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3 Connecting inputs & outputs
Most problems associated with electronic
equipment involve connecting leads, which are
usually either
‘BAD CONNECTION’ or a
‘WRONG CONNECTION’
. So it’s worth making
sure that you have good connections and that
your leads are the right way round.
Inputs
The amplifier will work with any standard piece of
hi fi e.g. CD, Tuner, Tape Deck, Mini Disc, TV,
Video Recorder, DVD etc having an output of
approx. 300mV or more, to get full power.
Balanced outputs need a suitable adaptor.
If you wish to use a turntable you will need a
phono pre-amp. Icon Audio make several pure
valve models ideal for the ST300. See our website
or your dealer can advise you.
“H, L, 0” sensitivity/Power Amplifier mode.
The sensitivity switch of the amplifier does not
attenuate the signal by resistors but by varying the
amount of negative feedback within the amplifier.
“H” (High) gives the sensitivity of an “integrated”
amplifier with a small amount of feedback.
“L” (Low) has a lower sensitivity giving a less
steep volume control and higher Damping Factor.
And is better suited if you are using a separate
line pre-amplifier.
“0” (Middle) This position uses no feedback
therefore has very high sensitivity and a lower
damping factor. Designed to be used mainly for
servicing but if preferred may be used normally.
We suggest “H” (upper) position initially.
Connecting a tape deck/Recorder/Equaliser
The STEREO 300 will work with any tape deck
having suitable output, and it is possible to record
from any connected source using the terminals
marked ‘REC OUT’. Playback via The STEREO
300 has a ‘Tape Monitor’ facility, which enables
you to use a ‘three head deck’ or an equalizer.
Some tape decks ‘Present a load’ to the amplifier
terminals, even when not in use, which can affect
sound quality. (You can do an audible check for
this by removing the plugs and listening for a
change). Therefore for best results do not leave
anything connected to “Rec out” unnecessarily.
Connecting loudspeakers
It is important to use good quality loudspeaker
cable. This should be relatively thick and multi-
stranded. e.g. QED ‘Original’ or better. Take care
to connect the correct polarity. The use of
‘Banana plugs’ or ‘spade’ connections will ensure
a good connection whilst minimising the risk of
‘shorts’. You also can either ‘hard wire’ your cable
to the amplifier by baring enough cable to fit in the
connector and twist together to avoid any spare
strands touching anywhere else (soldering the
stands together helps). The amplifier does not
have an output protection device, which can
degrade the sound. So a prolonged short due to
strands of wire touching could damage the valves.
In our experience valve amplifiers are more
tolerant of cables, therefore the benefits of ‘exotic’
cables may be wasted! But this is personal taste.
Icon or your dealer will advise you.
Speaker cables have minimal loss, keeping each
speaker cables shorter than 10m will help.
Speaker polarity. It is essential that you
observe the polarity of the terminals; they
must be the same for the left/right connections
at the amplifier end and at the loudspeaker
end
. Otherwise the sound will be ‘out of phase’
with the sound stage ‘inside out’ with reduced
bass.
If you are unable to check this or confirm
the polarity
(e.g. if you have ‘built in’ wiring), try
the following; Connect the system up and play
some music with plenty of bass (e.g. dance
music), preferably in mono and stand the
speakers close together. If correct you should
hear plenty of bass,
reversing the terminals for
one channel only
should result in less bass. The
higher bass output is the correct setting to use.
Another alternative is to use a test disc.
The STEREO 300 is designed to work with full
range, medium to high efficiency speakers having
impedance of about 4-8 Ohms. Speakers having
efficiency of lower than 86db will have greater
difficulty in providing a high sound level. But this
will also depend upon individual speakers, room
size, type of music and positioning etc.
Loudspeaker impedance.
If using 15-ohm speakers use the 8-ohm
connections. If you are unsure or “6 ohms” or “4 to
8 ohms” is quoted; a rule of thumb guide is to try
both positions. The 4 Ohm position will have a
little more “bass weight”. Although your personal
taste should be the final deciding factor.
Do not connect to more than one pair of speakers
for each channel. If two pairs of speakers are
required to be connected, they must both be 8-
ohm and connected to the 4 ohm terminals.
Contact Icon Audio for more information. Sound
quality may be impaired if the amplifier is not
correctly loaded.
