Arcam Delta 90.2 - Manual (Page 7)

Volume control
The volume control Is of a split type and allows you to adjust
the levels of the left and right channels for both loudspeakers
independently. Normally, the two halves of the control knob rotate
together as they are locked by a friction clutch inside the volume control
itself. However, by holding the rear part of the control firmly with the
first finger and thumb of one hand, it is possible to alter the relative
position of the two parts of the knob and thus compensate for level
differences caused by the nature of the input signal or due to room
acoustics.
Mono
The amplifier is in its normal stereo mode when the mono
button is out. In this position, the left and right input signals are
amplified independently to feed the corresponding loudspeaker outputs.
When the mono button is pushed in the left and right signals are mixed
together and the combined signal is routed to both loudspeakers. This is
particularly useful when listening to mono records or tapes (as much low
frequency out-of-phase rumble can be eliminated) or to remove excessive
hiss from FM broadcasts. It is also invaluable for checking speaker
phasing in a stereo hi fi system.
Tone controls
The Delta 90.2’s bass and treble controls have been designed
to provide a limited but precise range of adjustment to the frequency
extremes only.
The bass control permits some compensation for room or
loudspeaker deficiencies without affecting the critical midrange
frequencies. The treble control is particularly useful for correcting the
frequency response errors of certain cartridges or for taming the
apparently overbright sound of some compact disc material.
The bass and treble controls progressively cut their respective
frequencies when turned anti-clockwise and boost them when turned
clockwise. The flattest response for each control is obtained in the 12
o'clock position, conveniently and positively located by a centre click
stop.
SP2 switch
When this switch is in the depressed position the output from
the amplifier is channelled through the loudspeaker outlets marked
'switched', in addition to those marked 'main'. The 'main' outputs work
all the time. If the SP2 switch is out no sound will be heard via
loudspeakers connected to the 'switched' terminals. (See Loudspeakers
page 5).
Phones
The headphone socket will accept any headphones fitted
with a standard quarter inch (6.35mm) stereo Jack plug. The headphones
may be operated in parallel with the loudspeaker outlets, or not, as you
wish (see Loudspeakers page 5).
Direct
The direct switch is located Just to the right of the tone
controls. With the direct switch in the depressed position the audio
signals completely bypass the tone control stages so that adjustment of
the bass or treble controls will not alter the sound. If the tone controls
are not often used then it is recommended that the direct switch be left
in to achieve the very best performance.