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IMPORTANT READ THESE NOTES THROUGH FIRST!
Your safety is paramount to us. Big triode
amplifiers like the MB 805s operate using high
voltages. Please take care when setting up
and adjusting. DO NOT OPERATE WITHOUT
VALVES FITTED. If you are uncertain how to
proceed at any point ask your dealer or Icon
Audio.
1 Unpack each unit carefully. Make sure that it
is in good condition. If not report to Icon Audio or
your dealer. It is important that you keep the
packaging for warranty/service return/shipping.
NOTE THE "LEFT" and "RIGHT" MB 805
orientation on each amplifier. Also keep the
left and right amplifier valves separate.
2 If necessary fit the valves, or check that they
are firmly in place.
SEE PREVIOUS DIAGRAM.
Fit the valves according to the numbers
written on the base of the valve, and on the
socket, normally V1-V6. Observe "Left" and
"Right". The 805s should be fitted first to the
REAR
socket
(the
transformers). Fit by locating the bayonet pin at
the side and twisting clockwise by 45 degrees.
Then fit the 2A3. Double check the orientation of
the small and large pins during fitting.
The small valves should be gently but firmly
pushed into place. The four 6SN7s as marked and
numbered.
Be careful to note the correct orientation of
the small valves central "spigot" between the
pins otherwise damage could occur.
To avoid damage to the valves, do not twist the
glass envelopes excessively as they may become
loose/detached. Hold the valves as close to the
base as possible. Damage to valves is not
covered by the warranty. These valves have
already been fitted and tested for quality.
3 Connect to source unit, e.g. Pre amp, Passive
pre amp etc via sockets on the rear.
4 Connect speaker terminals use "0" &"8 ohm"
terminals unless you have 4 ohm speakers (see
P5) Make sure that the polarity is correct. (See
speaker connections chapter 3). If 'bi-wiring' both
'common' should go to the black terminal and both
'positive' (or red) should go to the red terminals.
5 Connect to mains supply using supplied IEC
mains lead to 230/240v supply (or 117v)*. If for
some reason the welded plug must be
removed, please
remove
dispose of immediately. (As they can be a
danger to children if plugged in). The replacement
plug should be wired in the following way Brown
to Live terminal, Blue to Neutral terminal and
Green/Yellow to Earth terminal.
6 SWITCH ON! The blue mains indicator should
light up. The 805s will glow bright yellow. You will
likely hear a "humming noise" for a few seconds,
this is normal. After about 20 seconds the
*See engineers notes at rear
2 QUICK SET UP GUIDE
socket
nearest
the
plug
fuse
and
amplifier should now be working. The small valves
may have a visible orange glow from the cathode
heaters. With the pre amp volume control set to
minimum there should be no sound coming from
the speakers except a barely discernable hum. If
there are any unpleasant sounds coming from the
speakers, switch off and refer to the 'Trouble
Shooting' section or contact Icon Audio.
6a Sensitivity Switch
Located on the rear, this switch is "UP" (H) for
(high sensitivity) operation. If use with a pre-
amplifier is required, the switch should normally
be "DOWN" in the low sensitivity position, but this
is down to your personal preference.
7 Your unit should now be functioning. If not
check wiring again. Do not operate at a high
volume for the first five minutes to allow the valves
to warm up properly.
Please note all these things are normal for
valve amplifiers:
A, 805 Valves get very hot, BEWARE!
B, The transformer covers will get quite warm
C, There may be a "new" smell for a few weeks.
D, Mobile phone 'breakthrough' is normal. Move
your phone further away to cure this.
E, Valves may make a 'tinkling' sound when
warming up and cooling down.
F, One channel may come on before the other at
switch on.
G, There may be a 'click' when switching off.
H, The occasional "click" or "pop" is normal.
I, The hum level may higher for about 30 secs
after switching on.
8 Health and Safety. The valves when operating
have high surface temperatures. Keep out of
reach of children and pets. The use of the
supplied
guard
is
recommended
circumstances. Always unplug when making
adjustments. Like all amplifiers there are
potentially lethal high voltages inside, which
when switched off can take twenty minutes to
discharge! Do not remove bottom panel unless
you are a competent engineer. There are no user
serviceable parts inside. Like other household
electrical appliances do not leave unattended
whilst switched on. Do not adjust the 805 bias
pre sets without reference to the manual. Incorrect
adjustment could cause the valves to overheat,
in damage to valves and
with resulting
amplifier.
Bias Adjustment:
The bias adjustment is factory set. No initial
adjustment is necessary.
To maintain the best performance of the amplifier
you should check the bias of the output valves
from time to time (say twice a year). Full details
will be found in section 6.
in
these
Page 4
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