Hey Hink! AC hum/buzz

[greendoor]

Hink - thanks for your thoughts about my hum problem. I don't want to hijack the other solid state thread, so i've started this one. It might be useful to anyone else struggling with buzzing gear.

My problem is the common buzz from all guitars (whether single coil or humbucking) with all amps, all processors, even into a mixer. It's not the directional EMF problem: I can induce that too, by getting to close to transformers and other AC things. Most of the buzz goes away when I touch the strings. I've been sucking on a wire attached to my strings for the best effect. It's not hum - it's a strong buzz, with odd harmonics. I used Voxengo Span on a sample of the buzz, and the peaks were around 150,250,350,450, etc. So the fundamental 50Hz (i'm in New Zealand) and the first harmonic were not very strong.

Basically, any unbalanced cable buzzes - e.g. mixer, preamp. I think I have come a little closer to solving this.

I discovered that if I wear headphones and touch the input jacks on my mixer, I hear a buzz. I discovered that this happens even when the mixer is switched off! I then went around my house, and found that anything electrically grounded - even my hot water taps - can induce a buzz to.

Something I had noticed when recording guitars is that standing on different mats changed the buzz. My studio is a concrete floor, painted, with moveable carpet and matts.

My electrician had told me that my electrical ground was very good, and he said he couldn't improve it. This guy was recommended by our best hifi shop, and is familiar with putting in ground stakes, which is why I trusted him.

Anyway - I decided to create my own ground spike, I took a length of aluminum angle and hammered it into the ground. I bolted a wire onto this.

I took an extension cord, connected to an turned-off AC socket. I have an AC tester that lights up LED's for incorrect wiring and stuff - everthing is safe and good.

What I found, is that I can connect an 8 ohm speaker to the Neutral and Ground, and I hear a faint buzz. When I connect the speaker between Ground OR Neutral, and my new ground spike - I get a huge buzz. I put my voltmeter on, and measured 1.5 volts AC. There is no measurable voltage between Neutral and AC 'ground' - obviously if it can power a speaker there must be some, but my meter is cheapie.

So what I'm guessing is because of this 1.5 volts AC on my AC Ground or Neutral, my shields on my balanced cables are not functioning as a shield. I'm guessing that the closer my shield is to earth, the more current flows in the cable somehow. Probably some form of capactive coupling, maybe?

So I guess i'll be installing a good ground for my studio. I'm thinking of screwing a length of brass onto a length of PVC pipe and burying this upright. The idea being that I can water this from time to time.

I still have many unanswered questions. Like, why is the buzz from the speaker not a pure fat sinewave? Maybe I have bad AC quality as well as grounding problems. All of this is just with one single component. There are no ground loops (yet) because I've pulled everything apart.

It's probably amazing i've been able to record anything at all. I've had to use balanced gear and digital as much as possible, and tried to avoid unbalanced as much as I can. But i'm a guitar player, and it's devestating not being able to record clean guitar parts.

I blew a lot of money on the 5KVA transformer, hoping it would solve this problem. I'm still not 100% sure why this didn't work - maybe it's impossible to be buzz free with a concrete floor???