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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
•
Do not switch off and on without a short rest of 60 seconds (to reset the 'soft start')
•
Do not adjust the output valve grid bias without reading the procedure
•
Do not operate the amplifier without loudspeakers connected
•
Do not use valves other than listed as this could be dangerous and damaging to the amplifier
•
Remember to check the bias about twice a year for best performance.
•
Make sure the speakers are in phase.
•
Use the best possible source material.
•
Use efficient, well-designed speakers.
What is safe maximum volume?
The Stereo 40 MKIII 2A3 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 or phono stages.
Leaving the amplifier switched on
Do not leave the amplifier switched on 24/7. Your
valves will be worn out in approximately nine
months! 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. See (Standby Switch). We would always
advise that any item of home electronics is
switched off when not in use
Standby Switch
If the amplifier is not needed for a few hours, it
can be left in the "standby" state. This enables the
valves to be fully warmed and ready to use the
instant you put the standby switch down. In the
"standby" position the amplifier is only using about
50% of normal power. It also enables a healthy
cloud of electrons to build up around the hot
Amplifier Dead
Check the 1.6 amp 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. Replacements should be
1.6 Amp 'anti-surge'. Available from Icon Audio free.
The fuse in the plug should be a 3 or 5 amp fuse,
although unlikely, 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?
Distorted sound.
Try another source; if sound improves then it's probably
something wrong with the first source. If no improvement
cathode. Also it allows the silver "getter" inside the
valve to "mop up" any gas that has built up inside
and therefore keep the vacuum "hard" for best
performance. There is no benefit to leaving the
ST40 on standby indefinitely. If not in use switch
off!
As the amplifier has a valve rectifier, it is not
necessary to use this switch for warming up the
amplifier, as the rectifier acts as a time delay.
'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!
Good quality new valves sound better, have good
performance and reliability. The upgrade valves
supplied with selected models are the result of
careful comparison with other makes. But beware
paying excessive amounts for "New Old Stock",
second hand or "Fake", valves,
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
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 too 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.
Interference Problems
The amplifier design incorporates features and
devices which make it resistant to mains-born
interference. But some CH boilers/fridges/cookers etc
can generate RF (radio frequency) interference which
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