Page 5
4 Getting the best performance from your amplifier
•
Do not leave the amplifier switched on all the time. This is not necessary
•
Do not switch off and on without a short rest of 60 seconds (to reset th
e ‘soft start’)
•
Do not adjust the output valve grid bias without reading the manual
•
Do not operate the amplifier without loudspeakers connected
•
Do not use valves other than listed as there could be danger of shock or damage
•
Make sure your speakers are in phase.
•
Use the best possible source material.
•
Use efficient, well-designed speakers. Generally the bigger the better!
What is safe maximum volume?
The Stereo 25 will run happily all day long at a
high undistorted volume; the valves are not
stressed any more at full power than at zero
volume. Running into distortion will 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 power. However this position
will vary according to the level and type of music
and the output of the source unit. Be careful of
high level transients which could damage the
amplifier, speakers and blow fuses.
Leaving the amp switched on
DO NOT leave the amp 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.
‘Burning in’
Although the amplifier 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’.
Changing and Upgrading Valves!
New good quality valves will sound better. The
upgrade valves supplied with selected models are
the result of careful comparison with other makes.
But beware of paying a premium for “New Old
Stock” valves where you may be paying for rarity
value and not performance. Used valves are not
recommended. YOU MUST USE A MATCHED
SET!
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 IEC socket 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 bade 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
‘anti-surge’ or “T” (for time),
these are available FREE OF CHARGE on request.
The fuse in the wall plug (where applicable) should be a
3 or 5 amp fuse, although unlikely to fail, this should be
checked if the amplifier fuse is OK.
Valves glowing but no sound (on either or both channels)
Have you selected the right input? Is the volume control
advanced? Are all the connections OK? Is everything
switched on? Are the speakers connected?
If the amp lights up but there is no sound it could be one
of the two internal HT
“T250ma” fuses. They should be
checked by a competent electrician with the bottom off.
REMOVE POWER FIRST. There are two spare fuses
inside. Repeated blowing of the fuse would indicate a
fault. Refer to your dealer or Icon Audio.
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 it is likely to
be an amplifier problem.
Distorted sound at higher volumes may be because
one of the output valves is not working. This could be
due a faulty valve. A symptom of this would be no 8v
bias voltage at the test point. Refer to an engineer or
Icon.
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.
(b) Amplifier or speakers.
Sound will not move.
