Saturday, January 30, 2010

Check My Math

I saw this years ago at Guitar Center. A dingus that sits between your gear and your power to take away noise. In the store, they had it on a thing with a neon sign, showing that the noise that the neon sign generated would not come through your gear.

I am sure this is it. The Hum X from Ebtech, which seems to be a part of Morley.
The Hum Xtm filters out unwanted voltage on the ground line that can cause ground loop hum.
Elsewhere, it says "Not A Ground Lift", but it seems to serve that function, but in a safe way.

Here's the thing. The place where I'm most likely to put it, it's on a power strip where I plug power adapters to a device that takes DC power, my ToneWorks AX1500G multi-effects unit, and if that has no ground plug, like most DC power supplies, then how can it experience ground problems? Will this thing even help me?

1 comment:

patrick said...

Time for EMI/RFI 101:
All EMI/RFI problems (such as your 60-cycle hum) have three components.
1. A Source.
2. A Path.
3. A Victim.
If you don't understand all three components of the problem, then the best you can do is randomly throw solutions at the problem until you fix it.
You've told me about your problem, but I don't know enough about your specifics to characterize 1, 2 and 3. The Source is originally 60 Hz mains power, but that isn't really specific enough to help. There is something specific involved with the system that is putting that 60 Hz signal onto the Path. The Path might be through air, it might be through wires. It might be through your body. Most likely it is some combination of the three. The Victim is ultimately your amplifier (and your audience), although it's probably safe to assume that the cable going into the amplifier and the amp itself are just doing their jobs and amplifying what is sent into it. It's probably more helpful to characterize the Victim as the first place where the interfering signal enters the otherwise inviolate system.
Once you've identified 1, 2, and 3, you have three suggested approaches for dealing with the problem.
A. Reduce or remove the Source.
B. Reduce the effectiveness of the Path, or remove it entirely.
C. Reduce or remove the susceptibility of the Victim.
Ground loop is a very particular case of EMI, in which the Path goes between two different grounds, which also suddenly becomes the Source. If you were actually experiencing ground loop this thingy might help. I don't think ground loop is your problem, and even if it were, the thingy would have to be plugged in at the soundboard end, not into your gear.
Identify 1, 2, and 3. Verify by experiment. Figure out which of these you can most easily address, and address it. If that doesn't solve (or at least improve, remember Amdahl's law) the problem, you did not correctly identify one or more of 1, 2, and 3, or your solution did not properly address 1, 2, or 3.