Brooks RM 909 reviews Echo

1) One distinct repeat of a sound because of the sound reflecting off a surface.
2) Loosely, used to mean reverberation (the continuing of a sound after the source stops emitting it, caused by many discrete echoes closely spaced in time).

Hum
The 60 Hz power line current accidentally induced or fed into electronic equipment.

Brooks Hi Fi reviews Capacitance
The property of being able to oppose a change in voltage or store an electrical charge.

Amplifier (Power amp, Head)
It's the part of the sound system that actually magnifies or "amplifies" the sound. In other words, it makes stuff louder.

Brooks Hi Fi speakers Flange
An effect caused by an approximately even mix of a modulated (varying) short delay with the direct signal.

Equipment Rack
A cabinet with rails (or free standing rails) that have holes to accept screws at standard spaces and used to house outboard gear.

Electromagnetic Field
Magnetic energy put out because of current travelling through a conductor.

High Impedance
Impedance of 5000 or more ohms.