Ariston RD 40 - 4. Special Instructions

- —
5. HINTS ON TUNING
Acoustic Feedback.
Acoustic
Feedback
occurs
when
the
isolation
of
the
pick
up
from
the
loudspeakers
is
inadequate.
Vibrations
from
the latter
are
received
by
the
pick
up,
turned
into
an
electrical
signal
and
returned
via
the
amplifiers
to
the
loudspeakers,
The
process
is
rapidly
repeated
and
unless
the
equipment
is
switched
off
or
the
volume
control
retarded
the
resulting
signal
level
may
cause
overload
damage
to
the
amplifiers
and
loudspeakers.
If feedback is suspected, carry out a simple check as follows:
a)
Switch
off
the
turntable
and
place
the
stylus
on
a
stationary
record,
slowly
advance
the
volume
control
up
to
and
a
little
beyond
the
normal
maximum
listening
level.
b)
Hf
and
when
feedback
occurs
it
will
be
heard
as
a
howl
of
rapidly
rising
intensity,
so
be
ready
to retard
the
volume
control
quickly.
c) If the test shows that feedback occurs within or close to normal listen-
ing levels, attention should be given to the foregoing points.
d} Experiment with the positioning of the turntable should reveal marked
differences
in
the
level
of
feedback.
Ensure
the
sub
chassis
is
not
short-
circuited and is quite free to move both vertically and horizontally.
e} The spring suspension should be adjusted to as low a pitch as possible.
The
higher
the
platter
and
chassis
sits
on
the
turntable
the
greater
acoustic feedback likelyhood.
Mechanical Noise
There
are
various
areas
which
may
contribute
to
mechanical
noise,
the
likeliest
of
these
are
the
bearings
which
may
require
oil,
the
suspension
which
may
be
short-
circuited
or
the
motor.
Check
the
electrics
and
all
connections,
ensure
the
wiring
is
correct
tor the
electrical
current
and
frequency.
Wow
The
most
likely
source
of
wow
is
the
drive
belt,
which
may
have
become
contam-
inated
with
oil,
Remove
the
belt
and
clean
it
with
lighter
fuel,
subsequently
dusting
it
with
chalk.
Clean
the
belt
faces
on
both
the
pulley
and
the
hub
with
lighter
fuel.
Rumble
As
the
word
implies,
this
term
describes
the
intermittent
low
frequency
sounds
heard
through
the
loudspeakers
and
can be
caused
by
foreign
matter or
imperfect-
ions
in the
moving parts
of
theturntable,
The
importance
of mechanical
excellence
in
these
areas
Cannot
be
overstated
since
the
pick
up
cannot
discriminate
between
the
information
on
the
record
and
unwanted
vibrations
within
the
turntable.
Always
ensure
the
bearing
is
topped
up
with
light
machine
oi].
Ensure
the
sub
chassis is
decoupled,