Switchable Tetrode - Triode please explain

If I do not power down the amps I can hear and see how speaker drivers are poppin'.
just don't like to have my speaker blown. even when I place a cartridge needle on the groves I do mute my phono before.

The System I am using ...
CJ Premier 14
Linn Lp-12 with lingo , Grado
Sonic frontiers SFCD1
Aerial 10T 's

I listen to Pop rock , Jazz , Blues and Classic rock. I like to play mostly at concert levels !
I think the Tetrode mode produces more forceful bass and is a little more lively. Powering down as per VTL does make it more difficult to compare. I like the VTL amp very much! I just think the explaination of this issue on the VTL web site is weak.

I find myself about to write what Piezo described so I ditto his excellent description... I also find triode (I use VTL 450s) to be lush, exuding a luxuriant 'thereness' and beautiful instrument separation - particularly notable in massed strings, and choral works where individual voices both make up the group and somehow seek to escape it. On SACD, triode can be downright scary. I appreciate tetrode however for 'live' rock music played at 'concert' SPLs, where it seems to better convey the sense of being too close to the stage for one's own good. I used both modes evenly at first but use it in triode most of the time now - more shivers and stupid grins (though tetrode on music with BIG dynamics can leave me breathless).

Piezo, have you used a different preamp with your system? Do you find the 5.5 affects your choice of use of triode or tetrode? Would you recommend it (or another preamp)? I use a passive attenuator and wonder if that is one reason why I lean to triode so much...

I have used Manley Reference 200/100's for the last few years with either Maggie MG3A's or Stax F-81's; both wonderfull combinations in most respects. Luckily, I don't listen at particularly loud levels so this dilemna is tolerable: In triode mode both these power hungry speakers benefit from a much more refined presentation as far as timbre and microdynamics. Instruments seem a bit leaner, but with their harmonic structures much better preserved, and their leading edges more incisive in a natural way.The soundstage appears to be somewhat smaller, but the dimensions of it are far more obvious, and there is a lot less texture in the spaces between instruments. Microdynamics are actually more natural, although ultimate dynamic range is compressed. On those occasions when I feel like listening at louder than usual levels or the music is extremely complex and dynamic (big orchestral works and some rock) the music reaches a dynamic ceiling sooner than it should. Since on those times, I'm usually not doing serious listening (working out or running around the house), switching to tetrode is the ticket. I can play the system at louder levels without obvious compression, and although I find that the sound, in general, gets a bit thicker than life with less harmonic detail, the increase in bass drive makes up for it. I am always reminded of when I switch between my Vandenhul MC and my Grado. Overall, I much prefer triode mode.

By the way, from Evana Manley herself: "You can switch between the two modes without powering down, but MAKE SURE THAT YOU MUTE YOUR PREAMP FIRST!"

Hope this helps and Happy New Year.