VTL Tetrode/Triode

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...

Zaikesman...Very interesting indeed. Thanks.

I had this same swith on a pair of Manley's 120Deluxe Mono amps, and after trying to just stick to one position (including the variable feedback option), I ended up using that unique future depending of the kind of music.

Fernando

Eldartford: I was prompted to do further research by this question of tetrode vs. pentode catagorization. What I noticed is that beam-tetrodes, lacking the suppressor screen of a true pentode, but with the beam-forming plates (which are not electrically-connected elements of the tube, otherwise known as electrodes) between the cathode, grid, and screen on the emission side and the anode (plate) on the collection side, are nevertheless often described as pentodes or 'beam-pentodes' - even in their original manufacturer's technical description papers. This finding, though I don't know the explanation for it, does help me understand why I've seen certain popular audio output tubes variously refered to as both tetrodes and pentodes in magazine reviews and the like. (Here is a page showing helpful diagrams of the differences.)

I also had forgotten that the British "KT" designation in fact stands for Kinkless Tetrode (duh!) - in other words, beam design. So obviously my KT-88EH's do not have an unused electrode element when run in tetrode in my VTLs, and the same would go for 6550's. Further confusing matters (for me) was the fact that my previous tubed audio amplifier used EL-34's (a true pentode) but ran them in ultralinear connection. The RCA 6L6 was apparently the first production beam-tetrode - see this link for the backstory. Though both suppressor screens and beam-formation plates are intended to deal with secondary emission from the anode, it does seem likely to me, as possibly alluded to in the article I linked in my post of 12/7, that the two constructions might behave somewhat differently when triode-connected.