Page 5
4 How to get the best out of your amplifier
•
Check bias at least twice a year for best performance
•
Do not switch off and on without a short rest of 60 seconds
(to reset the ‘soft start’)
•
Do not leave the amplifier switched on all the time. This is not necessary
•
Do not adjust the output valve grid bias unless you know how
•
Do not swop the output valves round as they are set up individually
•
Do not operate the amplifier without loudspeakers connected
•
Do not use valves other than listed as there could be danger of shock and damage to
the amplifier
•
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 300 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 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.
DO NOT LEAVE SWITCHED ON 24/7
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 of
very roughly 5000 hrs
WHICH IS ONLY SIX
MONTHS CONTINUOUS USE!
(or 4½yrs at 3 hrs
a day).
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 should have a good service
life, maintain their performance and should be
reliable, the last three items will make a valve
sound better 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
paintwork etc, with a soft paintbrush. Other marks
can usually be removed with a damp cloth.
On no account use anything wet on the amplifier,
and always clean with the power disconnected.
5 Trouble Shooting
Amplifier Dead
Check the 3 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 3.00
Amp ‘anti-surge’.
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.
Each 300B is protected by a 300ma “T” (or “anti-
surge”) fuse. If the left or right pair have blown
there will be no sound on that channel. A single
fuse will result in distorted sound at higher levels.
Also the valve(s) in question will be much cooler
(beware if touching). Replacement will require the
amplifier inverting on to a soft cloth (beware the
height of some 300Bs!) and the bottom removed.
Ensure that power is removed at least 10 mins
before hand. The supplied meter will assist in fuse
checking. Only replace with correct type.
(available from Icon free).
Only attempt if you
feel confident, or contact your dealer for
assistance.
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,
