Electric Circuits in Audio Science

Flashcards reviewing electrical circuit principles, audio signal flow, unbalanced vs. balanced audio lines, interference, connectors, and Direct Boxes.

Electrical Circuit

A path between two or more points along which an electrical signal is carried, either between separate audio devices or within a single audio device.

Electricity

The flow of electrons through a given medium, typically copper wire or conductive plastic.

Resistance

The opposition to the flow of an electrical circuit, measured in ohms ($\Omega$).

Capacitance

The property of a medium absorbing electrical energy, which lessens signal intensity over length.

Radio Frequency Interference (RFI)

Atmospheric interference caused by radio frequencies attaching to conductive audio wires acting as antennas.

Electro-Magnetic Interference (EMI)

Atmospheric interference created by magnetic fields that attach to nearby conductive audio cables.

Console Pre-amp

The console stage that receives low voltage current from a microphone and increases its voltage level.

Unbalanced Circuit

An audio transmission circuit that utilizes a single conductor wire and a shield wire, common in consumer electronics and susceptible to interference.

Balanced Circuit

An audio transmission circuit that utilizes two conductor wires (hot and cold) plus a shield wire to eliminate common-mode interference over long distances.

Pin 2 (XLR)

The pin in a balanced XLR connector that carries the non-phase reversed, positive ($+$), or HOT signal.

Pin 3 (XLR)

The pin in a balanced XLR connector that carries the phase-reversed, negative ($-$), or COLD signal.

Pin 1 (XLR)

The pin in a balanced XLR connector that connects to the ground or shield wire.

Differential Amplifier

A transformer or circuit at the receiving end of a balanced line that flips the phase of the Pin 3 COLD signal back into phase with Pin 2, doubling signal amplitude ($+3\,\text{dB}$) while cancelling common-mode noise.

TS Connector

A 1/4 inch unbalanced connector featuring a Tip connected to the signal wire and a Sleeve connected to the shield wire.

TRS Connector

A 1/4 inch balanced connector consisting of a Tip (non-inverted signal), Ring (inverted signal), and Sleeve (shield).

XLR Connector

A 3-pin balanced audio connector widely used for microphones and professional audio equipment.

RCA Connector

An unbalanced audio connector type widely found on consumer media devices and home theatre equipment.

Bantam Connector (TT)

A miniature balanced connector commonly used in professional recording console patch-bays.

Direct Box (DI)

A device used for interfacing unbalanced audio signals to balanced audio inputs.

15-Foot Limit

The maximum recommended length for unbalanced cable runs to avoid significant noise and signal degradation.