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Corsair CX750M PSU Review

Corsair's CX line is aimed at users with limited budgets who still want a branded, reliable, and well-supported PSU. Today we're reviewing the second-strongest member of the family, the CX750M.

Efficiency, Temperature, And Noise

Efficiency

Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the CX750M's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

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The CX750M's efficiency is low compared to Corsair's CX650M, and under light loads this model takes last place. We wanted to see higher efficiency levels, but this platform isn't up to the challenge.

Efficiency At Low Loads

In the following tests, we measure the CX750M's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedFan NoisePF/AC Volts
11.208A0.490A0.481A0.195A19.6760.17%760 RPM25.2 dB(A)0.922
12.096V5.057V3.314V5.062V32.69115.0V
22.443A0.985A0.995A0.396A39.8070.44%760 RPM25.2 dB(A)0.960
12.089V5.050V3.309V5.054V56.50115.1V
33.676A1.475A1.510A5.044A59.8377.15%760 RPM25.2 dB(A)0.980
12.083V5.045V3.307V5.044V77.55115.1V
44.905A1.983A1.995A0.791A79.8080.07%760 RPM25.2 dB(A)0.980
12.077V5.039V3.303V5.036V99.66115.1V

The unit barely scrapes past the 80% mark during the last light-load test. In addition, the fan could be quieter with a lower minimum speed.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.

We take four measurements: one each at 100, 250, and 1000mA, and one with the full load the 5VSB rail can handle. 

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.102A0.5276.47%0.066
5.069V0.68115.1V
20.251A1.2779.87%0.143
5.065V1.59115.1V
31.002A5.0681.48%0.317
5.046V6.21115.1V
43.002A14.9979.23%0.417
4.995V18.92115.1V

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Strangely enough, the 5VSB rail is very efficient, taking the lead from many Gold-rated PSUs. Apparently CWT used the same 5VSB circuit found in the CX650M, which offers similar performance levels.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Mode12V5V3.3V5VSBWattsPF/AC Volts
Idle12.088V5.061V3.317V5.071V12.400.756
115.1V
Standby0.060.006
115.1V
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Vampire power is low with both voltage inputs.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 33°C (91.4°F) to 46°C (114.8°F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 33°C (91.4°F) to 46°C (114.8°F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28°C (82.4°F) to 30°C (86°F).  

Up to around 330W load the fan's noise stays low, but it quickly increases beyond that, and above 480W the noise exceeds 40 dB(A).

  • Bit early for a review,but just installed mine to replace my old one that was power surging.
    Very easy to install and only use the extra cables you need.
    Piece of mind knowing the 3 year warranty that comes with it.
    Reply
  • RCFProd
    Thanks for the review!
    Reply
  • turkey3_scratch
    Funny how it doesn't have OTP, when as a matter of fact, OTP was the very thing that saved the original CX750M's butt in Jonnyguru's testing; but the majority of people, rather than realizing that was a good safety measure, took it instead as "the CX750M can't do more than 650W" when in fact it was just Oklahomawolf's hot box. So maybe to avoid another mishap like this altogether they just removed OTP and cheered over the money savings at the same time?

    I don't care for this PSU too much anyway. It seems to be a power supply that likes to focus on good ripple (as every modern PSU does these days) and decent voltage regulation but falls short in nearly every other aspect. I don't see it being much of any improvement over the original CX750M, the whole purpose of was probably just to cut costs. I'd happily take 60mv of ripple on my 12V rail in turn for some better holdup time, a higher quality fan and perhaps caps (if those Suscons aren't the best), and OTP.
    Reply
  • jonnyguru
    It does have OTP. There's something wrong with Aris's unit and I'm going to investigate it.
    Reply
  • JackNaylorPE
    I keep reading posts referencing the new CXM series, but the conclusions section which most readers skip to seem to follow Mom's advice ... "if ya don't have anything good to say, don't say anything" ... anything negative is left out. If the CX750M is going to be competitive, it has to address the elephant in the room that is the EVGA 750 B2 that sells for $50.
    Reply
  • RCFProd
    18929743 said:
    I keep reading posts referencing the new CXM series

    Aren't those usually either the 450w, 550w and 650 watts? Those are different units compared to the 750 watts I think.

    18929743 said:
    If the CX750M is going to be competitive, it has to address the elephant in the room that is the EVGA 750 B2 that sells for $50.

    Plenty of better options for power supplies around CX750M's price range, must be said. Isn't the EVGA B2 750w 65 dollars?
    Reply
  • turkey3_scratch
    Ya B2 is well priced http://www.newegg.com/Product/Product.aspx?Item=N82E16817438028&cm_re=evga_750_b2%5c-_-17-438-028-_-Product
    Reply
  • JackNaylorPE
    The CX450M, CX550M and CX650M were redesigned last year and manufactured by CWT using a custom Corsair design, while the CX750M (and I think the 850 model) was based upon CWTs PUQ B patform. This latest revision seems to be even newer .. and even beyond that, it appears to have changed yet again after the review samples went out as noted in the article the newer 650M's use a "470uF bulk cap but use instead a 330uF one".

    Note that the CXM series is reported as the lowest quality Corsair PSU available in the US.... yet several VS models remain available thru US e-tailers. One thing I have always observed, specifically with regard to PSUs and coolers is that forum posters, even when referencing an article that says the reviewed item was a "good budget model" or "good for the money, tend to drop the words "budget" and "for the money" when recommending it. So while it may be a logical choice for a G3258 or GTX 1050 build w/ no overclocking, I don't quite understand why a Hyper 212 or a CX series PSU gets recommended for a 6700k / 1070 build especially where OP states an interest in overclocking the bejeezes out of everything.

    Here's the only reviews I have seen besides this one:
    http://www.tomshardware.com/reviews/corsair-cx650m-psu,4770.html
    http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=486


    18929767 said:

    Aren't those usually either the 450w, 550w and 650 watts? Those are different units compared to the 750 watts I think.

    Plenty of better options for power supplies around CX750M's price range, must be said. Isn't the EVGA B2 750w 65 dollars?

    NCIX almost always has it for $50 in conjunction w/ Corsair MIR and instant savings... sometimes others like newegg

    NCIX = $45 (Savings Code 97531-1714. SAVE $25.00 off our regular price of $89.99 Special price ends 11/30/2016 + Save $20.00 USD with manufacturer's mail-in rebate!)
    http://www.ncixus.com/products/?usaffiliateid=1000031504&sku=97531&promoid=1714

    newegg = $89.99 - $20 instant savings - $20.00 rebate card = $49.99
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817438028
    Reply
  • powernod
    If i was short on budget i wouldn't hesitate to use Corsair's CX-M line of PSUs.
    Solid units for that kind of price.
    I don't expect to have Seasonic PRIME 750's performance with 80$ !!
    Reply
  • turkey3_scratch
    18930459 said:
    If i was short on budget i wouldn't hesitate to use Corsair's CX-M line of PSUs.
    Solid units for that kind of price.
    I don't expect to have Seasonic PRIME 750's performance with 80$ !!

    If I needed 750W and it was between the EVGA 750 B2 and the CX750M, I'd probably take the former.
    Reply