jazz bass wiring

[Geek99]

hi all
my 62 Ri is noisy when both pickups arent fully on (RWRP probably)

I've taken the bellplate off and I notice there is a copper plate at the back of the control cavity, to which everything, including the bridge presumably, is connected. There is a copper strip from the bridge going to the bridge pickup, I presume it connects into earth somehow.

I notice that there is no lead going to the smaller connection on the jack socket - (a white wire presumably for signal goes to the larger). The smaller one appears to have some solder on it. I'm not sure therefore, how the instrument is earthed as all the earth wires seem only to connect to the bridge. The jack socket has just one white wire attached, is this normal? Shouldnt there be a black wire from somewhere to the smaller connection of the jack socket?

thoughts? thanks

[BOD2]

It will be earthed through the metal control plate. Since the pots are mounted on this and they are usually connected to earth in some way, then mounting the jack socket on the same metal plate also earths the jack socket.

It's not the best way to earth and instrument - there is the potential for multiple small ground loops - but it's the way Fender has always done it.

Are the body cavities full sheilded with copper foil ? This can sometimes help reduce hum. Other than that check the stcicky at the top of this forum for common causes of humming and buzzing.

[Geek99]

thanks, I see what you mean about earthing through the plate. but note that the Seymour Duncan website has a jazz bass wiring diagram (not a circuit diagram) which shows the connection made. I may just try it to see if there is a noticeable improvement as that would perhaps alleviate a ground loop.

I have nt yet sheilded with copper foil. It may come to that.

[Geek99]

has anyone had this buzz problem on a jazz (when one pickup isnt on full) and actually [b]solved[/b] it with copper foil?

[Geek99]

Just took delivery of the copper tape (the conductive glue stuff mentioned in another thread) - will report.

[thebeat]

There's always some hum with J bass pups when they are'nt either both on full or at least both controls are around the same point...something to do with them being single coil?????

[BassBod]

Sounds like its the single coil hum you're hearing (direct from the pickup) rather than a sheilding problem. The only solution is a hum cancelling version of a J pickup - there are a few currently made, most of which claim to retain the "single coil sound" - but I've never tried any. Thought about it, but never had the funds/time/inclination. The DiMarzio model J is a humbucker, and is dead quiet when soloed, but hasn't got the real single coil top end - haven't heard one for a few years, but I always liked them.

Good luck

BB

[bremen]

This is probably due to lack of screening. If it was due to the lack of humbucking in the pickups it'd get louder as the volume was turned up. As it is, the volume controls show a high impedance to the amp when turned down, allowing capacitive (ie through the air and the wood of the body) coupling. It's the same sort of effect as using a non-screened cable between bass and amp. Fully lining the cavity with copper tape, and grounding this tape to the metal plate, should fix it.

Ground loops are not an issue when there are no heavy currents flowing. They are hugely significant in power amps and systems where multiple mains-powered devices are interconncted, but it really doesn't matter how the ground connections are arranged within a passive bass, so long as the connections are all there. The metal plate of the Jazz should be fine as a ground return (so long as the pot bodies are connected to the ground wires of the pickups and the bridge).

[thebeat]

[quote name='bremen' post='331759' date='Nov 18 2008, 08:21 PM']This is probably due to lack of screening. If it was due to the lack of humbucking in the pickups it'd get louder as the volume was turned up. As it is, the volume controls show a high impedance to the amp when turned down, allowing capacitive (ie through the air and the wood of the body) coupling. It's the same sort of effect as using a non-screened cable between bass and amp. Fully lining the cavity with copper tape, and grounding this tape to the metal plate, should fix it.

Ground loops are not an issue when there are no heavy currents flowing. They are hugely significant in power amps and systems where multiple mains-powered devices are interconncted, but it really doesn't matter how the ground connections are arranged within a passive bass, so long as the connections are all there. The metal plate of the Jazz should be fine as a ground return (so long as the pot bodies are connected to the ground wires of the pickups and the bridge).[/quote]




Still think it's just the fact that they're single coil pups ....what do you mean when you say 'If it was due to the lack of humbucking in the pickups it'd get louder as the volume was turned up' ? Do you mean when he turns the amps gain or output up? If so, he hasn't said that this doesn't happen. Most of the time the most obvious answer is the correct one.

Edited November 18, 2008 by thebeat

[bremen]

[quote name='thebeat' post='331787' date='Nov 18 2008, 08:48 PM']Still think it's just the fact that they're single coil pups ....what do you mean when you say 'If it was due to the lack of humbucking in the pickups it'd get louder as the volume was turned up' ? Do you mean when he turns the amps gain or output up? If so, he hasn't said that this doesn't happen. Most of the time the most obvious answer is the correct one.[/quote]

Because if it was because they were single-coil the noise wouldn't be dependent on the setting of the bass's volume controls. I may be wrong but the way I read Geek's post it was only a problem when they weren't fully on.

[thebeat]

[quote name='bremen' post='331799' date='Nov 18 2008, 08:55 PM']Because if it was because they were single-coil the noise wouldn't be dependent on the setting of the bass's volume controls. I may be wrong but the way I read Geek's post it was only a problem when they weren't fully on.[/quote]


The hum made by jazz bass, single coil pups is only audible when one or the other pups is at higher volume than the other, when both are at the same volume...no matter what that volume is, no hum is heard. Conversely, when the front pup is at a volume higher than the rear pup...or vice versa...hum can be heard.

[Geek99]

[quote name='bremen' post='331799' date='Nov 18 2008, 08:55 PM']Because if it was because they were single-coil the noise wouldn't be dependent on the setting of the bass's volume controls. I may be wrong but the way I read Geek's post it was only a problem when they weren't fully on.[/quote]
exactly correct. Its pretty much equally noisy all the time. I wouldnt want to play a gig (ie gig volume) with it as noisy as it is, yet people use Jazz basses in gigs all the time. I know that there is [i]some [/i]noise from a single coil, but I think I have an abnormal quantity of it.

the noise disappears when they are at equal volume, regardless of whether that is full volume. I'm not sure that you two arent arguing the same point really.

Edited November 19, 2008 by Geek99

[BassBod]

That sounds like normal Jbass hum to me - and it can be pretty loud, depending on what you are standing near. In a critical gig situation I adjust the volumes down as a song begins - this has become a habit. I even do it when I'm playing other basses that don't hum!

[bremen]

[quote name='thebeat' post='331941' date='Nov 18 2008, 10:56 PM']The hum made by jazz bass, single coil pups is only audible when one or the other pups is at higher volume than the other, when both are at the same volume...no matter what that volume is, no hum is heard. Conversely, when the front pup is at a volume higher than the rear pup...or vice versa...hum can be heard.[/quote]

Got you. The 2 pickups are out-of phase. Foil shielding won't make any difference in this case.

How come the sound isn't horribly thin then? Switching my PJ to out-of-phase the tone is useless.

[Geek99]

its the only jazz bass I've really played so I cant tell if its sounding thin or not. Its doesnt sound particularly thin. I'm comparing it to a active Stingray copy and its louder than that.

I did the foil shielding last night, and my zoom's noise reduction now kills the noise at setting 6 to 7 rather than at 9, so it [i]has[/i] made a difference. Didnt notice a change in tone, as some assert occurs. Please do also note that I havent checked the shielding [i]fully [/i]for continuity as my multimeter died. Its also possible that some of the common causes such as being near a light switch, dodgy lead may still apply.

Edited November 20, 2008 by Geek99