Noise caused by DAW PC

[C-Level]

hello,

I am looking for help with electrical noise, hissing, buzzing in my studio monitors. I am using a DAW pc with Audio interface connected to amplifier (samson) and monitors (Alesis)

Through a process of elimination, I believe it is the DAW pc causing the noise because If I connect the audio interface to a different computer, I am not getting the noise.

Headphones audio is fine its just the monitors.

The buzzing gets worse when I start up the DAW, (Live 11) But it is distinctly there as soon as the interface is connected to any USB port on the DAW pc, before Live is started.

Its a new win10, i9 pc. Audio interface is focusrite 8i6.

The amplifier and speakers are fine when an instrument is connected directly to them.

I've had the electrical sockets checked by an electrician, all good there.

I have installed the latest motherboard audio driver, which the pc supplier advised me to do, but no difference.

So it seems to be the pc. I am wondering if a loose connection inside, eg on the motherboard might be the cause.

Looking for any thoughts on this before I get back on to the pc supplier. Are there any other tests or changes I can try in settings to try and zone in on the cause of the issue?

Any help greatly appreciated, thanks

[James Perrett]

You are probably suffering from a ground loop. This is a common problem with computers but it isn't really a fault with any one piece of gear - it is a fault with the system as a whole.

The first things to try are to make sure that all your gear is plugged into a decent power strip going to a single power socket. The next thing to check is that you are using balanced audio connections throughout. This means using the TRS jack connections on the Samson amplifier (I'm assuming it is something like the Servo 170) with TRS to TRS cables between the Focusrite interface and the amplifier.

If the problem exists with balanced cables then you could also try cutting the cable screens at one end of the cables. If this doesn't work then you need an amplifier with a better designed input - one way of achieving this is to use a transformer box between the Focusrite and the Samson like the ART DTI.

[C-Level]

Thanks James, just wondering why would it be happening with DAW pc and not a different pc (laptop, plugged in. Zero buzzing when connected to the laptop. The focusrite software is installed on the laptop)

Also, I forgot to mention it actually is worse when all 3 (pc, interface, amp) are plugged in to the same circuit, When the amp and pc are on a different electrical circuit, the noise isn't quite as bad

I dont know if the cables are balanced on not.

I got them from thomann and the description doesnt say:

https://www.thomann.de/ie/the_sssnake_sk3613_kabel.htm

the sssnake IPP1030, length 3m mono jack-jack cable 1/4" jack - 1/4" jack, 0.22 mm² / AWG 24, overall diameter 6,0 mm, cable length 3m, colour black

When I use these cables to connect a keyboard (Juno 106) directly into the amp the sound is perfect.

I had a previous setup (win xp pc, motu 828mkii) going into the same amp and didnt have any noise problems. Same room, same sockets.

any further thoughts based on that?

I will try different audio interface and speakers which I can borrow from a friend but its very puzzling that it only happens on the daw tower and not a different pc

[C-Level]

also the sound is a bit tinny, lacking bass from daw pc to monitors.

Sounds great on earphones

[James Perrett]

I dont know if the cables are balanced on not.

I got them from thomann and the description doesnt say:

https://www.thomann.de/ie/the_sssnake_sk3613_kabel.htm

They are unbalanced so it isn't surprising that you are having problems. You need something like these

https://www.thomann.de/ie/cordial_em_3_vv_elements.htm

which appear to be intended for balanced connections.

Ground loops can be very unpredictable so it isn't surprising that just changing the computer can give very different results.

[Drew Stephenson]

Especially since your laptop probably doesn't have a ground to complete the loop.

[C-Level]

Thanks folks for your advice here. I will try the balanced cables and hopefully that will fix it. I will let ye know outcome

[C-Level]

would you recommend balanced cables for all connections - ie not just the audio interface out to amp but the inputs to the interface for keyboards, vocoder (vt4) etc?

[Wonks]

If the keyboards, interfaces and amps have balanced TRS outputs and inputs, then yes. But few keyboards have balanced 1/4" TRS outputs. Most are unbalanced TS, so there's no benefit in using a TRS to TRS cable in that instance, though it normally won't cause any problems and should work as a TS cable.

If both ends are balanced, then do use balanced cables (TRS to TRS, TRS to XLR or XLR to XLR).

[ajay_m]

I've posted on this before but worth repeating. The mysterious "ground loop" usually occurs when the external audio interface draws power in short duration spikes or alternatively this is the case on the pc side. In this scenario the power rail on one side induces a transient current flow on the earth side of the audio signal path between the pc and the interface.
Because the audio interface sees signal as a difference between its ground and the active input side, a ground induced ripple voltage is then amplified and appears as noise.
This can often be confirmed by connecting a stout piece of speaker wire between ground points on pc and interface (the shell on a jack socket will suffice if no other ground point is available. If the noise reduces this confirms the issue.
Balanced io may help but sometimes not because the transients have very fast rise times and the slew rate and common mode rejection ratio of the input audio stage may not handle these signals well.
In this scenario an audio isolating transformer or a usb isolator can help. I've written more about these in another post so if you search for that you'll find more info.

[C-Level]

https://www.gear4music.ie/G4M/Stereo-Ja ... DA3*_up*MQ..

Would this be a decent choice? I can get this quicker than the thomann one

[Drew Stephenson]

They're ok cable, I've got a couple of them. And they're easy to repair if necessary in the future.

[C-Level]

thanks

[C-Level]

I've posted on this before but worth repeating. The mysterious "ground loop" usually occurs when the external audio interface draws power in short duration spikes or alternatively this is the case on the pc side. In this scenario the power rail on one side induces a transient current flow on the earth side of the audio signal path between the pc and the interface.
Because the audio interface sees signal as a difference between its ground and the active input side, a ground induced ripple voltage is then amplified and appears as noise.
This can often be confirmed by connecting a stout piece of speaker wire between ground points on pc and interface (the shell on a jack socket will suffice if no other ground point is available. If the noise reduces this confirms the issue.
Balanced io may help but sometimes not because the transients have very fast rise times and the slew rate and common mode rejection ratio of the input audio stage may not handle these signals well.
In this scenario an audio isolating transformer or a usb isolator can help. I've written more about these in another post so if you search for that you'll find more info.

Hey, sorry I think I posted at the same time and didnt see this. Thanks for this.

I had a look over some of your previous posts and I still have a couple of q's if you dont mind

so to verify if the cause is as you suspect - I connect a piece of speaker wire (or just plain, thick copper wire?) between audio interface and pc. Other than a rim of jack socket, what is a good ground point on interface? whats a good ground point on the pc? Its a tower pc, metal and perspex case,

as far as the suspected cause itself - "when the external audio interface draws power in short duration spikes or alternatively this is the case on the pc side."
- is this a fault, why would this happen? Is it something on cheaper audio interfaces? My previous interface (Motu 828mk2 firewire) was very quiet. I only replaced it with the 8i6 because firewire seems to be going obsolete. The new pc doesnt have firewire connection anyway. Could the pc itself have a fault in the power supply?

I will certainly try the balanced cables anyway and hopefully that will help.

sounds like the Art DTI as suggested by James is the next step if I am still having the problem

Its all very depressing seeing as I just invested heavily in this new setup

[C-Level]

The balanced cables seems to have virtually eliminated the problem.

Sor some reason one or 2 live sets seem to cause a small amount of buzzing but its mostly silent.

I will probably get a DTI box anyway just to completely resolve it.

Many thanks again for the advice given here

[Drew Stephenson]

Thanks for coming back and closing the loop.

[C-Level]

Thanks for coming back and closing the loop.