I am currently looking to build myself a new gaming rig, and have chosen the Corsair 620HX as the powersupply.
I did some googling on peoples experiences on this powersupply, and came across this page.
I am studying Electrical and Computer Engineering at UoA, and thought I might be able to shed some light on this high frequency noise some users appear to be having.
As an introduction, AC power is by no means sinusoidal at all. All AC devices that you connect to the grid are "seen" by your power generation company as either capacitive or inductive; Devices that are 100% resistive are very difficult to produce. This capacitive and or inductive effect of the devices on your AC supply modify the sine wave of your AC voltage, and add non-linear behaviour such as spiking on either the leading or trailing edges of the wave, clipping, or cupping on the extremes. This is due to the fact that capacitive loads cause the current to lead the voltage, and inductive loads cause the current to lag the voltage. A perfect AC sine wave would have the current exactly in phase with the voltage (A phase difference of 0 degrees). Any capacitive or inductive effects will cause the current to lag or lead in comparison to this ideal 0 degrees. Devices that are purely resistive do not effect the phase difference between the voltage and the current at all, and thus are the best kind of devices as they are more efficient.
Also, the AC supply is always affected by devices. Power transmission is a two way street, any effects from devices not properly designed, such as lack of RF sheilding for example, can travel back into the AC line and wreak havoc on other devices in your home.
The active power factor correction in modern power supplies is a type of technology that accounts for these effects on your AC power sine wave created by the power supply, and attempts to correct itself so that it appears to be a resistive load (Power factor of 1) as opposed to a capacitive of inductive load.
The active PFC in power supplies depends greatly on a number of factors, such as:
- Power factor of incoming AC signal
- 'Quality' of the incoming AC signal
- Load on the power supply
The electrical noise that most of you hear from your computers will be in the higher end of the audible scale (18,000 Hz and above most likely). This could be generated from several sources, such external frequencies travelling back into your power supply (From things like the motherboards clock generators, un-ferrite blauned cables, bad case design, just to name a few). Also, the active PFC possibly could be a source of this noise, as it uses a series of capacitors and inductors to couple across the supply to bring it's power factor as close as possible to 1.
A note on cables: All cables act as giant antennas to RF frequencies! And also, nearly all devices emit RF frequencies! Cables that have a cylindrical "bump" in the cable have an RF ferrite blaun on the cable, to help reduce the effects of RF being picked up by the cable.
The power supply noise can come from several components within the psu. Capacitors, Inductors are generally the culprits, and if you want to do further back-reading on the magnetic fields produced by these devices, do a google. However, inductor noise is sometimes created by the windings of the inductors vibrating on a minute scale. This is due to the magnetic field produced by inductors, which in turn inacts a force on the inductor itself, and depending on the frequency of the signal through these inductors, the coils may vibrate at a frequency within human hearing range. As for capacitors, I am not 100% sure yet as to what effects are generated by them, but I do know that they can often create resonating frequencies within the human hearing range.
These problems of musical electrical components are pretty much unavoidable.
However, I have noticed that there are people whom are having high frequency electronic noise issues when running an extremely low load on their power supply. 40-60W? For these people, go out and buy a 200W power supply, buying a 500W+ power supply for a load that small is bloody rediculous, as power supplies are extremely inefficient when loaded at such a small load! As a rule of thumb, your rig should pull around 40-50% of the total load supplied by the power supply when your rig is idle.
Also, there are several things that might help this high frequency noise, such as:
- Using sheilded monitor cables (Look for ones with the cylindrical "bump" along the cord)
- Using sheilded/ferrited power cables
- Changing the load on your power supply
- Try changing the refresh rate of your monitor, the clock frequency of your cpu etc
- Try turning various devices on and off within your homes. (Other devices may be messing up the AC signal and the power supply is affected by these effects)
Also, ideally, the AC frequency is 50Hz, however in practice this can be anywhere from 45-65Hz in the most extreme cases, which also can affect your power supplies, and create unwanted electronic noise as your power supply attempts to correct this.
As for UPS', not all models have AC wave filtering and noise reduction. Very expensive models do, but for the most part, UPS' do not have corporate-grade AC smoothing.
Just my input
I hope that wasn't too confusing for some of you, and apologies about the length of my post. If anybody has more information than I do, feel free to correct me!
EDIT: And also, I have used Antec, Silverstone, and Atlas power supplies in the past, all of which have had this high frequency noise, albeit to different degrees. I have also had "squealing" motherboards, and both of my laptops (One Sony Vaio, one Toshiba) make some degree of high frequency noise in some conditions!