Page 4
Operation
About Gain
This can be confusing but is normally expressed as:
Max Gain= 13db (input voltage x4.5) at full volume.
In other words at full volume a 200mv input music
signal would become 1v (1000mv) at OUT 1&2. A
50w power amplifier with an input sensitivity of 1v
would then deliver full power. (20vx20v=400 /8=50
watts).
But this is not a very realistic situation.
A more usual situation is tabulated below showing the
gain
Volume Position
Output mv
Gain
O’Clock
5:00 (Full)
900
x4.5 13db
3:30
700
x3.5 11db
3:00
500
x2.5 8db
2:00
300
x1.5 3.5db
1:00
200
x1.0 0.0db
11:00
100
x0.5 -6db
10:00
50
x0.25 -12db
9:00
20
x0.1 -20db
8:30
10
x0.05 -26db
8:00
2.5
x0.012 -38db
7.30
1
x0.005 -46db
7:00
0
x0
So it can be seen in blue area that a signal at 1:00
0
’clock or below is either unity gain or attenuated.
OUTPUT 2 Attenuation
Normally OUT 2 is supplied from new with no
attenuation therefore the OUT 2 is identical to OUT 1.
Both may be used at the same time without loss of
quality.
Trouble Shooting
Amplifier Dead
Check the mains fuse at the back of the amplifier. To
gain access, remove the mains lead. The fuse is in a
small plastic drawer, which forms part of the socket
assembly. To open insert a flat bade screwdriver or
similar and prise open.
The fuse in use is the
innermost
the outer is a spare. Should the
replacement fuse also blow there is a fault.
Replacements should be 1Amp (2Amp USA)
‘anti-
surge’. If it is OK try a different IEC cable.
If that does not work refer to dealer or Icon Audio.
The fuse in the UK mains plug should be a 3 or 5 amp
fuse, although unlikely, this should be checked if the
amplifier fuse is OK.
No sound
Have you selected the right input? Are the
connections OK? Is everything switched on? Are the
speakers connected?
Distorted sound.
Try another source; if sound improves then it’s
probably something wrong with the first source. If no
improvement try different speakers, if no improvement
could be an amplifier problem.
Hum Problems
If you experience hum, try disconnecting all inputs, if
hum persists this is probably an amplifier fault.
If not, Identify which input is causing hum. Connect
one input at a time. A common cause is a ‘hum loop’
caused by having too many earths, and may be
identified by unplugging each input source from the
mains. One remedy for this is to use an interconnect
which only has the screen connected at one end.
Other causes of low-level hum can be from adjacent
equipment, so experiment with moving equipment
around to see if this makes the hum better or worse.
One channel missing.
Usually ‘bad’ connection on either the input or the
speakers. Try swapping the connection over to
establish if the cause is:
(a) Input to the amp.
Sound will move to the other
channel.
(b) Amplifier or speakers.
Sound will not move.
Strange noises coming from speakers
Turn volume to minimum on unused input, if problem
corrected either fault with source unit or with
connection. If noise persists, problem with amplifier.
A valve that is lit up is not a guarantee that it is
working properly; conversely a valve that is not lit up
will not be working.
If none of the above see below for valve replacement.
Valve Replacement
The three 6SN7/CV181s are generally very long
lasting. With normal use (3h x 365 x 5 years =
5475hrs) We would suggest replacement after 5
years. But valves can suffer sudden failure or
“go
noisy
” at any time in which case single or full
replacement will be required depending upon age.
Noisy or intermittent valves
May be identified by
swapping valves around. The left hand 6SN7
amplifies the LH channel, the right hand 6SN7
amplifies the RH channel. The centre 6SN7 is the
right and left output valve.
