Accuphase C-280 - Page 5

[3] HEAD AMP
LINE 1 /LINE 2
The two pairs of rear panel LINE
jacks are used with components having
high level output signals comparable
to tuners and tape decks. The C-280's
rated input voltage is 126mV (the
input voltage required to deliver the
rated output). Use the LINE jacks for
a COMPACT DISC player, second tuner,
third tape deck or other similar com-
ponent.
Head Amp Selector
Use this selector to turn the built-
in head amp on and off and select the
amount of gain when using an MC phono
cartridge. When the input selector is
in one of the DISC positions, the
muting circuit operates for about one
second when the position of this
selector is changed.
OFF / MM (MM cartridge position)
This position turns the head amp off
and is used for MM (moving magnet)
and other high output cartridges that
do not require a step-up device. Some
MC (moving coil) cartridges deliver a
high output voltage equivalent to MM
cartridges. However, we do not recom-
mend the use of high output MC
cartridges at this position, since
the high input impedance of the MM
position may cause noise.
+26dB and +32dB (MC cartridge positions)
Use one of these positions when
listening to a turntable equipped
with a low output MC cartridge. The
numbers refer to the head amp gain at
each position. At the +26dB position,
the cartridge output voltage is
amplified 20 times. That means a
0.1mV output cartridge would yield a
2mV voltage. The +32dB position
amplifies the cartridge output
voltage 40 times.
The +26dB position provides enough
gain for almost all MC cartridges. In
general, only MC cartridges having an
output voltage of 0.1mV (5 cm/sec, 1
kHz) max. should be used with the
+32dB position.
If there seems to be insufficient
gain when using the +26dB position,
the +32dB position may give better
results. However, if this position is
used with an MC cartridge having an
output voltage higher than 0.5mV at a
cutting velocity of 5 cm/sec, 1 kHz,
high level signals will be distorted
and overall sound quality will
deteriorate.
If the setting is raised from +26dB
to +32dB without changing the posi-
tion of the volume control, noise may
be caused if you are using very effi-
cient speakers. This occurs because
the degree of amplification has
increased while the amplifier's noise
level has remained the same.
If an MM cartridge is used with the
head amp, high frequencies will be
attenuated and overall tonal balance
will suffer.
[4] SUBSONIC FILTER
The subsonic filter suppresses extre-
mely low frequency signals below 10
Hz (that is, well below the audible
frequency range) with a slope steep-
ness of 18dB/octave and serves to
prevent extremely low frequency noise
from interfering with sound reproduc-
tion in the audible frequency range.
This filter is most useful in sup-
pressing extremely low frequency
signals generated by record warps
which could prevent the woofers from
operating properly. Press this switch
to turn the filter on (FILTER indica-
tor lights) and once again to turn
the filter off (indicator
extinguishes).
[5] MODE— Mode Switch
Use this switch to select STEREO-
PHONIC or MONOPHONIC reproduction.
The MONO indicator lights to show
when this selector is in the
MONOPHONIC setting. In the MONOPHONIC
setting, the left and right channel
signals are mixed and sent to both
speakers. This is useful for
adjusting the volume balance between
the two speakers. Press this switch
again to return to the STEREOPHONIC
mode (indicator extinguishes).
[6] mc LOAD (OHMS)—MC Load Selector
Use this selector to match the built-
in head amp's input impedance with
the load impedance of the MC
Ag