Pierre
Stratologist
First of, let me tell you something not many people seem to understand. If all you say is 'I want a pickup that can do metal, hard rock but have decent cleans', then maybe you shouldn't consider changing pickups at all (er... unless you love Slayer and you have a Squier strat, but you get what I mean...). An amplifier with differen channels and a footswitch will do most of the job, IF you REMEMBER THAT A GUITAR USUALLY HAS MORE THAN ONE PICKUP AND HAS A VOLUME CONTROL!!!! I can't emphasis this enough. USE THE CONTROLS!!! It's fun, it brings a lot more sound possibilities. With seperate volume controls it's easy to dial a clean-ish tone on the neck pickup then switch to the bridge pickup full on for crunching distortion, using the same channel.
Now onto a little description of a pickup...
I'm just going to treat single coils and humbuckers on here, maybe a couple of words of P90s and others.
Single coils: The magnets are the polepieces. The coil is wound around them. They have a brighter, less powerful sound than humbuckers. Due to their design they also produce a buzzing noise called a 60 cycle hum. At high gain it can be a hive, but a well designed high output SC won't be too much of a pain.
Humbuckers: they are NOT 2 single coils put together. They work slightly differently. The magnet is under the coils, in between them. Magnets used are Alnico (Aliminium, Nickel, Cobalt aloy) 2, Alnico5 and Ceramic. Some use A5 and A8 (I need to get my hands on an A8 magnet some day). The more number after the A, the more powerful it is. A2 is the least powerful, then A5, then A8... etc... Ceramic is more powerful than all these.
Humbuckers have a warmer, bassier sound than SCs, with a lot more power available.
The 2 coils' phase cancel each other out so the buzz is 'bucked'. Hence humbucker.
A standard humbucker is wired in series, out of phase. In phase has a nasally weak tone. You can also wire them split (one coil working only) and parrallel (single coil tone, but noiseless unlike split).
P90s: oversized single coils. They still buzz, but are a lot more midrangy and powerful than Single coils. Listen to the 2 first Sabbath albums for P90 sound Or to the solo to Another Brick in the Wall by the Pink Floyd.
DC resistance, output, resonant peak....:
The DC resistance is a measure comonly used in pickupology. What does it mean? By itself, nothing You NEED more information to know what it means, especially if you want to compare 2 pickups.
What affects the DC resistance is the number of windings and the wire gauge. Magnets DO NOT change it. Swap a A2 magnet for a Ceramic magnet in your Alnico2 pro pickup and it'll still read the same DC resistance.
A basic rule of thumb is: if 2 pickups have the same magnets and wire gauge, then the one with the most windings will have the more DC resistance, and the more perceivable output (I say perceivable output, just as another way to say how 'hot' a pickup is).
The perceivable output a pickup has, the more likely it is to overdrive a clean amplifier.
If 2 pickups use the same wire gauge and magnet, you can safely compare their DC resistance for the output. However, 2 pickups by different manufacturers may not match. BEWARE.
Measured in Kilo ohms, or simply K. The FullShred I have in my guitar now measured 15K I believe, with the A5 AND the Ceramic magnet.
Now onto a little description of a pickup...
I'm just going to treat single coils and humbuckers on here, maybe a couple of words of P90s and others.
Single coils: The magnets are the polepieces. The coil is wound around them. They have a brighter, less powerful sound than humbuckers. Due to their design they also produce a buzzing noise called a 60 cycle hum. At high gain it can be a hive, but a well designed high output SC won't be too much of a pain.
Humbuckers: they are NOT 2 single coils put together. They work slightly differently. The magnet is under the coils, in between them. Magnets used are Alnico (Aliminium, Nickel, Cobalt aloy) 2, Alnico5 and Ceramic. Some use A5 and A8 (I need to get my hands on an A8 magnet some day). The more number after the A, the more powerful it is. A2 is the least powerful, then A5, then A8... etc... Ceramic is more powerful than all these.
Humbuckers have a warmer, bassier sound than SCs, with a lot more power available.
The 2 coils' phase cancel each other out so the buzz is 'bucked'. Hence humbucker.
A standard humbucker is wired in series, out of phase. In phase has a nasally weak tone. You can also wire them split (one coil working only) and parrallel (single coil tone, but noiseless unlike split).
P90s: oversized single coils. They still buzz, but are a lot more midrangy and powerful than Single coils. Listen to the 2 first Sabbath albums for P90 sound Or to the solo to Another Brick in the Wall by the Pink Floyd.
DC resistance, output, resonant peak....:
The DC resistance is a measure comonly used in pickupology. What does it mean? By itself, nothing You NEED more information to know what it means, especially if you want to compare 2 pickups.
What affects the DC resistance is the number of windings and the wire gauge. Magnets DO NOT change it. Swap a A2 magnet for a Ceramic magnet in your Alnico2 pro pickup and it'll still read the same DC resistance.
A basic rule of thumb is: if 2 pickups have the same magnets and wire gauge, then the one with the most windings will have the more DC resistance, and the more perceivable output (I say perceivable output, just as another way to say how 'hot' a pickup is).
The perceivable output a pickup has, the more likely it is to overdrive a clean amplifier.
If 2 pickups use the same wire gauge and magnet, you can safely compare their DC resistance for the output. However, 2 pickups by different manufacturers may not match. BEWARE.
Measured in Kilo ohms, or simply K. The FullShred I have in my guitar now measured 15K I believe, with the A5 AND the Ceramic magnet.
Finding your perfect sound is fun but can be costly (I haven't yet found my perfect sound myself 
). I've experimented with a bunch of pickups, swapped out magnets... Still not there. But I'm really close now so it's all good I hope that if you ever decide to change pickups in your guitars, you have as much fun as I did, and still do. 
I hope you'll like reading this.
