Pickups can many factors that make them sound different even though they may look identical. There are many variables and some are listed below:

1. The number of turns on each bobbin
The number to turns per layer (pitch)
The number of layers per total turns
Tension in grams when winding
The winding speed of the bobbin
The de-reeling of the magnet wire from the master spool
The lubricant and seating of the magnet wire per-layer
Traverse and winding area
Precision pitch control for desired gauge of magnet wire
The gauge of magnet wire (Bare Wire)
Minimal diameter, Nominal diameter & Maximum diameter (bare dimensions)
Nominal area in circular mils
Nominal ohms per 1000′ @ 20? C
Nominal ohms per pound @ 20? C
Pounds per 1000′
Feet per pound
The insulation thickness on a particular gauge of magnet wire
Increase in film or insulation diameter
Minimal, Nominal & Maximum
The bobbin shape
The bobbin length
The bobbin width
The bobbin height
The bobbin material
More specific bobbin dimensions
The pole piece shape and material
Steel rod slugs
metal bar or blade (shape and size)
Fingers (single or multiple)
Magnet rod pole piece (various material and strength)
Screw pole piece (various threads, length, diameter and head shape)
Iron core material with shapes
Magnet bars of various shapes (various material and strength)
Magnet Material
Alnico’s (2,3,4,5,7)
Ceramics (various grades)
Cobalt steels
Rare earth magnets
electromagnets (DC with various power supplies)
Barium Ferrite rubber bonded magnets
Strength or weakness of magnet
fully magnetized, de-gaussed or calibrated
Electrical Phasing
Series In phase
Series out of phase
Parallel in phase
Parallel out of phase
Split adjustable
Split non-adjustable
In phase with accompanying pickup
Out of phase with accompanying pickup
Magnetic Phasing
In phase
Out of phase
In phase with accompanying pickup
Out of phase with accompanying pickup
The guitar string gauge
string gauge
String alloy
String age and use
String spacing from pole to pole
String height from pickup
Neck scale and string length
String pitch and tuning
Other factors that make a pickup sound different
Body and neck material
Body and neck weight
Electrical circuit (switches, volume and tone controls values)
Guitar cord
Effects being used
Fret height and width
Tail piece
Vibrato or Tremolo’s
Pickup covers- material, thickness & plating
Gauge of hookup wire-solid or stranded and number of strands
Pickup mounting-mounting ring, pickguard, mounted into body
Pickup placement-distance from bridge and neck
Angle of pickup-angled or perpendicular
Amplification being used
Speaker combination
Your individual ears- depending on the time, loudness and frequency will make your pickup sound different