The original power platform behind most high-powered British amplifier heads from the '60s onward. Output is generally between 20 and 25 watts, with pronounced mid-range 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.