Is it really possible to get a tweed sound and a British sound out of the same amplifier? Yep, you bet. The THD Flexi-50 does both and a whole lot more.
Few would argue that most amps fall into one of two categories; 6L6 (tweed) and EL34 (British). There are certainly a few other options out there, but for the most part, it’s a two-party system when it comes to power tubes. There are a few amps out there that can accommodate either tube type, but you need to know how to bias an amplifier, or pay someone else who knows how to do it. This is like a health-club membership: you’ll pay for that feature, but you will never use it. THD Flexi-50 50W/20W does double duty and you do not have to be a rocket scientist to switch hit.
THD boasts that this head can accept not only EL34 or 6L6, but “…accepts almost any preamp and power tubes in any combination….” That’s a mighty big claim, but they have never given me a reason to doubt them — not one bit. The fact that you can step this head down to 20 watts is given away in the name, but is nonetheless, a very cool feature. In full power mode, it is a very loud 50 watts. It ships with three 12AX7 pre-amp tubes, and two EL34 power amp tubes, for plenty of UK snarl. A first experiment might be to swap out the 12AX7 tubes for 12AU7 or 12AT7 tubes. Both are a bit mellower than 12AX7 and might yield some nice tones.
Although this is a single-channel amplifier, there is a foot-switchable boost section, with its own dedicated Gain and Tone controls. I could go on and on, but this is the kind of head that you don’t talk about — you try it. Sure, it’s a bit pricey, but if you are in the market for a high-end 50watt head and have some wiggle room in your budget, it’s worth a very close look.
Helpful Links for THD Flexi-50 50W/20W Class AB Amplifier Head
THD Product Page
THD THD Flexi-50 Instruction Manual