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4 How to get the best out of 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 the ‘soft start’)
•
Do not adjust the output valve grid bias unless you know how
•
Do not switch from Ultralinear to Triode without switching to Standby or switching off
•
Do not operate the amplifier without loudspeakers connected
•
Do not use valves other than listed as there could be danger of shock or overheating
•
Do check the bias regularly at least once a month 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 will run happily all day long at
a high volume; the valves are not stressed any
more 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.
Triode
Switch.
This
switch
causes
the
KT88/EL34s to operate as Triode valves. Please
remember to put the amplifier into
“Standby”
first as switching will stress the output
transformers.
The majority of listeners prefer the
“triode” sound believing it to be more pleasant to
listen to, but the power will drop to about 50%. As
the gain in triode is nearly the same the volume
will be the same. But at higher volumes you may
hear some distortion as you are running out of
power, in which case switch to ULTRALINEAR.
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 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!
‘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’.
Upgrading Valves!
Good quality new valves sound better, have good
performance and reliability. The upgraded valves
supplied with selected models are the result of
careful comparison with other makes. But beware
of
paying excessive amounts for “New Old Stock”,
second hand or “Fake”, valves. At this time we
recommend Tung Sol, our Russian and US NOS,
Shuguang, Treasure, Full Music, JJ.
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
1. Amplifier Dead
Check the 1.6 amp (3 amp USA) 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 (or 3 amp USA) a
mp ‘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.
2. No sound
ST40 lit up but no sound from either channel could
be internal fuses blown (unlikely) or GZ34/5AR4
failed. The bias reading is “zero” Try another GZ34.
Have you selected the right input? Are the
connections OK? Is everything switched on? Are the
speakers connected?
If you think you have tried everything and the meter
light is working and the heaters are glowing the
internal fuses may have blown. They are located
inside the amplifier and should be replaced by a
competent engineer. Replacements free on request
from Icon Audio.
