Home Recording - Guitar Hum

Hi guys

This is basically my setup:

Nocaster
TC Electronic Impact Twin
17" MacBook Pro
Logic Pro 9

I want to record direct but I get this incessant hum from the earth loop in the room.

I've tried:

- moving as far away from the laptop as possible
- switching all electronic equipment in the room off that don't need to be used
- switching lights off
- moving the audio interface away from the laptop

but I still get this awful noise! I also get it when I just plug into my AC30 too.

Any other ideas on how to get rid of it?

I have four double sockets in the room, I heard from a qualified electrician that it's possible to remove one of the earth wires from one of the sockets which would break the loop that's causing the noise...he assured me it would still be safe...would you guys agree? (I'm in the UK btw)

Thanks

Si

Is the Macbook running on battery?

Do you hear the hum in the interface headphone jack, even if disconnected from the Macbook?

Tried different cables, different guitars?

Hi guys

I also get it when I just plug into my AC30 too.



So if you plug the guitar straight into the amp you get the hum?

I relate to your problem as I had to try different AC sockets to get the hum on my amp (1978 Randall Commander II) to go away.

The fact that we try different AC sockets in a given room does not always mean they are on different circuits within the home wiring.
Along with what Martin R states being too close to the DAW monitor can also be a factor.

I'm damn little help here but these are typical problems that can occur so I hope you can get it figured out/solved.

Carry on.....

I usually have my MBP plugged in when I'm working.

I've not tried unplugging the AI from the MBP and listening for the hum using headphones, I'll try that.

I've tried different guitars and leads but it doesn't go away.

I get mains hum through the AC30 which is also annoying.

It really is a headache!!

Is there a flourescent light in the room?
Try putting everything in your chain that uses electricity on the same extension socket into a common AC wall connector.

Past that it would be some individual component which has a grounding issue.

Don't know that this is any help but most DI's have a "ground lift" switch. A cheap one of these may ease the problem if you go direct.

Try putting everything in your chain that uses electricity on the same extension socket into a common AC wall connector.


This would be my next step.

I should have mentioned this in my first response.

As inconsequential as it may seem...have you tried an extension cord from the AC30 into another room altogether just as another test related to my thought of different 'circuits' within the home?

I presume it's nothing in the wiring of your axe that is the culprit.

Good luck on your quest to defeat the hum monster.

Maybe you've tried this, but you didn't mention it. Actually it's one of the oldest tricks in the book.

I have a very noisy computer room, but I can get my guitar to record with practically zero hum simply by rotating sideways until I find the quiet spot, in other words changing the plane of the guitar in relation to the hum inducing culprit, whatever it is exactly. It makes it a little awkward to reach around and hit the keyboard, but that's a small price to pay.

As inconsequential as it may seem...have you tried an extension cord from the AC30 into another room altogether just as another test related to my thought of different 'circuits' within the home?

Definitely check this! I had a ground loop hum problem caused by the power points in my teaching room not being earthed. It took me weeks to find out that this was causing the problem. As above, took an extension from a different room in the house and the hum went!

You've just got to be logical when trying to work these things out - is it a piece of gear, is it a cable, is it the way things are hooked up, is it the power supply etc...

Good luck!

Rob

Hi guys

Huge thanks for the input!

I've tried moving around the room to find a "quiet" spot but not found one yet ;-(

I'll try the extension idea...

So if I connect directly to the audio interface, no amp, I'd need to plug in the MBP, audio interface and speakers all into an extension and then experiment with a single power source...is that the general idea??

I might upload a video so you guys can hear/see what's going on.

It's just trying to rule out all the possibilities really. At the end of the day, it's either a software or a hardware problem - hardware includes the wiring in your house!

I'd check it like this:

1) Just with the laptop, record internally from iTunes or other media payer, directly into Logic. Is there any hum? No? Then it's not a problem with Logic.

2) Connect the TC Impact Twin and plug your guitar directly in. Is there a hum? if so try:
- changing the guitar lead
- a different guitar
- a mic or another instrument, e.g. keyboard
- different inputs on the TC box
- different outputs

If it's humming after that, then depending on the type of hum, it could be a software or a hardware problem at this stage. To rule out any hardware connection/motherboard problems on the laptop, try plugging the TC Impact Twin in to another computer.

4) You've probably already checked this, but is the TC Impact Twin supported by the operating system you use?

5) Is Logic correctly set up with the TC Impact Twin?

6) If you're connecting via USB or firewire, try different ports. I don't know how it works on a Mac, but on a PC motherboard, different ports can be on a different Interrupt Request (IRQ). The higher up the IRQ list the audio hardware is, then the more "important" it becomes to the CPU. This can reduce glitches in recorded audio, and certain other types of distortion/unwanted sounds.

6) Try several other power points (or go to a mates house) and do the above again.

If there's still a hum, then you can rule out the power supply.

7) One other thing that I think someone mentioned earlier. In some studio gear (DI boxes for example) you get a "ground lift" switch which helps to eliminate any problems.

Can't think of anything else right now, but approaching these problems logically is the best way. Try to rule out what it isn't, then you should find out what is causing the problem!

To really isolate the guitar/cable part: use a *bus-powered* interface, and run your macbook on battery. If you hear it in the interface headphone jack, it's almost certainly your guitar or cable, or a combination of those, along with really a bad EMF source.

Good News!!!! I unplugged all my gear and used one extension lead into a single power socket and eureka!!! The noise monster is defeated!!!

I let you know when the follow up to the White Album comes out ;-)

Thanks to everyone who chipped in!!

Yeah I have the same issue at my house. I can't use both wall sockets because they are grounded different and it creates a hum. I have to send everything to the same socket. Glad it worked out.

That's great but I just use a gate if I get hum on a track.