Seymour Duncan P-Rails, Analysis and Review

[antigua]

www.seymourduncan.com/pickup/p-rails-set



This set up pickup is essentially a PAF-sized P-90-like pickup with a single rail beside it, all under a one piece plastic cover.

As you can see, I have these pickup mounted in a Seymour Duncan Triple Shot. I kept it wired to the Triple Shot for testing the various modes. Some small portion of the measured capacitance likely owes to the Triple Shot wiring, but these pickups and the Triple Shot ring pretty much go hand in hand anyway.



Electrical measurements:


Seymour Duncan P-Rails Bridge
- P-90 DC Resistance: 10.09K ohms
- P-90 Measured L: 6.250H
- P-90 Calculated C: 229pF (239 - 10)
- P-90 Gauss: 550G

- Rail DC Resistance: 8.48K ohms
- Rail Measured L: 4.517H
- Rail Calculated C: 613pF (623 - 10)
- Rail Gauss: 360G

Without load:
P-90: dV: 7.7dB f: 4.12kHz (black)
Rail: dV: 6.1dB f: 3.00kHz (red)
Series: dV: 6.6dB f: 2.50kHz (green)
Parallel: dV: 6.8dB f: 3.72kHz (gray)


With load (470pF & 200k):
P-90: dV: 3.0dB f: 2.13kHz (black)
Rail: dV: 2.4dB f: 2.06kHz (red)
Series: dV: 1.1dB f: 1.19kHz (green)
Parallel: dV: 3.6dB f: 2.61kHz (gray)







Seymour Duncan P-Rails Neck
- P-90 DC Resistance: 7.19K ohms
- P-90 Measured L: 5.052H
- P-90 Calculated C: 230pF (240 - 10)
- P-90 Gauss: 500G

- Rail DC Resistance: 5.39K ohms
- Rail Measured L: 2.757H
- Rail Calculated C: 518pF (528 - 10)
- Rail Gauss: 360G

Without load:
P-90: dV: 9.3dB f: 4.57kHz (black)
Rail: dV: 4.8dB f: 4.17kHz (red)
Series: dV: 7.2dB f: 3.21kHz (green)
Parallel: dV: 6.3dB f: 4.89kHz (gray)


With load (470pF & 200k):
P-90: dV: 3.3dB f: 2.38kHz (black)
Rail: dV: 2.7dB f: 2.86kHz (red)
Series: dV: 1.5dB f: 1.58kHz (green)
Parallel: dV: 3.8dB f: 3.36kHz (gray)





RLC characteristics...

I just recently evaluated some actual P-90's guitarnuts2.proboards.com/thread/7893/epiphone-90-soapbar-analysis-review . The P-Rails' P-90 coils have a lower inductance that most P-90 measurements I've seen, 6.25 henries in the bridge and 5.1 henries in the bridge. The P-90's I have measured 7.3 henries, and others for which I've seen the values also measure above 7 henries. Tonerider's Vitage 90's show lower inductances of 6.6 and 6.8 henries. The higher the inductance, the lower the resonant peak, the darker the pickup. The loaded peaks of the P-Rails' P-90 is 2.13kHz in the bridge and 2.38khz in the neck, compared to 2.03kHz and 1.92kHz for the real P-90's. The P-Rails' P-90's are therefore a bit darker, and so it appears that P-Rails are wound on the vintage side of vintage, for a P-90. Still nowhere near as bright as Strat, or even most vintage style PAF's, but bright for a P-90.

As for capacitance, the P-90 coils show about 230pF, which is about what I measured in the Epiphone P-90's. The DC resistance is almost similar. I assumed both use 42 AWG wire.

There is a strangely high capacitance in the rail coils, over 600pF in the bridge and 500pF in the neck. It's hard to say why, but it could be the rail itself, the proximity to the larger P-90 coil, or a tight wind with fine gauge wire. It's hard to say what gauge of wire is used, because the coils are so small. I can imagine that in order to get a DC resistance of 8k on that bridge rail, they might have used 44AWG.

All four coils have a clear insulation coat, showing a bright copper color.

Interestingly, the P-90 of the bridge and neck are not all that different in terms of inductance or DC resistance, but the rails coils are very different. The bridge rail has a DC resistance of 8k ohms, and and inductance of 4.5H, while the neck rail has a DC resistance of 5.4k ohms and an inductance of 2.8H. According to the bode plots, the bridge rail and P-90 even have almost identical loaded resonant peaks. The inductance is a lot lower, but that high capacitance brings the resonant frequency way down. To my ear, the bridge rail and P-90 do have a pretty similar treble response, though the voicing is quite a bit different since the two coils sit under different locations along the guitar string. The rail coil is also quite a bit quieter.

A rail also differs from a discrete pole piece in that a pole piece causes induction via perpendicular string movement, where as a rail does not, though this is a very subtle difference. Theoretically, the thinner rail also picks up higher frequencies than a wider screw or slug, but these higher frequencies are likely beyond the range of the guitar speaker's ability to reproduce acoustically. More info about that here www.till.com/articles/PickupResponse/index.html


Magnets...

Regarding magnetic strength, I measured around 500 gauss in the screws of the P-Rails, but barely 200 gauss in the Epiphone P-90s. I suspect that this is due to the P-Rails having AlNiCo 5 bars, while the Epiphone likely uses weaker AlNiCo 2 bars. According to Wikipedia, Gibson switched to AlNiCo 5 bars in 1957 en.wikipedia.org/wiki/P-90 , and according to the Gibson Store, current production P-90's feature AlNiCo 5 bars as well store.gibson.com/p-90-single-coil-with-soapbar-cover/ (On a side note, what the heck does "Output: 9.1" mean?)

The rail shares one of the bar magnets of the P-90. It's sort of a clever arrangement that naturally allows the two coils to mutually humbuck in series or parallel. It's fortunate that the spacing was such that all this could happen with mostly off-the shelf parts.

Counter intuitively, it appears that the rail side actually produces a wider flux dispersion across the string than the screws:







Construction...

The baseplate appears to be nickel silver, and it looks a lot like a PAF base plate with only one side wall. There are two bar magnets and a spacer, similar to a real P-90, though without the slanted angle on the magnets.

The P-90 bobbin is held in with two large brass looking flat heads. There is some wax in there, and what appears to be some glue holding the bobbins together, and the plastic top to the bobbins.





Overall impression...

I definitely prefer the clean tone of these slightly brighter pickups with the AlNiCo 5 bars than the hotter Epiphone P-90 with the apparent AlNiCo 2 bars. The blade and the parallel mode have nice, for Fender-like clean, though with a voicing that is unlike anything you'd hear from a Strat or Tele. For high gain, the series mode really turns this things into fireballs. It's an extremely versatile pickup, mostly excelling in clean tones.

The P-90 coils really are P-90 like, that's no joke. They compare closely to my Epiphone P-90s in terms of inductance, capacitance and resistance.

I'm not crazy about the looks. I wish they had painted the rail cream colored for the cream tops, in order to hide the rail a bit. A P-90 is possibly the most vintage of all pickups, best it stay looking vintage, IMO. They say rails have scared away a lot of guitarists due to their looks alone.




Pics:

[JFrankParnell]

Do these work well, together, if you have the neck on p90 and the bridge on humbucker? I'm not asking about having them both on, but separately. Lets say I have it on neck p90, playing some rhythm, and then for a lead, i want to switch to bridge humbucker. Will there be a large mismatch in tone, where you would have to adjust the tone knob or amp, to get the right balance, between the two?

Also, how are these, (humbucking bridge) compared to a lil'59? I think I've read that they are just a little hotter than a 59?

[antigua]

Mar 20, 2017 13:49:47 GMT -5 JFrankParnell said:

Do these work well, together, if you have the neck on p90 and the bridge on humbucker? I'm not asking about having them both on, but separately. Lets say I have it on neck p90, playing some rhythm, and then for a lead, i want to switch to bridge humbucker. Will there be a large mismatch in tone, where you would have to adjust the tone knob or amp, to get the right balance, between the two?

Also, how are these, (humbucking bridge) compared to a lil'59? I think I've read that they are just a little hotter than a 59?

The volume jump from P-90 mode to series humbucker fairly small. I just plugged the guitar in and tried it out. I'd guess about 4dB based on this tool www.audiocheck.net/blindtests_level.php?lvl=6  

Switching from the rail alone to either the P-90 or series humbucker is a much bigger difference, easily in excess of 6dB.

A Little '59 is right in between the P-90 and series mode, tone-wise. It's neither as clear as the P-90, nor as hot as P-Rails series mode.

Since we're on the subject of P-Rails, a fun fact is that the commenter in this thread guitarnuts2.proboards.com/thread/7907/string-pickup-sample , Frank Falbo, apparently played a big role in the design process of the P-Rails, while working for Seymour Duncan. 

[frankfalbo]

Mar 20, 2017 17:30:53 GMT -5 antigua said:

Mar 20, 2017 13:49:47 GMT -5 JFrankParnell said:

Do these work well, together, if you have the neck on p90 and the bridge on humbucker? I'm not asking about having them both on, but separately. Lets say I have it on neck p90, playing some rhythm, and then for a lead, i want to switch to bridge humbucker. Will there be a large mismatch in tone, where you would have to adjust the tone knob or amp, to get the right balance, between the two?

Since we're on the subject of P-Rails, a fun fact is that the commenter in this thread guitarnuts2.proboards.com/thread/7907/string-pickup-sample , Frank Falbo, apparently played a big role in the design process of the P-Rails, while working for Seymour Duncan. 

If you do, you'll see what a warm, loving welcome I've received in that thread from various individuals. I'm not sure if that's why he directed you there, I'm not sure what it has to do with this thread but...enjoy.  

As has been said, it's a big, loud humbucker but not off the charts. So the bridge humbucker does balance as you'd expect a healthy humbucker to do with a neck P90. Sometimes people think the neck humbucker is a little loud, I like it for thicker Santana type solos but I also like it in parallel. It's closer in output to the P90. I think if that's your main concern, you'll be happy with them. The rails are a big jump down, but not much different than if you'd set the guitar down, and picked up a vintage Strat style guitar.  

[antigua]

...

[frankfalbo]

Hey… Did you get the bridge P90 mixed up with the bridge rail?  It's the bridge P90 that is ~10k and the rail that is ~8K. 

[antigua]

Alright, since you're here now, no need to refer to that other thread. 

I know Kevin Beller www.seymourduncan.com/company/get-to-know-us/kevin-beller has held the title of "V. P. of Engineering" for a long time, and is called  "the designer" on their newly designed site. Did you cooperate with him in designing the P-Rails, or was it more your own project? 

[antigua]

Mar 20, 2017 20:16:39 GMT -5 frankfalbo said:

Hey… Did you get the bridge P90 mixed up with the bridge rail?  It's the bridge P90 that is ~10k and the rail that is ~8K. 

Mmm, you're correct. 

[frankfalbo]

Mar 20, 2017 20:25:17 GMT -5 antigua said:

Alright, since you're here now, no need to refer to that other thread. 

I know Kevin Beller www.seymourduncan.com/company/get-to-know-us/kevin-beller has held the title of "V. P. of Engineering" for a long time, and is called  "the designer" on their newly designed site. Did you cooperate with him in designing the P-Rails, or was it more your own project? 

As you must know from reading my posts over the years, I have to be very deliberate about what I say regarding  some of the work I do. Therefore I limit what I say on the subject to things that I have said in the past and placed into public domain while I worked there, as well as anything that predates the relationship. 

I invented the P-Rails in Illinois, began talking to Seymour Duncan about licensing it to them, during which their New Products guy left the company. I was hired to fill that position, and within about a year we released the P-Rails. The web page you linked uses apropos nicknames of sorts, but yes I am the designer of the P-Rails. I would also ask that, in total confidence, you would inform me if you've heard any different. That said, everything is a team effort. I did a lot of my own fab work for the prototypes, but aside from the ones I made in Illinois prior to the relationship, MJ wound the prototypes, Engineering drew the parts in Solidworks, Ops sourced the parts, etc. so I don't want to be misconstrued as overstating either. I hope that answers the question because there may not be much else I can add. 

[antigua]

Mar 20, 2017 21:03:15 GMT -5 frankfalbo said:

Mar 20, 2017 20:25:17 GMT -5 antigua said:

Alright, since you're here now, no need to refer to that other thread. 

I know Kevin Beller www.seymourduncan.com/company/get-to-know-us/kevin-beller has held the title of "V. P. of Engineering" for a long time, and is called  "the designer" on their newly designed site. Did you cooperate with him in designing the P-Rails, or was it more your own project? 

As you must know from reading my posts over the years, I have to be very deliberate about what I say regarding  some of the work I do. Therefore I limit what I say on the subject to things that I have said in the past and placed into public domain while I worked there, as well as anything that predates the relationship. 

I invented the P-Rails in Illinois, began talking to Seymour Duncan about licensing it to them, during which their New Products guy left the company. I was hired to fill that position, and within about a year we released the P-Rails. The web page you linked uses apropos nicknames of sorts, but yes I am the designer of the P-Rails. I would also ask that, in total confidence, you would inform me if you've heard any different. That said, everything is a team effort. I did a lot of my own fab work for the prototypes, but aside from the ones I made in Illinois prior to the relationship, MJ wound the prototypes, Engineering drew the parts in Solidworks, Ops sourced the parts, etc. so I don't want to be misconstrued as overstating either. I hope that answers the question because there may not be much else I can add. 

That's a great answer, thanks for sharing. I'd never heard different, there was just some ambiguity as to who played what role. Ultimately I'd love to know who thought up every pickup, but that's a lot to ask for. Surely there is something of a story behind every pickup, some stories richer than others, to be sure. I wish their was an equivalent to movie credits, where each person's contribution was explicitly stated. It helps people get a better understanding of who the players are, gets us more personally invested. 

Your story sounds particularly intriguing. A lot of guitarists probably have a dream pickup in mind, but few have the initiative or people skills to walk into the current industry leader, work some magic and see that creation come to life a year later, with the industry leader's name emblazoned over the top.

[trantalocked]

I was using your pickup data graph tool and found it strange that the loaded Rail bridge resonant peak doesn't look close to a typical loaded Strat bridge 4kHz resonant peak, even though the Rail is advertised as a Strat-like pickup. It looks far closer to the P90 it sits next to, but maybe I'm missing something?

[gckelloch]

Feb 19, 2023 4:39:19 GMT -5 trantalocked said:

I was using your pickup data graph tool and found it strange that the loaded Rail bridge resonant peak doesn't look close to a typical loaded Strat bridge 4kHz resonant peak, even though the Rail is advertised as a Strat-like pickup. It looks far closer to the P90 it sits next to, but maybe I'm missing something?

The neck rail inductance is in an average Strat pickup range, but the internal Capacitance is apparently nearly 4x higher than average. That's why the peak is so low. Hate to be a broken record and use the example I often refer to, but some Wilde pickups have thinner than 44AWG wire and the internal C is even lower than an average hand wound Strat pickup with 42AWG wire. Makes me think SD is winding coils so tight that the insulation is stretching around the bobbin edges. What else could it be?

[antigua]

The biggest reason the rail coil capacitance is high is probably because the coil is tall and thin. I've learned since that flat coils, like a Jazz Master or P-Bass coils, have a lower capacitance, because the electrical gradient from the coil start to finish is spread over a wider area, where as with a tall thin coil, coil start and finish are close, and in the case of the rail, maybe only a millimeter of coil thickness. The farther apart the two sides of the circuit are, the lower the parasitic capacitance will be in between. 

The Little '59 and Duckbucker measurements also showed high capacitance guitarnuts2.proboards.com/thread/7995/seymour-duncan-duckbucker-analysis-review " rel="nofollow" target="_blank">guitarnuts2.proboards.com/thread/7905/seymour-duncan-little-analysis-review  guitarnuts2.proboards.com/thread/7995/seymour-duncan-duckbucker-analysis-review  , though not as high as 600pF. The finer wire like 43 and 44AWG used in the rails and mini pickups usually shows a higher capacitance. I'd guess that thinner magnet wire also has a thinner insulation layer in order to keep the overall thickness of the wire smaller. A JB has about double the capacitance of a regular PAF, even though the coil geometry is about the same, which suggests the wire itself is to blame.  

If the coil start is "hot" and the metal rail is grounded, that will also make the capacitance higher than if the coil end is "hot", since that puts the hot and ground side of the circuit side by side, the inside of the coil and the rail it's wrapped around. For the blade to be counted towards the capacitance, the shielding would have to be connected to the alligator clips of the LCR meter or testing device, but I don't remember if I had the shielding wire included when I measured it, those are details I should have made note of at the time. I should pull the P-Rails out of the drawer and check. 

[gckelloch]

Feb 19, 2023 16:26:34 GMT -5 antigua said:

The biggest reason the rail coil capacitance is high is probably because the coil is tall and thin. I've learned since that flat coils, like a Jazz Master or P-Bass coils, have a lower capacitance, because the electrical gradient from the coil start to finish is spread over a wider area, where as with a tall thin coil, coil start and finish are close, and in the case of the rail, maybe only a millimeter of coil thickness. The farther apart the two sides of the circuit are, the lower the parasitic capacitance will be in between. 

The Little '59 and Duckbucker measurements also showed high capacitance guitarnuts2.proboards.com/thread/7995/seymour-duncan-duckbucker-analysis-review " rel="nofollow" target="_blank">guitarnuts2.proboards.com/thread/7905/seymour-duncan-little-analysis-review  guitarnuts2.proboards.com/thread/7995/seymour-duncan-duckbucker-analysis-review  , though not as high as 600pF. The finer wire like 43 and 44AWG used in the rails and mini pickups usually shows a higher capacitance. I'd guess that thinner magnet wire also has a thinner insulation layer in order to keep the overall thickness of the wire smaller. A JB has about double the capacitance of a regular PAF, even though the coil geometry is about the same, which suggests the wire itself is to blame.  

If the coil start is "hot" and the metal rail is grounded, that will also make the capacitance higher than if the coil end is "hot", since that puts the hot and ground side of the circuit side by side, the inside of the coil and the rail it's wrapped around. For the blade to be counted towards the capacitance, the shielding would have to be connected to the alligator clips of the LCR meter or testing device, but I don't remember if I had the shielding wire included when I measured it, those are details I should have made note of at the time. I should pull the P-Rails out of the drawer and check. 

Makes sense, but even the P90 C is a pretty high. If the winding machines are calibrated for tension when stationary, it doesn't take into account the tension increase when the wire slaps the back side of the bobbin end as it comes around. That could be enough to stretch out or mash the insulation without breaking the wire. The tension increase would likely increase with winding speed, and the heat from increased friction can soften the insulation. Again, Bill told me that's why he desiqned his machines to continually adjust tension as they wind.

A useful improvement for the P-rails (or any wide pickup design) would be two height adjustment screws on one side to set the P90 and Rail side to taste. Even 0.5mm up on one side and down on the other would make a big difference in output balance if the pickups are a standard ~2mm close to the high E string. Why every pickup maker doesn't do that now escapes me.

[antigua]

Color me skeptical that the insulation stretches along, but I could believe both the copper wire and the insulation mutually stretch under higher tension, I'd go so far as to say, how could they not?

I don't think there would ever be a revised P-Rails because I wouldn't be surprised if they never even made back the investment on the custom hardware that pickup required, but I was surprised that they didn't make high or low inductance, or ceramic magnet variants, as they do with a lot of their PAF type pickups.  

[gckelloch]

Feb 19, 2023 20:38:26 GMT -5 antigua said:

Color me skeptical that the insulation stretches along, but I could believe both the copper wire and the insulation mutually stretch under higher tension, I'd go so far as to say, how could they not?

I don't think there would ever be a revised P-Rails because I wouldn't be surprised if they never even made back the investment on the custom hardware that pickup required, but I was surprised that they didn't make high or low inductance, or ceramic magnet variants, as they do with a lot of their PAF type pickups.  

Whatever is pulling on the wire is actually pulling on the insulation more. The insulation on the outer edge of the wire at the bobbin ends would be stretched most, and the portion on the inside edge possibly squashed thin from friction heat. The hotter portion of insulation would be more likely to stretch than the cooler part, while the Cu wire might stretch more uniformly, since it would take much higher heat to significantly increase malleability. That would increase resistance a bit, but not have much affect on tone at all.