mm fan from Yate Loon with a ball bearing. The product number is D14BH-12 and it takes 0.70A. Again we would like to see a better solution here. Like mentioned before Great Wall is the manufacturer of the ZT-series.The PCB for the modular ports should get a thin plastic sheet since it's very close to the main PCB. Generally, the power supply case is well filled out. OCZ uses capacitors from Teapo and Rubycon (ZLH, a very good choice). Moreover EMI filtering is equipped well, but there is no MOV for overvoltage protection. The ferrite core on the conductors helps to reduce EMC troubles with high frequency current. All output voltages got their own regulation circuit; both +3.3 V and +5V have a magnetic amplifier. Crossload tests should be no problem with this configuration.

Voltage Regulation

Noise Levels

Efficiency and PFC

Some rails should be closer to the optimal value. +3.3V starts with a remarkable over voltage and ends with 1.81% under the optimal value. +12V is comparatively weak but we should keep in mind that our loads are quite high, according to the label. +12V has high absolute ripple, but as a percentage it's better than the other rails. The efficiency is good for an 80 Plus Bronze PSU, reaching up to 87% on 115VAC, though our 78.48% result at 10% load  is slightly below what we have seen from Corsair.

Comparison

Corsair TX550M vs OCZ ZT550W 550W

Differences got a yellow marking.

We compared two power supplies in the 550W region today. With $ 89.99 both models are comparatively expensive but users should realize when buying a 550W power supply that it simply cannot cost just $ 30-40 and still deliver decent quality. We saw two very good models from Corsair and OCZ with excellent performance and 80Plus Bronze. It looks like they are copying ideas from each other since most features are absolutely identical. Both provide enough (and almost the same) connectors to support PC configurations with a powerful graphics card. One point of criticism is the large case Corsair and OCZ used. Furthermore we would like to see different fan brands since both bearings made an annoying noise. Sanyo Denki provides the best fans with ball bearing. Otherwise Corsair and OCZ could choose FDB fans to reduce loudness. 

The TX series has flat cables while OCZ used a common sleeving. With six SATA and six HDD connectors both products are well equipped. As expected both PSUs have two 6/8-pin connectors and FDD adapters as well. As for performance and quality, all the results from our tests are very impressive. There is hardly any ripple and noise on any of the rails: OCZ reached less than 40mV on +12V while Corsair demonstrated even lower results on +3.3V and +5V. Up to 87% efficiency and a high power factor are the primary reasons for the costs; such results can only be reached with high quality devices, and those devices cost more than lesser offerings.

Performance-wise, the Corsair TX550M stands out today with more stable DC outputs, longer cables, and a slightly higher efficiency. In addition Corsair implemented a better main cap. Nevertheless the OCZ ZT550W is an interesting offer with fully removable cables, especially since the price is low ($ 69.99 after mail-in rebate at newegg.com). In summary, it can be stated that both brands are shaping up well. However, this time Corsair is ahead in terms of quality.