I have bought today brand new hAP ac² and its amazing when it comes to performance ( except glitchy 5 GHz wifi but hopes it will get fixed ), BUT it tends to get noisy when theres any WiFi transfer going on, its much more noisy on 5 GHz ( same transfer speed as in 2,4 GHz ), the sounds it makes are sort of hissing noises coming from unit itself, is it normal for this model or the one I bought have defect ?
For comparison I have RB951G and its totally noiseless. ( except when using its speaker )
When I am using cable connection on hAP ac² its generally noiseless.

I checked power supply using multimeter as I was reading sometimes its due to bad power supply, and multimeter showed 23.4V ( its 24V power supply ), it should be fine then ?

I have bought today brand new hAP ac² and its amazing when it comes to performance ( except glitchy 5 GHz wifi but hopes it will get fixed ), BUT it tends to get noisy when theres any WiFi transfer going on, its much more noisy on 5 GHz ( same transfer speed as in 2,4 GHz ), the sounds it makes are sort of hissing noises coming from unit itself, is it normal for this model or the one I bought have defect ?
For comparison I have RB951G and its totally noiseless. ( except when using its speaker )
When I am using cable connection on hAP ac² its generally noiseless.
I checked power supply using multimeter as I was reading sometimes its due to bad power supply, and multimeter showed 23.4V ( its 24V power supply ), it should be fine then ?

• Can you translate "hissing" into frequency in kHz? The point is that the younger you are, the higher frequencies you can hear, plus the initial range and the rate of deterioration is of course individual per person. So my own hAP ac² may well behave exactly the same like yours but I may not hear it at all.
  "Spectrum analyzer" applications for smartphones usually help anwer this question, but the smartphone's microphone has to be good enough to let the frequency in, could you give it a try and post the result when WiFi is on and when it is off (if they differ of course)?
• I assume that to be able to measure the power supply output voltage, you have disconnected it from the router, so it was not loaded at all. Such measurement doesn't say anything about how it behaves under load. If you have any other power supply with output voltage withing hAP ac²'s permitted range (12-28 V) which is rated to 15 W at least (so the adaptor from the RB951G with its 12 V /1 A is not sufficient), can you try with that one whether the effect is the same?
• is it enough to switch the wireless interface on, or do you have to transfer data constantly to make the box start producing sound?

I also noticed that 5Ghz connection was a bit glitchy with hAP ac2.

I couldn't hear any noise during any transfer in 5Ghz channels. I might have a problem with my ears.
When I leaned my left ear on hAP ac2, I could then hear some scratchy noise during a 5Ghz transfer.

I also noticed that 5Ghz connection was a bit glitchy with hAP ac2.

This has been reported in several topics including those related to current and rc software so I believe guys at Mikrotik are already busy dealing with it.

I couldn't hear any noise during any transfer in 5Ghz channels. I might have a problem with my ears.
When I leaned my left ear on hAP ac2, I could then hear some scratchy noise during a 5Ghz transfer.

I've just tested with my own one - yes, if I hold the box on my ear, I can hear the data flow, a scratchy noise as you describe (to me it sounds like a busy 2,5" hard disk). The server in home network is not extremely fast, but transferring the same data (a bunch of relatively small files) over the 5GHz wireless ran at about 15 Mbit/s, while transfer of the same data over a gigabit wire between the hAP ac² and my notebook ran at 30 Mbit/s. So yes, there is something wrong with the throughput there. I was checking the speed while the router was not on my ear so that wasn't the reason of throttled speed.

My teenage son declares to hear that from a 0,5 meter distance in a room where I have to stick my ear on the box (where a dishwasher and a refrigerator, both declared to be "silent", are running about 6 meters away). The spectrum analyzer in the mobile phone doesn't catch anything but that's no surprise due to the absolute volume of the noise.

So the age of the OP may make the difference, or his particular piece may have an issue, hard to say.

• Can you translate "hissing" into frequency in kHz? The point is that the younger you are, the higher frequencies you can hear, plus the initial range and the rate of deterioration is of course individual per person. So my own hAP ac² may well behave exactly the same like yours but I may not hear it at all.
  "Spectrum analyzer" applications for smartphones usually help anwer this question, but the smartphone's microphone has to be good enough to let the frequency in, could you give it a try and post the result when WiFi is on and when it is off (if they differ of course)?
• I assume that to be able to measure the power supply output voltage, you have disconnected it from the router, so it was not loaded at all. Such measurement doesn't say anything about how it behaves under load. If you have any other power supply with output voltage withing hAP ac²'s permitted range (12-28 V) which is rated to 15 W at least (so the adaptor from the RB951G with its 12 V /1 A is not sufficient), can you try with that one whether the effect is the same?
• is it enough to switch the wireless interface on, or do you have to transfer data constantly to make the box start producing sound?

I have recorded it and it sounds pretty the same on recording as irl ( added as attachment )
I tried also with 12V power supply from my RB951G and hAP ac2 was hissing the same as with original power suply
To hear the sound I have to transfer data, when only wifi is on the device doesnt produce any hearable sounds.
Also as to my age I am not far from 30

I can hear the noise from .flac file although it is not loud.

I can hear the noise from .flac file although it is not loud.

Well maybe it is not VERY loud but I try to keep all my equipment in room I sleep as quiet as possible,
and thats the only router so far in my life that is making such noises, and I had 20+ routers including routers from Linksys ( cisco ), Netgear, D-link, TP-Link, Asus, and some other smaller vendors.
Even from Mikrotik I had few routers, including one with 5 GHz but none of them were making such noises.
I am thinking about returning this one to shop and buying another one from different shop just the question is if all hAP ac2 are making such noise ?
In this case I would probably buy hEX + some AP.

• Can you translate "hissing" into frequency in kHz? The point is that the younger you are, the higher frequencies you can hear, plus the initial range and the rate of deterioration is of course individual per person. So my own hAP ac² may well behave exactly the same like yours but I may not hear it at all.
  "Spectrum analyzer" applications for smartphones usually help anwer this question, but the smartphone's microphone has to be good enough to let the frequency in, could you give it a try and post the result when WiFi is on and when it is off (if they differ of course)?
• I assume that to be able to measure the power supply output voltage, you have disconnected it from the router, so it was not loaded at all. Such measurement doesn't say anything about how it behaves under load. If you have any other power supply with output voltage withing hAP ac²'s permitted range (12-28 V) which is rated to 15 W at least (so the adaptor from the RB951G with its 12 V /1 A is not sufficient), can you try with that one whether the effect is the same?
• is it enough to switch the wireless interface on, or do you have to transfer data constantly to make the box start producing sound?

I have recorded it and it sounds pretty the same on recording as irl ( added as attachment )
I tried also with 12V power supply from my RB951G and hAP ac2 was hissing the same as with original power suply
To hear the sound I have to transfer data, when only wifi is on the device doesnt produce any hearable sounds.
Also as to my age I am not far from 30

The part of the recording which I can hear myself is the same in character like the sound produced by my own hAP ac², but my PC's microphone is unable to catch that even if I place the hAP ac² directly on it. The maximum in the spectrum of the recording is somewhere between 17 and 18 kHz which I've just tested to be out of my current range.

So @Mitar, I'm afraid that you'll have to test with another piece to make clear whether it is normal or not. I should get two other pieces next week so I'll check with them as well.

My "qualified guess" is that the inductance in the DC/DC converter of your particular piece is poorly manufactured so the wire in the coil can move mechanically, and the load coming from operation of the wireless network makes it do so.

If you can hear it, it's in a relatively low frequency as far as electronics go, and probably coming from the dc/dc circuitry. Put your ear next to all the electronics you have(and/or their power supplies) and you will most likely hear something in all of them. It doesn't make a difference in performance or reliability.
I wouldn't worry about it unless you have it in a place where you are regularly close enough to hear it.

MWAAF, MikroTik Wireless Activity Audio Feedback™. My mAP Lite already had the same feature two years ago. Too bad it's not optional. I ended up putting it in place where I don't hear it.

I wouldn't worry about it unless you have it in a place where you are regularly close enough to hear it.

Well I live in a small flat and router is ~ 2 meters from my bed and half a meter from my desk so its extremely annoying.
Its even actually doing those noises on cable only transfers but they are a lot more quiet.
So I was really thinking about returning it to shop and buying hEX instead + some ap, if not that my old RB951G is too weak for 900 Mbit I wouldn't change it as it was extremely quiet.
Or just try to fix it myself, maybe ? Most likely warranty doesn't cover noisy coils...
I was reading ppl recommends nail polish / super glue to put on the coil and its supposed to make it ultra quiet.

I managed to open the case very carefully and yes that is the coil problem, even applying a little pressure on it with finger and it generally becomes noiseless.
This coil is sort of closed in a case but it have small 1mm holes which could be used to insert needle with super glue.
Just the question remains wont it damage the coil ?

I added picture with board ( I didnt made it ) with how the coil looks like. ( red circle )

I managed to open the case very carefully and yes that is the coil problem, even applying a little pressure on it with finger and it generally becomes noiseless.
This coil is sort of closed in a case but it have small 1mm holes which could be used to insert needle with super glue.
Just the question remains wont it damage the coil ?

I added picture with board ( I didnt made it ) with how the coil looks like. ( red circle )

If you mean a cyanoacrylate superglue, it is quite fragile after it cures so you should use something which remains rubberish after curing - the so-called contact glues which you have to evenly spread at both surfaces, then let them dry for 10-15 minutes, and then press the two items together are the best choice. I cannot recommend a brand name not knowing your country.

If you can hear it, it's in a relatively low frequency as far as electronics go, and probably coming from the dc/dc circuitry. Put your ear next to all the electronics you have(and/or their power supplies) and you will most likely hear something in all of them. It doesn't make a difference in performance or reliability.
I wouldn't worry about it unless you have it in a place where you are regularly close enough to hear it.

Username checks out.

Put hot glue over it. It stays elastic and can be easily removed if necessary.

Do not interfere with it, just return it as faulty and describe the reason for useful feedback to all. This is clearly a hardware QA issue, i.e. probably not even an issue with the model at all.

Also, why are you considering to interfer with the faulty hardware of a brand new device, especially for home use (the most protected status legally), unless you want to keep that specific sample anyway.

The photo of the internals is nice though. Thank you for that.

Do not interfere with it, just return it as faulty and describe the reason for useful feedback to all. This is clearly a hardware QA issue, i.e. probably not even an issue with the model at all.

Also, why are you considering to interfer with the faulty hardware of a brand new device, especially for home use (the most protected status legally), unless you want to keep that specific sample anyway.

The photo of the internals is nice though. Thank you for that.

I decided to fix it myself, I was reading that noisy coils are not enough reason for warranty repair.
So I put some nail polish inside syringe and with small needle ( I have cut first the beginning of needle so it wouldn't damage coil) and I stuffed the coil till it began overflowing.
And after it settled around hour later it was almost noiseless and next day ( today ) can't hear the coil at all even at close range.
No idea why Mikrotik decided to ruin like that new product, I would gladly pay that 1$ more if they put there some nice noiseless coil.

There are more photos here, at this Rus website http://www.pvsm.ru/sistemnoe-administrirovanie/275169

The same is true with the cAP ac, on 5GHz there is noise...

The same is true with the cAP ac, on 5GHz there is noise...

on hAP ac² there was noise coming from it even when only 2.4 GHz was ON.

The same is true with the cAP ac, on 5GHz there is noise...

on hAP ac² there was noise coming from it even when only 2.4 GHz was ON.

Depending on how loose the wires on the coil are, the same current passing through it generates a different acoustic pressure = loudness. So the smaller current corresponding to 2.4 GHz operation is enough to make it audible in one case but not in another.

There is no wonder that cAP ac and hAP ac² behave similarly as they are built around the same SoC and designed at about the same time so probably most parts of the hardware design have been used for both, so the current drawn during wireless operation is the same for both. The fact that cAP ac's input voltage range is somewhat shifted up as compared to that of hAP ac² likely makes little difference as the current runing through the coil is mostly determined by the consumption of the output side.

So the remedy options are the same for both models - ask the distributor for replacement or take the DIY path with flexible glue, which means you'll be up and silent in half a day but you'll lose the right for warranty repair if something else breaks down on your unit.

I don't know Mikrotik's policy, but for this price category of product, a typical approach is that the distributors receive some percentage of extra pieces from the manufacturer as a warranty exchange buffer, and no warranty repairs exist because the associated logistics would be too expensive. So the distributor is likely to do anything legal to keep these extra pieces to cover the "real" malfunctions and play down the importance of noise, causing a damage to Mikrotik's reputation implicitly or even explicitly.

So I would definitely try to claim that, and if the shop refuses to provide a warranty replacement, I would require an official written statement from them that they will accept a warranty claim for a "real" reason even if you apply the glue to the coil.

I decided to fix it myself, I was reading that noisy coils are not enough reason for warranty repair.
So I put some nail polish inside syringe and with small needle ( I have cut first the beginning of needle so it wouldn't damage coil) and I stuffed the coil till it began overflowing.
And after it settled around hour later it was almost noiseless and next day ( today ) can't hear the coil at all even at close range.
No idea why Mikrotik decided to ruin like that new product, I would gladly pay that 1$ more if they put there some nice noiseless coil.

There are more photos here, at this Rus website http://www.pvsm.ru/sistemnoe-administrirovanie/275169

Included exchange for better capacitors. I would gladly pay too.
search.php?keywords=capacitor

Do not interfere with it, just return it as faulty and describe the reason for useful feedback to all. This is clearly a hardware QA issue, i.e. probably not even an issue with the model at all.

Also, why are you considering to interfer with the faulty hardware of a brand new device, especially for home use (the most protected status legally), unless you want to keep that specific sample anyway.

The photo of the internals is nice though. Thank you for that.

I decided to fix it myself, I was reading that noisy coils are not enough reason for warranty repair.
So I put some nail polish inside syringe and with small needle ( I have cut first the beginning of needle so it wouldn't damage coil) and I stuffed the coil till it began overflowing.
And after it settled around hour later it was almost noiseless and next day ( today ) can't hear the coil at all even at close range.
No idea why Mikrotik decided to ruin like that new product, I would gladly pay that 1$ more if they put there some nice noiseless coil.

There are more photos here, at this Rus website http://www.pvsm.ru/sistemnoe-administrirovanie/275169

Can you give a more details photo how you do this. In what hole you put needle? I bought router with same problem. I want to fix the problem on their own.
I will be grateful for the help. I think many peoples interested in this.