guybrush threepwood Posted August 3, 2012 Share Posted August 3, 2012 Last night I was putting the final touches to my recently converted P/J, but ran across a couple of issues. The first, I think I have in hand; while the bass was in pieces I painted the cavities with shielding paint, and now I have ridiculous hum. I didn't do two coats, but one thick coat, and my meter reads zero on all of it. I've read about screwing a wire into the painted area, so I'll give that a try later, as well as reflowing all my solder joints. Anyway, onto the second problem... I've wired the pickups in a telecaster configuration (volume, tone and 3-way switch), and each pickup sounds great on it's own, but together I'm getting a strange phasing issue; the D/G half of the P pickup sounds great, but the E/A sounds weak, thin, and out-of-phase. I read up on this last night, and the solution seems to be cutting the joining wire between the 2 halves of the P, and swapping the lead which connects to the other half and the lead to ground. However, this apparently leads to hum, as the pickup is now wired like a single coil. So how come everyone else can have a P/J that only hums when the J pickup is added into the mix? Is there anyway around this solution, other than a push/pull pot? Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted August 3, 2012 Share Posted August 3, 2012 I'm not at home so can't have a peep, but I am pretty sure the Jag on my Avatar is a standard P/J set up, albeit with 2 volumes. It sounds like you have a wire (or more) connected to the wrong tab on either the volume or tone pots or switch. If you have a short (the other possibility) I would expect one or other p/up not to work OK on its own. Relook at the wires, starting with following the hot from each pickup to and through the switch and to the volume pot tab - I reckon somewhere there is one in the wrong place. Quote Link to comment Share on other sites More sharing options...
guybrush threepwood Posted August 3, 2012 Author Share Posted August 3, 2012 I'm pretty certain that it's wired correctly, but I shall have another check when I get home later! I know that I've seen wiring diagrams in the past where the hot is connected to the opposite lug on the pot, would that make a difference? I shall have a gander on Google images too! Cheers for your help. Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted August 3, 2012 Share Posted August 3, 2012 Hi Worth a double check - the number of times I've wired a 3-way wrong... Two other thoughts - one is that yes, a shielded cavity should be earthed (just a solder tag connected to earth screwed in through the paint should do). However, I wouldn't think that shielding without earthing would ADD a hum. The other thought, [b]if you are absolutely sure that your wiring is correct[/b], is whether you have inadvertently reversed the two blocks of the staggered P pickup. I think they are reverse wound/reverse poled to each other so would sound OK whichever way you put them on their own, but the closer one to the Jazz P/up MIGHT (unlikely at the distances involved) interact and reinforce the hum rather than buck it (that is, the closer G D block might be same polarity and winding as the Jazz, with the humbucking E A block further away from it). If so, unscrewing both staggered blocks and rotating the whole assembly 180 degrees might make a difference. Hope it helps - let me know Quote Link to comment Share on other sites More sharing options...
iiipopes Posted August 3, 2012 Share Posted August 3, 2012 (edited) Is you J pickup a single coil? If so, that in and of itself can cause phasing issues. Are they different aftermarket pickups? If so, the coil and magnet orientation can be different, using different coloured leads, etc. My P-J has a Rickenbacker humbucker in the position where the D-G precision segment usually is, and a DiMarzio UltraJazz in the bridge position. I had to try every orientation of wiring on the J to find the proper orientation so that the pickup was wired both electrically and magnetically in phase with the Rick. Does everything come to one ground/earthing point so there is no "loop" to induce hum? Yes, in the late '80's when Fender started using the black shielding paint in their cavities, one wire came off one of the pot casings to a lug screwed into the cavity to make a ground/earthing contact. It also sounds like the E-A segment leads are swapped the wrong way. The best way to wire a P-J is to use the jazz bass V-V-T configuration, wire the P-pickup segments conventionally, find a J pickup that is also humbucking, and make sure it is in wired in both electrical and magnetic phase as the P pickup. Edited August 3, 2012 by iiipopes Quote Link to comment Share on other sites More sharing options...
guybrush threepwood Posted August 3, 2012 Author Share Posted August 3, 2012 [quote name='Andyjr1515' timestamp='1344012258' post='1758770'] The other thought, [b]if you are absolutely sure that your wiring is correct[/b], is whether you have inadvertently reversed the two blocks of the staggered P pickup. I think they are reverse wound/reverse poled to each other so would sound OK whichever way you put them on their own, but the closer one to the Jazz P/up MIGHT (unlikely at the distances involved) interact and reinforce the hum rather than buck it (that is, the closer G D block might be same polarity and winding as the Jazz, with the humbucking E A block further away from it). If so, unscrewing both staggered blocks and rotating the whole assembly 180 degrees might make a difference. [/quote] This sounds interesting, I shall give it a try tomorrow, but I have found another wiring diagram (which attaches to different tabs on the pots), so I shall give that a try first. [quote name='iiipopes' timestamp='1344028081' post='1759047'] Is you J pickup a single coil? If so, that in and of itself can cause phasing issues. Are they different aftermarket pickups? If so, the coil and magnet orientation can be different, using different coloured leads, etc. My P-J has a Rickenbacker humbucker in the position where the D-G precision segment usually is, and a DiMarzio UltraJazz in the bridge position. I had to try every orientation of wiring on the J to find the proper orientation so that the pickup was wired both electrically and magnetically in phase with the Rick. [/quote] They are different pickups, the precision is a Wizard Thumper, and the jazz is made by Tonerider. I did try changing the electrical polarity of the whole precision pickup, but it just meant that the phasing issue was shifted to the other 2 strings. [quote name='iiipopes' timestamp='1344028081' post='1759047'] Does everything come to one ground/earthing point so there is no "loop" to induce hum? Yes, in the late '80's when Fender started using the black shielding paint in their cavities, one wire came off one of the pot casings to a lug screwed into the cavity to make a ground/earthing contact. [/quote] I'm going to put in a ground wire to the cavity, but I've never understood the idea of star-grounding within a guitar. In an amp, yes, but in a guitar there's only one physical earth contact, so in my head, there's no possibility of ground loops. [quote name='iiipopes' timestamp='1344028081' post='1759047'] It also sounds like the E-A segment leads are swapped the wrong way. [/quote] Yes, but I've read that swapping these will counter the hum-cancelling effect of the pickup; as I said above, it isn't an issue on other pickups/basses, why this one? [quote name='iiipopes' timestamp='1344028081' post='1759047'] The best way to wire a P-J is to use the jazz bass V-V-T configuration, wire the P-pickup segments conventionally, find a J pickup that is also humbucking, and make sure it is in wired in both electrical and magnetic phase as the P pickup. [/quote] That is, essentially, what I'm trying to do, albeit with a switch and master volume pot. However, I've had humbucking J pups before and I really don't like them - I'm just a massive single coil fan! Quote Link to comment Share on other sites More sharing options...
ikay Posted August 4, 2012 Share Posted August 4, 2012 One half of the P being out of phase with the J indicates that the J wiring/polarity isn't correctly matched with the P (rather than the P wiring being at fault). Assuming the P is correctly wired with both coils being RWRP, then the J needs to be the same winding and polarity as one of the P coils to work. If it's not then there will always be a phasing issue with one of the P coils, regardless of whether you reverse the P wiring. The attached diagram may help. It should work as shown. But if the J was instead wired N-CCW then there would be a phasing issue. First check that the P is correctly wired with reverse winding and reverse polarity. Then try changing the wiring on the J (rather than the P). If you've already done that then sorry for wasting your time and please ignore this! [attachment=114897:P-J wiring.jpg] Quote Link to comment Share on other sites More sharing options...
Lozz196 Posted August 4, 2012 Share Posted August 4, 2012 Every bass I`ve owned with a PJ configuration hummed when the J pickup was on, aside from my Aerodyne, in which I put a Seymour Duncan Hot Stack J pickup, which was hum-cancelling. Quote Link to comment Share on other sites More sharing options...
guybrush threepwood Posted August 4, 2012 Author Share Posted August 4, 2012 [quote name='ikay' timestamp='1344078962' post='1759452'] One half of the P being out of phase with the J indicates that the J wiring/polarity isn't correctly matched with the P (rather than the P wiring being at fault). Assuming the P is correctly wired with both coils being RWRP, then the J needs to be the same winding and polarity as one of the P coils to work. If it's not then there will always be a phasing issue with one of the P coils, regardless of whether you reverse the P wiring. The attached diagram may help. It should work as shown. But if the J was instead wired N-CCW then there would be a phasing issue. First check that the P is correctly wired with reverse winding and reverse polarity. Then try changing the wiring on the J (rather than the P). If you've already done that then sorry for wasting your time and please ignore this! [attachment=114897:P-J wiring.jpg] [/quote] I've tried a different wiring scheme today, and although I've eliminated the awful hum, I'm still having the same phasing issue, so I'll try reversing the polarity of the J tomorrow. Cheers to everyone for all the help! Quote Link to comment Share on other sites More sharing options...
guybrush threepwood Posted August 4, 2012 Author Share Posted August 4, 2012 [quote name='Lozz196' timestamp='1344080763' post='1759477'] Every bass I`ve owned with a PJ configuration hummed when the J pickup was on, aside from my Aerodyne, in which I put a Seymour Duncan Hot Stack J pickup, which was hum-cancelling. [/quote] Aye, I don't mind a little single coil hum, it's just awful when it's happening when the single coil isn't on! Quote Link to comment Share on other sites More sharing options...
bremen Posted August 20, 2012 Share Posted August 20, 2012 (edited) [quote name='ikay' timestamp='1344078962' post='1759452'] One half of the P being out of phase with the J indicates that the J wiring/polarity isn't correctly matched with the P (rather than the P wiring being at fault). Assuming the P is correctly wired with both coils being RWRP, then the J needs to be the same winding and polarity as one of the P coils to work. If it's not then there will always be a phasing issue with one of the P coils, regardless of whether you reverse the P wiring. The attached diagram may help. It should work as shown. But if the J was instead wired N-CCW then there would be a phasing issue. First check that the P is correctly wired with reverse winding and reverse polarity. Then try changing the wiring on the J (rather than the P). If you've already done that then sorry for wasting your time and please ignore this! [attachment=114897:P-J wiring.jpg] [/quote] I'm now the proud owner of the P pickup in question. When they're wired as shown (ie to avoid the E and A being out-of-phase with the D and G) there's a huge amount of hum. An unuseable amount. Reversing one coil cures it completely and it sounds really, really good. I'm using it on its own in a Precision. I can see no way of using it in a PJ without either hum or incompatibility with the bridge pickup. Looks to me like the magnets in one half of the pickup should be reversed compared to the other? Meaning the two parts should be 'mirrored' rather than identical, and the OP has been sold a metaphorical pup as well as a literal one... Edited August 20, 2012 by bremen Quote Link to comment Share on other sites More sharing options...
guybrush threepwood Posted August 20, 2012 Author Share Posted August 20, 2012 Hehehe, in the end I just sucked it up and got dimarzios. They actually sound great! Quote Link to comment Share on other sites More sharing options...
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