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Post by slideguy123 on Jan 12, 2007 10:05:40 GMT -5
I'm hoping to find a solution to a hum problem. I have a one pickup lap steel. Used to have a Bill Lawrence L250XL -- high output, strat-size humbucker. Not the tone I want, so I just put in a single coil blade pickup. The new p'up's tone is awesome, but I now have a very noticeable hum.
I have shielded the pickguard and cavity with heavy duty aluminum foil. Using my multimeter, I checked continuity of the ground wire from the pickup to the cavity to the bridge to the jack -- it's all there. Ground wiring is like this:
Black (ground) wire to back of volume pot. Back of Volume pot to back of tone pot Back of Tone pot to ground lug of jack Ground lug of Jack to brass screw in cavity Brass screw to bridge
I also looked for anything else that might be touching ground, and added a layer of electrical tape around the jack, just to make sure nothing was touching the foil.
Here's the wierd part: the hum doesn't change when I touch the strings. Also, it goes away if I hold the steel like a regular guitar, but otherwise it is always there, always at the same level. Moving around the room doesn't make a difference, changing the position of the amp doesn't make a difference. Only tiltingg the instrument helps.
Of course, it could be my basement causing the problem. But I'm concerned about the next gig -- who knows what I'll run into in the club?
Suggestions are most appreciated.
Thanks, all.
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darkcyde
Apprentice Shielder
Posts: 47
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Post by darkcyde on Jan 12, 2007 16:21:53 GMT -5
I know this is going to sound like a really stupid thing to check. Do you have floro lighting in your basement? If so, when you turn them off, does the hum go away?
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Post by slideguy123 on Jan 12, 2007 17:10:45 GMT -5
Not dumb at all -- it took me a while to look up and see the compact fluorescent bulbs. Didn't make a difference to the hum. Also, I tried various outlets that I know are on diffferent circuits, no change.
Does the fact that the hum doesn't go away when I touch the strings mean anything?
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Post by UnklMickey on Jan 12, 2007 17:37:01 GMT -5
... Not the tone I want, so I just put in a single coil blade pickup. The new p'up's tone is awesome, but I now have a very noticeable hum.... hi Slideguy123, welcome to GuitarNuts2. there may be something you missed, but i suspect you may have a wicked field problem in your house. indeed, you might not have as much hum problems in a club........but then again, some of them may have even worse fields. the fact that the hum doesn't go away when you touch the strings, might mean that the strings have no continuity to the ground of the output jack. (does touching the output jack make a difference?) or it might mean that what ever field that is causing this problem is getting straight to the pickup, and your body is irrelevant. i don't know if i should, but i am leaning toward the latter. especially since you said the orientation of the "axe" (or in this case would it be "anvil"?) has such a profound effect. do you still have the L250XL? you mentioned it was high output. that suggests to me it is overwound so the inductance will be high, and the tone will be dark. but, if it is a 4-wire HB, you could change the series connection to a parallel connection. that would reduce the inductance to 1/4 of what it was. that should make it much brighter. that might be an easy way to get you back to where you were, in terms of hum, and still have a tone that you will be satisfied with. cheers, unk
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Post by ChrisK on Jan 12, 2007 20:09:14 GMT -5
Well, if the only thing that you changed was the pickup from a humbucking one to one that is not (clue),
Welcome to the land of single coil pickups.
Also, if you want to brighten up a pickup, put a cap in series with it (high-pass filter). I'd experiment with 0.002 to 0.047 uF.
You may need to shield the pickup as well.
You don't happen to have embedded mains coil-based slab heating, do you?
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Post by slideguy123 on Jan 12, 2007 21:06:25 GMT -5
THanks for the suggestions guys. The L250 is a 3 wire pickup. I had been using a.022uf cap -- brightness wasn't the issue, it was just harsh. It was kind of sterile when clean, then metallic when overdriven, at least in an all maple lap steel through a Blues Jr. I wanted more character and soul -- more of a vocal quality. I can get that with the new pickup, but I guess everything is a trade-off.
unklmickey, no touching the output jack doesn't do anything to the hum at all. "Anvil" -- I like that. I'm willing to wager it's the basement environment -- I need to try some other locations to see if this keeps up. The good news is, the hum isn't overpowering the music, so I can definitely gig with it. I guess I'm just not sure what is a reasonable amount of hum.
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Post by sumgai on Jan 13, 2007 13:19:54 GMT -5
slideguy, Hi, and to these forums! If touching the output jack's outermost contact (the jack's mounting nut) doesn't make any difference in the hum level, then you should suspect the intrument cable going over to the amp. HTH sumgai
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Post by slideguy123 on Jan 13, 2007 15:39:54 GMT -5
Thanks for the friendly welcome, everyone. I appreciate you pitching in to help with this. I thought it might be useful to show you how I have this wired. Let me know if you have any other suggestions. I'm not finding much info on one pickup, V & T, no switch wiring schematics online. Thanks again.
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Post by gfxbss on Jan 13, 2007 16:04:34 GMT -5
try taking all wires that need to be grounded to one common point like the volume knob, instead of having them looped from vol, to tone, to input, to screw and then finally to the bridge.
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Post by slideguy123 on Jan 13, 2007 16:35:23 GMT -5
Thanks! I'll give it a shot -- I was thinking there might be a ground loop, especially since the back of the pickguard and the cavity are shielded. I'll try the ring connector method.
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Post by slideguy123 on Jan 14, 2007 21:01:54 GMT -5
Ok, here's what I did -- Since the pickguard and cavity are lined with foil, I took off all of the ground wires that went to the back of the pots. Instead, I connected the 3 grounds (black wire from pickup, ground leg of tone cap, tab from volume pot) directly to the ground tab on the jack. I kept the wire from the cavity to the bridge.
It seems to have made a difference -- it's humming a bit less, and at least it changes when I move around. I still don't get any difference when I touch the strings, which seems odd, but that may be the effect of magnetic fileds in the room.
I'll report back when I try playing more later. Thanks, all.
Peter
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Post by gfxbss on Jan 14, 2007 23:29:24 GMT -5
do keep in mind that you are using only one single coil. this means that there is no hum canceling.
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Post by sumgai on Jan 14, 2007 23:36:26 GMT -5
slidey, Big clue, that. Try putting it at the same point as the other grounds, directly on the output jack. Also, check to be sure that the other end is making contact with wherever it is supposed to. It's probably under the baseplate, being held in place by mere pressure.
If you have a multimeter, lay the leads across the strings and the output jack. If you don't get real close to zero ohms, then it's time to go on a Search and Repair mission. ;D
HTH
sumgai
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Post by slideguy123 on Jan 15, 2007 10:51:55 GMT -5
sumgai - just to be clear, are you saying I should run a wire from the bridge directly to the jack, and delete the one from the cavity to the bridge?
Also, when I test the strings to jack resistance, I get 0.2 - 0.3 ohms -- seems pretty low, should it be lower?
Thanks, Peter
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Post by sumgai on Jan 15, 2007 20:21:15 GMT -5
Peter, No, 0.2Ω is plenty low enough! Yet you still get hum, eh? I'm back to suspecting the cable from axe to amp, have you tried others? And yes, it is time to get out and try your rig at other venues. Like they say in Real Estate and Business: Location, Location and Location. ;D sumgai
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Post by slideguy123 on Jan 16, 2007 10:47:26 GMT -5
Nyuk, nyuk, nyuk...
I took it apart one last time and ran a wire directly from the tailpiece (better continuity than the bridge, based on the multimeter) to the jack. I tested for continuity all the way down the chain, including each string to the sleeve of the guitar cable. I also tested for hot-to-ground connections -- everything's clean. Hum is about the same -- less than before I cleaned up the grounds, but still more than seems reasonable. Also, it doesn't change when I touch the strings or tailpiece.
I've tried a couple of cables -- the hum is still louder (but less than it initially was) than on my 1970's Emmons lap steel, which has a single coil pickup that is no more than 3/8" thick. It's a surface mount pickup, but it is covered in metal and sits on a metal pickguard, so I'm assuming that's why it's so much quieter. It's not a great instrument, which is why I don't play it with the band, but the pickup has a great, vintage sound. I may have to find a way to mount it on another guitar. NOTE: the slight hum I get from this guitar doesn't change when I touch the strings. It may just be my basement's wiring (yes, I tested the outlets for correct grounding).
I've tried other guitar cables -- hum is the same. It's not unbearable, and once I start playing, the instrument is loud enough to cover it up. Some of the issue is my expectations, since I switched from a single-coil size humbucker to a true single coil, but I don't know what is a realistic level of hum.
We'll see how it does at band practice tomorrow nite, and at the gig on Saturday...
Thanks for the help, Peter
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Post by slideguy123 on Jan 16, 2007 19:36:22 GMT -5
Update -- still making me a little crazy. I moved to a different floor of the house, but I still get more hum than I think is reasonable when I hold the steel in normal playing position (perpendicular to the floor). When I tilt it so the edge is pointing to the floor, it is as quiet as a humbucker.
I've tried changing positions around the amp, tried tilting the amp. The only thing that quiets the hum is holding the steel like a regular guitar, which obviously won't work for lap-style playing. And I still don't get why touching the strings doesn't change the hum.
ARRGGGHHH!!!!!!!
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Post by UnklMickey on Jan 16, 2007 20:06:24 GMT -5
Peter,
you did connect the shielding to ground. right?
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Post by slideguy123 on Jan 16, 2007 23:55:00 GMT -5
unklmickey -- good question. I tried to follow the Guitarnuts method -- the shielding is connected to ground because the back of the pickguard is covered in foil (so is the cavity). When I checked with the meter, I had continuity and very low resistance from back of the pickguard to each of the pots, tone pot to volume pot, and pickguard to ground tab on the jack. Should I have a separate wire from the cavity to the jack? Or should I connect the tailpiece (which gives me better continuity than the bridge) to the cavity, with a .1uf 200v capacitor (a la the S-Tastic circuit)? Here's what it currently looks like: Thanks, Peter
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Post by UnklMickey on Jan 17, 2007 12:07:44 GMT -5
...When I checked with the meter, I had continuity and very low resistance from back of the pickguard to each of the pots, tone pot to volume pot, and pickguard to ground tab on the jack. Should I have a separate wire from the cavity to the jack? ... hi Peter, the important thing is that you do have a low resistance path from the shielding to the ground of the output jack. since you already have that covered, i don't think adding a wire from the cavity to the tailpiece or the jack will make any difference. the capacitor you mentioned, serves to protect against DC shock in the event of a rare type of failure in a tube amp. if anything, adding that cap will make the hum slightly worse. unk
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Post by slideguy123 on Jan 17, 2007 13:34:32 GMT -5
Thanks, Unk -- This has been frustrating, especially since the steel is so quiet when I hold it like a regular guitar. I know it can be quiet, I jsut don't know how to get it there!
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Post by UnklMickey on Jan 17, 2007 14:13:21 GMT -5
hmmmmm................hold it on your lap, but lay on your back?
okay, bad joke. or at least, bad time for a joke. sorry.
kinda ran out of ideas.
unk
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Post by sumgai on Jan 17, 2007 15:34:23 GMT -5
Peter, Waidda minute here...... you say the instrument is very quiet when it held like a standard guitar, but noisy when held as a lap guitar? Then there are only two possible solutions to this problem. Either: It is indeed your environment. Electromagnetic fields are polarized, and all that. But you said that this happens no matter where you are, right? So that leaves..... There is something loose inside the guitar, and when you reposition the guitar, that 'something' causes your internal wiring to be less than effective. How, I dunno, I can't answer that without seeing the instrument first hand. I see no other possibilities here. But then again, this wouldn't be the first time I've been accused of being short-sighted and narrow-minded. If the guitar works in at least one position (is hum-free), then it is wired correctly. But if it hums in every environment into which you take it, then the only common denominator is the guitar itself. Truly a puzzle worthy of Solomon hisownself. Personally, I'd still vote for the guitar being the problem. Can you tip the thing slowly from hum to no-hum? At what point does it switch states? Is it a snap action, or does the hum slowly fade in/out? Could it be the pickup itself? If the guitar didn't exhibit this problem with the previous pickup, then you're gonna have to give in and place the blame on the pickup itself. Seems damned strange to me too, but there you be. Like unk, I'm about out of possible answers, sorry. sumgai
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Post by slideguy123 on Jan 17, 2007 16:06:45 GMT -5
I appreciate all the help, sumgai -- thanks for sticking with me. The hum fades as the guitar is rotated from one plane to the other. It goies away almost entirely whether the pickup side or the back side of the steel is facing the amp.
I have looked for loose wires, pots, anything, and it's all snug and tidy. I've only tried the guitar and amp in my house, on different floors using different circuits. Tonite is band practice at the drummer's house, so we'll see if it's any better or worse there.
Since the previous pickup was a Bill Lawrence noiseless, it may have masked issues that were there all along. I started out just replacing the pickup -- no other changes. I've now rewired the thing literally 5 times. The shielding made some difference, but the whole situation is just plain odd.
Since touching the strings doesn't change the hum, that means the strings are as grounded as they are going to get. Everything seems to be as it should - maybe single coils are just noisier than I'm used to, and I need to change my expectations.
I'm curious if all guitars are like this -- since most people don't play their guitars lap style, how many would notice if their axes got noisier with the "face" up.
The tone of this pickup is much bette than the one it replaced, so I want to make it work.
I wonder if a shielded pickup cover would help or hurt?
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Post by UnklMickey on Jan 17, 2007 16:44:43 GMT -5
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Post by slideguy123 on Jan 17, 2007 17:11:09 GMT -5
Intersting, unk -- thanks for the link. I haven't seen this woven copper material before, but I may look into it. Thank you for sticking with me on this.
Peter
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Post by slideguy123 on Jan 18, 2007 9:05:28 GMT -5
Unk, sumgai - thanks again for sticking with me. Last night was band practice at the drummer's house -- he's also an electrician. No hum at all from my steel, but our guitar player's Strat was buzzing like crazy (it's stock, no shielding).
On the one hand, I feel pretty good about it, on the other hand, the drummer thinks my house wiring is the culprit -- he's seen it before that there could be continuity between the neutral and common lines somewhere in the system (maybe at the meter, the panel, or any of the outlets). He'll try to have one of his guys check it out as soon as he can.
Meanwhile, thanks to the advice you gave me, I have a well-shielded axe. The wiring is neat and minimal -- I got rid of extraneous wires and ground loops and now have an instrument that sounds great.
I appreciate all of your time and effort on my behalf, and I thank you for treating a new member of the board so well.
Best regards, Peter
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Post by sumgai on Jan 18, 2007 16:54:11 GMT -5
Peter, Yer welcome! ;D But something you said got me to thinking...... When I spoke earlier of 'environment', I intended that to mean all of your other gear - only the lap steel should go with you to a new location. Thereat, you should be plugged into a different amp, with a different cable. The idea was to isolate your guitar as much as possible by eliminating the rest of 'your' gear. Sorry if I wasn't very clear on that point. Your amp's power transformer may have radiation issues. Was your quitar quiet at practice with your amp, or with someone else's amp? Another thing...... I should hope so! Since the early 70's, the National Electrical Code has decreed that neutral (or common) and ground WILL be tied together at the distribution panel. But yes, there are myriad possibilities within a residence that could cause your problems. And finally, do your Strat-owning buddy a favor and turn him on to GN2, it sounds like he needs us! ;D sumgai
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Post by UnklMickey on Jan 18, 2007 18:44:59 GMT -5
Peter, we always try to treat new members well. it's only after you get really comfortable here, that we give you mass quantities of abuse. ....No hum at all from my steel, but our guitar player's Strat was buzzing like crazy (it's stock, no shielding).... ...the drummer thinks my house wiring is the culprit -- he's seen it before that there could be continuity between the neutral and common lines somewhere in the system... scary thought: i wonder what that Strat would sound like, in your basement! there should be very good continuity between the neutral and ground............... the connection should be at the first distribution panel in the house. also there should be a very low resistance path to true ground, i.e. a ground rod or water pipe, at the same panel. problems sometimes occur, when some genius "bonds" the ground and neutral on a connection elsewhere in the house's wiring. this can allow a high current load, to "modulate" the ground, because the ground wire is now carrying current. (current should only be carried by the neutral and hot.) this does bear further examination. however, you could consider your basement as a "proving ground" of sorts. if you can beat the hum there, it seems like nothing a club will throw at you will cause you a problem. on the other hand...................you didn't mention if that Strat had a problem if in was laid flat, in the same plane as your steel, when you were at your drummer's house. or if your steel hummed when held like a guitar. maybe the orientation of the field at the drummers house, gave the Strat a problem. just a few things to think about....
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Post by slideguy123 on Jan 18, 2007 19:53:53 GMT -5
You guys are making my brain hurt... I didn't try another amp, because things were so quiet. I didn't get additional noise when I moved the steel to different planes. The strat was noisy no matter what poisition it was in (didn't change no matter what plane, but changed as usual when he held it normally and rotated), unless the guitar player had his hands on the strings. I'll have to look into this further and try the suggestions you mentioned. Is my next move going to be checking every outlet with a tester? Whee!!!! I'll let you know what happens next. Thanks for the ideas. Peter
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