Sonic atributes ultralinear vs tetrode vs pentode

You won't hear so much difference between Tetrode and Pentode, but you will hear a difference between Ultralinear and the others. Ultralinear allows the tubes to approach triode linearity, while retaining most of the power that Tetrodes (or Pentodes) otherwise make.

So Ultralinear circuits make less distortion and tend to have a lower output impedance. If the designer is crafty and takes advantage of this, the result will be an amplifier that is smoother and more detailed, as removal of distortion usually has that effect. Ultralinear amps need less loop feedback in order to work, and in some cases don't need any at all. Loop feedback adds brightness to almost any amplifier, so if you can run without it you can have a more relaxed presentation.

However, not all designers will do that, so YMMV.

Trelja, obviously we see things very differently :)

I've done a lot of work over the years with ultralinear amps (quite a lot of those were Dynaco amps)! There is no way I would say they rule the day, I would put ultralinear as a distant second to real triodes.

With regards to your prior paragraphs, I think we are pretty much saying the same thing.

One way I use to deal with the linearity issues that allow me to get the amp to work better is to cross-couple the cathode circuits around the output of the transformer. In this way I get greater linearity, with lower output impedance, and that is what has allowed me to run zero feedback to the driver section. IMO that is how you get the amplifier to be low distortion and listenable at the same time; if you use feedback the amplifier will pick up a harder edge.

OK- here's my text:

Ultralinear allows the tubes to approach triode linearity, while retaining most of the power that Tetrodes (or Pentodes) otherwise make.

here's your assertion:

If you compare an amplifier running in the three modes, if triode put out 20 wpc, UL would do 40, and pentode 60. Those figures work out in the absolute linear, proportional, and expected manner

If we take 60 watts as being 100% of power, 40 watts is then 2/3 of that, or 'most of the power' as I stated above. I don't see that being significantly different from your position. Some hairs are in danger of getting really thin here.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1323578084&openflup&4&4#4

Despite the distraction, this still holds true.

Trelja, IM(H)O, you need to step back a couple of paces and look consider how most audiophiles would see this:

The fact that a triode makes 20-30% of pentode power means to most anyone that if you have a pentode amp of 60 watts, if it was then wired in triode, it would make maybe 20 watts. Similarly, if I say that UL makes most of the power of pentode, while approaching triode linearity, its not going to be skin off of anyone's back to find out that the result is about 40 watts, which is 'most' of 60 watts, since 40 watts is more than half of the power. We're not talking rocket science here; its pretty common to trade off between power and linearity.

The rub comes when the statement is made that we can meet that measure AND "approach triode linearity" at the same time. Impossible.

Possible:

"approach triode linearity" = linearity curve lacking the 'kink' of pentodes, looking far more like a triode curve than that of a tetrode or pentode. How it misses triode linearity is that a triode will typically have a nearly straight portion of its curve where a UL will always have a bit of a 'bow' in its curve. But at the same time we have power output that is easily double that of a triode circuit. Its a nice compromise...

Of course, if you don't want compromise you will have to seek an amp with real triodes.

Pete Millett has a nice website with a lot of tube-related information. Table 1 at the end of the document at this link (a quick read) tells the story:

http://www.pmillett.com/file_downloads/ultralinear.pdf

The document also has comments about OTLs that I don't agree with, as it comes from the 1950s. But the UL stuff it has in it, while obviously biased (if you will pardon the pun) is representative of the general technical/engineering understanding of ultralinear operation- its easy enough to find plenty more articles like this one. I just clicked on one of the higher-page hits on Google. I can find some of the stuff on the UL curves and that bow I mentioned if you are interested.

Full credit and abundant praise must be given to the persistent courage of the Japanese in regard to the triode tube amplification renaissance. Many of us, AtmaSphere included, reap the benefits.

For the most part the Japanese seemed to justify our stance on triodes, which we have used since the late 1970s. Back then, people thought triodes were 'quaint' (I suppose many still do). These days they have a lot more acceptance.