Creative Stage Air V2 potentially damaging my stuff?

[ElectronicsEnjoyer]

Some relevant background to this, so please do bear with. Note that this soundbar contains an internal battery, which may be relevant to the issue.
In November 2022, I bought a Creative Stage Air V2 soundbar to go under my central PC monitor. Space is an issue, this product seemed ideal. When I switch on the soundbar at the mains, one of my monitors briefly desyncs, the screen goes blank and it takes a few seconds to reappear, the same behaviour as when you change PC resolution. The monitor is plugged into the same power strip as the soundbar, but the soundbar itself is connected to a Scarlett 4i4 which sits under the soundbar and goes via USB to my desktop PC. I thought this behaviour was a bit odd but perhaps a lack of general shielding leading to an RF spike problem.

Start of June 2025, I bought a second Air V2 to go near a CRT I use for older gaming and connected it directly to my Mega Drive's headphone jack to avoid bright screen audio hum/crosstalk. After half an hour or so without problems, the screen started showing intermittent video interference, with snow and occasional flickering to black and white. I checked all the connections were seated correctly but the interference continued. It only stopped when I removed the Air V2 from the setup and has never happened before or since. The soundbar was located more than a foot away from the CRT and console and was plugged into the mains, as the internal battery doesn't last that long.

I tested today with the following results:
Plugged into mains and speaker switched on: Audible hum from the speaker when the 3.5mm plug is floating. A multimeter shows a fluctuating voltage at various values between 1.2v and -1.2v every 1/4 of a second or so on the earth section of the 3.5mm plug.
Unplugged from mains and speaker switched on: No audible hum from the speaker when the 3.5mm plug is floating. No reading from the multimeter.

Given I bought these two soundbars 2 1/2 years apart, it seems to me that this is not a one-off fault and the Air V2 has something about its electrical design that feeds voltage out through the headphone plug when the unit is plugged in, as well as a possible shielding problem in the body of the unit.
The temporary fix appears to be to only use these soundbars unplugged, which is inconvenient when the battery only lasts 2-3 hours and I need sound all day or forget to plug them in to charge after use. Given what appeared to be electronic feedback into the Mega Drive, I'm also now loathe to plug one of these into my stuff anyway as I'm not made of money to replace things that get zapped.

My questions are:
1) Is this a known problem with the Air V2? I can't find anything about it online.
2) Is there any way to resolve or fix this? I'm not averse to opening things up and doing some very basic soldering. I was advised to perhaps remove the battery, though don't know if this would stop current going up the headphone jack, so advice there would be great.
3) Or should I dump them both and look for alternatives? Is this something I should expect to happen with all PC soundbars when mains powered?
Many thanks.

[Kean]

I don't know anything about the Air V2, but this does seem like it might be a ground loop issue.  You can get audio ground loop isolators pretty cheaply, and it is worth a try.

They are about the size of a tube of lipstick, and have two audio jacks.  You can find them on most of the usual shopping sites like ebay or Amazon, but here is an example (not endorsing this one, just first result on a search).  https://www.aliexpress.com/item/1005008457896101.html

[ElectronicsEnjoyer]

I did some further research and what you suggested appeared to be relevant to the issue and a possible solution.
Picked myself up two of these: https://www.ebay.co.uk/itm/187560990379
I tried both in various combinations of isolator and 3.5mm cable and they've stopped the desyncing of the PC monitor when the speaker's mains plug it switched on, but instead have added a hum to the audio that wasn't present before! Daisychaining both isolators reduced the hum but didn't entirely eliminate it.
Any further ideas?

[Kean]

Weird.  In a vehicle, these are normally used to reduce hum (caused by the engine/alternator).

I meant to ask earlier, do you have a USB connection from your computer to both the Scarlet and the soundbar?

What power supply are you using for the soundbar?  I presume it charges via the USB port.  A crappy USB charger could be an issue, so I'd try swapping it.

[Nominal Animal]

Yup, sounds like a ground loop plus crappy USB power supply.

I'd recommend you get a MeanWell NGE12I05-USB or NGE18I05-USB to power your soundbank, unless you want to build your own low-noise USB supply based on a low-leakage isolated 5V supply, with additional output filtering (even say RPMS-30-7.5 + linear regulator to 5V).  The NGEs do have 60mVpkpk of noise (1.2% of 5V output), which isn't usually a problem but might matter if the sound bar doesn't filter its power rail properly.  The datasheet for the soundbar says its USB charging is 5V 2A max.

The key is to get a 5V 2A+ supply, whose output is not referenced to mains neutral so it will "float" to whatever ground your audio equipment has, has minimal leakage (so medical MOPP×2 rating), plus as little noise as you can get.  Even leakage through the safety capacitor across the transformer can be hummy.  Because adding a Pi filter etc. might interfere with the sound bar power circuitry, I think that if the NGE wall warts don't fix it, making your own supply with a linear post-regulator is the only way to get rid of the humming.

I've also seen audio outputs with common mode noise between ground and the audio channels, but an audio isolation transformer ("ground loop isolator") eliminates that.

Full disclosure: I know nothing, and my use of various (digital) isolators has been ridiculed here before.

[ElectronicsEnjoyer]

The Scarlett is powered by USB from the PC, the Creative soundbar is powered by an Apple 10 watt USB plug that outputs 5.1v at 2.1amps. I've tried a different model of Apple PSU with the same result. The soundbars were both bought new and weren't supplied with a power supply. They provide a USB-A to USB-C cable and a 3.5mm jack cable, both of which I'm using as supplied.
When I had one connected to the Mega Drive, I was using a different plug to the one at the PC.

To complete the picture, the audio cable arrangements are:
PC: Stereo RCA from the Scarlett into 3.5mm jack at the soundbar.
Mega Drive: 3.5mm stereo jack to 3.5mm jack at the soundbar.

For me, as this involves the use of two different soundbars that are the same model, it feels like it points to something in the soundbar charging circuit electrical design. Note that the problems do not occur when the soundbar is unplugged and running from battery, but "simply use it unplugged" isn't a convenient overall solution due to the length of time of use.

[Nominal Animal]

The Scarlett is powered by USB from the PC, the Creative soundbar is powered by an Apple 10 watt USB plug that outputs 5.1v at 2.1amps.

Apple wall-warts (if genuine and not knock-offs) tend to be good quality, but PC USB supplies can be noisy.
Something like 50mV to 100mV peak-to-peak ripple and noise on the USB 5V is typical.

I think we can blame the soundbar internals here instead.

The problem is we do not know if the noise is from the USB power supply because the soundbar lacks the necessary filtering on it, or from the soundbar's own internal charging circuitry (that likely involves a DC-DC converter).  A custom low-noise 5V supply will only help with the former.  If it is the latter, then other than modifying the soundbar itself, there is nothing we can do to help with the noise.

When I had one connected to the Mega Drive, I was using a different plug to the one at the PC.

Note that the ground loop could also be between the Mega Drive and the PC, so please verify the hum occurs even when only one of them is connected to the sound bar, and not only when both of them are.

I like quiet, and have suffered from external PC speaker hum (including Creative speakers'), exactly because they do not filter their supply enough at low volumes to hide the supply hum.  I also detest flicker and tend to use low level backlights; most displays I use have their backlight intensity set to between 0% and 15%.

One "trick" you could do is use a power-only USB cable with a switch in it for the soundbar, so you wouldn't need to unplug it, just flip the switch as needed.

[ElectronicsEnjoyer]

The problem is we do not know if the noise is from the USB power supply because the soundbar lacks the necessary filtering on it, or from the soundbar's own internal charging circuitry (that likely involves a DC-DC converter).  A custom low-noise 5V supply will only help with the former.  If it is the latter, then other than modifying the soundbar itself, there is nothing we can do to help with the noise.

Yes, I agree, so the next question is what am I looking for inside the soundbar to determine if this is the case?

Note that the ground loop could also be between the Mega Drive and the PC, so please verify the hum occurs even when only one of them is connected to the sound bar, and not only when both of them are.

They aren't both connected to the same soundbar. I have two soundbars of the same model. I've tried both soundbars on both machines to see if it was a problem with one and not the other, but both soundbars act the same. The PC and Mega Drive are plugged into different power outlets on opposite sides of the same room, though these power outlets are on the same house ring served by the same circuit breaker. When the PC is on, the Mega Drive isn't plugged in. When the Mega Drive is on, the PC is plugged in but not switched on. Note also that, e.g. when I plug in the PC soundbar and my LCD TV is on (same wall outlet as the Mega Drive), the TV doesn't lose sync, only the PC monitor does. And again to clarify against any possible further confusion, yes, I do have an LCD TV and a CRT in the same room.
So I don't think this point is relevant and I think it's a design problem with the soundbars themselves. So, as above, I'm happy to open one up and see what should be reading things and what shouldn't, in which case, what should I be looking for to discover where this apparent electrical noise is coming from when the soundbar is plugged in but doesn't make noise when it's on battery only?

[Nominal Animal]

Yes, I agree, so the next question is what am I looking for inside the soundbar to determine if this is the case?

These usually have separate sections, sometimes even on different PCBs: one is the power supply and battery charging unit, another one is the audio amplifier circuit, and in this case a third one is the bluetooth part.

Do you have an oscilloscope (even a cheap $30-$40 one)?  Measuring the output of the supply circuit for ripple and noise within the audio frequency range (say 20 Hz to 20 kHz), when on battery power and when powered from USB, would be my suggestion.  Short the audio input to ground, for example making a custom plug or cable with left and right shorted to ground, so only the inherent noise of the amplifier is visible.

On the audio amplifier side, you should be able to identify the audio opamp(s) used, and determine the power rails from those.  It will very likely use a single-sided supply, i.e. VDD at some positive supply rail, likely 5V, and VSS at 0V/GND.  Then, the input audio will be biased to somewhere around 1.8V or 2V or so (line audio is about ±1V, and the DC component will be rejected on input using a capacitor), and exactly how it is done matters a lot: a resistor divider between the supply and ground is most likely, and the noisiest, since supply rail noise is output only halved.  Analog AN-581 from 2002 describes better voltage biasing schemes, and they are simple enough to be bodged in if you can reverse-engineer the amplifier part.

I'm just a hobbyist, but I did try to find its schematics or pictures of its (MF8395) PCB(s) to see what specifically to investigate, but couldn't find any.  I'm pretty sure its schematics and repair manuals and such are out there somewhere..

They aren't both connected to the same soundbar.

Ah, apologies; my mistake.

when I plug in the PC soundbar and my LCD TV is on (same wall outlet as the Mega Drive), the TV doesn't lose sync, only the PC monitor does.

To clarify, the sound bar is not connected to the PC monitor at all, just sits beneath it?

That sort of glitching does usually indicate a ground loop or at least a bounce or spike in the PC monitor signal ground.  It could also happen due to sudden change in surrounding magnetic fields, and speakers are basically just huge coils, so it could be just due to the magnetic fields when the speakers are first energized; I dunno.

what should I be looking for to discover where this apparent electrical noise is coming from when the soundbar is plugged in but doesn't make noise when it's on battery only?

With input shorted to ground, one would need to track the audio signal to see where noise appears when running from USB, and disappears when running on battery only.

My bet is on it using single-sided supply and a voltage bias for the amplifier IC(s) that passes half the supply noise to the output audio; see the above AN-581.

The question is, since this is a design issue and not a fault, are you willing to risk the unit to hack the noise away?
Or, would you rather first set up a low-noise 5V USB supply, for example from a lab power supply, optionally at 7-8V and linearly regulated to 5V (needs a heatsink!) at over 2A current, to see if a true low-noise USB supply gets rid of the noise?

[Kean]

I don't think you mentioned the type of monitor, or how it connects (USB C, DP, HDMI, ...).

As Nominal mentions, the de-syncing issue sounds like ground bounce on the video cable.  If it isn't ground loop or a bad power supply, then it is likely coupling via the cables running parallel to each other.  See if you can re-route the cables so they are spaced further apart.  I'd focus on the separating the power cables from the video, to eliminate the de-sync.  Then see how the audio hum improves as a secondary thing.

[rteodor]

Some relevant background to this, so please do bear with. Note that this soundbar contains an internal battery, which may be relevant to the issue.
In November 2022, I bought a Creative Stage Air V2 soundbar to go under my central PC monitor. Space is an issue, this product seemed ideal. When I switch on the soundbar at the mains, one of my monitors briefly desyncs, the screen goes blank and it takes a few seconds to reappear, the same behaviour as when you change PC resolution.

NB: I did not read the whole thread this time so its possible I'm repeating things already said.

This sounds a lot like video reset due to SMPS AC leakage: when one device has earthing and another does not and one of them is a monitor or TV there is a small spark and video reset. Try measuring AC voltage between GND and EARTH for each individual device (disconnected from each other).

[wraper]

In November 2022, I bought a Creative Stage Air V2 soundbar to go under my central PC monitor. Space is an issue, this product seemed ideal. When I switch on the soundbar at the mains, one of my monitors briefly desyncs, the screen goes blank and it takes a few seconds to reappear, the same behaviour as when you change PC resolution

Sounds like shitty substandard HDMI/DisplayPort cable with poor/no shield connection. As the other issue was a single occasion, likely it was just a coincidence with bad contact in video connector.