Low output on one pole piece

[Troglodyte1911]

I have a G&L Tribute SB-2 and the D string has always seemed quiet to me. I raised the pickup and also the individual pole pieces and it only helped a little bit. I pressed the string down and one piece makes the expected static-like click/pop, but the other one makes very little noise.
i guess I’ll pull the pickups and see if there is a bad connection. Any other suggestions on what to look for?

 

[NoiseNinja]

I have a G&L Tribute SB-2 and the D string has always seemed quiet to me. I raised the pickup and also the individual pole pieces and it only helped a little bit. I pressed the string down and one piece makes the expected static-like click/pop, but the other one makes very little noise.
i guess I’ll pull the pickups and see if there is a bad connection. Any other suggestions on what to look for?

Are you sure it isn't an issue with this specific D string, and not the pickup?

 

[Troglodyte1911]

2nd set of strings, both did it. Bridge pickup soloed sounds fine.

 

[dwizum]

Tapping the pickups and getting noise or not is a little bit of a hit or miss thing, depending on how the pickup is wound. It's sometimes the case that poles on the ends of the coil will naturally tap louder than poles near the middle. If (or how) the poles are grounded can make a difference too. So, I wouldn't put a ton of stock in your tap test.

That said, there could still be issues with the pole piece. I'm not familiar with that pickup, but generally that style comes in two flavors. The traditional Fender design was the simplest - the coil was wound directly on alnico pole pieces. Alnico demagnetizes easily. It may be the case that one of your poles has been demagnetized. You can check by holding a paperclip or something near the pole and see how strongly it pulls (if it does at all) compared to the "good" poles on the pickup. Or you can just assume the pole is demagnetized and recharge it - which can be done very easily. Get your hands on a much stronger magnet - small neo rods or discs work well. Hold it in the orientation you want the pickup magnetized and just tap it against the top of the pole a half dozen times and you're done.

The other common style this pickup comes in has steel pole pieces and one or more ceramic bar magnets below the coil to charge the steel poles. Ceramic magnets are much harder to demagnetize, and a demagnetized ceramic bar would mean that all the poles would lose their charge. But ceramic bars are very brittle and can crack. I've seen pickups where pieces have cracked and fallen off, or shifted out of place. Pretty easy to spot by looking at the bottom of the pickup.

If none of the above helps, show us some photos of the coils and maybe someone here will spot something. Pickups are dirt simple and there's not a whole lot that can go wrong.

 

[sunbeast]

The G&L MFD P used in the SB-2 uses a single ceramic bar magnet glued underneath each coil half with a copper plate glued on the bottom of the magnet. The only likely “off” things I could think of that would decrease output on this design are a damaged magnet as mentioned above, bad magnet alignment that leaves the magnet closer to one side of the coil, or loose or badly placed adhesive either between magnet and coil or magnet and copper plate that leaves space in between the layers. I have had a number of these pickups in different basses and have had old magnet adhesive give way on one before that mostly just resulted in a highly microphonic pickup, though I’ve never found balance issues as you mention. I would pull the coil out and inspect the bottom to see magnet alignment and glue integrity.

Here’s a pic of the coil-magbet-copper plate stack I stole from a TB classified ad:

Curious how well do the strings align with the pickup in your bass? I’ve had an SB-2 with pretty terrible string-to-pickup alignment from the factory (and mine was a US bass), though I was able to balance the output just fine on that bass with pickup height adjustments. I find that pickup needs a little more clearance underneath for the best performance vs a typical alnico P pickup FYI. I also find the polepieces better at slight tonal adjustment than output volume adjustment.

Also when you say the pickup height adjustments made little difference, that seems suspect- raising the pickup under just the D should make a pretty noticeable difference

 

[Troglodyte1911]

Thanks for the reply. That pole piece is thoroughly demagnetized. I wasn’t able to get it magnetized, so I called G&L support and they will send a replacement pickup.

 

[Troglodyte1911]

The G&L MFD P used in the SB-2 uses a single ceramic bar magnet glued underneath each coil half with a copper plate glued on the bottom of the magnet. The only likely “off” things I could think of that would decrease output on this design are a damaged magnet as mentioned above, bad magnet alignment that leaves the magnet closer to one side of the coil, or loose or badly placed adhesive either between magnet and coil or magnet and copper plate that leaves space in between the layers. I have had a number of these pickups in different basses and have had old magnet adhesive give way on one before that mostly just resulted in a highly microphonic pickup, though I’ve never found balance issues as you mention. I would pull the coil out and inspect the bottom to see magnet alignment and glue integrity.

Here’s a pic of the coil-magbet-copper plate stack I stole from a TB classified ad: View attachment 4465871

Curious how well do the strings align with the pickup in your bass? I’ve had an SB-2 with pretty terrible string-to-pickup alignment from the factory (and mine was a US bass), though I was able to balance the output just fine on that bass with pickup height adjustments. I find that pickup needs a little more clearance underneath for the best performance vs a typical alnico P pickup FYI. I also find the polepieces better at slight tonal adjustment than output volume adjustment.

Also when you say the pickup height adjustments made little difference, that seems suspect- raising the pickup under just the D should make a pretty noticeable difference

Alignment was poor, but like you said, by adjusting the pickups I was able to clean it up a bit.
I had pulled off the PG and pulled the pickups, the pickup in question looked odd to me - the springs were angled to the bridge end of the cavity and the foam was a wedge, not flat.

 

[NoiseNinja]

Tapping the pickups and getting noise or not is a little bit of a hit or miss thing, depending on how the pickup is wound. It's sometimes the case that poles on the ends of the coil will naturally tap louder than poles near the middle. If (or how) the poles are grounded can make a difference too. So, I wouldn't put a ton of stock in your tap test.

That said, there could still be issues with the pole piece. I'm not familiar with that pickup, but generally that style comes in two flavors. The traditional Fender design was the simplest - the coil was wound directly on alnico pole pieces. Alnico demagnetizes easily. It may be the case that one of your poles has been demagnetized. You can check by holding a paperclip or something near the pole and see how strongly it pulls (if it does at all) compared to the "good" poles on the pickup. Or you can just assume the pole is demagnetized and recharge it - which can be done very easily. Get your hands on a much stronger magnet - small neo rods or discs work well. Hold it in the orientation you want the pickup magnetized and just tap it against the top of the pole a half dozen times and you're done.

The other common style this pickup comes in has steel pole pieces and one or more ceramic bar magnets below the coil to charge the steel poles. Ceramic magnets are much harder to demagnetize, and a demagnetized ceramic bar would mean that all the poles would lose their charge. But ceramic bars are very brittle and can crack. I've seen pickups where pieces have cracked and fallen off, or shifted out of place. Pretty easy to spot by looking at the bottom of the pickup.

If none of the above helps, show us some photos of the coils and maybe someone here will spot something. Pickups are dirt simple and there's not a whole lot that can go wrong.

Know it is kind of off topic, but could the magnetic strength of Alnico pole piece slug magnets be boosted simply by leaving a strong bar neodymium magnet across the pole pieces in the same direction as their current magnetic field for say 1 or 2 days, then remove it and have the strength of the pickup's magnetic field increased that way, or do you have to tap them back and forth for the magnetification to happen?

Also how would just increasing the magnetic strength of a pickup effect it's tone in roughly general terms, beside obviously increasing the output, like for instance would it shift the tonal balance towards the top or the bottom end of the frequency spectrum?

 

[dwizum]

Know it is kind of off topic, but could the magnetic strength of Alnico pole piece slug magnets be boosted simply by leaving a strong bar neodymium magnet across the pole pieces in the same direction as their current magnetic field for say 1 or 2 days, then remove it and have the strength of the pickup's magnetic field increased that way, or do you have to tap them back and forth for the magnetification to happen?

Also how would just increasing the magnetic strength of a pickup effect it's tone in roughly general terms, beside obviously increasing the output, like for instance would it shift the tonal balance towards the top or the bottom end of the frequency spectrum?

Magnetic materials like alnico have a saturation point - you charge them, they "become" magnetic, and the more you charge them the stronger they get - up until the point at which they're saturated and they can no longer be charged any further. For the most part, alnico magnets in guitar pickups are saturated by default, or at least assumed to be close enough to saturated that it makes no difference. There are a few builders who are "tuning" their magnets by charging them to specific strengths (usually measured with a gauss meter) but that's splitting hairs.

Alnico is very "soft" magnetically in that it will take or lose a charge very easily. You can fully charge an alnico 5 pole piece almost accidentally just by waving a strong neo magnet nearby, much less actually touching them together at all. My pickup charging rig doesn't even allow contact, I just slide the Alnico magnets between spacers that are held stationary between a pair of neo discs.

If you do not change the material of the magnet or any other properties of the pickup, and you just increase the charge on the magnet, the pickup's output will increase. This will essentially be a straight increase across the EQ, there won't be any tonal difference - just a higher output.

If you change the material of the magnet to a material with a different composition - i.e. alnico 5 to ceramic 8 - you'll get a tonal difference and a difference in output. The specific differences will depend on the changes you made. Changing to a material that's stronger magnetically (as C8 is compared to A5) will result in more output, same as above. Changing to a material that has a different electrical conductivity or other differences in EM parameters will cause a change in tone that depends on the specific change. Alnico is conductive enough, electrically, that it acts similar to an iron slug in the magnet - it tends to roll off high frequencies and emphasize the "passive pickup" upper mid peak. A material like ceramic, that's not electrically conductive, doesn't do that - the "natural" tone of the pickup isn't changed, so you retain the high frequencies and don't get as big of a peak. Hence why ceramic magnets can have a reputation for being harsh. A ceramic magnet with steel slugs or some other combination of the two can sound convincingly like Alnico but result in a stronger output. Neat trick if you want more output but don't want more wire in the coil.

 

[iiipopes]

It sounds to me like the D pole isn't making proper contact with the bar magnet under the pickup. I've had that happen on other pickups. On one, I was able to scrape off a glue overrun film and restore the direct contact between the pole and the magnet, and therefore the output. Whether alnico, ceramic, etc., if there is not proper contact between the pole and the magnet, the magnetic field will be compromised and act just as the OP describes. Let's see what happens when he installs the replacement pickup.

 

[dwizum]

Looking at the info @sunbeast posted it does seem likely that it's a problem with the bar magnet - it's shifted or broken. The vast majority of "bar magnet under steel slug" bass pickups have ceramic bars and they don't demagnetize easily, so that's almost certainly not the problem here.

@Troglodyte1911 - since the manufacturer is sending you a new pickup, did they want the old one back? It might make a fun project to take it apart and try to fix it. No harm done since you have a replacement.

 

[Troglodyte1911]

Looking at the info @sunbeast posted it does seem likely that it's a problem with the bar magnet - it's shifted or broken. The vast majority of "bar magnet under steel slug" bass pickups have ceramic bars and they don't demagnetize easily, so that's almost certainly not the problem here.

@Troglodyte1911 - since the manufacturer is sending you a new pickup, did they want the old one back? It might make a fun project to take it apart and try to fix it. No harm done since you have a replacement.

They didn’t say anything about returning it, I’ll just have to see if there is a return envelope included. If I can keep it, I’ll definitely check it out to see what can be done to either fix it or destroy it in the process.

 

[Troglodyte1911]

I finally received the replacement bridge pickups and replaced them. Presumably I did something wrong when soldering them back in because now I have to have volumes near 100% to get sound. As I desoldered one connection I soldered in the new pickup wire, so I don’t think I mis-wired anything. But since it’s me, who knows? Anyone know what could cause such low output?

 

[dwizum]

Can you show us some photos?

 

[Troglodyte1911]

Let me know how these pics are.

 

[dwizum]

Looks ok though it's hard to tell in photos. I'd start by checking your new solder joins and reflowing any that look questionable.

 

[Troglodyte1911]

Thanks, most likely poor re-soldering on the output jack. When I took it apart to replace the pickups, those two connections came apart. As for re-soldering, I don’t have a fine tip, just a big chisel tip but I can make it work.

 

[Troglodyte1911]

Yep, hack soldering job from me. Thanks @dwizum for the suggestion. I touched up the output jack connections and there is improvement, but it isn’t great. Time for a new soldering iron to re-do all the connections.

 

[Troglodyte1911]

Solder joints have been fixed, including several done (attempted?) at the factory. I had always heard about how hot the MFD pickups were, but they never blew me away. After re-soldering everything and with the replacement pickup installed, I was stunned how loud it now is.