Tetrode vs Triode mode in Tube amps

Below is an explanation of tetrode vs triode mode in tube amps from the VTL website. I've never owned a tube amp before.....If they do not all have this switching ability, which mode do tube amps usually operate in generally speaking? Or is this an individual thing per user.
VTL Tetrode-Triode Switching Capability

The VTL range of power amplifiers offer a unique feature that makes them even more flexible: On-the-spot switching between tetrode and triode modes of operation that is easy to reach and user switchable.

At lower volume levels, and with efficient speakers, the sound of the triode mode offers a level of delicacy, liquidity, and sweetness to vocals, chamber and jazz instrumental quartets and solo instruments with 3-D imaging in the mid-range that will get you even closer to the real event.

Tetrode mode offers the detail, soundstage width and depth, and weight to the music that on large-scale orchestral or big band will transport you to the concert hall with all the visceral power and detail rendition of your favorite music.

A changeover switch is provided on the back of the VTL amplifiers to make changing between the two modes a breeze - just power down the amplifiers, flip the switch to the desired mode, and power the amplifiers up again.
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Showing 1 response by elevick

I've got a triode/ultralinear switch on my Dynaco ST-80 (1996). I don't even have to power the amp down to switch modes. It makes a very subtle difference but noticable. It's kind of like having 2 amps in one.
I usually run in triode but if I want to "rock" I go to ultralinear for more power and more "bite". I recently found a new use for the switch. I was tube rolling and was really bored by the quad of shuguangs that I bought. I switched to ultralinear and found much more life in their sound.