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3 Connecting inputs & outputs
Many
problems
associated
with
electronic
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
These power amplifiers require some kind of pre
amplifier to accomplish switching and volume
control. This could either be achieved by either a
“passive” or powered unit. Icon Audio make ideal
pre amps. You may wish to consult your dealer. If
you wish to use a turntable you will need a
suitable phono pre-amp. Your dealer or Icon
Audio can advise you. Our new PS1 MM/MC all
valve phono stage is an ideal partner.
Connecting loudspeakers
It is important to use good quality loudspeaker
cable. This should be relatively thick and muti-
stranded. i.e. 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 Icon valve amplifiers are more
tolerant of cables, therefore the benefits of some
very ‘exotic’ cables may be less apparent. But this
is also personal taste.
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 cause damage.
Alternatively use
good quality ‘banana’ plugs or spade connections,
once fitted they are trouble free.
Speaker polarity. When using a pair of MB90s
it is essential that you observe the polarity of
the terminals; they must be the same for the
left/right connections at each 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 (FM
tuners are usually switchable to 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 MB 90 is designed to work with full range, low
to medium efficiency speakers having impedance
between 4 ohms to 8 ohms. Speakers having
efficiency of lower than 84db 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.
