Wattage and headroom

[frus]

UL was actually developed as a way to get more triode like linearity and distortion figures from tetrode and pentode valves without the associated loss of power that from conventional triode operation of those tubes.

Apparently Fender didn't even aim for that...

Paul P's Amps: Ultralinear vs Distributed Load in the Late 70s through Early 80s Fender Twin Reverb

[potatofarmer]

Apparently Fender didn't even aim for that...

Paul P's Amps: Ultralinear vs Distributed Load in the Late 70s through Early 80s Fender Twin Reverb

Ah geez, I gotta update that as its conclusions are somewhat erroneous. There's a later blog post where I point that out, but ultimately everything I have on my blog is said better by smarter people in this thread, who hopefully I credited: http://music-electronics-forum.com/t35295/ The blog really only exists so I can write this stuff down without boring people on the forums or irritating people I know on Facebook. I need to at least add a disclaimer that I'm just some guy and don't take me seriously.

But!

Ultralinear will get you more "headroom" partially because it serves as an additional local feedback loop, and partially because it requires you to bias colder, meaning you need to hit the power stage with a larger-voltage signal from the pre + phase inverter. It has nothing to do with ultimate loudness directly. It can allow you to build a louder amp by providing a mechanism to protect the screens from blowing up when you push the supply voltages higher, but even then it doesn't produce quite as much output as an ordinary pentode power section. One exception is tubes that were designed for UL, such as the KT88, where the output increases by maybe a watt or two in UL instead of pentode, but you guaranteed will never hear the difference.

If what you need is more volume before distortion, you're way better off adding a second speaker cabinet after you tweak the amp to get the tone you like. Visit a bass forum sometime; you'll find people puzzled that their 500W amps "aren't loud enough" through a small speaker cabinet. Meanwhile a 100W amp through a pair of 8x10s will probably leave you sterile.