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4 How to get the best out of your amplifier
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Do not leave the amplifier switched on all the time. This is not necessary
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Do not switch off and on without a short rest of 60 seconds (to avoid a current surge)
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Do not adjust the output valve grid bias unless you know how
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Do not swop the valves round as this will damage the amplifier, and may be dangerous
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Do not operate the amplifier without loudspeakers connected
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Do not use valves other than listed as there could be danger of shock or damage
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Make sure the speakers are in phase.
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Use the best possible source material.
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Use efficient, well-designed speakers.
What is safe maximum volume?
The Stereo 20SE will run happily all day long at
maximum power; the valves are not stressed any
more at full power than at zero volume. Running
into gross distortion will however stress the whole
amplifier. To find the maximum safe volume, play
full range music and advance the volume until
distortion occurs, (this is normally between 12 and
3 o’clock on the volume control) back off the
volume control about 30 degrees, this is
approximately full music power. However this
position will vary according to the level and type of
music and the output of the source unit. For
example CD players tend to be higher than say
tuners.
Leaving the amp switched on
People sometimes ask if the amp should be left
running 24/7 without switching off. Whilst the
amplifier will sound at its best when it is properly
warmed up, there is no advantage leaving it
switched on when it is not in use. It is using
electricity and as valves have a finite life.
Conversely the valves and other components are
stressed more at switch on; therefore do not
switch on and off unnecessarily.
We would always advise that any item of home
electronics is switched off when not in use
‘Burning in’
Although the amp should sound good within about
10 mins it can take up to an hour to sound at its
best and will take several months of regular use
before it is fully
‘run in’.
Upgrading Valves!
This can be a controversial subject, but in our
opinion quality valves always sound better, have a
better service life and maintain their performance
longer. The upgrade valves supplied with selected
models are the result of careful comparison with
other makes.
Cabinet Care
To remove dust we suggest gentle brushing of the
polished stainless steel cabinet with a soft
paintbrush. Other marks can usually be removed
with a damp cloth. The Perspex valve cover may
need a gentle wipe with soapy water and drying
with a duster. On no account use anything wet on
the amplifier, and always clean with the power
disconnected.
5 Trouble Shooting
Amplifier Dead
Check the 20mm mains fuse at the back of the
amplifier. To gain access, remove the mains lead.
The fuse is in a small plastic drawer, which forms
part of the socket assembly. To open insert a flat
blade screwdriver or similar and prise open.
The
fuse in use is the innermost
the outer is a
spare. Should the replacement fuse also blow
there is a fault you should disconnect from the
mains and seek qualified help or Icon Audio.
Replacements should be the correct type
‘anti-
surge’.
The fuse in the wall plug should be a 3 or 5 amp
fuse, although unlikely to fail, this should be
checked if the amplifier fuse is OK.
No sound
Have you selected the right input? Are the
connections OK? Is everything switched on? Are
the speakers connected?
If the KT88’s are only
just hot check the internal T630ma fuse inside.
Distorted sound.
Try another source; if sound improves then it’s
probably something wrong with the first source. If
no improvement try different speakers, if no
improvement could be an amplifier problem.
Hum Problems
If you experience hum, try disconnecting all
inputs, if hum persists this is probably an amplifier
fault.
If not, identify which input is causing hum.
Connect one input at a time. A common cause is
a ‘hum loop’ caused by having to many earths,
and may be identified by unplugging each input
source from the mains. One remedy for this is to
use an interconnect which only has the screen
connected at one end. Other causes of low-level
hum can be from adjacent equipment, so
experiment with moving equipment around to see
if this makes the hum better or worse.
One channel missing.
Usually ‘bad’ connection on either the input or the
speakers. Try swapping the connection over to
establish if the cause is:
(a) Input to the amp.
Sound will move to the
other channel.
