THD FLEXI-50 INSTRUCTION MANUAL
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8. Boost Gain:
A special feature of the Flexi is that the boost circuit is voiced differently
than the main channel, so when the Boost circuit is engaged, this control adds both an
additional gain stage and a more “British” EQ voicing, with thicker low and lower-
midrange frequencies.
9. Boost Tone:
A unique Flexi feature is its full-frequency sweeping Tone knob. This
control can completely change the texture and tone of the boost from dark and woody to
searing and open.
10. Boost ON/OFF:
This switch engages or disengages Boost circuit. The red LED
above the Boost controls will light when the Boost is engaged. The Boost can also be
toggled with the included footswitch.
11. Master:
The Master knob controls the overall output volume by limiting the amount
of signal to the power amp tubes. Some classic amplifiers did not have a master volume,
and their volume and gain were both a function of the single input volume. The Flexi
allows you to switch the Master completely out of the circuit to better emulate the signal
path of those amplifiers.
12. Master Switch:
This switch engages or disengages the Master control. If the green
LED above Master control is lit, the Master is engaged. The Master can also be toggled
with the included footswitch.
13. Cut
: This control functions much like a presence control in other amplifiers, but with
a significant difference. A Presence control uses negative feedback from the amplifier to
simultaneously adjust both gain and brightness. The Cut knob on the Flexi adjusts the
overall brightness, but not the gain.
14. 50W/20W switch:
The 50W/20W switch toggles the Flexi’s plate voltage to the
power tubes from 475v (50W) to 325v (25W). Lowering the Flexi’s plate voltage both
reduces the volume of the amp slightly and changes its character. In 50W mode, the Flexi
is slightly tighter and more aggressive; in 20W mode it is a bit warmer and smoother.
15. Standby Switch:
Standby mode keeps the power tubes powered and the amplifier
itself off. Always power up in Standby mode and allow the tubes to heat up for at least
two minutes before switching to Play.
16. Power On/Off:
The Power switch turns the amplifier on or off.
