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OPERATING THE SIGMA PREAMPLIFIER
Front Panel Controls:
Although most of the front panel controls (Volume, Power, Mute) are self explanatory, VAC
has outfitted this unit with several advanced features which bear further description:
Phono Section MM (option): When fitted, input “L6" will be connected to a discrete, pure
tube phono preamplifier, providing 40 dB of gain, suitable for use with MM (moving
magnet) and many high-output MC (moving coil) cartridges. Your VAC dealer can
recommend the proper phono cartridge(s).
Phono Section MC (option): As above, this will be fitted to “L6", and provides
approximately 60 dB of gain. It should not be used with high output pickups, which may
generate excessive distortion. Your VAC dealers can recommend the proper phono
cartridge(s). A switch on the back panel selects between MC (60 dB) and MM (40 dB)
mode.
Monitor: This switches between “Source” and “Tape”. In the “Source” position, input
selection is determined by the Source Selector Switch. In the “Tape” position, the Source
Selector is overridden, and the Tape inputs are activated. [Important: The Sigma
Preamplifier is outfitted with a full “tape loop”, including a line level tape input and a fixed
level recording output. In addition to driving the recording inputs of a tape deck, this output
can supply signal to any typical line level input, enabling it to control a second zone in multi
room installations.]
Cinema: This switches between “Source” and “Cinema”, a fixed volume pass-through. In
the “Source” position, input selection is determined by the Source Selector Switch. The
“Cinema” position provides access to one of the Sigma Preamplifier’s most unusual feature.
When set in the “Source” position, input choice is governed by the Input Selector switch.
This is the normal setting, and enables the unit to be used as a typical preamplifier. Selecting
the “Cinema” position bypasses all preamplifier controls (including volume) and passes the
output from your surround sound processor (i.e., the front left- and right-channel outputs of
a multichannel processor) directly to your power amplifier. In this case, the users’ analogue
stereo sources would be connected, as usual, to the line, phono and tape inputs. A/V inputs
(DVD, Laserdisc, DSS, etc.) would be connected to the home theater processor, and the
processor’s main outputs would be connected to the pair of rear panel RCA jacks labeled
“Home Theater Direct”. When the control is set to the “Cinema” position, the Sigma
functions as a pass-through ONLY, and is controlled by the external processor, preamplifier,
or other component connected to the “Home Theater Direct” (a/k/a “Cine”) inputs.
Mute: This knob is spring loaded; moving the control clockwise will toggle between the
