THD Flexi-50 - 50 Watt Amp Head 2000s Black & Silver

Brand New
Local Pickup Only
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Local Pickup Only
Gilroy Guitars
Canberra, Australia
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About This Listing

For Sale is the THD Flexi-50, 50 Watt Guitar Head in the original Cage Head format

Shipping: Listed as 'Local Pickup' - you can arrange your own shipping, or we can obtain best quotes to your area.

The Flexi-50 is a precision hand-built 50-watt Class-AB guitar amp with foot-switchable overdrive and boost, foot- switchable master volume control, and the ability to use almost any preamp and power tubes in any combination….
6L6, EL34, 6V6, 6CA7, 8417, 6550, KT66, KT77, KT88, KT90, KT100, EL84 (with Yellow Jacket adaptor), 6K6, 6F6, 12AX7, 12AY7, 12AU7, 12AT7, 12AZ7, 12DW7, 12BH7, ECC83, ECC82, ECC81 and many more, giving the user a huge diverse range 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.

The external bias test points and controls allow the user to quickly and accurately bias the output tubes using a digi-meter, eliminating the need for matched power tubes or an amp tech. So… Switching tubes is easier than ever before. You can easily and accurately set the bias in about 20 seconds, even with two completely mismatched or different tubes.

What does all of this mean for the player? It could very well mean that the search for your sound is finally over. While our UniValve and BiValve-30 amplifiers offer the same flexibility and choice of tubes, they do so in a Class-A circuit. Class-A amplifiers do have a strong following due to their smooth, even character. But many guitarists have had a fifty-year love affair with the clichéd sound of the 50’s Rock and Roll Class-AB amplifier… it’s right here in the Flexi-50.

THD have brought together an ideal combination of simplicity and flexibility, hence the name ‘Flexi-50’. Why strive for simplicity? Robust design and construction are among the reasons. Ease of use is another prime reason. We heard every day from guitarists who purchased 3- and 4-channel guitar amplifiers, only to discover that aside from varying gain levels, the channels all sound and feel more or less the same, dashing their dreams of flexibility. Another by-product of an overly complex amplifier is that it can take a very long time to discover a sound that really works for you.

How is the Flexi-50 different? Firstly, it’s a single-channel amp, and one that can be switched and blended among a number of different sounding and different feeling voices. These changes can come from a number of methods, including foot-switching, a pre-set boost level with its own dedicated tone control… you can make your boosted sound darker than the clean sound, or brighter, or anywhere in between. Not to mention the many and varied tonal pallette available by tube switching or blending.

The unique combination of the touch-sensitive input circuit and the amazing active and reactive tone control section that took a year to perfect, makes 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 pedal. Back off on the volume control and the amp gets much cleaner, without losing the fatness of the full-volume sound. How do we do this? We could get as technical as you want, but what really matters is that it works, not so much how it works.

Switch from an over-wound bridge pickup to a clearer, lower-output neck pickup and suddenly the amplifier responds very differently. Our input is quite sensitive to the individual impedance curves and inductance characteristics of your guitar’s pickups, so you will not experience the all-too-common situation where every guitar you own sounds the same through your amplifier. PAFs sound like PAFs. Strats sound like Strats. Filtertrons sound like Filtertrons. Lipstick pickups sound like, well…. like nothing else on the planet. You’re into exotic handmade guitars and pickups? Wouldn’t it be nice to have an amp that lets you hear the difference between 9000 and 9200 turns of wire in a pickup? Plug into a Flexi-50 and you’ll see (and hear) for yourself.

You like to use pedals? There are many talented pedal makers coming out of the woodwork from all corners of the world. The THD Flexi-50 has no trouble helping you hear the difference between a NOS military-grade germanium transistor and a modern ‘equivalent’. You decide if they are the same or not, and with the Flexi-50, you can to do so. Does it like pedals? It LOVES them.

More about the overdrive capability of the Flexi-50... With its modified design, custom-tuned, post-phase-inverter master volume circuit, the Flexi-50 can give you a luscious palette of overdriven sounds before you even get the output stage working, and these sounds are all highly touch-sensitive as well.

Other features include a line-level effects loop, and a 50-watt/20-watt switch right on the front panel, letting you drop the plate voltage on the power tubes from 475 V to 325 V, giving not only lower output, but also smoother, more even response and even longer tube life. We also have a series/parallel switched impedance selector that can take any extension cabinet from 2 ohms to 16 ohms impedance, and always uses 100% of the transformer windings all of the time, another THD innovation. This assures you a full, even output sound, regardless of the impedance setting. The power and output transformers are fully shielded to ensure that hum and noise are kept to an absolute minimum, and that pickup-feedback from transformer coupling is all but eliminated.

The THD Flexi-50 will have you selling your other amps, simply because you just won’t need them any more.
Designed and manufactured by: THD Electronics - USA

Full 12 Months Warranty from date of purchase, on any unlikely repairs on parts and labour... with free return shipping. Warranty does not cover damage, tubes, fuses, or bulbs.


All tubes – 2x EL34; 3x 12AX7

THD’s Dual-switch heavy duty Foot-switch and Planet Waves dual-connect Cable w/ 1/4” jacks

Australian Power Cable

Full User Manual

Shipping: Listed as 'Local Pickup' - you can arrange your own shipping, or we can obtain best quotes to your area.

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Product Specs

ConditionBrand New (New)
Brand New items are sold by an authorized dealer or original builder and include all original packaging.learn more
Made In
  • United States

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