Warm-Up Sequence; The Big Picture - VHT Valvulator GP3 Preliminary Owners Manual

WARM-UP SEQUENCE

As with all tube amplifiers, gradual warm-up greatly extends tube life and tone quality. There are
two major wear factors which can noticeably impact the performance of preamp tubes. The first is
Filament Stress. The second is called Cathode Stripping.
Filament Stress occurs when a cold tube is allowed to heat up too quickly. If this stress is
allowed to occur too often, it is possible to destroy the filament, in which case the tube will cease
to function. This is not a big problem in vintage amplifiers with AC powered heaters, which
normally exhibit an inherently slow warm-up characteristic. However, AC filament generated
hum can become intolerably loud in amplifiers with very high-gain capability. A regulated DC
filament supply like that used in the GP3 totally eliminates the hum. As low maintenance is a top
priority in the GP3, great care has been taken in the design of the filament supply in order to
prevent Filament Stress. To insure low noise and long tube life, the Regulated DC Filament
Supply in the GP3 has a "Ramp" feature, which upon power-up slowly raises the heater voltage
up to the optimum voltage required by the tubes.
Cathode Stripping occurs when high voltage is supplied to the tube before the tube filament or
heater is adequately warmed up and fully stabilized. Cathode Stripping eventually causes the tube
to lose gain prematurely, resulting in dull tone and loss of sustain. To prevent Cathode Stripping,
we've incorporated another exclusive feature into the GP3, the High Voltage Auto-Standby
Timer.
During power-up, the channels automatically MUTE and the three channel LED indicators begin
to flash, indicating that the warm-up sequence has begun. After 15 seconds, the time it takes for
the tube filaments to reach operating temperature, a timer function in the GP3s microprocessor
sends a "Turn On" command to the high voltage supply and the Clean channel LED turns on.
Note: If you have previously powered down your GP3 in a different channel, that channel
and its global settings will activate after the warm-up sequence is complete. Once the high
voltage supply has been activated and stabilized, the output mute relay deactivates and the GP3 is
ready to play. The entire Warm-Up Sequence takes 18 seconds to complete.
Of course, there may be times when it is not convenient to wait 18 seconds for the GP3 to begin
operating. If you are mid-solo at a gig or recording session for example and there is a momentary
interruption in AC power, the GP3 may still be warm enough to begin operating immediately. In
this case, simply press the global CHANNEL key right after power has been restored to the GP3.
This will initiate a modified 3-second turn-on sequence, which will then automatically return you
to your previous settings.

THE BIG PICTURE

The Valvulator™ GP3 is a complete, self-contained Very Low Power amplifier. Utilizing its
groundbreaking Dynamic Sensing Technology™ incorporating a unique output power circuit;
the GP3 reacts to playing dynamics the same way a conventional guitar amplifier does. With user
control over this dynamic "expression", you can dial in the ideal dynamic response of the GP3 to
suit your style.
A typical tube guitar amplifier is made up of a preamp stage, which consists of preamp tubes,
gain stages and a tone control system, and a power amp stage, which consists of power tubes and
an output transformer. A great guitar amplifier is born when the preamp and power amp
complement and interact with each other such that the whole becomes greater than the sum of its