Noise on one speaker from X32 Compact to pc USB connection?!

[johnr10]

Hi all,

When my X32 Compact is connected to my PC (a hackintosh) using the USB cable to the 32/32 sound card, I get some noise in the left speaker.

I've tried various things including but maybe not limited to:

Checking the ground on the cables using a multimeter
Reversing all the plugs (it's in Spain so plugs can go in either way).
Changing plugs
Changing XLR/Jack (balanced) cables
Changing USB cables
Putting PC/Speakers/X32 into same strip
Putting them into different strips

The noise never comes out of the other speaker, no matter what combination of cables I change.

I can only make it stop by unplugging the usb cable from the x32 to the computer.

Any ideas please?

Thanks
John

ps. speakers are HS5's

[Funkyflash5]

Have you tried sending the left output from the x32 to the right speaker and vice versa? would tell us if the noise is tied to the left channel at the mixer or the left speaker itself.

[johnr10]

Yes, well, I swapped the cable from left to right, and right to left, and same problem with left speaker. and I also left the same cables in but changed them from l to r and r to l on the mixer, and same problem.

[Funkyflash5]

That sounds to me like the problem is with the left speaker itself. Perhaps try the TRS input if you've been using xlr, or vice versa.

[Drew Stephenson]

Yep, that would be my assumption. Do you have a completely independent source you could connect to the speaker to check it directly and bypass everything else?

[johnr10]

Thanks. I'll give that a try in a bit and report back.

My previous AI was a Rubix 24 (which I still have) and that has a ground lift switch on it. Something like that to disconnect the ground from x32 to the pc (via the usb cable) would be good.

But yes maybe it's the speaker itself. Fairly new though (maybe 2 years?) and not left the room they were put in since I bought them so now damage etc.

[Sam Spoons]

Two things, first, if unplugging the USB between the computer and X32 makes the noise go away that suggests an earth loop issue of some kind. Second, could the building's mains earthing be dodgy?

What is the nature of the noise, buzz/hum, digital 'hash' or what (can you pose a recording)?

[johnr10]

Here's a recording

To confuse things, I've swapped the speakers around physically, so it's now the 'right' speaker making the noise.

This is the left speaker - https://workdrive.zohopublic.eu/file/4j ... 3fa45b0f41

The is the right speaker - https://workdrive.zohopublic.eu/file/4j ... 0525736b14

This was recorded via the Rubix 24 using a condenser mic on full gain placed right at the speakers. In the 'right' recording near the end, I unplug the USB to the X32. It briefly goes quiet but then cuts off as logic decided the change of USB on output was worthy of stopping the recording But never mind, it basically goes to the same as the one on the left. ie, some general noise. Just to be clear, the output on the X32 was turned off - I wasn't outputting the input of the mic

The general noise on the 'good speaker' (left here) is hardly affected by the level pot on the speaker - I have them set to the middle which is +4db - turning them down to min makes no difference, turning them up to +10db makes a small difference.

The bad noise on the 'right' speaker is not affected by the level pot at all (but the same background hiss that you can hear on the 'good' speaker is affected the same way on the 'right' one by the pot).

I have swapped cables. I have tried TRS to TRS instead of TRS to XLR. But no change. Basically whenever the speaker is connected to the X32, it has this noise.

It also has it when connected to the Roland Rubix 24 (powered by USB - not tested it powered by 5v input). But the 24 has a ground lift, and turning that on makes the speaker go as quiet as the other one. So it's a ground issue, but only affecting the one speaker.

Maybe I need to open it up and check inside?

[Hugh Robjohns]

Are the speakers plugged into different mains sockets?

[johnr10]

Are the speakers plugged into different mains sockets?

no, the desk, both speakers and the pc are on an extension from one socket.

[johnr10]

I just double checked the earth on the pc and that is fine (carefully unscrewed the IEC socket, plugged in the power and use a multimeter).

[Hugh Robjohns]

In that case it's very odd that one speaker is picking up ground noise and not the other one.

I'm a bit confused with all your swapping, but if your tests confirm the 'ground noise' always stays with one particular speaker regardless of the mixer output, different cables etc... then you have a faulty speaker.

The fact that you can remove the audible noise by disconnecting something else just proves that the speaker is allowing ground noise to get into the audio circuitry when it shouldn't be.

[johnr10]

In that case it's very odd that one speaker is picking up ground noise and not the other one.

I'm a bit confused with all your swapping, but if your tests confirm the 'ground noise' always stays with one particular speaker regardless of the mixer output, different cables etc... then you have a faulty speaker.

The fact that you can remove the audible noise by disconnecting something else just proves that the speaker is allowing ground noise to get into the audio circuitry when it shouldn't be.

Yep. Sorry for the confusion over swapping over. But the bottom line is it is always the same speaker that makes the noise, regardless of cables, position, left/right from mixer etc.

I've just tested the ground on the noisy speaker itself, and that is fine.

Unplugged everything else (monitor, all other usb etc).

Tried it both with a usb hub and directly into the pc (with everything else unplugged).

Also unplugged the X32 itself. The noise is still there as long as the usb is connected to the X32 <--> pc, and the speaker is connected to the X32.

What I did notice though, is it doesn't happen when the PC is rebooting - even up to the stage of logging in to osX. It's only after typing the password and it starts loading apps etc, that it happens. Maybe I need to check on a hackintosh forum? Perhaps it's something to do with the way the USB is setup (it is a ballache on hackintosh's)

Anyone know the HS5 well enough (or know where the schematics are?) to see what could cause this on both the XLR and TSR inputs? I presume the ground must be connected on them. There's no 'good' reason the speaker should be faulty (ie, never damaged it etc). Unless it has been since day one and I've never noticed before - the ground lift on the Rubix 24 did the trick, it's the upgrade to the X32 that has made it noticeable.

[johnr10]

Found the service manual, will take a look.

[Hugh Robjohns]

...the bottom line is it is always the same speaker that makes the noise

Then, as I said, you have a faulty speaker. Something is allowing noise in the cable screen
and/or mains ground to get into the audio path.

That could be something as simple as an internal grounding screw on a circuit board having worked loose, so the circuitry is not getting grounded correctly, or it could be a construction error, or a circuit fault.

Do the two speakers have similar serial numbers? It's possible that the internal wiring or circuitry was modified to cure a ground noise problem early in the production run, and one speaker is from before the update and one after?

What I did notice though, is it doesn't happen when the PC is rebooting - even up to the stage of logging in to osX....

All this is doing is identifying where the ground noise is coming from... and that's the computer... which is not really a surprise.

But the problem isn't about where the noise is coming from -- there's always going to be noise on the grounds from one source or another.

The problem is that it's getting into the speaker's audio circuitry when it shouldn't be.

The whole point of balanced audio is that it doesn't require a ground reference, and so should be immune to ground noise... yet one of your speakers is managing to allow ground noise into the audio circuitry when it shouldn't. And as the other speaker doesn't suffer the same problem the noisy speaker is clearly defective. End of story!

Unless it has been since day one and I've never noticed before

Quite probably!

If you don't want to get the speaker fixed, and you're sure the previous ground lift circumvented the problem (which is quite possible), then the simple and obvious solution would be to reintroduce ground lifts... and the tidiest way to do that is by modifying the balanced cables feeding the speakers.

Simply open up the male XLR plugs at the speaker ends of the cables and cut out (and insulate) the cable screen connection going to pin 1. Reassemble and enjoy the ground-lifted audio!

It would also be sensible to mark the cables as being modified, because if they later get put into your general collection and used for a mic you'll be wondering your capacitor mics don't work but dynamic mics do, and blaming the interface for that too...!

[johnr10]

Serial numbers are 4 apart

I'll take a look myself at the internals (I'm FAR from an expert but I've resorted vintage equipment before so ok to check for something simple like loose grounding). But if that isn't it, I'll probably go down the route of just hacking the cable.

I'll report back. Thanks!

[johnr10]

Ok, I had to solve it by cutting the ground on the cable (marked with a warning!)

I opened the speaker up, checked the ground in every place I could think of checking, all fine. Then opened the other working speaker, and did the same. Can't see or test any obvious differences but obviously there is something wrong with the faulty one.

I even tried swapping the boards (all one piece) with each other in case it was 1) something to do with the drivers themselves, or 2) loose cabling, but the problem followed the boards, not the drivers.

I'll see about getting it fixed at some point in the future when I don't need them but for now this will have to do.

Still a bit disturbed by how much floor noise both of them have though regardless of the fudged-fix on the ground loop problem. Maybe I'm being fussy though

Thanks for the help and advice all.