Page 4
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
250mv or more, to get full power.
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.
“H” will give good sensitivity if using as an
“integrated” amplifier with a small amount of
feedback.
“L” will reduce the sensitivity and increase the
Damping Factor and is ideal for use with a
separate pre-amplifier. This setting may be useful
if you find the volume control “too steep”.
“0” will increase the sensitivity higher and
operates the amplifier without any feedback. The
final position is personal choice.
Feedback.
The sensitivity switch does not
attenuate the signal, but alters the gain by
adjusting the feedback within the ampl
ifier. In “H”
the feedback is low, in “L” position the feedback is
moderate.
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 ‘Pre-out’. 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 con
nected 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’.
In our experience valve amplifiers are more
tolerant of cables, therefore the benefits of very
‘exotic’ cables may be wasted! But this is personal
taste. Icon or your dealer will advise you.
As all speaker cables have losses, keeping the
speaker cables shorter than 10m will help.
You 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 ST300 amplifier
does not have an output protection device,
which would degrade the sound. So a
prolonged short due to strands of wire
touching
could
damage
the
valves
.
Alternatively use good quality ‘banana’ plugs,
once fitted they are trouble free.
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, if not
reverse the terminals
for one channel only,
You will now hear more, or
less bass. The higher bass output is the correct
setting to use. Another alternative is to use a test
disc. If you are ‘bi-wiring’ your speakers with only
two terminals, you must use only 4 or 8 ohms, not
both, as this will not load the amplifier properly.
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.
Speaker impedance.
It is important to use the
correct speaker impedance terminals, as this will
give the best sound quality and power matching. 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 terminals
for each channel. If two pairs of speakers are
required to be connected, they must both be 8-
ohm and connected 4 ohm terminals. Contact
Icon Audio for more information. Damage could
be occur if care is not taken.
