QUAD VA-One - Page 8

FURTHER
INTRODUCTION
Burn
In
New
Equipment
Burn in
is
very important. Valve
components work
at
high voltage and temperatu
re
and
when new th
ey
should
spend an e
xt
ended
period
at
those temperatures
to
bed in. We recommend you burn in the amplifier
for
at
least
four
or
preferably
twelve
hours
before you first using it.
If you run in your equipment
for
this extended period, make
doubly
sure that
all
the
sa
fe
ty conditions
covered in this
manual
are
fully
met. Supervise the equipment
for
the first
hour
or
so and
if
you have to
leave
the unit unattended
thereafter,
look
in
occasionally
to
make sure
all
is
well.
Warming
Up
Before Use
Allow
at
least
fifteen minutes
for
the amplifier
to
'warm up' before
use
.
If
you
play loud
music
while
the
system
is
cold.
The output
valves will
not
be fully
op
erated and the amplifier
will be starved
of
voltage
and current. The r
es
ulting
di
stortion
is
unpleasant
and potential damage to the amplifier's valves
and your loudspeakers.
Intensive
use
of
the equipment before it has w
ar
med up
will
shorten valve's
life.
Valve
Lifetimes
Valves
contain a heating element. This heats up the valv
e's
cathode, which
is
coated
to
gi
ve off a steady stream
of
electrons.
After a few years this coating will
begin
to
wear out
and
performan
ce
will gradually
deteriorate. The KT66 output valv
es
are
likely
to dete
ri
orate first but the driver valves will also eventually
wear
out
.
As
the
valves
start to wear
out
the sound
will become
les
s well
defined and a
lack
of
dynamics and power
will
become evident.
Replacing the
valves
with a new set
will fully
restore the audio performance
of
the amplifier. When replacing
valves
it
is essential
to
use
the highest quality
available.
Poor quality
valves will
adversely affect the sound quality and may in extreme cases damage
the amplifier. When replacing the output valves,
use
matched
sets
for
be
st
resu
l
ts.
Do not
leave
the amplifier permanently switched on or you will
se
ri
ously shorten the lif
es
pan
of
yo
ur
valves!
Output
Transformer
After installing
or
changing the wiring to your speakers, keep the
volume
control
at
zero,
let
the amplifier warm up and turn up
the main volume gradually.
If
you don't hear sound, switched
off
immediately and investigate.
The output transformer is
de
signed
to
match the high
voltage, low c
urr
ent condi
ti
ons in w
hi
ch the output
va
l
ves
oper
at
e to the
low
vo
ltage high current requireme
nts
of a loudspeaker. Although robust,
an
output transformer can be
damag
ed and in
ex
treme
cases wrecked, by careless use.
If
you
play
a
valve
amplifier into a short circuit, the output transformer will
soak
up
a
lot
of
energy before
failing,
but
if
the short persists the transformer
could
be damaged.
Operating
a
valve
amplifier
at
high output
level
with loudspeaker connected can
also
damage
an output transformer. .
The machine must be used on the connected lo
ad
conditions, otherwise
it
may cause damage to the output transformer.
5