Laney IRT-STUDIO - Manual (Page 16)

TUBE AMP 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. The IRT-Studio uses three 12AX7 preamp tubes, and 2 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. Use the
following steps as a guide for how to take care of your amplifier:
Take care when moving the amplifier. Tubes are fragile glass components, they can easily be damaged if thrown in and out of
vans.
Make sure the impedance of your cabinets matches the setting on your amplifier. Improper impedance matching will result in
reduced output power and compromised sound at best, and amplifier failure/shortened tube life at worst.
Allow the amplifier to warm up to room temperature before switching it on: the sudden thermal shock can crack a cold glass
tube enclosure, plus any moisture is bad news around high voltage electronics.
After playing, allow the amplifier to cool down before moving. Hot tubes are more fragile than cool ones.
Always use good quality loudspeaker cables: instrument cables are not capable of handling the load requirements of the
loudspeaker and can short out.
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 deterioration in your amplifiers
sound or performance. Otherwise, they need not be changed at any regular interval.
Typical problems with preamp tubes can be crackly noise, hiss, hum, and microphony. If they fail or exhibit reduced performance,
preamp tubes can simply be swapped out with no further action required.
Typical output tube problems can include a blown HT fuse, sound lacking in punch, sound lacking extreme highs or low, and low
level hum. The output tubes can be replaced singly if you replace them with the exact same type AND grade as factory fitted,
otherwise they should be replaced as a matched pair.
The user should not attempt to service this product.
Method of replacing tubes for Qualified Service Engineers
To change a tube, firstly switch off and unplug the amplifier from the mains supply. Wait for the tubes to cool down. Remove the
top cover. Preamp tubes are protected with a screen can; to remove, push down and twist the can anti clockwise and then pull
up. The tube can now be gently pulled out. Output tubes have a spring retainer which grips the base of the tube; push down on
this with one hand, whilst gently rocking the tube with the other to remove. Take care when inserting the new tube to make sure
all pins are correctly aligned. Replace the top cover before connecting to the mains supply.
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