Up for sale, a THD Flexi-50 boutique tube amplifier head in exceptional condition and in perfect working order, complete with the original two-button footswitch, padded carry case, and manual. The Flexi-50 is a precision-built 50-watt Class A/B amplifier with foot-switchable overdrive and Master Volume control, as well as the ability to use almost any preamp and power tube combination. Matching options include 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, and ECC-81, giving the user a huge palette of available sounds simply by changing tubes. The head is currently fitted with a pair of Wing C Svetlana 6L6 power tubes which have plenty of life.
The amplifier has a fat, full clean sound reminiscent of late '50s American combos and an 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 a touch-sensitive input circuit and the wonderfully active and reactive tone control section refined by THD provides a front-end that dynamically responds to subtle and not-so-subtle changes from the signal source. Other features include a line-level effects loop and a 50-watt/20-watt switch right on the front panel, dropping the plate voltage on the power tubes from 475v to 325v, delivering not only lower output, but also a smoother, more even response and longer tube life. A series/parallel switched impedance selector can take any cabinet from 2 ohms to 16 ohms and always uses 100% of the transformer windings for a full, even output sound, regardless of the impedance setting. The power and output transformers are fully shielded to assure that hum and noise are kept to an absolute minimum, and that pickup-feedback from transformer coupling is all but eliminated.
Cosmetically, the head is extremely clean, and the gold plexi faceplate is practically flawless with a full complement of original knobs. The head comes complete with the original two-button footswitch and padded bag embroidered with the THD logo.