Manley MASTERINGROOM STANDARD REFERENCE PREAMPLIFIER - Manual (Page 6)

FRONT PANEL
A SELECTOR SWITCH Switch to select between inputs. Counterclockwise: Phono
(MM or MC), AUX (auxilary), DIG (CD), TAPE, TUNER, VIDEO. NOTE: always
turn volume control (level) down before switching selector switch.
B LEVEL CONTROL Adjust the stereo gain of the selected signal. Both channels
are always amplified by the same amount.
C FULL / REDUCED SWITCH Provides a course volume adjustment of 5 dB. The
level control will have better resolution when set to reduced, but less gain.
D STEREO / MONO SWITCH Switch up for stereo signal. Switch down to MONO
or sum the two channel signals.
E L - BALANCE - R CONTROL Modifies the gain of the left and right channels.
When set to 12 o'clock (straight up) both channels will produce the same gain.
Rotating the control fully clockwise or counterclockwise will reduce the gain of the
corresponding channel by approximately 10 dB.
F LED POWER INDICATOR Illuminates when the preamplifier is powered and
running.
G POWER SWITCH Switch up to turn on the power, down to turn the power off.