THD FLEXI-50 INSTRUCTION MANUAL
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THD Flexi-50
Instruction Manual
Thank you for your purchase of the THD Flexi-50 amplifier! The Flexi-50 is a precision
hand-built 50-watt Class-AB amplifier with foot-switchable overdrive/boost, foot-
switchable master volume control and the ability to use almost any preamp and power
tubes in any combination, including 6L6, EL-34, 6V6, 6CA7, 8417, 6550, KT-66, KT-77,
KT-88, KT-90, KT-100, EL-84 (with Yellow Jacket adaptor), 6K6, 6F6, 12AX7, 12AY7,
12AU7, 12AT7, 12AZ7, 12DW7, 12BH7, ECC-83, ECC-82, ECC-81 and many more,
giving the user a huge pallet of available sounds simply by changing tubes. The amplifier
has a fat, clear, full clean sound reminiscent of late 1950s to early 1960s American
combos, and overdrive to rival the best British heads. Even at the highest overdrive
settings, the amp still demonstrates dramatic touch sensitivity, cleaning up very well
when the volume on the guitar is reduced. Additional features include external bias test
points and individual bias controls, permitting the user to quickly and accurately set the
output tube bias with any digital voltmeter. The dual bias controls permit the user to
correctly bias even mismatched tubes, eliminating the need for matched power tubes.
The unique combination of our touch-sensitive input circuit and the wonderfully active
and reactive tone control section (that we slaved a year to perfect) make for a front-end
that really responds to subtle and not-so-subtle changes in the signal being fed into the
amplifier either by the guitar or any effect that may be between the guitar and the
amplifier.
