[Niteshade]

What would you say are the differences between triode amplifiers (24, 2A3, 45, etc..) and pentode based amplifiers (6L6, El34, etc....). I have both but would like to hear what others think.

This isn't a 'what's better' question. I just want to know your thoughts.

[Tyson]

Fuller lower mids and warmer overall sound from the triode's, while pentode more neutral and has better dyanmics.  Of course those are huge generalizations because parts and design choices will affect the ultimate sound any amp produces.

[wilsynet]

I once owned an Antique Sound Labs integrated amp and it had a triode and pentode switch.

In general, I agree with Tyson.  With respect to this particular integrated amplifier, the triode mode was lush, textured and round.  The pentode was more dynamic, neutral, and accurate with more extended highs and tighter bass.

I liked one or the other depending on my mood and the music that I had playing.

I also blew a tweeter because I didn't know that that I shouldn't switch between the modes while playing music.  Lessons learned.  Occasionally I have some anxiety around switching inputs on my preamp. =)

[Niteshade]

My 6N7 and 300B amplifiers sound similar, even though the 6N7 amp is a push-pull. To clarify something, the 6N7's are in the output stage. What I noticed the most was the extremely articulate highs. The bass has more form and the mids are sharper. The 6L6 push-pull amp I reference to has more body, is  more linear and has a fullness to it not visible with the triodes. The fullness is in part due to the higher output power. I do not like running pentodes in triode mode- they 'run out of gas'  too quickly.

It was mentioned that the circuit defines 90% of the sound qualities and that's absolutely true. I have heard an 845 SET amplifier which sounded exactly like a push-pull 6L6 amp, perhaps with a bit more warmth, but that was all.
 

[Freo-1]

What would you say are the differences between triode amplifiers (24, 2A3, 45, etc..) and pentode based amplifiers (6L6, El34, etc....). I have both but would like to hear what others think.

This isn't a 'what's better' question. I just want to know your thoughts.

It's a bit more involved than that:

For example, there is a all pentode setup, such as the Citation V, a pentode front end/ultraliner output, such as the Citation II, mods to the Citation II to make the output triode.

My modified Citation II uses triode front end (5687), and ultraliner output. ALL of these topologies have different sounds. For me, the triode front end with ultraliner output provides an ideal combination of openness with power. 

[jon_010101]

Out of my push-pull triode, pentode, and ultralinear amplifiers, I don't think I can fairly compare them since they have dramatically different topologies, etc... And, of course, speakers make a huge difference in discernibility.

Similarly, I'd caution that comparing ultralinear/pentode/triode with a single amp is also not really fair - unless you completely re-do the feedback circuits to make up for the gain changes, etc.

[Niteshade]

Instead of comparing them in this situation, just say what each mode or type of amplifier sounds like to you. I was asked to compare two completely different amplifiers recently and it was difficult because EVERYTHING was different between them. It came down to me depicting their tonality while leaving wattage out of the descriptions.

Different topologies will have unique slants on what's coming in through their inputs. I find it fascinating and enjoyable. It's typically more of this or less of that and so on.

Here's another question: Does anybody have a hybrid amplifier where the driver stage is transistor or FET and the output stage is tube? What do you think of this setup VS. a regular tube amplifier?

Note: You're right, the playing field is never the same. But- certain characteristics should always surface as long as the speakers are decent and the sources are good quality. I have horn loaded speakers and am sensitive to high frequency detail as a result. That's why my description of the triode amps I have used centered around the high frequencies. The other frequencies are depicted very well too- but the horns really let you see sharp differences between amplifiers and operating modes.

Another thought: How many of you have solid state as well as tube amplifiers?
Does anybody Bi-Amp using one of each kind?

Out of my push-pull triode, pentode, and ultralinear amplifiers, I don't think I can fairly compare them since they have dramatically different topologies, etc... And, of course, speakers make a huge difference in discernibility.

Similarly, I'd caution that comparing ultralinear/pentode/triode with a single amp is also not really fair - unless you completely re-do the feedback circuits to make up for the gain changes, etc.

[kyrill]

i have 2 Jadis amps (Orchestra and pre ochestra DA-5) and found the mod to make pentode triode very worthwhile

the sound of the pentode was less 3D, less palpable more studio like in a sense that i listened more to an electronic recording than to life . It is this live aspect which i "worship" in very good amps. It is also the reason i prefer tubes over SS although i liked Vinnie's Red Wine Audio 30.2 very very much but prefer in the end the JAdis over it That is why ( in my system) i sold the RW 30.2 and bought a second Jadis

[Niteshade]

What tonal aspects became more favorable? Such as- did the high frequencies become more articulated? What happens to the mids and bass?

i have 2 Jadis amps (Orchestra) and found the mod to make pentode triode very worthwhile

the sound of the pentode was less 3D, less palpable more studio like in a sense that i listened more to an electronic recording than to life . It is this live aspect which i "worhip" in very good amps. It is also the reason i prefer tubes over SS although i liked Vinnie's Red Wine Audio 30.2 very very much but prefer in the end the JAdis over it That is why ( in my system) i sold the RW 30.2 and bought a second Jadis

[kyrill]

PENTODE TO TRIODE
1) more 3D deeper soundstage, more 3 D notes as well, for instance the pluck of a guitar sounds more like round strings
2) more lifelike voices somehow related to 1) but also to 3)
3) more controlled bass

no real difference with highs but this was with stock capacitors, maybe there is difference when i had modded the caps first, after the cap mod, much more 3 D highs and so on

at least with Jadis in my system

[BobM]

The classic comparison uses a 2A3 and 6CA7 in the same amp. Many that use these tubes allow a substitution of the other type, but you will need to rebias when you swap them. 6CA7's tend to be a bit punchier and have a smidge more extension at both ends. 2A3's tend to be a bit softer but have a midrange magic that is hard to beat.

Again, generalizations for sure.

Enjoy,
Bob

[DaveC113]

In my Simple SE 6550 amp, I prefer running the 6550s in triode mode, it sounds more natural... UL is punchier and appears to be more dynamic at first, but it wears on you and triode just sounds more real. I do not use any sort of feedback in my amp.

[rklein]

I recently build a ST-120 tube amp from a kit supplied by Bob Latino.  I am currently running GenLion Kt-88's in it.  The amp has two toggle switches on the top.  In Pentode it puts out 60 watts per channel and 30 watts in Triode.  I love Triode for acoustical jazz and chamber music.  I feel more drawn into the music in Triode.  I have heard for larger and more complex recording that Pentode is the way to go.  However, again I prefer Triode for that genre as well.  I have heard the word "neutral" to describe Pentode.  I find Pentode to be more open and perhaps a little spread in it's presentation whereas Triode has a denser core to the sound which I prefer.

It is true that different topologies plays a part in this discussion.  I also believe that different musical backrounds play a part as well.  I come from a classical backround and have dealt with acoustical music and live concerts for over 40 years.  Someone coming from a Rock backround could have a totally different take on this talk.

Yours,
rklein