Triode vs. Ultra-Linear vs. SET

I came across some information when researching this same question you may find helpfull. Not an expert myself by any means but here it is.

SET is an abbreviation for Single Ended Triode.

Triode, tetrode and pentode are types of vacuum tubes. A triode is a vaccum tube with three active elements: anode, cathode and in between them a grid. The current through the valve (from anode to cathode) can be controlled by applying a varying voltage on the grid.

Tetrodes and pentodes have additional grids compared to the triode.

The tetrode has a fourth electrode inserted between the anode and the control grid in order to lower the capacitance in the tube. Tetrodes are rarely used in audio amplifiers. Beam tetrodes (KT88 et al) have included a pair of electrodes to "direct" or "focus" the flow of electrons towards the anode to lower the amount of electrons bouncing back (secondary emission) to the screen thereby creating a current flow from anode to screen.

Pentodes (6550, EL34...) have yet another grid, the supressor grid, inserted between the screen and the anode. The function of the supressor grid is to make sure that the electrons bouncing off the anode do not reach the screen grid.

Designers have found that beam tetrodes and pentodes can be connected in triode mode... i.e. they are working as a triode even though they have the extra electrodes for working as a beam tetrode / pentode. Some say they sound better connected this way but the available output power usually goes down.

Ultralinear, push-pull, single end, paralell single end are all configurations of the circuit in which the tube works.

One tube driving one speaker means the configuration is single end. Two (or more?) such tubes in paralell gives you paralell single end. Two paralell output tubes means double the output power. In a push-pull configuration (always tubes in pairs) one tube gets a negative input at the same time as the other tube gets an identical positive input (one tube pushes while the other pulls). In this configuration the even order harmonics are cancelled so that the output power becomes more than double that of a single tube.

In UL operation, it is the screen grid which is connected to the output transformer through a separate tap. This provides local feedback because the screen voltage also controls the current through the tube to some extent. Connecting the control grid this way would cause far too much feedback. In addition there can be significant current on the screen which is captured by the UL connection to help drive the OPT. Grid currents are almost always very small.
This is supposed to give lower disortion and a flatter frequency response. Ultralinear can be used push-pull or single ended.

>>>>Sonicly, is it advisable to set a push-pull tube Amp in triode mode if I've got enough power?

Guess that depends but generally sure. Depends on what you like. Both can do a nice job if done well.

>>>>I've go a 60 watt Rogue Tempest Magnum integrated and I'll soon be receiving a pair of Von Schweikert DB-100's which are 100 db. 30 watts in triode would seem to be enough.

30 watts might be too much! It depends. Different types of noise become an issue at 100db. You could get by nicely with a SET at 2-8 watts w/ a true 100db.

>>Also, sonicly, does a push-pull triode setting approach a SET in quality?

Quality? Sure. But it does not necessarily sound the same from what I've generally heard. But a lot depends on the circuit and how the tubes are driven.

>>>I'm just beginning to learn about ultra linear, triode and SET's and I've got a ways to go. Any advice would be greatly appreciated.

Hey, we all are. You are a David Hafler and Herbert Keroes fan. My advice. How about something to read?

I attach a few things to read if you are as you say "just beginning."

"A taste of Tubes" below has a very basic talk about ultra linear if I remember right.(not always the case)

The first group are real intro general articles.
1) ✔ A Taste of Tubes (50 pages), Sonic Frontiers: http://www.anthemav.com/OldSitev1/frames/tubesfr.html
2) ✮ The National (British) Valve Museum. http://www.r-type.org/static/.contents.htm
3) The Cool Sound of Tubes, E. Barbour: http://www.spectrum.ieee.org/select/0898/tube.html
4) How A Vacuum Tube Works, E. Barbour: http://www.svetlana.com/docs/tubeworks.html.
5) Vacuum Tube Valley FAXs, E. Barbour: http://www.vacuumtube.com/FAQ1.htm.
6) Vacuum Tube FAX, H. Pasternack: http://home.earthlink.net/~busenitz/vac.html.
7) A History of Tube Companies: http://vintagetubeservices.com/page8.html
8) Vacuum Tube Primer, R. Hamm: http://www.audioasylum.com/audio/faq/tubeprimer.html

If you are interested in ultra linear you might want to know a little circuit basics because you have to know the difference between a plate and a grid and how to make a little feedback loop.

http://www.electronicstheory.com/html/e101-1.htm. A short overview of how a tube works beginning on page 37.

More on a triode:http://www.john-a-harper.com/tubes201/
a little harder

The most recent article from Tube Cad Journal. Nice intro to triode circuits. http://www.tubecad.com/articles_2003/Grounded_Cathode_Amplifier/Grounded_Cathode_Amplifier.pdf

Keep ya busy for awhile.

Cheers
I remain,

The Rogue 88 sounds better in triode than it does in ultralinear. Since the Rogue can be set very easily in either mode you should try both and see (hear) for yourself which you prefer.

I compared the Rogue 88 in triode against a 300b SET and found that they are more similar sounding than different. The 300b worked better with single driver speakers (Lowther, Fostex, etc.), while the Rogue had more punch with efficient multiple driver speakers. Also, if you run the Rogue without the cover you can disable the fan, which adds noise. E-mail Mark O'Brien at Rogue and he will tell you how.