Legacy Car Audio LA738 - Manual (Page 7)

High squeal noise from speakers.
• This is almost always caused by a poorly-grounded RCA
patch cord.
Amplifier(s) gets very hot.
• Check that the minimum speaker impedance for that model
is correct.
• Check for speaker shorts.
• Check that there is good airflow around the amplifier. In
some applications, an external cooling fan may be required.
Distorted sound
• Check that the Level control(s) is set to match the signal
level of the head unit.
• Check that all crossover frequencies are properly set.
• Check for shorts on the speaker leads.
Amplifier will not power up.
• Check for good ground connection.
• Check that remote DC terminal has at least +12v DC.
• Check that there is battery power on the + terminal.
• Check all fuses.
• Check that Protection LED is not lit. If it is lit, shut off amplifier
briefly and then repower it.
High hiss or engine noise (alternator whine) in
speakers.
• Disconnect all RCA inputs to the amplifier(s) – if hiss/noise
disappears, then plug in the component driving the amplifier
and unplug its inputs. If hiss/noise disappears, go on until the
faulty/noisy component is found.
• It is best to set the amplifier's input level as insensitive as
possible. The best subjective S/N ratio is obtainable this way.
Try to drive as high a signal level from the head unit as possible.
Protection LED comes on when the amplifier is
powered up.
• Check for shorts on speaker leads.
• Check that the volume control on the head unit is turned
down low.
• Remove speaker leads, and reset the amplifier. If the
Protection LED still comes on, then the amplifier is faulty.
troubleshooting
Troubleshooting Speaker Connections
2 CH Mono-Bridged Output
Bridged Mono Output
speakers
L R
MINIMUM
SPEAKER
IMPEDANCE
4 OHMS!
STOP
YES! NO!
2 -c hannel A m p l i f i e r (Operating in Stereo)
4 ohm
4 ohm
Two 4-ohm speakers, wired in stereo,
will present a 4-ohm load to each
channel of the amplifier. Most two-
channel amplifiers will work well in this
configuration. Two 4-ohm speakers, wired in parallel
to a bridged two-channel amplifier.
will present a 2-ohm mono load to the
amplifier.
MOST TWO-CHANNEL AMPLIFIERS DO NOT SUPPORT 2-OHM MONO OPERATION! AMPLIFIER DAMAGE COULD RESULT! sound around, Inc. 1600 63rd s treet. b rooklyn. ny 11204
4 ohm
4 ohm
2 -c hannel A m p l i f i e r (Operating in Bridged Mono)
STOP
YES! NO!
Four 4-ohm speakers, wired in stereo,
will present a 4-ohm load to each
channel of the amplifier. Most four-
channel amplifiers will work well in this
configuration. Four 4-ohm speakers, wired in parallel
to a bridged four-channel amplifier,
will present a 4-ohm mono load to the
amplifier.
MOST FOUR-CHANNEL AMPLIFIERS DO NOT SUPPORT 2-OHM MONO OPERATION! AMPLIFIER DAMAGE COULD RESULT! sound around, Inc. 1600 63rd s treet. b rooklyn. ny 11204
4 -c hannel A m p l i f i e r (Operating in Bridged Mono)
4 ohm
4 ohm
4 ohm
4 ohm
4 -c hannel A m p l i f i e r (Operating in Stereo) 4 ohm
4 ohm
4 ohm
4 ohm
2CH AMPS
L A 4 3 8
L A 5 3 8
L A 7 3 8
L A 9 3 8
LA 1438
LA 1838
LA 2038
11
4CH AMPS
L A 6 3 8
L A 8 3 8
LA 1038
4CH AMPS
L A 6 3 8
L A 8 3 8
LA 1038
2 CH Stereo plus
Mono-Bridged
Subwoofer Output
speakers
L
Mono
Subwoofer
MINIMUM
SPEAKER
IMPEDANCE
4 OHMS!
R
speaker
MINIMUM
SPEAKER
IMPEDANCE
4 OHMS!