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EQUIPMENT FORUMS >> MINI TORII >> 6V6 is a Beam Tetrode & a Beam Pentode
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Message started by Fireblade on 01/26/13 at 04:17:27

Title: 6V6 is a Beam Tetrode & a Beam Pentode
Post by Fireblade on 01/26/13 at 04:17:27

Interesting explanation that may bring understanding to some of us intrigued by the ambivalence involved in the SEP denomination for the 6V6 Tetrode-based Mini-Torii. Although there are better references out there, this is just a typical example. From the Audio Asylum forum:

[b]Posted by Ron Oehlert (A) on December 10, 2007 at 18:48:25

In Reply to: 6V6's in Pentode mode? posted by gusser on December 10, 2007 at 12:13:55:

Make no mistake even tho some schematics may draw it as such, 6v6 is not a screen-grid pentode, altho it can be wired as such. A Beam Tetrode has a cathode, control grid & suppressor grid, & anode (total of 4 elements IN the electron flow) with addition of beam-forming plates OUTSIDE the electron flow. If you refer to those beam-forming plates as a fifth element, THEN this tube is a Beam Pentode rather than a traditional Pentode with screen grid (which electrons pass THRU, thus 5 active elements in the electron path). Note the heater filament is never included in the # of elements denoting triode, tetrode or pentode, yet it also has a role in operation just as beam plates.
[/b]

Although the issue is not of any essential value, it is more comfortable to understand why a Beam Tetrode could also be a Beam Pentode and therefore the Mini-Torii fitted with 6V6 output tubes can be technically called a Beam SEP, or SEBP.

Of course, when the Mini-Torii is fitted with screen-grid-in-the-electron-path true Pentodes, like the 6F6, 6G6, 6K6, 6M6, etc., then the SEP notation is implicit.

I'd personally expect the 6V6 to sound the best in this design, ceteris paribus, but cannot attest to this yet as I have not tried other alternative spec output tubes myself.