Laney LION HEART L20H Operating Instructions Manual page 12

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 L20H uses top quality tubes, three 12AX7 preamp tubes, and four EL84 output 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.
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Take care when moving the amplifier. Tubes are fragile glass components, they can easily be damaged if thrown in and out of transit vans,
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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.
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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.
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Allow the amplifier to cool down after playing before moving. Hot tubes are more suseptable 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 amps don't like running into a short 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 crackley noise, hiss, hum and microphony. The preamp tubes can
safely be changed with no 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. Exact replacement preamp tubes and 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.
OPERATING INSTRUCTIONS
V1 RT030 005570
V2 NN001 005550
V3 NN003 005548
V4-V7 EL84STR x 4 005563