Triode vs. Pentode

Hello Tvad. I think Trelja and the others here painted the triode/pentode mode picture in the proper perspective here. Speaker efficiency as well as the impedance load the amplifier will see can also have a profound influence in ones mode of operation as well. I have a pair of el-34 based vac pa90-c monos that output 90 watts in pentode or 45 watts triode. However,I used the genelex kt-77 for output tubes[a beam power tube like a kt-88]as opposed to the el-34 [ a pentode] to drive 98 db efficient Tannoy Westminsters. In my case, I personally preferr the triode mode no matter what music type I'm listening to. They are more focussed and transparent in triode mode and just sound tighter in my rig.

Hey Zaikesman. A great post here sir, well said and very well written. Yes, the Vac pa90 has an ultralinear mode. Cheers

Hello Springbok. Most commercial push/pull tube amplifiers can be wired for triode output. Another great post here Zaike and some interesting observations. Depending on the type of output tube used for comparing each mode can also have an influence on your observation here. Example:observing the change in the sound of an amplifier employing a KT-88 output tube [beam power tube] when switching from ultralinear mode to triode mode may or may not be consistent with your analogy when the amplifier employs an el-34[pentode]output tube, not to mention the power factor or speaker load the amplifier is reacting to. The quality of the transformers and the amount of negative feedback employed in the output stage will be a major factor and will have a large influence as well.

Zaike .A very good question,and your guess is as good as mine here. The little CJ is a honey of amp and is always very engaging with the right speaker. I used a CJ mv52 for many years with the roger ls3/5a or the original proac response 2, sold it to a good friend whereby I do get to revisit it regularly and still very much adore the sound of it, it's like seeing a good friend after a long absence. What I find very intriguing regarding the sound of different output tubes and the output configuration in which their wired...... Have you ever heard the CJ with the KT77[beam power tube] output tubes in it? Quite the contrast from the el-34, and it elevates the amp to a whole higher league in every parameter! particularly the bass response. Sounded like a much more powerful amplifier than it's 45 watt spec would suggest. Unfortunately.... a quad of strong Genelex KT-77's will cost you more than the amplifier itself,and that's if your lucky enough to even find them. My VAC pa-90 monos can be configured to operate with 4 el-34's or 2 kt-88's in both ultra linear mode or triode mode with the flick of a switch.I much preferr the amplifier in triode with the el-34 tubes in it, however... when the kt-88 is employed I do prefer the ultra linear setting. The most intriguing thing about this is: Regardless of what mode I choose when the KT-77's are employed in the vacs, they raise the bar to a higher level regardless of power rating.Funny as it may sound.... when the amps are in triode with the kt-77, they sound more powerful than the 90 watts of ultra linear of the el-34. Go figure!