The original power platform behind most high-powered British guitar stacks from the ’60s onward. Output is generally between 20 and 25 watts, with pronounced midrange punch, tight low end and crisp top end that breaks up relatively smoothly and gets a little crunchy when pushed hard. It provides a great voice that stands out in a band mix as the mids tend to power their way through an overall mix. Big brother to the EL84.A more modern implementation of the original at an affordable price, and currently standard issue on many U.K. amps. Very durable and consistent, which is good for manufacturing, but the distortion can be slightly harsh, and it lacks a little high end. This makes it more forgiving, but can sound a little dull.Matched quartet of EL34-R tubes rated from power range 1-10. Each quartet has a specific rating (i.e. R2, R7, etc.) and is matched and biased to a specific output level