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3 Connecting inputs & outputs
Many problems associated with Hi Fi equipment
involves 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 equipment having
an audio “Line Output” e.g. CD, Tuner, Tape
Deck, Streamer, TV, DVD etc having an output of
250mv or more, to get full power.
If you wish to use a turntable you will need a
suitable phono pre-amp. Icon Audio or your dealer
can advise you. Our all valve phono stage is an
ideal partner.
“H” & “L” sensitivity/Power Amplifier mode.
Located on the rear of the amplifier the High and
Low sensitivity switch has two functions. The
“High” setting is optimised for use as an integrated
amplifier and will give you the most gain.
The “Low” setting may be used if the ST40 is used
as a power amplifier together with a pre amplifier,
as pre amplifiers generally have a higher output.
In this mode it is suggested that the volume
control be fully clockwise, and volume be
controlled on the pre-amplifier for best results.
The tape input will provide the most direct signal
path. If you have too much gain Icon Audio can
modify to suit you requirements. The
“Low” setting
may also be used if the slope of the volume
control is too steep. Feel free experiment for a
setting which suits your needs.
There is also a middle position which has no
feedback therefore maximum gain. This primarily
for use by engineers for testing the amplifier.
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 moderate.
Connecting a tape deck/Recorder/Equaliser
The STEREO 40 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 40 has a ‘Tape
Monitor’ facility, which enables you to use a ‘three
head de
ck’ 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
Use only good quality loudspeaker cable. This
should be relatively thick and multi-stranded. e.g.
QED ‘Classic” 79 strand 2.5mm is more than
adequate (for amplifiers up to 2,200w!) 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 very
tolerant of loudspeaker cables, therefore the
benefits of very ‘exotic’ cables may be wasted!
But this is personal taste. Icon Audio or your
dealer will advise you.
As all cables have losses, keeping the speaker
cables short is best. It may be better and be
cheaper to re-arrange your room and use shorter
cables than to spend a fortune on longer cables!
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).
Be warned this 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 (
most 1950’s
recordings are mono) and stand the speakers
close together. If correct you should hear plenty of
bass, if not
reverse the terminals for one
channel only, either at the amp or speaker.
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 only two terminals, you must
use only 4 or 8 ohms, not both, as this will not
load the amplifier properly.
The STEREO 40 is designed to work with full
range,
medium
to
high
efficiency
having
impedance of 4 ohms to 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 un
sure or “6 ohms” or “4 to
8 ohms” is quoted; a rule of thumb guide is to try
both positions. The loudest being the best match.
Although your personal taste should be the final
deciding factor.
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.
