I just asked this on strat-talk as well... help Hi guys, I'm new here. signed up to ask this question...searched "grounding" and not much came back up. ----------- The problem: This regards two separate guitars. One is a partscaster i put together. This was my first project, and naturally with a weak soldering job. The more recent project is a P bass i put together, this time with better soldering job! (with the help of alligator clips, clean solder tip, flux. etc.) A typical grounding issue i think, when i touch the metal components of the guitar, pot shafts, the bridge, the strings, etc. , the hum from the amp goes away. This happens for both of the guitars that I wired. I didn't have this problem with my other bass (wired by the pros in the wonderful nation of Korea), which has an onboard preamp & eq, which i mighta read somewhere those have a different mechanism for dealing with ground noise. Also, it doesn't occur with my acoustic that has onboard electrics.. it has the under-the-bridge pickup/mic blend type of things... When I leave the amp on, without any guitars plugged in, there is similar hum, but not as loud. Perhaps this is normal...some hum is expected in a turned-on amp that doesn't have a guitar plugged in. (right??? but in this wonderful youtube bit, the wise man says otherwise...from what i'm understanding from his video is that you shouldn't really get much hum even without a guitar. Noise Reduction Pt. 2 - YouTube) Some background info: i don't think it's simply a single pickup hum issue...positions 2 and 4 are indeed quieter, but in any positions, when i touch the strings, the hum goes away. I am not sure if my apt is well grounded! i looked for a ground checker at the local store, but they didn't have em. so I am not sure if it's the apartment problem or a guitar-internal problem. But i did try different wall jacks in my apt, and they all lead to the same results. Another interesting thing related to wall jacks; the hum gets worse when i plug in my laptop, through an extension cord, simultaneously with the amp on the same wall jack. The laptop plug does not have a ground lug. But perhaps this is a separate issue that just adds on top of the hum in question. On my P bass, I checked each ends of the cold wires within the wiring with a pretty good multimeter. I used the continuity mode of the multimeter to check the connections of each cold wire. They seem ok. But perhaps I should measure the resistence of each segments? I would think the continuity mode would be enough... Could cheap wire be a problem? I used the ones from Home Depot, 22 gauge, (or maybe 20) insulated but not shieded. Lastly, i'm pretty sure it's not an error in the wiring scheme...followed the diagrams to the word. Wiring guitars is pretty fun. the first project was sorta crazy, but the second one i enjoyed. i found the soldering relaxing haha. And as a poor college student, it sure beats actually having to buy the real thing! Anyhow, thanks for reading, and any input will be appreciated.