Loud Hum at All Times M8 Hero

[Ruarc88]

This is the first time I've gotten a gaming mobo and went with the M8 Hero. First thing I did was update the BIOS to 2202 as it is a fairly old model at this point. Typically I don't do this.

Right from the first power up I've had a loud humming similar to a fan with bad bearings but couldn't figure out where it was coming from.

Initial build specs (nothing else was in the system for the first week):
M8 Hero
i7 6700k
Kingston 32GB 2133 (2x16GB)
CoolerMaster Master Liquid Pro 240 (only ran 1 fan (also tried running fan from my old Nepton 240m as it was dead silent))
CoolerMaster V750 PSU
Intel 600p system drive

With nothing else present in the system the hum was present and happens at load, idle, stock settings, OCed, etc.

So far from the above list, I've replaced the PSU with a Corsair AX750 from my old system (never heard any humming even at load).
Recently replaced the cooler with a new CoolerMaster Nepton 240m (tried both only 1 fan and currently with 3 (1 used as rear case fan)) as this unit was dead silent in my old rig and is currently also dead silent on a P8z77-V LK with i7 3770 OCed to 4.1GHz
Hum is present with or without mechanical drives, with and without GPU (eVGA 980 SC ACX).

Literally the ONLY time it wasn't present was during a failed shutdown where OS had fully closed out and displays went black but power to the board remained. All fans and water pump were still running when this happened but hum had completely vanished.

Seen other threads regarding this but they all seem to be limited to happening while at load and/or OCed. Currently, system is at stock speeds but hum was also present when overclocked to ~4.8GHz (46x104) and didn't seem to be any worse or better. Hum doesn't get worse or better when system downclocks at idle (lowest 16x99 as read by AI Suite). Idle temps are around 40C. Load temps cap off around 55C.

[Korth]

Is the humming audible from something/somewhere inside the chassis, or is it only audible through headphone/speaker outputs?

It seems you've already determined it's not caused by the PSU (along with PSU fan), by the CPU cooler (along with pump and fans), by the GPU card (along with fans), or by any mechanical HDDs.

Could the humming be caused by your monitor?

Does the humming sound like a 20Hz, 24Hz, 30Hz, or 50Hz/60Hz electrical/transformer hum? (Don't be alarmed if your audio processor and headphones/speakers cannot coherently play the lowest of these frequency test tones, lol.)
If so, you might have electrical "line noise", harmonics, or phase impedance coming from your AC wall receptacle (especially if you're near strong EMI/RFI sources like industrial machinery or radio broadcast stations). You might have a Switching Power Supply or an Uninterruptable Power Supply with a similarly "noisy" AC-AC transformer, AC-DC inverter, or DC-DC switch rectifier. The common (cheap) solution is to wrap your appliance (PC) power input cable around a "line filter" toroid, though in extreme cases you may require line filters on one or both ends of every cable connecting the PC to every other piece of hardware.

VRM components on motherboards and GPU cards (and perhaps even within processors) can mechanically oscillate into audible frequencies, but the effect is typically described as high-frequency "coil whine", not low-frequency "humming".

You could use a stethoscope to isolate the cause of the hum, although it might be more difficult to pinpoint the cause if loose chassis panels/cables intermittently come into contact with actively vibrating components.

[Ruarc88]

Korth wrote:
Is the humming audible from something/somewhere inside the chassis, or is it only audible through headphone/speaker outputs?

It seems you've already determined it's not caused by the PSU (along with PSU fan), by the CPU cooler (along with pump and fans), by the GPU card (along with fans), or by any mechanical HDDs.

Could the humming be caused by your monitor?

Does the humming sound like a 20Hz, 24Hz, 30Hz, or 50Hz/60Hz electrical/transformer hum? (Don't be alarmed if your audio processor and headphones/speakers cannot coherently play the lowest of these frequency test tones, lol.)
If so, you might have electrical "line noise", harmonics, or phase impedance coming from your AC wall receptacle (especially if you're near strong EMI/RFI sources like industrial machinery or radio broadcast stations). You might have a Switching Power Supply or an Uninterruptable Power Supply with a similarly "noisy" AC-AC transformer, AC-DC inverter, or DC-DC switch rectifier. The common (cheap) solution is to wrap your appliance (PC) power input cable around a "line filter" toroid, though in extreme cases you may require line filters on one or both ends of every cable connecting the PC to every other piece of hardware.

VRM components on motherboards and GPU cards (and perhaps even within processors) can mechanically oscillate into audible frequencies, but the effect is typically described as high-frequency "coil whine", not low-frequency "humming".

You could use a stethoscope to isolate the cause of the hum, although it might be more difficult to pinpoint the cause if loose chassis panels/cables intermittently come into contact with actively vibrating components.

It is definitely coming from the chassis. Noise is much louder when I'm up close to the case. Unfortunately can't get quite close enough inside to identify exactly where. Headphones do not have any audible hum/whine/etc when audio isn't playing. Same for speakers, even when cranked.

Using the same monitors I used on old rig and they are silent. One of the DC transformers does have very low coil whine but you need it right against your ear to hear it.

Will confirm those noise samples when I get home but I am plugged into a UPS that hasn't produced any noise in the past at loads of up to 500W. Averaging around 200-360W during idle/gaming. UPS also has a power bar for system and all monitors that I've replaced with no change.

Not near any EMI/RFI sources and I have tried multiple power cables for the PSU

No stethoscope but will try to use an old mic to see if I can find whereabouts exactly the noise is coming from inside the chassis.

[Ruarc88]

Korth wrote:
Does the humming sound like a 20Hz, 24Hz, 30Hz, or 50Hz/60Hz electrical/transformer hum? (Don't be alarmed if your audio processor and headphones/speakers cannot coherently play the lowest of these frequency test tones, lol.)

Here is a recording of the noise, perceived sound is slightly lower pitched and can be heard clearly from across the room.

This was taken with the mic directly under the CPU between the water block and the 1st PCIe slot.

Sound was not audible on top of the CPU or under the GPU.

Recording was done with 1 of 3 fans on and 2 of 3 mechanical drives removed at idle

[Korth]

I'm guessing it's caused by your UPS. Or more specifically, by the power inverter inside it. The UPS converts wall AC to DC (because it uses DC internally to charge the battery) then converts DC to AC (so it can output power to your computer PSU). The inverter is the part which converts DC to AC, it uses digital PWM to simulate an AC sine wave. If this simulated waveform has a low digital resolution it could be good enough to fool your PSU while introducing line harmonics which are too "rough" and "choppy" for your sensitive (and perhaps aging) motherboard VRMs.

Try measuring again, without the UPS in circuit. I think bad UPS inverter harmonics are straining your mobo VRMs beyond their low-end tolerances. If so, you need to replace the UPS with a new one which filters out harmonics or with an old one which uses a mechanical circular-phase inverter.

By the way, how are temps on your motherboard VRMs, near the source of the humming noise? Maybe just cooling them better would correct the problem.

[Ruarc88]

Korth wrote:
I'm guessing it's caused by your UPS. Or more specifically, by the power inverter inside it. The UPS converts wall AC to DC (because it uses DC internally to charge the battery) then converts DC to AC (so it can output power to your computer PSU). The inverter is the part which converts DC to AC, it uses digital PWM to simulate an AC sine wave. If this simulated waveform has a low digital resolution it could be good enough to fool your PSU while introducing line harmonics which are too "rough" and "choppy" for your sensitive (and perhaps aging) motherboard VRMs.

Try measuring again, without the UPS in circuit. I think bad UPS inverter harmonics are straining your mobo VRMs beyond their low-end tolerances. If so, you need to replace the UPS with a new one which filters out harmonics or with an old one which uses a mechanical circular-phase inverter.

By the way, how are temps on your motherboard VRMs, near the source of the humming noise? Maybe just cooling them better would correct the problem.

Negative. Plugged directly into the wall outlet with no change. Also tried surge-protection only outlet on UPS with no change. Just got the board this past Christmas. Just got the UPS this past summer and is rated 1325VA. Load at idle is ~120W

During reboot measured VRM in BIOS at 39C. At load AI Suite is measuring around 46-48C.

[Korth]

lol then I have no answer. Temps seem fairly normal, nothing obviously cooking your hardware, probably not a thermal paste issue.

If your mobo is generating this hum then perhaps it has a faulty, borderline, or derated component. Can you compare your hum vs other M8 mobos?

Any chance you have an electrical ground loop inside your chassis?

[Ruarc88]

Korth wrote:
lol then I have no answer. Temps seem fairly normal, nothing obviously cooking your hardware, probably not a thermal paste issue.

If your mobo is generating this hum then perhaps it has a faulty, borderline, or derated component. Can you compare your hum vs other M8 mobos?

Any chance you have an electrical ground loop inside your chassis?

Unfortunately can't compare to another M8 board. Colleague has an M7 I'll check if he's had this at all. This is the first time I've bought a gaming board so didn't really know what to expect but every other system I've owned has never done this.

As far as I know there's no loop. Case is on hardwood floor with rubber feet. During install didn't notice any exposed wires. Only ground should be the PSU.

[Ruarc88]

Colleague's M7 does not have this at all. Will check to see if this is covered under my IPR later today

[Ruarc88]

Figured it out while removing the board to do IPR. It was rattle from the water pump. TL:DR, combination of PWM mode and running ~3 times faster than the same pump does in my old rig. Moved to chassis header and reduced to 40%. Will monitor temps but likely going to drop it even further.

Always wondered why the pump light was so much brighter than my old rig 😛