Triode versus Ultralinear/Pentode

Switching an amplifier from pentode to triode can be a bit tricky inside a single amplifier. The reason is that triodes tend to have a lower impedance than pentodes and so will want to operate at a different impedance on the output transformer.

That is tricky to set up and a lot of amplifier manufacturers 'fudge' that parameter a bit.

Its also interesting to observe the behavior of a pentode wired in triode as opposed to a real triode- it becomes obvious that real triodes have better performance. It is often difficult to demonstrate this fact because there are so many variables that get introduced, but- if you are thinking that triodes might have something to offer, you would be right. One of them is *not* power :)

You use triodes when the best sound possible is your goal. They offer lower distortion meaning little or no feedback is required, and lower output impedance which means less turns on the primary of the output transformer (that translates to: less distortion and more bandwidth and *that* translates to 'more detail, better highs and lows') or maybe no transformer at all.

The trick is like it always is- get the right speaker to take advantage of those advantages. There are high power triode amplifiers but they tend to be rare.

No. With my Mesa Baron, Triode is preferred for acoustic and smaller scale music, but adding some pentode helps a great deal with rock, orchestral, some jazz, piano and even solo guitar sometimes. and it solidifies imaging a bit. I suspect it's as we've always heard: it's all in the implementation. Unless you listen only to chamber music, there are times when pure triode is subobtimal.

Lloydc, your amplifier might be a good example of what I meant- that even though there is some advantage of the 'triode mode', that mode is not optimized in the amplifier in order to allow for the switching in the first place. Were it optimized, there would be no trade-offs in sonic performance, only power.

So I take it that if I were to convert the Music Reference to triode it should be triode only, optimized for triode, and not a triode/ultralinear via switch approach.

What does Roger Majeski say about the potential result of the conversion? Benefits v liabilities? There is always some trade off - what does he think they are with his amp?