Wiring, without
the folklore.

The signal path, honestly

A passive magnetic pickup is a coil of wire — an inductor with resistance and a little internal capacitance. Everything you connect to it forms a filter with it. Your volume pot, your tone pot, your cable and your amp's input all load that coil, and loading a coil means losing treble. That is the entire theory. Every "upgrade" on the market is a variation on how much treble you lose and where.

Potentiometers

The pot value is a resistance sitting across the pickup. Higher resistance loads it less and keeps more high end.

Value	Usual pairing	Effect
250 kΩ	Single coils	Rolls off some top end. Tames the brightness of a Strat or Tele.
500 kΩ	Humbuckers	Brighter and more open. A humbucker on 250k often sounds muddy.
1 MΩ	Very dark pickups, P-90s	Maximum brightness. Can get glassy and thin.

Audio versus linear taper. Your ear responds to volume logarithmically, so a linear pot appears to do everything in the last third of its travel. Use audio taper for volume. For tone, either works, and plenty of people prefer linear because the sweep feels more gradual.

The treble bleed question

Rolling a volume pot down also rolls off treble, because the pot and your cable capacitance form a filter that gets worse as you turn down. A small capacitor across the volume pot's input and output lets highs pass and keeps the tone consistent. Roughly 470 pF to 1 nF, sometimes with a resistor in parallel to stop it going harsh. Whether you want this depends entirely on whether you use your volume knob as a tone control, which many players do deliberately.

Tone capacitors

The tone control sends high frequencies to ground through a capacitor. The value sets the corner frequency — bigger capacitor, more treble dumped, darker sound at full roll-off.

Value	Character at full roll-off
0.010 µF	Subtle. Takes off the fizz, keeps definition.
0.022 µF	The humbucker standard. Warm, still musical.
0.047 µF	The single-coil standard. Genuinely dark, the classic "woman tone".
0.100 µF	Almost entirely muffled. Rare outside of bass.

Switching

• 3-way toggle — neck, both, bridge. The Les Paul arrangement.
• 5-way blade — the Strat layout, adding the two in-between positions that give you the quacky out-of-phase-sounding tones.
• Coil split — grounds one coil of a humbucker to leave a single coil. Thinner and quieter in output, and it does not truly sound like a real single coil, whatever the marketing says.
• Series/parallel — wiring two pickups in series stacks their output for a thicker, louder tone. Often more useful than a coil split and rarely offered from the factory.
• Phase reverse — flips one pickup's polarity. Thin and nasal, and only usable with both pickups on. A one-trick switch, but it is a good trick.

Shielding and grounding

Single coils hum because they are antennas. Two things reduce it: shielding the cavities with copper tape or conductive paint, all connected to a single ground point, and a ground wire to the bridge so that touching the strings grounds you.

Star grounding. Run every ground to one point — usually the back of the volume pot — rather than daisy-chaining them. Ground loops are a common source of buzz in home builds and are entirely avoidable.

Shielding kills electrostatic interference well. It does very little against magnetic interference from transformers and lighting dimmers. If your guitar still hums under fluorescent lights after a full shielding job, the fix is a hum-cancelling pickup, not more copper tape.

A sensible order of work

1. Shield the cavities and test continuity across the whole shield with a meter.
2. Wire the loom on a board outside the guitar, where you can actually reach the joints.
3. Test every switch position with a meter before it goes in.
4. Fit the loom, connect the bridge ground and the output jack last.
5. Plug in before you screw the cover on. Everybody who skips this ends up taking it off again.