"Real" PAFs

Question: What is a real PAF? You hear it all the time - "PAF sound"... but what does that mean?
Answer: "NOT HOT"

PAF pickups, to traditionalists, do not mean hot, or high output. PAFs are usually medium output on a humbucker range of output. Some of them were wound hotter than others, but what's preferred by players can be all over the board. Talking resistance, PAFs ranged from 7.1k to 8.4k but sometimes a bit in between. Ideally, you'd want the lower k in the neck and the hotter one in the bridge, but they weren't always installed that way.
Both pickups had the same 49.22mm string spacing. Gibson used A2, A3, A4, and A5 alnico magnets in PAFs, but Seth Lover remarked they mostly bought A4s.

A "traditionalist" guitar fanatic would want a PAF that has most to all of the genetic makeup of an original. Others don't care, and just want the sound. There is nothing wrong with either approach or attitude. There is a difference in price, as the original spec is a bit more expensive. It is possible to use poly-wire, plastic bobbins and spacers with an A5 to get a PAF sound. 

There are some who believe that having identical materials (examples below) underneath gets you closer or at least gives you that mental "mojo" that what you have is original spec. We can do either:

Most characteristics of an original PAF 1957-1964-ish and (changes made later)
  • Machine guided wound in Kalamazoo Michigan, USA (later changed to Nashville, TN)
  • Enamel-coated wire 42 awg (later changed to poly-coated wire)
  • Butyrate bobbins (later changed to PVC or similar plastic)
  • Maple Spacer (later changed to plastic)
  • Long legged baseplates
  • A2, A3 or A4 Alnico magnets whatever bulk was cheapest (later changed to A5 as standard)
  • 2-Conductor braided wire (some now can be 4-conductor)
  • Wound to 7.1k to 8.4k resistance (some "PAF" style reissues can be hotter)
  • USA made materials (now pickup parts can come from anywhere)

What's up with all the magnets? Here are commonly described characteristics of pickup magnets:
I personally prefer Alnico 4 because the majority of original P.A.F.'s used them, although many different grades of Alnico were used throughout the early P.A.F. era. Plus if your guitar is dark sounding or shrill, a different magnet might help compensate that. Most bar magnets are polished, but some can be ordered as 'roughcast' too (lumpy pitted surfaces). Roughcast smooths out the high end, probably due to a more complex magnetic field.

Alnico 2 - Creamy and round highs, strong and lots of mids, warm lows, and open vintage dynamics. Used in both bridge and neck. (example: Burrstbuckers, Slash Duncans, etc.). The midrange hump is apparent on these, and in my experience, I like them in 4 piece bands where you need the mids to get your guitar to stand out in the mix.

Alnico 3 - Similar to Alnico 2 but with sweeter and more dynamic sounding highs, and clearer, more articulate lows. Less mids than an A2. Popularly used in the neck slot.  Lowest output. A3 magnets sound like vintage or even "aged" pickups.

Alnico 4 - Flat EQ. Lets the natural EQ of the guitar and PU come thru. A good happy medium between Alnico 2 and Alnico 5 tonal characteristics, with a very natural sounding and flat EQ range. Moderate output. Good in both neck and bridge. (example: Fralin '60 PAFs). In my experience, if the guitar sounds fantasic when not plugged in, and you want pickups that don't "color" that sound, this is a good choice.

Alnico 5 - Most popular alnico. Higher output, lots of treble and bass, scooped mids. Tighter EQ with heavier punch and attack. Slightly less mid presence with stronger, and clearer dynamics on the lows and highs. Great in the neck slot, and can be thin in the bridge. (example: 57 Classics, etc.) You see A5's in Epiphones and guitars that need to be brightened up due to their wood, construction, or thickness of lacquer. If you have a dark sounding guitar, the A5 will brighten it up.

Alnico 8 - Described as the sound of Alnico 5 with the strength of a ceramic (example: heavy metal, or high resistance 11k+) They'll be powerful like a ceramic, but not sterile.