Technical information

Line level An electrical signal at a voltage level suitable for transferring a signal
between components of a home entertainment system (for example, CD player to
amplifier, amplifier to VCR). Most modern equipment operates with a maximum of
level of not much more than two volts RMS. Line level signals demand high
impedance inputs. At least 10,000 ohms is suitable, although the de facto
standard is 47,000 ohms.
Loudness control An unnecessary circuit on a preamplifier, that boosts the bass
and, to a lesser extent, the treble of an audio signal. The idea was to overcome
the reduced sensitivity of the ear to bass and treble at low volumes, but in fact
this could only be achieved with any degree of realism by providing a complex
means of calibration, which was never actually provided.
Loudspeaker A device for transforming electrical energy into acoustic energy (i.e.
vibrations in the air). A loudspeaker normally consists of one or more drivers, a
crossover network and an enclosure.
Low pass filter An electrical circuit that impedes signals above a particular
frequency. In other words, it lets signals below that frequency pass through. An
example is the circuit in a home theatre receiver that allows bass frequencies to
go to a subwoofer. Compare high pass filter and bandpass filter.
LP Long Play record. The vinyl record that was introduced in the early 1950s to
replace the shorter-play records previously used. Rather than their 78 rpm
rotational velocity, the LP rotated at 33 1/3 rpm and used narrower grooves.
Accordingly, it gave a playing time of between 15 and 30 minutes per side,
depending on the how heavily the signal was modulated, the amount and
character of its bass content and the amount of material available.
LPCM Linear Pulse Code Modulation. For all practical purposes, the same as
PCM. This tends to be called LPCM when dealing with DVDs.
LSB Least Significant Bit. The bit of the binary number that varies the value of the
binary number by no more than one (which is why it is the least significant). This
bit is often randomised in PCM digital audio in order to add dither to the signal.
M
Magnetic cartridge A turntable cartridge that produces the signal by moving a
magnet within a coil (moving magnet cartridge), or vice versa (moving coil
cartridge).