Thermionic Culture THE CULTURE VULTURE SUPER 15 Stereo Valve Distortion - Manual (Page 5)

© Thermionic Culture Ltd, 2014 4
2 Controls & Meters
2.1 Drive
This control is really in 2 parts, a switch and a rotary pot.
The switch gives a coarse control and the pot a fine control
of the signal input level. At the first position “Normal” (for
line level signals) the frequency response is flat. The mid
position increases the gain by 10dB and adds some top
end for extra bite. “Overdrive” is 28dB above “Normal” and
can be used for extreme distortion effects at line level, also
guitars and other low level sources.
The drive pot controls the amount of signal you are feeding
to the 2
nd
“distortion” valve, a 5725, so the higher it’s set
the more effect. It should be used in conjunction with the
output level control.
2.1 Output Level
This simply controls the signal going to the output valve. A
-10Db switch is provided for more accurate control when a
Vulture is driven hard, also for comparison – see 2.5.
2.3 Bias (and meter use)
This control varies the current through V2 by changing the
positive voltage on its cathode. The actual current is shown
on the milliammeter.
When the Vulture is starved of current the sound is thinner
and when over-fed it becomes warmer and fatter. The best
setting for low distortion is 0.25mA. When the Vulture is
being pushed into heavy distortion the meters will twitch.
N.B.
The bias pot is naturally noisy in operation as all of
the valve’s current is flowing through it, but it should be
silent when set.