It could cause problems ... but it may not.

Here's your potential problems:

1) Power surge, lightening strike, static electricity, voltage buildup and overcurrent damaging your gear (or you) because there's no way to de-energize the access or faulty circuit.

2) You reduce the ability to use the ground or lift the ground on your gear in order to reduce 60-cycle (60Hz) noise/hum ... or noise from other electrical devices in the home (e.g. fluorescent lighting, air conditioner, etc.).

There are other safety reasons to have grounded AC outlets, especially in a garage, but I'll leave it at that.

Personally, I would spend the money to ground your garage.

If the AC outlets don't physically have a ground, flip the breaker, remove the outlet from the gang box and look to see if the wiring has a ground wire there. If so, just replace outlets with ground AC outlets ... assuming the ground wiring actually runs to your breaker box and the ground wire is in fact grounded.

I installed my own grounding rod for my studio back in Dallas. It's easy to do, but you may need to hire a master electrician for safety reasons and/or city regulations. I have a strong background in electronics (long story) and have worked with many master electricians in my younger years (another long story), so I feel comfortable doing my own wiring and working with the breaker box.

I wouldn't risk it personally ... I'd have a ground put in. If it's an old house, you'll want the ground there at some point just to be able to sell at some point.

If you can, put some GFCI outlets in and make sure the breakers you do have for the garage will handle the amps you will be pulling. Since your garage isn't grounded, the breakers may not be rated very high ... like you would think.

Replacing the ungrounded wire from your garage to the Circuit breaker box isn't rocket science and should not cost too much (although copper has doubled over the last couple years, thank you China!). You really should have a SAFETY grounded source for garage work anyways.

You CAN run a heavy duty extension cable from a grounded outlet elsewhere. In USA terms, use a 12AWG cable. Having all the audio gear sharing the same ground, through a surge suppressor or a splitter box on the extension cord, will get rid of any differences in ground potential that cause MOST AC noise problems. For surge suppressors to work, they have to be able to discharge voltage through the safety ground.

Ground Fault Interupters (GFIs) are often enough incompatible with many surge suppressors. There are SOME GFIs available that will work with 2 wire ungrounded AC systems.

In the USA, just adding a ground rod is NOT enough. And there are specs for where and how long the ground rod must be. The grounding rod is for LIGHTENING protection of the building curuits.

Boomerweps

Except that without a ground, some equipment will pick up and enhance 60Hz and other extraneous frequencies. Without a ground you have no choice to use or lift the ground on audio equipment (i.e. amps, direct boxes, etc.). Not having a ground as a choice can be a real pain. Having a ground can be a pain as well, which is why lifting it is sometimes necessary. Personally I'd rather have it there so I can choose. With no ground present, you have no choice or options available.

If a re-wire is out of the question, I would be inclined to run a one or more extremely heavy duty extension cables from grounded sockets in the house...

Obviously being careful of rating so you don’t over load socket or extension.

Just a thought..

 

N

I guess I should have phrased that better!  The GFCI detects the difference as you noted however the NEC requires it to be installed with a ground.  There were many updates concerning GFCIs in the 2005 and 2008 and lots of fine print notes specifically for GFCIs. 

I will agree that installing a GFCI without a ground is better in some cases is than not but consider the case of a guitar amp and a PA using the outlet with a GFCI installed without a ground.  If one piece of equipment has a defect there is a possibility of potentially lethal voltage being present on the case of the equipment (or the guitar strings or mic housing) and if you touch the other piece of equipment the voltage has a path through your body.  The GFCI will still see a balanced load on the hot and neutral and not exceed the 4 - 6 millamps needed to trip the breaker unless your body is grounded somewhere else.  If A ground were present and the same fault developed the internal equipment grounding would give this fault current  a path that would trip the breaker immediately and not pose a hazard. 

Go to home Depot or Lowes and buy an outlet tester.  It cost a couple of bucks and has three LEDs.  plug it in an outlet and use the markings on the side to see if the outlet is wired correctly and is grounded. 

Great advice, I am an Electrical Engineer and that would be the professional recommendation. Also, if you find an oulet problem, ungrounded, floating ground or neutral, hot and neutral wires reversed, consider calling a qualified electrician.

Thanks.  I have such a device from my youth, and it only has two LED's.  I didn't realize the newer ones test for ground as well. (Am I dating myself?)