TUBE AMPLIFIER SURVIVAL TIPS
• Tube amplifiers; generally sound much warmer/sweeter than solid state transistor amplifiers but they also need a little
more respect due to the fragile glass tubes themselves. The L20T-112 uses top quality tubes, which should give you years of
trouble free service, however like all tube amps; it is important to treat it with a certain amount of care.
• Tubes are fragile glass components; they can easily be damaged if thrown in and out of vehicles,
• Make sure the impedance; of your cabinets matches the setting on your amplifier. Improper impedance matching will
result in reduced output power output and compromised sound at best and amplifier failure/premature tube failure at worst.
• Allow the amplifier; to warm up to room temperature before switching it on, The sudden thermal shock generated can
crack the cold glass tube housing plus any moisture is bad news around high voltage electronics.
• Allow the amplifier; to cool down after playing before moving. Hot tubes are more susceptible to damage than cool
ones.Use good quality loudspeaker leads, cheap leads are often not up to the job of handling the large requirements for
loudspeakers and can often short out.
• Tube amplifiers; don't like running into a open circuit. A tubes life expectancy is based upon a number of factors which
include operating temperature, how hard and how often it is played, vibration due to travel etc. Tubes should be changed in
your amplifier if you notice any change in your amplifiers performance etc. They need not be changed at any regular interval.
• Typical problems; with preamp tubes, can be a crackly noise, hiss, hum and microphony. The preamp tubes can safely be
changed with no other action required if they fail or reduce in performance. Typical output tube problems can be blown HT
fuse; sound lacking in punch, sound lacks extreme highs or lows and low level hum. The Output tubes can be replaced singularly
if you replace them with the exact same type AND grade as factory fitted otherwise they should be replaced as a set. See the
diagram following to see how to check the tube grade fitted. Exact replacement preamp tubes and matched sets of output
tubes are available from Laney via your dealer.
• To change a tube; switch off the unit and unplug from the mains supply. Wait for the tubes to cool down. Lay amplifier
down on its front face and remove the protective grille held in place with four screws. You should now be able to access the
underside of the amplifier chassis. Preamp tubes are protected with a screen can, to remove; gently twist the screen can anti
clockwise and then pull up. The tube can then be gently pulled out. Take care when pushing the new tube in to make sure the
pins are all aligned properly. Output tubes have a spring retainer which must be pulled away before the tube will come out.
• ;Amplifier connection In order to avoid damage, it is advisable to establish and follow a pattern for turning on and off
your equipment. With all system parts connected, effects processors etc. BEFORE turning on your guitar amplifier. Many
products have large transient surges at turn on and off which can cause damage to your speakers. By turning on your guitar
amplifier LAST and making sure its Volume controls are set to minimum any transients from other equipment will not reach
your loudspeakers.
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(20 pages)
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