Kirkus, "60 watts from a quad of EL34s in Ultralinear is a bit conservative, but not by a huge margin . . . I'd say that a "70-watt" rating of the Marantz 9 is probably the most typical of what's found in a high-quality hi-fi amp with this output stage."
Kirkus, "in guitar amps, a quad of EL34s will easily put out 110 watts or so"
Guitar amplifiers typically feature pentode operation, as opposed to ultralinear. That explains a lot, if not most of that gap. Also, as has been mentioned by Auxetophone, cathode (self) bias versus fixed bias factors into the equation to at least a moderate degree. While there certainly are some famous examples of cathode bias guitar amplifiers such as the Vox AC30, fixed bias (Ampeg, Fender, Marshall, Mesa Boogie, etc.) represents the far more ubiquitous topology.
Kirkus, "in guitar amps, a quad of EL34s will easily put out 110 watts or so"
Guitar amplifiers typically feature pentode operation, as opposed to ultralinear. That explains a lot, if not most of that gap. Also, as has been mentioned by Auxetophone, cathode (self) bias versus fixed bias factors into the equation to at least a moderate degree. While there certainly are some famous examples of cathode bias guitar amplifiers such as the Vox AC30, fixed bias (Ampeg, Fender, Marshall, Mesa Boogie, etc.) represents the far more ubiquitous topology.