Laboga AD 5300 User Manual - page 13
Hints concerning tubes
Leave tube change and bias setting for qualified personnel. Tubes could get heated
intensively. If you touch them, you can get burnt. That is why, before you change tubes, turn
amplifier off, take the plug out and wait for them to cool down.
Before you change tubes, pay attention if their “feet” are straight because the feet have to be
positioned in a certain way.
The first symptom that tubes should be replaced is worsening the tone of the amplifier. The
sound gets flat and the dynamics are worse. There are certain signs that imply tubes should be
changed: red outer metal cover, which is normally gray, flashes inside the tube, or other unusual
signs.
Use only new tubes. Power tubes should all be changed at the same time for a quartet of
EL84 tubes. It is a pentode, which is characterized by having a longer life span and is more
mechanically reliable than EL34 for example. A quartet of power tubes, like any other tubes, can be
purchased in a Laboga service.
It is recommended to use V1 and V2 with low noise and/or “low microphonics”. Because the
amplifier has high sensitivity, hums may appear when all the knobs are set “to the right” position
and the amplifier is on the distorted channel.
HOW TO USE THE AMPLIFIER IN ORDER TO PROLONG TUBES’ LIFE-SPAN
1). The amplifier should always be switched on in the following way: first turn Power on and wait
for 1 minute. Then, you can turn the Standby. Switching the amplifier off is the other way
around – first turn Standby off, then wait 1 minute, then you can turn power off.
2). Always use a matched quartet of power tubes, from Laboga or renowned producers.
3). Before transporting the amplifier, wait for the amplifier, especially for the tubes, to cool down.
4). When you don’t use the amplifier, it is advisable to keep Standby to position “0”
5). An excessive amount of dust on the tubes may decrease heat distribution of the tubes, which
could shorten tube's life-span. Use an original Laboga cover or hard case to prevent damage
and dust.
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