icon Audio Stereo 40 6AS7 Limited Edition, Instruction Manual

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Page 5
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
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
suitable phono pre-amp. Icon Audio or your dealer
can advise you. Our new 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 should normally be used when used
as an integrated amplifier.
The “Low” setting may
be used if the ST40 is used as a power amplifier
with a pre amplifier, as pre amplifiers generally
have a higher output. In this mode of operation it
is suggested that the volume control be fully
clockwise,(the volume control is then effectively
“out of circuit”) 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 your
requirements. The feedback switch may also be
used if you prefer a generally lower volume level.
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 lo
w, in “L” position there is zero
global feedback.
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 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 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 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 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 (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
use only two terminals, you must use only 4 or 8
ohms
(plus “0” black terminal), 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 unsure 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.
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.