FRONT
Stand by
There are two different levels of voltage controlling the tubes:
1) the basic voltage intended to warm the tube to minimum operational temperature. This
voltage is always applied to the tube whenever the power switch is in the on position.
2) the operating voltage (plate voltage) which drives the tube. The operating voltage is turned
off with the STANDBY switch.
The green LED indicates the unit
is in standby mode,
the red LED above the STANDBY switch
indicates normal playing mode.
If you are using only one channel of the
switch the other channel into standby mode.
Volume
VOLUME controls how much the input signal is amplified, thereby controlling the output
volume of the channel. Due to the special LINE DRIVER
circuitry
in each channel’s input,
VOLUME offers a very wide range of control which also accommodates devices with very low
output levels (300 mV are perfectly adequate to drive the output stage; voltages up to 10 volts
can be accepted without overloading the input).
Presence
With tube amplification, the higher frequencies (PRESENCE) are most effectively controlled at
the power amp stage. This frequency range plays a major role in determining the character of
the guitar sound and its ability to cut through.
The intensity of the PRESENCE control depends to a great degree on the guitar sound itself: a
heavily overdriven sound with a great deal of overtone energy will respond to the PRESENCE
control much more dramatically than will a clean sound with little overtone content.
Over the last 30 years of tube amp tradition, two different types of PRESENCE control have
established themselves as standard:
the " British” type, which only affects higher frequencies, and only boosts, and
the “American” type, which affects a broader range of frequencies from high mids to
harmonic overtones, and can either boost or cut.
Since both PRESENCE philosophies make sense, and both allow for very different characters,
particularly with overdriven sounds, the VS 250 offers both types.
PRESENCE 1 is the “American” type. The signal is unaffected when the control is in the
" 3-o'clock" position.
PRESENCE 2 is the " British” type. in the fully counterclockwise position, the sound is
unaffected.