Epiphone P-90 Soapbar, Analysis and Review

[antigua]

This is my first P-90 set, so I don't have any others to contrast against, although what I really wanted to do was see how they compare to PAF type pickups, since the PAF is more or less the evolution of a P-90, and they appear in most of the same Gibson guitars.

Specs:

Epiphone P-90 Bridge "Lead"
- DC Resistance: 8.11K ohms
- Measured L: 7.303H
- Calculated C: 168pF (178 - 10)


Epiphone P-90 Neck "Rhy"
- DC Resistance: 8.08K ohms
- Measured L: 7.395H
- Calculated C: 249pF (259 - 10)


Bridge unloaded: dV: 6.2dB f: 4.41kHz (black)
Bridge loaded (200k & 470pF): dV: 1.0dB f: 2.03kHz (red)
Neck unloaded: dV: 5.9dB f: 3.64kHz (green)
Neck loaded (200k & 470pF): dV: 1.2dB f: 1.92kHz (gray)





It appears that these have brass base plates. I'm not sure whether or not that's standard to P-90, or just cost conscious Epiphone variants. I'm very surprised by the low Q factor, consider the lack of a metal cover. It could owe to a combination of the the base plate, bar magnets and screws, all broadly intersecting the magnetic path of a very wide, flat coil.

The overall response curve is very similar to a PAF, though the loaded resonant peak is lower, measuring 1.92kHz for the neck and 2.03kHz for the bridge. Most "average" PAFs have peaks closer to 2.5kHz. The only PAF formatted pickup I've measured with a peak as low as these P-90s is the Seymour Duncan SH-5 Custom guitarnuts2.proboards.com/thread/7763/seymour-duncan-custom-analysis-review Spec wise, it's almost identical to a Seymour Duncan SSL-4 guitarnuts2.proboards.com/thread/7739/seymour-duncan-ssl-analysis-review with an inductance that is just slightly lower at 7.1H, and a loaded peak of 2.08kHz.

Usually the bridge should have a higher inductance and lower peak, but in this case the reverse is true. It looks like these pickups are supposed to be substantially similar by design, and that the aberration probably results from manufacturing tolerances.

My hunch is that a P-90 is, tonewise, essentially what is thought of as a "hot PAF", and that this is one reason why rock musicians like them so much for a good "growl" tone. To my ears they have a very dark clean tone, again, like a hot PAF. In the 1940's, the P-90 was one of the only games in town. It would have been a luxury at the time to be picky choosey about the exact resonant peak of a pickup. It is decidedly a hot pickup by modern standards, but is still considered acceptable as a clean pickup for historical reasons. People are familiar with the dark, jazzy clean tone it produces. It's otherwise unheard of to think of a 7 henry single coil as having a good "clean" tone. Few people would say that an SSL-4 has a good clean tone, but P-90s are classics, long predating rock music and high gain. It just goes to show how perception and bias informs people's opinions about what they're hearing.

[pj]

Not really having posted much before I wanted to start by thanking you for the efforts and lengths you go to, you've kept me rooted at every turn and I think you' approach is fantastic. Long may you continue.

As a long time P90 fanatic I agree you have hit a nail on the head regards peoples perception of a pickup. I think this is worsened by a lack of understanding of resonance and manipulation of eq. I play in the grey area between clean and dirty generally but it rarely sounds that dirty as I make sure the lows are kept in check. There's an awful lot of gear that would achieve peoples ideal tone were they tone learn to use it, but as you've stated they are primed to get on the pickup merry go round. Something we've all done.

What I was wondering reading this analysis is how much effect the epiphone cabling was having, similar to your study of the 57ch pickup?

A friend of mine has gone to great lengths rolling magnets with epiphone pickups and Ive many times suggested he get some plastic rather than chrome covers on his dog ears and replace the cabling so that he might hear some of what (if anything) is going on. Sadly it just doesn't have the same cognitive weight as "swapping the magnet".

All the best and thanks again

[antigua]

Oct 6, 2017 5:54:35 GMT -5 pj said:

Not really having posted much before I wanted to start by thanking you for the efforts and lengths you go to, you've kept me rooted at every turn and I think you' approach is fantastic. Long may you continue.

As a long time P90 fanatic I agree you have hit a nail on the head regards peoples perception of a pickup. I think this is worsened by a lack of understanding of resonance and manipulation of eq. I play in the grey area between clean and dirty generally but it rarely sounds that dirty as I make sure the lows are kept in check. There's an awful lot of gear that would achieve peoples ideal tone were they tone learn to use it, but as you've stated they are primed to get on the pickup merry go round. Something we've all done.

What I was wondering reading this analysis is how much effect the epiphone cabling was having, similar to your study of the 57ch pickup?

A friend of mine has gone to great lengths rolling magnets with epiphone pickups and Ive many times suggested he get some plastic rather than chrome covers on his dog ears and replace the cabling so that he might hear some of what (if anything) is going on. Sadly it just doesn't have the same cognitive weight as "swapping the magnet".

All the best and thanks again

I didn't wire a "treble tone knob" (where you variably put the signal in series with a capacitor) with P-90's, but I've done it with SSL-4's and SSL-5's, and it really does clean it up by pulling back the lower frequencies. There's a guy on YouTube who actually refers to this type of tone controls as a "clean knob"  . I imagine it would do the same for P-90s. 

Regarding the cable, all the P-90's I've come across have the braided wire, I found the capacitance to be 75pF per foot guitarnuts2.proboards.com/thread/7725/capacitive-coupling-various-guitar-parts which is about twice what it would be for one foot of guitar cable. The only interesting distinction is that when you turn down the volume, the guitar cable capacitance gets cut off, but the hookup wire's capacitance remains in parallel with the pickup to full effect.

There's one internet forum in particular that seems to be drunk on magnet swapping. Magnets are just fun to play with in general. They stick to things! If his P-90 has a chrome cover, the issue could be that it's a brass or stamped steel cover, instead of nickel silver.  As noted above, even the plastic cover P-90 has a low Q factor, probably due to the use of two AlNiCo bars. Your friend might like the effect of ceramic magnets, or getting an "underwound" P-90 from Lollar. I don't love P-90's, I just want some around to cover artists who use them, like Neil Young, and I think in order to genuinely like them, I'd want under-wound P-90s that get closer to 2.5kHz to 3kHz loaded. In general if the P-90 has a 8k to 9k resistance, it's going to be dark, so an underwound P-90 would probably have to be wound to 7.5K or less.

[pj]

Thanks for your response.

I have wired a bass cut on humbucker guitars previously after being inspired by a g&l I had, but I found that unless you made it very severe, backing the volume down reduced the parallel load on the volume pot and moved the high pass filter point formed with the bass cut back, somewhat negating the effect. I some time later noticed the old hagstroms had done it post volume getting round this issue, but I do use a variety of different input impedance effects and it drove me mad with my compulsion to keep the harmonic content consistent.

I just tend to carry a simple preamp I built around that means if I need to use a provided backline I can tweak things without much stress.

Ive got Duncan antiquity p90s in my main Les Paul. I would never ever justify the usual price, but they came unused in a deal and I couldn't resist trying them as the guitar was just too dull as was. The Gibson p90s in the guitar already were severely lacking any real perceivable peak or clarity, as Im not a fan of the fatter darker p90 tones that are very popular. I have a pair of p94s in my standard (thats too heavy on my chest since I got a defib implant) and they are pretty underwound as are these antiquities, compared with what some may aim for this is. I suspect the Gibson ones were wound under serious tension as the coil is very tight and lean and they are lacking top, rather than having a huge low resonance or inductance etc. I must buy another LCR meter and find out some specifics.

Noted the comment on braided hook up, his are a standard plastic coated lead. He's seriously anti anything ceramic, its a 'vintage' mentality seemingly. Personally I think there’s a place for that as you say. Interestingly he has a pair of P Rails in a strat and he loves those leaner p90s as do I.

I remember reading a Bill Lawrence comment where he referred to the p90 as a pickup that was, by design, more resistant to eddy currents. I always thought it might be due to the unusual 'magnetic circuit'. I've not thought about that in some time but then considering the fact that the alnico magnets are in such close proximity to the coil, you have a point. Perhaps my memory is skewed there.

I still have the Gibson p90s sitting around. I should move them on. In fact, seeing how competitive the market is now I'm sure I could probably shift the antiquities too and have some even more satisfying tones for a fraction of the cost.

Thanks again for taking the time to respond.

[antigua]

Oct 6, 2017 12:03:23 GMT -5 pj said:

Thanks for your response.

I have wired a bass cut on humbucker guitars previously after being inspired by a g&l I had, but I found that unless you made it very severe, backing the volume down reduced the parallel load on the volume pot and moved the high pass filter point formed with the bass cut back, somewhat negating the effect. I some time later noticed the old hagstroms had done it post volume getting round this issue, but I do use a variety of different input impedance effects and it drove me mad with my compulsion to keep the harmonic content consistent.

I just tend to carry a simple preamp I built around that means if I need to use a provided backline I can tweak things without much stress.

Ive got Duncan antiquity p90s in my main Les Paul. I would never ever justify the usual price, but they came unused in a deal and I couldn't resist trying them as the guitar was just too dull as was. The Gibson p90s in the guitar already were severely lacking any real perceivable peak or clarity, as Im not a fan of the fatter darker p90 tones that are very popular. I have a pair of p94s in my standard (thats too heavy on my chest since I got a defib implant) and they are pretty underwound as are these antiquities, compared with what some may aim for this is. I suspect the Gibson ones were wound under serious tension as the coil is very tight and lean and they are lacking top, rather than having a huge low resonance or inductance etc. I must buy another LCR meter and find out some specifics.

Noted the comment on braided hook up, his are a standard plastic coated lead. He's seriously anti anything ceramic, its a 'vintage' mentality seemingly. Personally I think there’s a place for that as you say. Interestingly he has a pair of P Rails in a strat and he loves those leaner p90s as do I.

I remember reading a Bill Lawrence comment where he referred to the p90 as a pickup that was, by design, more resistant to eddy currents. I always thought it might be due to the unusual 'magnetic circuit'. I've not thought about that in some time but then considering the fact that the alnico magnets are in such close proximity to the coil, you have a point. Perhaps my memory is skewed there.

I still have the Gibson p90s sitting around. I should move them on. In fact, seeing how competitive the market is now I'm sure I could probably shift the antiquities too and have some even more satisfying tones for a fraction of the cost.

Thanks again for taking the time to respond.

That's an interesting observation regarding the tension. If you can ever collect and DC resistance / inductance values from your P-90's on hand, that would be great. Just remember that  when testing the inductance of pickups with steel screws or slugs, you need a very low test frequency. A lot of cheaper LCR meters only seem to test at 1kHz, while fancier models offer lower test frequencies. The Extech meter tha is popular with pickup testers allows testing at 120Hz, which is acceptable. 1 kHz induces eddy current resistance, and give a false reading. You can see this first hand if you test and Fender AlNiCo pickup at different test frequencies, then try the same with a Gibson pickup. The Fender pickups are consistent at various frequencies, but the Gibson's will give higher inductance values at higher test frequencies.

What I like to do is establish ranges and trends. For example, as a trend, "hand wound" Fender style pickups tend to have a lower tension and a lower capacitance, while Fender's own machine wound pickups are quite tight have show, on average, about 25% more capacitance, so if a pickups is wound to 6K ohms, it's more likely to result in a lower peak than if a guy in his garage winds to 6K. Seymour Duncan's SSL-1 are in fact wound by machine, but show a lower tension associated with hand winding, so the picture isn't so simple, but as more data is collected, the picture becomes more clear.

I don't see how a P-90 is resistance to eddy currents. That's pretty much not true, and I'd be surprised if Bill Lawrence indeed thought otherwise, as he seemed to have a good grasp of that sort of thing. The steel pole pieces cause a lot of eddy currents, and you can prove it by watching the Q factor skyrocket when the screws are removed.