VTL Tetrode/Triode

Zaikesman: Thanks, I'll do that. Rechecking the bias is pretty easy to do and doesn't take much time. I guess all I wanted to convey that triode mode (with new tubes) has an incredible immediacy and clarity, which I didn't experience before.

Are there any real triode amps, or even real triode tubes? When an amp equipped with KT88 or similar pentode tubes is opearated in "triode mode" it means that some extra hardware in the tube (grids) are just left unconnected. Can this be good?

Eldee: I've wondered about that before myself. In fact, VTL amps always operate with at least one element disconnected, since there is no pentode mode. I think the decision not to run in pentode is probably a good one from a sonic standpoint (I say this not from hifi system pentode experience but with guitar amps), but I don't know how a similar circuit would sound with EL-34's or 6L6's instead. Triode wiring of 6550 types has also been exploited by amp makers like ARC and CAT, so VTL is not alone in considering the unused screen elements to apparently be no handicap. But to answer your first question, of course there are "real triode amps" (and power tubes, which were around before tetrodes and pentodes were invented) - for instance, not even counting all the SET designs, VAC offers high-powered push-pull amps using paralleled 300B's, and the 6AS7 output tube used by Atma-Sphere is a true triode, along with the Russian 6C33C-B used by BAT.

Zaikesman...EL34 and 6V6 tubes are pentodes, but of course I now remember that the 300B tube is a triode.

I note that a guitar amp is part of a sound creation system, not a sound reproduction system, so sounding "nice"
is more important than sonic fidelity.

Sorry, my rather obscure point about the guitar amps was supposed to allude to the fact they are pentode (or beam) designs (using EL-34's or 6L6's) which don't sound as natural in fidelity as my (6550-equipped) VTL's run in triode, but do seem to share some of the less harmonius characteristics shown by the VTL's in tetrode. But as you correctly suggest, for a variety of reasons this probably isn't very good evidence for anything though.

Anyway, here is an interesting webpage on the main subject...