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OCZ have had many successes in recent years, and one of the most noticeable would be their StealthXstream series of power supplies. Today we are looking at a very competitively priced power supply in their new value range, the ZS Series 550W which replaces the StealthXstream 2.
The new ZS Series 550W supply has changed from a multi rail to single rail design and uses higher grade components with 80 Plus Bronze Certification. OCZ have also upgraded the size of the fan from 120mm to 135mm to offer better cooling proficiency.
Unit Overview
- OCZ PowerWhisper Technology
- Internal 135mm ball-bearing fan
- Can power SLI and CrossFire GPU configurations
- 150 x 160 x 86mm (W x L x H)
- ATX12V v2.2 and EPS12V
- 86% Efficiency (Typical Load)
- Overvoltage/Overcurrent/Short-Circuit protection
- Active PFC
- MTBF: 100,000 hours
- 3 year warranty backed by OCZ’s exclusive PowerSwap™ replacement program.
The OCZ ZS Series 550W power supply is shipped in a dark box with an image of the product on the left, with a list of key selling points down the right side.
OCZ claim:
- Simply Powerful:
Featuring a single +12V rail for efficient power distribution, the sleek ZS Series 550W power supply is designed specifically for the demanding computing environments of PC enthusiasts, Power Users and Gamers. - Silent Operation:
PowerWhisper technology diminishes noise to ensure silent, yet efficient operation. - Multi-GPU ready:
The durable and powerful ZS Series is equipped to fuel the demands of gaming rigs - Superior Cooling:
Supreme air flow, courtesy of an ultra quiet, yet vigorous 135mm fan.
The power supply is protected between foam pads, and the cabling is held within a cardboard section on the right side of the box. They also supply a full colour user manual, mounting screws and a region specific power cable.
| Cable | Connectors |
| MB 20+4 pin | x1 (500mm) |
| CPU 4+4 pin | x1 (700mm) |
| PCI E 8 pin (6 pin +2) & 6 Pin | x1 (of each – 550mm + 150mm) |
| SATA | x4 (750mm + 100 mm) |
| SATA | x4 (400mm + 100 mm) |
| MOLEX | x3 (500mm + 100 mm) |
This power supply will work fine with a modest Crossfire or SLI system as the ZS Series 550W power supply has two PCI E connectors, a single 8 pin and a single 6 pin.
The OCZ ZS Series 550W supply is finished in plain black with ‘sporty' blue stickers on the sides.
The fan on the new model is bigger than the previous version, scaling up from 120mm to 135mm. Surprisingly there is no OCZ badge in the middle however, which looks slightly unfinished.
The rear is vented to aid the airflow. There is a power connector and switch offset to the right.
As this is not a modular design, all the cabling is native to the supply. OCZ have a protective ring around the metal chassis to ensure the cable doesn't fray.
The unit is reasonably attractive, and will fit into any system build, without standing out like a sore thumb.
Product specifications are listed on a sticker at the top of the supply.
| OCZ ZS Series 550W Power Supply | |||||
|
DC Output
|
+3.3V
|
+5V
|
+12V
|
-12V
|
+5Vsb
|
|
Max Output
|
22A
|
22A
|
38A
|
0.3A
|
3A
|
| Total Power | 130W | 456W | 3.6W | 15W | |
| 550W | |||||
The +12V output can handle up to 38A, for 456W of the total output.
OCZ are using a Globe fan, the RL4z B1352512M. This is a popular choice among manufacturers.
This power supply seems to be a Sirfa design. It is a basic design, but one that has been used now (in various forms) for many years, with a lot of success.
The first stage of the transient filter uses two Y capacitors and a single X capacitor. There are two rows of heatsinks ensuring adequate cooling reaches the components. The primary capacitor is Panasonic, and rated to 85c. Secondary capacitors are Chemi Con, which is an improvement over the previous generation. The overall design is basic, but clean throughout.
On this page we present some super high resolution images of the product taken with the 24.5MP Nikon D3X camera and 24-70mm ED lens. These will take much longer to open due to the dimensions, especially on slower connections. If you use these pictures on another site or publication, please credit Kitguru.net as the owner/source.
Additional technical assistance: Peter McFarland and Jeremy Price.
Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.
We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA
|
DC Output Load Regulation
|
||||||||
|
Combined DC Load |
+3.3V
|
+5V
|
+12V
|
+5VSB
|
||||
|
A
|
V
|
A
|
V
|
A
|
V
|
A
|
V
|
|
|
110W
|
3.05
|
3.37
|
3.07
|
5.08
|
6.52
|
12.26
|
1.50
|
5.05
|
|
220W
|
6.24
|
3.35
|
6.21
|
5.07
|
13.51
|
12.21
|
1.50
|
5.04
|
|
340W
|
9.32
|
3.32
|
9.21
|
5.06
|
21.12
|
12.17
|
1.50
|
5.04
|
| 445W |
12.43
|
3.30
|
12.42
|
5.05
|
27.55
|
12.12
|
1.50
|
5.03 |
|
550W
|
15.71
|
3.28
|
15.67
|
5.04
|
34.59
|
12.06
|
1.50
|
5.02
|
A fairly good set of results across the board and there are no concerns with voltage regulation.
| OCZ ZS Series 550W PSU | Maximum Load |
| 603.5 |
The power supply managed to output just over 603 watts before shutting down safely.
Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.
| Cross Load Testing | +3.3V | +5V | +12V | -12V | +5VSB | |||||
| A | V | A | V | A | V | A | V | A | V | |
| 493W | 1.0 | 3.35 | 1.0 | 5.07 | 40.0 | 11.93 | 0.2 | -11.99 | 0.50 | 5.03 |
| 153W | 15.0 | 3.27 | 15.0 | 4.98 | 2.0 | 12.21 | 0.2 | -12.15 | 0.50 | 5.01 |
Cross loading shows minor +12V fluctuation, dropping from 12.21 to 11.93 when hit with 40 amps. Nothing to concern a prospective customer, but noticeable.
We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum. ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.
|
ATX12V Ver 2.2 Noise/Ripple Tolerance
|
|
|
Output
|
Ripple (mV p-p)
|
|
+3.3V
|
50
|
|
+5V
|
50
|
|
+12V1
|
120
|
|
+12V2
|
120
|
|
-12V
|
120
|
|
+5VSB
|
50
|
Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.
| AC Ripple (mV p-p) | ||||
| DC Load | +3.3V | +5V | +12V | 5VSB |
| 110W | 10 | 10 | 20 | 15 |
| 220W | 10 | 10 | 25 | 15 |
| 340W | 15 | 15 | 40 | 20 |
| 445W | 15 | 15 | 50 | 20 |
| 550W | 20 | 15 | 65 | 20 |
Noise suppression is within the rated tolerance parameters, although a maximum of 65 mV on the +12V output is not the best we have seen in recent months.
|
Efficiency (%)
|
|
|
110W
|
81.98
|
|
220W
|
84.77
|
|
340W
|
85.89
|
|
445W
|
84.46
|
|
550W
|
83.35
|
Efficiency from the supply is very good for a bronze rated unit, achieving almost 86% at around 50% load. It falls to 83.35% efficiency at full load.
We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.
Today to test the Power Supply we have taken it into our acoustics room environment and have set our SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.
As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.
KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refridgerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum
|
Noise (dBA)
|
|
|
110W
|
29.8
|
|
220W
|
31.4
|
|
340W
|
33.7
|
|
445W
|
34.5
|
| 550W | 35.9 |
The supply is audible at around 50% load, depending on the emissions of your partnering hardware. At full load the fan is clearly spinning fast, emitting around 36 dBa of noise.
|
Temperature (c)
|
||
|
Intake
|
Exhaust
|
|
|
110W
|
36
|
38
|
|
220W
|
38
|
42
|
|
340W
|
39
|
47
|
|
445W
|
42
|
50
|
|
550W
|
43
|
53
|
The active fan helps maintain good temperature variables, rising to a 10c above ambient intake at full load.
|
Maximum load
|
Efficiency
|
|
603.5W
|
82.3
|
Pushing the PSU above its rated limits generates an efficiency level of around 82.3%. This is not a viable ‘real world’ situation, but its interesting nonetheless.
The OCZ ZS Series 550W Power Supply is a competent design and one that will find its way into many systems this year, especially when factoring in the low asking price.
In regards to appearance, the unit is well finished, with a ‘sports car' like sticker on the side. The plain black paint finish is professionally applied and could handle some long term abuse. It is surprising that there is no OCZ badge at the top of the unit, above the fan, but perhaps every penny counts in this sector.
Technically, it is a basic, yet tried and trusted Sirfa implementation and is an improvement over OCZ's older ‘value' designs. The new product features higher efficiency, a single rail output and Japanese capacitors. They are using a bigger fan this time around for stronger airflow, although it is still clearly audible when loaded above 400W.
Noise suppression, while not class leading, doesn't raise a red flag, although the 12V+ output did register 65 mV at full load, which is more than some other designs in the same price bracket in recent months. This is not a concern and well within the rated guidelines, but worth mentioning.
In the UK, this supply can be bought for £47.98 at Dabs, which is a really good deal, especially when considering the improvements to the internal design when compared against the previous generation. The Stealthxstream is still available for £44 in the UK and for an extra £4, it seems like a no brainer to us.
Pros:
- Appearance will suit any system build.
- upgraded capacitors help overall performance.
- larger fan improves airflow.
- good efficiency.
Cons:
- Is clearly audible when loaded hard.
