Those dreaded hums.
“I have a modest setup at home with a few pieces of recording equipment and processing in one room with some performance gear in another. My system always hums. I can utilize AC ground lift adapters to get rid of a lot of it, but in reading some of your old tips you say this is unsafe, which I don’t doubt. Since my problem seems related to the electrical grounds as opposed to audio wiring is there anything SIMPLE (read cheap) I can do to make it better? I’m not looking for perfection, and I don’t have time to rewire the whole mess.”
Hmm… That sort of sounds like the guy who goes to the doctor with a pain in his side. When the doctor tells him he has to eat salads every day the guy says he hates salads and prefers hamburgers. Your body and your doctor aren’t going to negotiate with you about care. You simply do what you must do or face the consequences.
In this case, however, there are a couple of simple things you can try that are likely to improve your results. First, know that it is not necessarily true that ground loop problems are either power or audio wiring related. Quite often both can be okay, and it is simply the combination of the two that gets us, or the gear itself can be causing the problem. It’s analogous to flying in an airliner. You have no sensation that you are 30,000 feet in the air traveling at 600 M.P.H., or even at 50 feet traveling at 200 M.P.H. just prior to landing. When you come into contact with anything that isn’t traveling with the same speed and direction (i.e. the ground, no pun intended) the system is stressed and energy is transferred. Tie yourself to two horses facing the opposite direction and the problem becomes clear. Neither horse is right or wrong. When you connect the grounded bass amp in the other room to a DI that connects it to the board you have just created a ground loop, the severity of which depends on all the gear connected at both ends of the chain and the electrical wiring of the house.
In these circumstances we normally recommend lifting audio cable grounds because it is safer. Of course this is difficult when a lot of your equipment uses unbalanced connections (the ground wire is one of the audio conductors). In some systems it simply isn’t practical to change the audio wiring so you pretty much have to look at the electrical wiring, but you do NOT need to lift AC grounds. You simply need to get everything connected to a common ground. You can do this by distributing all power to everything from one electrical outlet.
Connect two power strips to a standard wall outlet, and to those power strips, connect other power strips in the most symmetrical way possible until you have enough holes to plug in all your gear. You can also use a two-to-six outlet adapter that screws into a standard wall outlet; all strips then plug into that. The emphasis here is to use a single outlet. And EVERYTHING in the system must be connected to it. Once piece plugged in somewhere else will corrupt the whole thing.
Power up slowly so as not to overload the circuit breaker. You don’t want to exceed 75% of the rating of the breaker (that’s 11.25 amps on a standard 15 amp breaker). Unless you have a way to monitor this about all you can do is get everything turned on and test it. The breaker will certainly do its job if it needs to. In a small system it is highly unlikely the overall load would exceed 10 amps so you should be fine. Your system should now be significantly quieter. You may be able to improve it further by finding all the wall warts and make sure none of the audio cables go near them. Then you can start to isolate problem pieces of equipment. Take certain pieces out of the system and see if there is an improvement. Finding the problem gear is not always easy, but the clue is to look for plastic-insulated jacks and products with unbalanced inputs. If you find one or two consider hooking them up to everything else through isolation transformers (we sell a good one called the Hum Eliminator).
This is a sort of stopgap solution. You can and should ultimately take a close look at all of the audio wiring. A lot of the noise is often a combination of using unbalanced sources and cabling (MIDI modules or effects) to a mixer that hums with so many cables connected. Taking advantage of balanced inputs and cabling can help tremendously, even with unbalanced sources. We’ve explained a couple of ways to do this in past tips. Perhaps we can dig in further in the future.
An audio pro I know once said, “The downside to affordable technology is that it makes a professional installation seem rather expensive.”