Anti-hum Pickups

[GregP]

OK,

My apartment is so littered with electromagnetic interference that even humbuckers aren't doing the job. I've turned off all CRT monitors and fluorescent lights. In fact, I went so far as to turn off ALL electronics except for my computer, LCD monitor, and mixer.

But there's still a bunch of hum.

I've considered the possibility that it's just shoddy mains, but I don't imagine there's much I can do about it, unless I want to try a 'voltage purifier', but if I can't borrow one, that's not going to happen. Don't want to drop coin on something that's not going to fix the problem!

It's also worth mentioning that my phone has a crazy hum on it, too. All inter-connected, I'm imagining.

Now, the question is--

Since plain old humbuckers aren't doing it, are there other pickups I can use that don't pick up, amplify, or re-transmit any electromagnetic interference bouncing around in my apartment here? Are EMGs or Lace Sensors good options? How about Bartolinis?

I'll confess, I don't have the money to run out and buy them right now, but at least I'll be able to spot a bargain if I stumble across one in the meantime.

Thanks!

Greg

[JohnH]

Just a couple of shots in the dark - from some recent experience of hum that Ive had, short of replacing pickups:

With the amp turned on, and no lead plugged in, do you get too much hum? I had this recently on a new amp, and the answer was a bad valve (tube)

With a guitar chord plugged in but no guitar, do you get the hum? My son got a guitar with free chord, which hummed like crazy. We 'recycled' it (it is now used as a piece of string), and replaced it with a budget, but properly designed chord and all is OK.

Shielding the inside of the guitar helps, particularly with the hum that is not removed by using humbuckers, being picked up by the wiring. I managed a neat job with kitchen foil recently (I wanted to see how little I could spend), using spray contact glue to cover the back of the pick guard and a rubber glue to fix it to the cavity.

EDIT - Ive just noticed you are a regular and experienced member - appologies if the above is missing the point!

John

Edited September 23, 2005 by JohnH

[GregP]

Pffft, I'm a regular member, but a complete amateur and numpty! I haven't even built a guitar yet! It's in pieces at my father's house right now and I'm almost never over there anymore. I think post count should be hidden, because my post count (and that of others) is highly misleading.

Regarding your points, though:

1. I'm plugging into the computer, actually. I'm going through a mixer and then into a soundcard, and then into a VIRTUAL amp.

2. When the cable is unplugged or the volume is turned to 0, the hum is gone, so it's not just the cable, unfortunately. I wish it was as easy as replacing a cable.

3. I've shielded my guitar, the same way you did.

But, the biggest and most telling point is this:

Nothing has changed in my setup whatsoever except for the location. When I moved into this apartment (which is recent), that's when the problems appeared. Nothing else is new at all, so I'm confident that it's the apartment. It's a concrete basement apartment in a fairly old building... the concrete doesn't help (from what I've heard), and the age might indicate poor electrical mains. So, I'm still not entirely sure which of those 2 problems it is.

Your help is much appreciated anyhow. If nothing else, it gave me the opportunity to answer questions that other trouble-shooters might have also had.

Greg

[ansil]

if you have a tube amp pull the first tube ie the preamp tube .. does it still hum ..

if not..its not the power section.

[GregP]

No tube. Actually, no amp at all. Just a preamp, which is also not tube.

[lovekraft]

OK, I'm mystified too, but maybe a couple more questions will help. Are there any large electrical appliances nearby (refrigeration, HVAC, lighting control, etc.)? Can you plug something else into the mixer to verify that it is the guitar, perhaps a dynamic mic? Is it hum (60Hz) or buzz (120Hz)? Have you tried another cord? What mixer are you using? What output goes to the soundcard, and what input on the soundcard are you using? How is your guitar wired? I'm just kinda shadow-boxing here, but maybe somebody will have an epiphany here shortly, and get you squared away. I'm sure there's a solution, the question is whether or not we're collectively clever enough to arrive at it.

[GregP]

Ah,

I think it's a buzz, rather than a hum. When I switch to single-coils, I can hear the 60-Hz hum (which is normal) alongside the other sound (which I guess we'll henceforth call 'buzz').

- I'm not near any appliances

- Dyanamic and condenser mics don't exhibit the same problem (or at least not as accutely, because I haven't noticed at all)

- I have tried another cable just to be thorough, but went back to the original because I didn't notice a difference and I actually have more confidence in this cable than any of my others

Now, the pre-amp isn't exactly "pristine". I've tried either an ART TubeMP, or my Behringer UB802 mixer. Neither are "pro" quality. However, I used them for ages at my old place, so even though they're not pristine, I'm familiar with their limitations. Since moving to the new place, the noise levels are a whole new problem. I think my noise floor is at about -30dBu right now. Yuk.

I'm still open to more trouble-shooting, but I'm fairly convinced still that it's either:

a ) my mains

b ) the concrete walls of my apartment are capturing electromagnetic interference and bouncing it all around

Further evidence that it may be option "b":

* My old cell phone got CRAP reception, even though I'm in the middle of the city now and there are nodes all over the place. The new phone seems to be fine, but I never had problems with the old phone until moving here. When I had the old phone, going outside to talk on it cleared up the problem.

* As mentioned, the land line phone is buzzy, too

* I get mediocre (at best) reception for FM radio, even with the antenna installed.

Thanks to everyone for their continued time and assistance.

Greg

[JohnH]

All I can think of further, short of lining your apartment with kitchen foil (hey - theres an idea!, a sort of retro b-movie sci-fi look!), is:

Check your apartment grounding - may need an electrician for this, or:

to really look closely at your cable / guitar screening. I know you have done this, and that it works OK elsewhere, but something is putting more pressure on it than normal, and if you cant solve it at the source of the interference, then screening it out may be the only way.

A screening job that is adequate for most cases, may reveal that it is not 100% when interference is very high

Make sure your cavity screening really is electrically continuous.

The following is a view I have - any electro-folk please correct if disagreed:

I believe screening really needs to be acting as sealed can - rather than a series of seperate pieces, even if they are connected. THe idea is to allow loops around and within the screening to occur, hence induced currents circulate around the screen and are dissipated. Although pieces of screening may not need to be absolutely continuosly connected, they should be at close intervals

Any wires outside of the screen (eg wire to jack), should be screened wire. If you have un-shielded pickup wires outside of the cavity screen, maybe they could be wrapped in foil, and grounded.

With all of that radiation - you might want to think about wearing a hat made of kitchen foil (oh -have I just blown my credibility?- oops!)

John

Edited September 24, 2005 by JohnH

[lovekraft]

Maybe something like this?

Sorry, I know that doesn't help, but I couldn't resist. It sounds like (maybe) it's something that's riding the power ground - maybe an isolation transformer on the AC line would help?

FWIW, I thought our old rehearsal space was the worst possible electrical Twilight Zone on the continent, but it sounds like you've got us beat! Except for the occasional blast of Mexican pirate radio late at night, heroic shielding quieted everything down to a dull roar, but it was definitely an effort! Hope you get it sussed!

[JohnH]

Yes mate - Now THATS what i'm talking about!

[GregP]

That's awesome, LK.

Thanks for the continued assistance--

John,

my guitar is long-overdue to be re-shielded anyhow. When I first did it, it was with kitchen foil and all the 'fold-over' tricks to keep it contiguous. Also, I didn't star ground the electronics.

It gives me the opportunity to re-wire the guitar while I'm at it, though I worry that I'm going to do a shoddy soldering job. Still, nothing ventured nothing gained, and it wouldn't be the FIRST time I've soldered anything. I've done a decent amount of soldering, but not enough that I consider myself truly 'confident' with it.

The 'volume knob as coil tap' was a fine gimmick for a long long time, but I'm tired of it now and I think a 5-way switch will be more reliable in the long run. It'll also give me more confidence that I've got the pickup in 'humbucker' mode.

Regarding the cabling-- there are certainly weak links. My soundcard has unbalanced inputs. I've used a fairly high-quality RCA cable to connect it to the mixer; however, an unbalanced connection will always be more prone to pick up noise than a balanced one. That said, it's not until the guitar is plugged in and turned up that there's noise, so I don't think the other cables are destroying the noise floor too badly.

As for the apartment, I still need to check the ground. An isolation box is certainly an option I've always considered anyhow, but I don't know how much they cost and I'm skint right now. Might be cheaper to line it with kitchen foil.

Back to the guitar for a moment-- assuming everything else gets shielded "seamlessly", isn't the front of the pickup still "open", for all intents and purposes? There are still 12 little polepieces and nothing but a plastic shield (which does nothing for electromagnetic signals) to protect the coils of the pickup from the big bad world... or is that flawed thinking?

Greg

[darren wilson]

My connection is very wonky today... see next post.

[darren wilson]

Being in a basement apartment (is it in a house or an apartment building?) you could be near to the location where the electrical supply comes into the building, so it could be a poorly shielded electrical panel or meter.

If you're getting EM interference on your land-line phone, that would indicate to me that it's not your guitar. You clearly have higher-than-normal EM radiation in your apartment.

Also, do you have any dimmer switches? Those things are also notorious for introducing buzzes and hums into A/V equipment.

You could buy an AC circuit analyzer and see if it gives you any useful answers.

[darren wilson]

Whoops... connection difficulties. (triple post)

[lovekraft]

Greg, don't let the soldering worry you all that much - if the joint is shiny and mechanically sound, it's good. If anything doesn't shine, simply reheat it until the solder flows, and it's fixed. If you can find some 63/37 solder (if lead solder is still available in your area), it's almost perfectly eutectic, and it makes cold joints a lot harder to make, since it changes almost immediately from liquid to solid without that granular plastic stage that causes most cold joints.

[GregP]

Thanks Darren and LK,

Darren-- I definitely suspect that you are correct, which is why I mentioned the land line phones. While my guitar could be re-shielded, etc., anyhow (would make a good afternoon project), I'm not anticipating a drastic reduction in noise from it.

I have no dimmer switches except one that's on a lamp that is turned off. I mean, when it's off it won't be creating any problems, right?

If it turns out to be a poorly shielded electrical panel or meter, there's not much I can do about it myself, is there? How would one double-check for such a thing? (ie. once all other trouble-shooting is done, is there a way to check for sure?) I'm also on a fairly main street which means there are substantial power cables nearby.

I didn't realize those AC checker gadgets were so cheap. I have to hit the Source (formerly known as Radio Shack) tomorrow anyhow, so I'll see if they have one while I'm at it. I was going to borrow dear ol' da's, but I haven't been out there in a while, and last time I was out there I forgot.

LK - cheers, I'm not TOOOoooo worried about it. After all, I did the original coil-tap mod myself once upon a day. I gotta admit, I've half a mind to throw one of the pickups (originally meant for my project) into the neck position while I'm at it. Trouble is that it's a tele-style guitar and the pickup is a humbucker. I'd have to create an appropriately-sized hold in the pickguard. Either way, those are good pointers and they give me renewed confidence. Cheers!

--------------

Now, assuming I try everything within my power, and I'm still unable to get interference-free (or at least, reduced enough to make an impact). I'm likely going to be in this apartment for another 2 years, and I can't go that long with noisy recordings. Are there any special types of pickups that are less prone to such interference? Lace Sensors, perhaps? EMGs? Some configuration of Bartolini?

Greg

[GregP]

HOLY SHNIKIES!!!

I don't know if this has anything to do with my noise, though I suspect it doesn't help:

Finally got my hands on an outlet tester and:

NONE OF THEM ARE GROUNDED!

Worse yet, one of the outlets I use regularly has... you guessed it...

REVERSED polarity!!

Holy heck.

Now, I'm going to get it sorted out, if for no other reason than safety. But since this is a guitar forum, I gotta ask:

Will this be affecting the 'interference' noise levels in my gear and in my apartment in general?

Greg

[lovekraft]

No grounds, and one reversed polarity? It sounds like the wiring was done by the low bidder - you're lucky you just have hum! A consistent ground (and correcting the polarity) should help clear up at least some of your problems. A floating ground potential on the mains is never a good thing! To quote Count Floyd, "EEEW! Pretty scary, eh!!?!"