'50s P90 magnets

kiwi blue

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I've been working out what specs I want for a P90 neck pickup. When I researched vintage P90s from the 50s the received wisdom seems to be that they mostly used A3 magnets then switched to A5 from the the late 50s and through the 60s.

Today I came across this:


According to the article, a physicist and guitarist named Roland Kastl did some scientific testing on vintage P90s and humbuckers and compared the results to modern A2, A3, A4, and A5 bar magnets. He found the measurable characteristics were consistently closest to modern A4.

It seems the idea that Gibson used mostly A3 at that time is based on interviews and not testing of actual pickups. Is anyone aware of any other actual testing that might be relevant here?

Here are some quotes from the article:

************************

The physicist and guitarist Roland Kastl, who lives in Munich, had informed me several years ago that he had carried out extensive research on a large number of dated Gibson magnets from the 1950s and 1960s. The dates resulted from the construction years of the guitars, which were chosen at random. This means that not only the magnets of one type of instrument were examined, but magnets of different guitar models.

The longer block magnets, which Roland Kastl examined, were from P-90 pickups and PAFs and covered the years 1956 to 1960.
I was able to extend this time window by my own measurements, so that the examined magnets cover the period between 1952 and 1960. Magnetic properties as well as measurable effects on the electrical pickup parameters were examined in comparison with reference samples of today's AlNiCo types of the alloys AlNiCo II, III, IV and V.

With the older, long magnets, the result was astonishing in two respects: On the one hand, all original magnets behaved in the same way, on the other hand, there was no correspondence with AlNiCo II, III or V, but a clear similarity to today's AlNiCo IV samples.

***

It was obvious to formulate a thesis, supported by measurements and sound tests but deviating from the common opinion, that Gibson used at least predominantly, if not exclusively an AlNiCo IV alloy for their P-90 and humbucker magnets in the years between 1952 and 1960 and to have this thesis verified by further investigations.

This was followed by various material analysis laboratory tests (permagraph, spark erosion spectroscopy, mass spectroscopy, X-ray fluorescence analysis), which confirmed Roland Kastl's assessment and allowed the exact chemical composition of the magnets to be determined. And indeed, all long magnets from the period under investigation were without exception a variant of AlNiCo IV that is no longer produced today.

***

AlNiCo III, which has come into fashion in recent years for seemingly historical reasons, could not be detected in the older magnets of the 1950s or in the shorter magnets of the 1960s.

***

In addition to the extensive analyses, there are other indications that Gibson used AlNiCo IV magnets predominantly, if not exclusively, in the period from the mid to late 1950s and also in the early 1960s. Tom Holmes tells in an interview with the magazine ToneQuest Report that he was able to look at old Gibson order lists from the 1950s at magnet manufacturer Thomas & Skinner, which prove that Gibson ordered AlNiCo IV block magnets at that time.

Also A. R. Duchossoir writes already in 1981 in his book “Gibson Electrics" about the introduction of the P-90 pickup in 1946:
“This new pick-up had two flat rectangular Alnico (II or IV) type magnets. . . “ This information is particularly interesting because Duchossoir had access to lists of material and was able to conduct many interviews with Gibson employees - and this at a time (late 1970s) when there were still many contemporary witnesses and archive material available.
 

Rob DiStefano

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Magnet Gauss rate and their size/shape are what matters most. There is no direct sound or tone in magnets - it's their magnetic strength that will determine signal output strength. Magnets in passive pickups are the "fuel" that power the strings. An A5 rod magnet will have about double the Gauss rate/strength of a same size A3 rod magnet. The stronger the strings are magnetized, the greater the signal created, the greater the resulting output.


Gibson ES125 and ES150 1946 guitars all appear to feature rod magnet pickups that have the footprint and size of current P90s. I have no clue what those pickups were called, nor if in that year those were replaced with the common P90 build most are familiar with (bar mags, screw poles).

9.png

es125c.png

es125b.png
 
Last edited:

hamerfan

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I own an original 52 which was analyzed, because it was rewound. The pre PAF magnets were indeed A3 and had a different size than PAF magnets. They were rough cast as one long bar and then cut in two pieces.
So, first of all you have to decided which way to go: pre or post PAF
 

takauya

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In addition to the extensive analyses, there are other indications that Gibson used AlNiCo IV magnets predominantly, if not exclusively, in the period from the mid to late 1950s and also in the early 1960s.

This alone sounds like BS.
 

hotcoffeenochill

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My buddy has orig 56 gold top. Tad more upper mid than most. Gibson current p90 line and sd antiquities sound darn close.
The P90 that came stock on my 2019 SG Junior is the best sounding P90 I’ve played (granted I have never played a 56 gold top). But I regularly preach modern Gibbo P90s to anyone who will listen.
 

Antoon

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Magnet Gauss rate and their size/shape are what matters most. There is no direct sound or tone in magnets - it's their magnetic strength that will determine signal output strength. Magnets in passive pickups are the "fuel" that power the strings. An A5 rod magnet will have about double the Gauss rate/strength of a same size A3 rod magnet. The stronger the strings are magnetized, the greater the signal created, the greater the resulting output.


Gibson ES125 and ES150 1946 guitars all appear to feature rod magnet pickups that have the footprint and size of current P90s. I have no clue what those pickups were called, nor if in that year those were replaced with the common P90 build most are familiar with (bar mags, screw poles).

View attachment 1031542
View attachment 1031544
View attachment 1031547
So you are saying a ceramic Magnet would sound the same as an alnico magnet as long as the magnetic strength is equal?
 

Swirling Snow

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So you are saying a ceramic Magnet would sound the same as an alnico magnet as long as the magnetic strength is equal?
No, he said they'd have the same output if the magnetic strength was equal. To get the same tone, I think you need the shape of the magnetic field to be the same.
 

Swirling Snow

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I said magnetic strength.
My point was, you said "sound" which is a very generic noun. It's also a verb, as in, "Do these two things sound the same?" Sound as a thing has several properties, including loudness, pitch, and overtones. I used the word "tone" instead of "sound" to specify what I meant was just the overtones.

I hope this helps.
 

kiwi blue

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I own an original 52 which was analyzed, because it was rewound. The pre PAF magnets were indeed A3 and had a different size than PAF magnets. They were rough cast as one long bar and then cut in two pieces.
So, first of all you have to decided which way to go: pre or post PAF

Thank you Hamferfan. From memory, the articles I saw that said the magnets were A3 didn't cite any scientific analysis or order book evidence. I was wondering if they were all just articles quoting other articles, the internet feeding off itself. So now we have some hard evidence.
 

monkeybanana

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Magnet Gauss rate and their size/shape are what matters most. There is no direct sound or tone in magnets - it's their magnetic strength that will determine signal output strength. Magnets in passive pickups are the "fuel" that power the strings. An A5 rod magnet will have about double the Gauss rate/strength of a same size A3 rod magnet. The stronger the strings are magnetized, the greater the signal created, the greater the resulting output.


Gibson ES125 and ES150 1946 guitars all appear to feature rod magnet pickups that have the footprint and size of current P90s. I have no clue what those pickups were called, nor if in that year those were replaced with the common P90 build most are familiar with (bar mags, screw poles).

View attachment 1031542
View attachment 1031544
View attachment 1031547
I never knew they made the rod version...

Very cool. I think it's called a Jazz Master ;)
 

hamerfan

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Thank you Hamferfan. From memory, the articles I saw that said the magnets were A3 didn't cite any scientific analysis or order book evidence. I was wondering if they were all just articles quoting other articles, the internet feeding off itself. So now we have some hard evidence.
The winder who rewound my pickup charged and decharged the magnets several times and said that they acted and measured like a modern A3.
 

schmee

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I can only say this: The older P90's I have played were almost always muddier in the neck. But that IS part of that 50's sound I guess. The modern Gibson P90's seem cleaner in the neck but still growl.

But the other thing is that the P90's were special winds for certain guitars back then........ not all the same like many today. I have seen a neck P90 as low as about 6.1k ohms back then. And each of the 3 P90's in a Switchmaster Gibson were designed different impedance.
 

AndrewG

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I've been working out what specs I want for a P90 neck pickup. When I researched vintage P90s from the 50s the received wisdom seems to be that they mostly used A3 magnets then switched to A5 from the the late 50s and through the 60s.

Today I came across this:


According to the article, a physicist and guitarist named Roland Kastl did some scientific testing on vintage P90s and humbuckers and compared the results to modern A2, A3, A4, and A5 bar magnets. He found the measurable characteristics were consistently closest to modern A4.

It seems the idea that Gibson used mostly A3 at that time is based on interviews and not testing of actual pickups. Is anyone aware of any other actual testing that might be relevant here?

Here are some quotes from the article:

************************

The physicist and guitarist Roland Kastl, who lives in Munich, had informed me several years ago that he had carried out extensive research on a large number of dated Gibson magnets from the 1950s and 1960s. The dates resulted from the construction years of the guitars, which were chosen at random. This means that not only the magnets of one type of instrument were examined, but magnets of different guitar models.

The longer block magnets, which Roland Kastl examined, were from P-90 pickups and PAFs and covered the years 1956 to 1960.
I was able to extend this time window by my own measurements, so that the examined magnets cover the period between 1952 and 1960. Magnetic properties as well as measurable effects on the electrical pickup parameters were examined in comparison with reference samples of today's AlNiCo types of the alloys AlNiCo II, III, IV and V.

With the older, long magnets, the result was astonishing in two respects: On the one hand, all original magnets behaved in the same way, on the other hand, there was no correspondence with AlNiCo II, III or V, but a clear similarity to today's AlNiCo IV samples.

***

It was obvious to formulate a thesis, supported by measurements and sound tests but deviating from the common opinion, that Gibson used at least predominantly, if not exclusively an AlNiCo IV alloy for their P-90 and humbucker magnets in the years between 1952 and 1960 and to have this thesis verified by further investigations.

This was followed by various material analysis laboratory tests (permagraph, spark erosion spectroscopy, mass spectroscopy, X-ray fluorescence analysis), which confirmed Roland Kastl's assessment and allowed the exact chemical composition of the magnets to be determined. And indeed, all long magnets from the period under investigation were without exception a variant of AlNiCo IV that is no longer produced today.

***

AlNiCo III, which has come into fashion in recent years for seemingly historical reasons, could not be detected in the older magnets of the 1950s or in the shorter magnets of the 1960s.

***

In addition to the extensive analyses, there are other indications that Gibson used AlNiCo IV magnets predominantly, if not exclusively, in the period from the mid to late 1950s and also in the early 1960s. Tom Holmes tells in an interview with the magazine ToneQuest Report that he was able to look at old Gibson order lists from the 1950s at magnet manufacturer Thomas & Skinner, which prove that Gibson ordered AlNiCo IV block magnets at that time.

Also A. R. Duchossoir writes already in 1981 in his book “Gibson Electrics" about the introduction of the P-90 pickup in 1946:
“This new pick-up had two flat rectangular Alnico (II or IV) type magnets. . . “ This information is particularly interesting because Duchossoir had access to lists of material and was able to conduct many interviews with Gibson employees - and this at a time (late 1970s) when there were still many contemporary witnesses and archive material available.
The only test I find relevant is what my ears tell me! Nothing else matters.
 

kiwi blue

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I need to make a couple of things clear here.

This isn't a best P90 thread. I'm not asking for anyone's help. And I certainly don't need to be told to use my ears FFS. It's also not an opportunity to sell your off-topic pickups.

It's simply a question of historical accuracy. I read article after article telling me one thing but giving no hard evidence and no sources. This is the "received wisdom", the "everyone knows ..." that keeps getting repeated ad infinitum on the Internet. The one article I found with real hard evidence contradicts all that. So what is the evidence for A3? And no I don't care whether you think it matters.
 

63 vibroverb

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I have more experience with PAF's than P90's, so take what I say for what you will. I've tried a bunch of PAF replicas from various winders as well as swapped magnets in many of them. Alnico IV nails that vintage burst sound/texture/tone to my ears. From my understanding, the bulk of Gibson's magnet bars supply were Alnico IV - but they also had III, II, and V in smaller quantities. Workers putting together pickups just grabbed magnets from the bin indiscriminately. Paul Kossoff's burst had A3's, as did the bridge pickup in Duane Allman's cherry burst. BB King's early 355 had A2's (and it sounds like it, to my ears). Majority of those early bursts sound like A4 though.
 

plexi69

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I find this thread very interesting as I am a big fan of the P90’s from the 1950’s. I do feel that there’s a difference in tone and versatility in them that isn’t available in the newer versions. Just curious as to what the procedure is too test what type of magnet one has? Thanks
 




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