OCZ ZX 1250W Power Supply Review

1. Introduction2. OCZ ZX 1250W Power Supply (Bundle & Cables)3. OCZ ZX 1250W Power Supply (External)4. OCZ ZX 1250W Power Supply (Internal)5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

OCZ have been delivering quality power supplies now for over five years and one of their most historic claims to fame was when they purchased PC Power & Cooling, a company well known in enthusiast circles for their extreme high end designs. OCZ have released a new, high end ZX 1250W power supply which is 80 Plus Gold Certified and a fully modular design.

The new ZX series has three family members, the 850W, 1000W and 1250W models. These are created for demanding enthusiast gamers who need the highest levels of power available. All of them are 80 Plus Gold Certified with single 12+ rails.

As well as 80 Plus Gold certification, OCZ have wanted to focus on lowering noise as much as possible, incorporating an ultra quiet 140mm fan into the design. OCZ are backing up the impressive specifications with their 5 year ‘power swap' warranty.

Technical Specifications

• 1250W Continuous power
• Ultra quiet 140mm ball-bearing fan
• +12VDC @ 104A Single Rail Design
• SLI™ and CrossFire™ support
• Fully modular cable management system
• 150 x 175 x 86mm (W x L x H)
• ATX12V v2.2 and EPS12V
• 80-Plus Gold Certified
• 92% Efficiency (Typical Load)
• Overvoltage/Overcurrent/Short-Circuit protection
• Active PFC
• MTBF: 100,000 hours
• 5 year warranty backed by OCZ's exclusive
• PowerSwap Warranty replacement program.

The OCZ ZX 1250W power supply arrives in a stylish box with a quick list of specifications and a high resolution picture on the front.

Inside, the power supply is shrink wrapped (no cloth bag unfortunately) and contained between two soft heavy duty pieces of foam. There is a large box to the right which contains all the accessories.

Inside the accessory box is a pouch with all the modular cables. A user manual, an 80 Plus Gold ‘certificate' and another box containing power cables, velco cable ties and mounting screws. It really is a comprehensive package and one indicative of a high end flagship product. The cable pouch is packed with cables and is actually difficult to repopulate fully once some of them are removed.

OCZ even supply both a UK and European power cable in this box, which is unusual.

There are no shortage of cables, although as this is a model catering to the elite, high end user base, OCZ can't afford to make any compromises.

Modular Connectors

• 20+4 pin ATX
• Dual 4+4 pin CPU
• 6 x PCIe 6+2 pin
• 12 x SATA
• 9 x Molex
• 1 x Floppy

It is worth pointing out that not all of the SATA and Molex cables can be connected to the unit simultaneously. The PCIe, ATX and EPS are thicker 16 AWG cables while the others are 18 AWG. All of the cables are all fully sleeved, so bonus points for a thoroughly impressive set of cabling. They are all initially 560mm in length with + 150mm for each of the Molex or SATA connectors after that.

The OCZ ZX 1250W power supply is a simple looking unit with a pure black and accented yellow colour/gold scheme. It measures 150 x 175 x 86 mm (WxLxH) and has a MTBF of 100,000 hours. The matt finish does tend to attract fingerprints however.

The rear is full vented to allow for good airflow, and there is a power connector and power switch set to the side.

The large 140mm ball bearing fan takes centerstage at the top of the unit. It is a plain black fan with the ‘Z' logo stuck in the middle.

The unit is a full modular design, much like the Corsair AX series and all the connectors at the front are clearly marked and colour coded to help installation.

OCZ ZX SERIES 1250W Power Specs
Rail	3.3V	5V	12V	5VSB	-12V
Max. Power	30A	30A	104A	3A	0.6A
	170W		1248W Max
Total Max. Power	1250W

Specifications are impressive, with the single 12+ rail capable of delivering 104A. Hopefully the insides are just as impressive.

The OEM of this specific power supply is Great Wall – they are a quality OEM who have made some great units over the years. This particular design doesn't use LLC resonant topology to achieve the Gold efficiency specifications (like the Corsair AX1200).

The fan, we are pleased to see, is a Yate Loon model … the D14BH-12. We have seen this fan used in plenty of quality supplies recently. Considering the ‘ultra silent' claims, this is actually one of Yate Loon's more powerful fans, rated to 2,800 rpm @ 48.5dBa while producing a whopping 140 CFM airflow. Obviously OCZ will have ensured the fan never gets close to this speeds with PWM control. At least we hope so.

The AC receptacle has one X and two Y capacitors. It feeds into the main PCB with three coils, two X and two Y capacitors. Unusually there is no Metal Oxide Varistor with this design.

The capacitors are 105c, 420V, 390µF rated (each) and are supplied by Teapo.

The two bridge rectifiers are cooled by three substantial heatsinks. There is also a thermistor and an electromagnetic relay that bypasses once the PSU is turned on. The PWM/PFC controller is a Champion CM6802.

The secondary side uses seven mofsets and the minor rails are generated from the +12V with the help of two DC-DC converter modules. All filtering capacitors for the DC outputs are Teapo branded and rated to 105c. Soldering quality is very good throughout, so lets get onto the testing.

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
• Extech digital sound level meter
• 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		-12V
	A	V	A	V	A	V	A	V	A	V
330W	5.50	3.38	5.50	5.07	21.25	12.15	0.87	5.01	0.20	-12.08
620W	11.00	3.36	11.00	5.05	42.50	12.09	1.75	4.98	0.40	-12.09
918W	16.50	3.33	16.50	5.03	63.75	12.05	2.62	4.96	0.60	-12.10
1249W	9.05	3.28	9.45	4.98	95.01	11.97	3.5	4.95	0.80	-12.14

OCZ ZX 1250W	Maximum Load
	1367W

We managed to get 1367W out of the unit before it would shut down via the protection circuitry. It would run happily at 1350W for some time.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
1190W	1.0	3.32	1.0	4.97	95.0	11.92	0.05	-12.18	0.05	5.01
195W	22.0	3.28	22.0	5.02	1.0	12.04	0.05	-12.15	0.05	5.00

A very good set of results, highlighting that the design can handle dramatic load changes with relative ease and well within specification.

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 OCZ unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
330W	5	5	10	5
620W	10	10	15	10
918W	10	10	20	15
1249W	15	15	30	15

Ripple suppression is fantastic and even at full load it is reading only 30mv on the +12v output. We recorded a maximum of 15mv at full load via the other minor rails. Incredible results indeed.

Efficiency (%)
330W	90.07
620W	92.32
918W	91.13
1204W	88.45

The efficiency results are fantastic, although they do fall a little short when directly compared to the Corsair AX1200W unit which we reviewed some time ago. The Corsair unit does use an LLC converter topology design however so it is understandable.

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 Corsair Power Supply we have taken it into our acoustics room environment and have set our Digital Sound Level Noise Decibel Meter Style 2 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)
330W	28.7
620W	29.3
918W	31.5
1249W	35.7

These results are good and under most circumstances you would be hard pressed to hear the power supply, even up to 1000W load. In the upper 15% of power delivery the fan does become audible, however this would mean a power drain of 1050W or more. Not often a PC would be draining this much power at the socket.

Temperature (c)
	Intake	Exhaust
330W	35	37
620W	38	43
918W	42	47
1249W	46	55

Thanks to the high levels of efficiency, the exhaust temperatures are really good, rising to a 9c above ambient under full load.

Maximum load	Efficiency
1367W	85.76%

For those interested, we measured the efficiency when stressing the unit to breaking point.over 85.76% at 1367W.

The OCZ ZX 1250W is certainly an impressive power supply and one which excelled throughout all our testing over the last couple of days. If you need a substantial supply for multiple high power demand graphics cards then this should certainly be shortlisted, along with the Corsair AX1200 and the less expensive 80 Plus Bronze certified ADATA HM 1200W.

This is a heck of a comeback for OCZ in the high end sector and it is going head to head with the class leading units. All our testing showed positive results, with stable output regulation delivery and quick response with demanding cross loading. The 12V rail in particular is a monster and one of the best we have tested, easily delivering 95A+ without a problem.

Ripple suppression is another highlight, with all minor rails peaking at 15mV under full load. The 12V+ rail hit 30mV at full load, which is basically a quarter of the recommended safe limits under the tolerance guidelines. Any power supply which can output 1250W with such strong ripple suppression deserves special mention.

The appearance is both attractive and well finished, with a modest colour scheme deliberately selected to suit a wide cross section of windowed system builds. The only downside is that the matt finish can attract finger prints, but it is such a minor niggle that a simple rub of a cloth rectifies. The colour coded modular connectors are well thought out and the cabling itself is of the highest quality, with sleeves to enhance the appearance.

Internally, the Great Wall design is very clean and a proven design which works well. The adoption of high grade 105c capacitors, helps ensure long life and stable high temperature power delivery. With OCZ's five year ‘power swap' coverage prospective customers are clearly in good hands.

UK pricing is not yet confirmed, but in the states it is selling for $240. This, in theory should translate to a price around £200 including VAT which means this is extremely good value.

Pros:

• Good pricing
• exceptional build quality
• high quality components used in the design
• Ripple results are class leading
• Bundle is fantastic

Cons:

• We didn't like the shrink wrapping, a felt bag would have been much nicer
  

KitGuru says: OCZ are back in the high end, and in damn fine form we might add.

Become a Patron!