Basic Electric Guitar Circuits

Introduction

• Author: Kurt Prange
• Concept: Passive electric guitar circuits are straightforward, allowing for endless customization.
• Components Needed: Understanding of pickups, potentiometers, capacitors, and switches.

Pickups

Functionality

• Pickups as Transducers: Convert mechanical energy of vibrating strings to electrical energy via electromagnetic induction.
• Working Principle: Changing magnetic field induces current in a coil wrapped around the string.
• Output: AC signal, alternates with string movement.

Types of Pickups

• Single-Coil Pickup:
  • Early 1930s by Rickenbacker.
  • Susceptible to electromagnetic interference.
• Humbucker Pickup:
  • Developed in 1950s by Gibson.
  • Uses two coils to cancel interference noise (in-phase string signal, out-of-phase noise signal).
  • Sound Characteristics: Fuller, darker sound.

Connecting Multiple Pickups

• Phase Relationship: Important for correct sound output, determined by coil winding and magnet polarity.
• Stratocaster: Often includes a reverse-wound middle pickup for hum canceling in combined positions.

Pickup Specifications

• DC Resistance: Lower resistance = lower output, brighter sound.
• Inductance: Higher inductance = higher output, darker sound.
• Peak Frequency: Higher peak frequency = brighter sound.

Choosing Pickups

• Variety available to match desired sound (e.g., vintage tone, noiseless single-coil).

Potentiometers and Tone Capacitors

Potentiometers (Pots)

• Function: Adjust volume and tone by changing resistance.
• Ohm’s Law: Resistance affects current flow; lower resistance increases current.

Tone Control

• Tone Pot: Works with tone capacitor to drain high frequencies, adjustable via resistance.
• Capacitors: Higher capacitor value drains more high frequencies, resulting in darker sound.

Volume Control

• Configuration: Uses all three terminals for voltage division.
• Taper: Affects output-to-input voltage relation; audio taper for tone control, linear taper for volume control.

Special Potentiometers

• Types: Push-pull, no-load, blend pots for customization.

Switches and Output Jacks

Pickup Selector Switches

• Purpose: Allows switching between pickups for varied tonal output.
• Types: DPDT, SPDT, DP3T, with varying pole and throw configurations.
• Example: Stratocaster switch offers multiple pickup combinations.

Output Jacks

• Function: Connects guitar signal to amplifier.
• Standard: Mono jack with tip (signal) and sleeve (ground).

Wiring Diagrams

• Resource Availability: Easily accessible online for DIY modifications.
• Customization: Encourages creativity in personalizing guitar sound.

Author Information

• Kurt Prange: Sales Engineer, Amplified Parts in Tempe, AZ. Guitarist and tube amp designer with a passion for DIY and tone customization.