P-Rails + triple shot + 5 way switch

[mrosebrock]

Wow, that sounds like an awesome project. Post some pics when you get the P-Rails installed.

I finally got this done. It seems
to me that the P-rails hum quite a lot in p90 and in single coil mode, more than I would have expected, they seem hooked up correctly though. Even the regular humbucker mode hums more than my other guitar by a lot. I’m not getting any hum cancelling in the middle single coil/ neck single or bridge p90/middle single. Is this expected for p-rails due to the uneven windings between the pickup types? Nothing a noise gate can’t fix but just curious. At low gain settings they are completely fine.

[Mincer]

I don't notice a ton of hum from my P-Rails. No more than a regular single coil. Anyone else?

[Jack_TriPpEr]

I finally got this done. It seems
to me that the P-rails hum quite a lot in p90 and in single coil mode, more than I would have expected, they seem hooked up correctly though. Even the regular humbucker mode hums more than my other guitar by a lot. I’m not getting any hum cancelling in the middle single coil/ neck single or bridge p90/middle single. Is this expected for p-rails due to the uneven windings between the pickup types? Nothing a noise gate can’t fix but just curious. At low gain settings they are completely fine.

If you're getting hum in humbucker mode of either of the 2 p-rail pups when they are active all by themselces (i.e. just Neck active or just Bridge active), then either there is some part of the wiring job that is not quite right, or your guitar needs shielding.

And unless you wired the stk-4 to be split in positions 2 and 4, then you won't get hum-canceling because there would be an uneven # of coils active (the 2 coils of the hum-bucking stk-4 middle pup plus the coil of the bridge or neck that its being paired with). Hum-canceling is only possible when the number of active coils is an even number.

Also regarding the STK-4, we'll need to know if you ordered a Middle Position version of that pickup or not. Middle Position versions of this pup are different (reverse wind, reverse polarity (RWRP)).

If you post some pics of the wiring work inside the cavity, then we can try to begin to troubleshoot.

Also, please post a pic of the wiring diagram that you used.

[mrosebrock]

If you're getting hum in humbucker mode of either of the 2 p-rail pups when they are active all by themselces (i.e. just Neck active or just Bridge active), then either there is some part of the wiring job that is not quite right, or your guitar needs shielding.

And unless you wired the stk-4 to be split in positions 2 and 4, then you won't get hum-canceling because there would be an uneven # of coils active (the 2 coils of the hum-bucking stk-4 middle pup plus the coil of the bridge or neck that its being paired with). Hum-canceling is only possible when the number of active coils is an even number.

Also regarding the STK-4, we'll need to know if you ordered a Middle Position version of that pickup or not. Middle Position versions of this pup are different (reverse wind, reverse polarity (RWRP)).

If you post some pics of the wiring work inside the cavity, then we can try to begin to troubleshoot.

Also, please post a pic of the wiring diagram that you used.

Ok thank you. I did not do the wiring, it was done by a luthier. My guitar is a bit complex because it has piezo saddles and synth output so the cavity has a big circuit board in it. To answer a couple of questions, I ordered the STK-4 middle position. The P-rails were ordered with triple shots so the wiring of the triple shots to the p-rails was done prior to delivery to me. Basically, my guitar has a 5-way switch and positions 2 and 4 just blend "all" of the neck or bridge pickup with the middle so whatever is selected by the triple shot gets blended with the STK-4. The triple shots have the white wire soldered to the 5-way switch and the black and silver wire are attached together and attached to a common ground that goes into the circuit board. From the 5 way switch, there is a single red "hot" wire that goes into the circuit board. There is also what appears to be another ground wire that goes into the circuit board and is grounded on the outside case of the 5-way switch. For the STK-4M, the red wire is taped off by itself and not attached to anything. The white wire is attached to the 5-way switch. The black and brown are attached together and attached to the common ground. Every "hot" wire is on the switch and all of the grounds are bundled all together along with a common ground going into the circuit board. As you can see, the circuit board has wires going into it from the magnetic pickups, and my volume control and tone pot are all under the circuit board. There are some "unused" terminals on the 5 ways switch but they were not used. I took the zip tie off the bundle so you can see the wires better. I don't have the wiring diagram as I did not do the work but according to what I've seen, it's done correctly and you are right, the extra hum-cancelling won't work because of the way it is not split and using triple shots.

[Jack_TriPpEr]

mrosebrock,

Thanks for supplying that helpful info.

From the pics, I don't see any obvious issues except that because the STK-4M's Red wire is taped off, that means that pup is always running in humbucking mode, and so when it is combined with a single coil from either the Bridge or Neck P-Rail, the result won't be hum-canceling.

But most worrisome is that you say you are hearing hum when either of the p-rails are active by themselves and in humbucking mode. That shouldn't be happening. My suspicions would be that there is either a loose ground or cold solder joint on one of the grounds, or the guitar needs shielding added. Maybe some of the other forum members here will have some more specific insight into what the issue is.

Additional info:

STK-4M Main coil polarity is South Up. Other SD Stack models have North Up polarity.


Ref:

Classic Stack Plus - how its wires should be routed:
https://forum.seymourduncan.com/foru...ups-on-a-strat

STK-4M vs Other Stacks magnetic polarity:

https://forum.seymourduncan.com/forum/the-pickup-lounge/6063477-stk4m-classic-stack-plus-strat-rwrp-polarity

Diagram attached of 3 Classic Stack pups wired up showing that White wire is hot, Brown & Black goto to Ground, and Red is an optional series-link wire that can be used for coilsplitting or taped off.

[mrosebrock]

mrosebrock,

Thanks for supplying that helpful info.

From the pics, I don't see any obvious issues except that because the STK-4M's Red wire is taped off, that means that pup is always running in humbucking mode, and so when it is combined with a single coil from either the Bridge or Neck P-Rail, the result won't be hum-canceling.

But most worrisome is that you say you are hearing hum when either of the p-rails are active by themselves and in humbucking mode. That shouldn't be happening. My suspicions would be that there is either a loose ground or cold solder joint on one of the grounds, or the guitar needs shielding added. Maybe some of the other forum members here will have some more specific insight into what the issue is.

Additional info:

STK-4M Main coil polarity is South Up. Other SD Stack models have North Up polarity.


Ref:

Classic Stack Plus - how its wires should be routed:
https://forum.seymourduncan.com/foru...ups-on-a-strat

STK-4M vs Other Stacks magnetic polarity:

https://forum.seymourduncan.com/forum/the-pickup-lounge/6063477-stk4m-classic-stack-plus-strat-rwrp-polarity

Diagram attached of 3 Classic Stack pups wired up showing that White wire is hot, Brown & Black goto to Ground, and Red is an optional series-link wire that can be used for coilsplitting or taped off.

Just some additional info. The humbucker modes are pretty quiet overall but still can have some noise at high gain levels. The single coil setting on the p-rails has more hum than that and the P90 hum is about twice that of the single coil. I carried the guitar around the room last night and I definitely found a few positions where the hum went mostly away. I turned off the lights and tried to pinpoint a common cause but could not find it. I also tried this with another guitar with the same results but the other guitar was much quieter overall (it is just a HSH with no fancy stuff). I opened up the cavity and messed around with a guitar cable connected and the hum increased by a ton when I put my fingers on the common red wire or touched on the circuit board on the 2 dots on the upper left corner of the circuit board. Moving the cables around or away from each other didn't do anything.

[Jack_TriPpEr]

Just some additional info. The humbucker modes are pretty quiet overall but still can have some noise at high gain levels. The single coil setting on the p-rails has more hum than that and the P90 hum is about twice that of the single coil. I carried the guitar around the room last night and I definitely found a few positions where the hum went mostly away. I turned off the lights and tried to pinpoint a common cause but could not find it. I also tried this with another guitar with the same results but the other guitar was much quieter overall (it is just a HSH with no fancy stuff). I opened up the cavity and messed around with a guitar cable connected and the hum increased by a ton when I put my fingers on the common red wire or touched on the circuit board on the 2 dots on the upper left corner of the circuit board. Moving the cables around or away from each other didn't do anything.

If either p-rail in humbucking mode is exhibiting hum only when high level of gain is applied, then that sounds normal and not unusual.

Also, just in case you were not already aware, when either of the individual coils of the P-rail are used all by themself, they should be expected to exhibit hum. They are singlecoils after all, so they will have 60 cycle hum. And the hum will sound louder on the P90 coil vs the Rail coil because the Prail coil is a louder/hotter coil.

If you sre noticing changes in hum that are dependent on whether lights are on or off, or whwre you are located in the room, then that is hum due to EMI/RFI interference, which is separate from 60 cycle hum and the solution for that is adding more/better shielding to the wiring in the guitar.

[mrosebrock]

If either p-rail in humbucking mode is exhibiting hum only when high level of gain is applied, then that sounds normal and not unusual.

Also, just in case you were not already aware, when either of the individual coils of the P-rail are used all by themself, they should be expected to exhibit hum. They are singlecoils after all, so they will have 60 cycle hum. And the hum will sound louder on the P90 coil vs the Rail coil because the Prail coil is a louder/hotter coil.

If you are noticing changes in hum that are dependent on whether lights are on or off, or whwre you are located in the room, then that is hum due to EMI/RFI interference, which is separate from 60 cycle hum and the solution for that is adding more/better shielding to the wiring in the guitar.

Yes I do expect some hum on higher-level gain but this guitar seems very extreme compared to my other one and any other guitar I have had. I'm in Australia so I'll get 50 cycle hum. I did take the guitar around the room the other day and found a few small places where the hum went away or at least down to normal levels. Nothing I turned off or on had any effect. I used a multimeter today and all of the grounding seems ok. Even all the pole pieces on the single coil are grounded all the way to the output jacks. On both p-rails, only 1-2 of the pole pieces per pickup are registering a beep. I'm not sure if this is normal or not as I haven't done it before. I thought all 6 would register. On the rail side, one of them registers and the other pickup doesn't.

In terms of shielding, I have some aluminium tape and have seen some videos but I'm not quite sure how to ground the shielding in the cavity or in the pickup slots. I'm not against it though. I did buy a new expensive power strip today with RF reduction so I'll try that too. The luthier has also agreed to have another look and properly check all the grounding (which he didn't do before). I'm also wondering if some of the wires were left too long and the silver wire of the p-rail is exposed in some places in the cavity.

[mrosebrock]

If either p-rail in humbucking mode is exhibiting hum only when high level of gain is applied, then that sounds normal and not unusual.

Also, just in case you were not already aware, when either of the individual coils of the P-rail are used all by themself, they should be expected to exhibit hum. They are singlecoils after all, so they will have 60 cycle hum. And the hum will sound louder on the P90 coil vs the Rail coil because the Prail coil is a louder/hotter coil.

If you sre noticing changes in hum that are dependent on whether lights are on or off, or whwre you are located in the room, then that is hum due to EMI/RFI interference, which is separate from 60 cycle hum and the solution for that is adding more/better shielding to the wiring in the guitar.

Hmm, so tonight I hooked my guitar up to a portable audio device and virtual amp on my phone and used the same exact amp and tone. I went into another room and everything was completely within tolerance on all pickup modes. This made me think maybe the wiring or audio interface in my guitar room was causing this. However, when I came back to my room with the portable amp solution and turned off the noise gate, I got exactly the same ridiculously loud hum. Despite this, I still unplugged absolutely everything in the room and the noise persisted. I took a walk outside carrying my mobile rig and look what I found precisely behind the wall of my guitar setup...60+ years old substandard wiring with ceramic fuses and on top of that, the main power line to the house also comes there too at the corner of my room. I guess it has always been there but something about this guitar and the p-rail setup amplifies it.