My amp has a switch in which I can go between the Pentode and Triode settings. I find that I prefer the Triode setting. In the triode setting the sound is refined / smoother and the sound stage seems to be better defined. I have approximately 32 watts in this setting verses the Pentode setting which gives me 75 watts. My speakers are efficient so the reduced power doesn't seem to be an issue. Question, what is the difference between the two settings technically, and when switched to the Triode setting is the amp truly running in Triode mode or a "mock" Triode setting? Last does it make sense that the sound in Triode would be more refined / smoother and create a more defined sound stage?
Who manufactured the amp and what model? I have 3 amps with this feature, two are MFA (Moore Franklyn Associates) and the other is AES (a kit division of Cary). Both manufacturers claimed that triode mode offers less power, higher distortion and less linear frequency response, thus was provided only for comparison, not recommended as the best performance option. So triode mode sounds more "tubey", well, sounds more warm and romantic than "accurate". That is exactly what I hear, and personally enjoy, with the particular speakers I use them with. It is best not to assume technically better will inherently sound better. These manufacturers recommended that we listen to both options, in any particular audio system, to choose a personal favorite setting. This is true of choosing output impedance taps also. Even if there is a technical reason to assume one of the taps "should" sound best, many amp manufacturers suggest we listen for ourselves to determine a personal favorite impedance tap with any given pair of speakers.
The amps are mono blocks, Consonance - Cyber 800SE with the Pentode/Triode switch. There is a subtle difference in sound but I do like the Triode mode better. Was wondering if this is not a "true" Triode design what would I gain if anything by purchasing a straight Triode amplifier? My speakers are 8 ohm and I've tried both taps, not sure I hear a difference so I keep them set for 8 ohm.
Actually, your amps are switching between Ultra-Linear (UL) and Triode modes. In triode mode only the grid is used to control the output, with the screens being strapped to the anode or cathode and disabled. This is a perfectly valid way of using EL34s, it is what I use in my own SET amp. In UL mode the signal is being fed back from the OPTs to one of the screens, but in this case it increases gain. Pentode operation is different and requires an additional power supply. There are some pentode hifi amps but not many. There is no guarantee that UL operation is lower distortion vs triode, it depends on the tube and the where the UL tap is on the OPTs. I find triode operation much more natural sounding, but this may not be the case with all amps. Some people really like KT88 push-pull using UL mode. Some pure triode amps are better but often it is only because the amp is built to a higher standard as the tubes are quite a bit more expensive. I have an optimized EL34 SET and have compared it to high end Fi 2a3 SET monoblocks and my EL34 amp was it's equal or better. The circuit and parts quality matter more than the tube type. Big $$ power tubes make no sense to me but it all depends on one's own financial priorities.
This is making me wonder if it's worth seeing whether I could send my amp to Cary and have them install a triode/ultralinear switch (and a 4/8ohm switch)... I know my amp /can/ be run in both UL and triode modes, but I don't think I'll ever get in there and do the rewiring on my own.
I really do not notice much from flipping between the two settings - in my head - I like the UL mode best - but that could be imaginary - it is tough to notice. It is a nice feature to have - but to buy it - you might be let down as it is very subtle.
I guess a lot of people will find the whole "triode thing" to be tough to understand. It is in that we are not looking at just the technical implementation but we are doing so to bring about a sonic change. That change is what is important, not how we go about it. It is hard to categorize an amp as being a "real triode" amp as it can have a couple of guises. There is the lowest powered and most pure of the type, also the most simple and so the most effected by its load, the single-ended triode or SET amplifier. These in their most pure form use triode output tubes and are designed to be run this way only. Then we have amps that use pentode or tetrode output tubes and are connected as triodes. These are similar in design if made single-ended or parallel. They have a bit more power, perhaps twice as that of the weaker SET amps. Finally, we have what most people find and what you have there, which is a pentode or ultra-linear amplifier that has the ability to be wired in triode mode. This is a push-pull amplifier with a lot more power and has the lowest distortion and greatest outut when used in its Pentode or Ultalinear modes. Power is cut just about in half when they are switched into triode mode, and distortion doubles at the same input level, perhaps tripling as it is increased. The switch connects the screen grid and the plate of the tubes together with a resistor, forming the new triode arrangement. So that is basically what is going on. Now, the important bit is what does all of that do to the sound coming from my speakers?! Right, that is where it gets fuzzy, often literally. It depends upon the speakers. In your case, not much. When it really matters is when you have reached a point of power loss and distortion increase due to having lower efficiency speakers that the amps sound dramatically different in their various modes. If you have enough power to drive a speaker without distortion to a given level. they all sound more similar than different. of course there are some other factors such as bandwidth which also effect that whole, but in general it is the power and distortion that is being changed. Triodes have a more linear transition from clean to being overdriven and so gradually have an increase in distortion with output that makes it sound smoother and softer. It can lose top end and sometimes bottom end extension, certainly bottom end control, as the power demand is increased. Pentode connection offers much more power and flat response while at the same time lower distortion up to its point of being overdriven, at which time it starts to distort in a much more non-linear fashion. Basically, you need to avoid that or it isn't pleasant. Ultra-linear is a refined version of pentode or tetrode connection that involves a special transformer winding and is the most linear and lowest distortion, just as the name implies. What will sound better with any particular speaker in your particular environment and operating condition (desired output level in db)? Just flip the switch, sit back, and listen. -Bill
My Line Magnetic EL34 amp has this switch. I feel that while the triode mode is interesting and makes the midrange pretty fun, ultimately the overall sound suffers, the music just lacks weight and body. I don't mess with the switch much anymore. I imagine it's a YMMV thing based on the amp and music selection.
From all that I have read in these posts I am going to perform an informal experiment. Take two well recorded CDs and two that tend to be bright and fatiguing at louder volumes. I will play each in the Triode and then Pentode (Ultra-linear) modes. My guess is the well recorded CDs will sound great on both settings, with a bit more gusty in the Pentode(Ultra-linear) setting, but the bright and fatiguing recordings will sound better in the Triode mode. I will see if this plays out. Yes I notice the additional power and gusto when in the Pentode (Ultra-linear) setting, 75 watts verses 33 watts should give a different presentation, but with my speakers that are 91 db SPL the 33 watts is plenty powerful and doesn't become an issue on most recordings. I guess this is why the Triode setting is what I always go back to.
Just to be clear Pentode is not Ultra-Linear... UL is actually a type of tetrode operation (4 elements). Pentode (5 elements) requires a power supply for the suppressor grid, not many amps use pentode... Also, there is no guarantee UL is more linear than triode mode. Only a narrow range of OPT tap % will provide distortion less than triode and it depends on the tube type. To me UL sounds less natural but that's in an el34 SET, in a pp amp it's not the same, and really most people seem to prefer UL operation with kt88s instead of el34 in a PP amp. The most common UL tap % is made for kt88 types. With el34 triode is most likely to perform better. In any case, doubling your power isn't a huge difference due to the logarithmic nature of SPL perception, it'll only give you 3 dB more headroom.
So I have been experimenting between Triode and Pentode (Ultralinear) settings on my amps. Seems to reinforce what everyone is saying. I've played around with really well recorded CDs and others that seem to have little DR but are still, pretty nicely recorded along with some that just have a slightly sizzling high end. In the Ultralinear setting the well recorde CDs and even the ones with little to no DR but still recorded well, assumption is not over compressed, the sound is clear at all levels but sound best at moderate to lower playing levels. The CDs with little DR at higher volumes the highs are a little too extended but still not fatiguing and very listenable. The music does become a little more sterile and the sound stage doesn't seem as large as in the Triode setting. The CDs recorded poorly with the sizzling high end just can't be listened to at high volumes without the high end at times being a little bothersome to my ears. The Triode setting doesn't seem as analytical, and the sound stage is much wider. At higher volume settings the sound is more forgiving. When I say analytical I do not mean it in a bad way, the Ultralinear setting just seems so much cleaner sounding but this isn't to say the Triode setting produces muddy or a soft sound because it doesn't, it is a small subtle difference between the two. The Triode mode seems more forgiving at louder volumes, maybe because as someone said it distorts more forgivingly? I don't know why the sound stage is so much more wide and deep, but I love this and will gladly accept this feature with the Triode setting. I think I will use the Ultralinear setting when I know I will predominately be listening at moderate to low levels and the Triode when wanting to really rock out at higher listening levels or doing an extended listening session that I know I will be listening to a wide variety of CDs for a longer sitting session. The bottom line is it nice to have this ability to switch back and forth, both have their purposes.
How efficient are your speakers? I wonder if that is the issue with lack of weight in Triode mode? I do notice more force coming from the Ultralinear setting but in the Triode mode there is plenty of weight and the smoothness that you gain is worth the slight reduction in weight. My speaker are really quick and dynamic but are 91 dB SPL so they are pretty efficient.
Mine are 91 DB as well. I'd say the issue is we have different amps - your amps in triode mode are putting out the same power mine does in ultralinear.
I had to add one final note to my testing of the two setting since I just switched back to the Pentode setting - it's more musical, plan and simple. Yes it's not as forceful in its presentation or maybe not as razor sharp in its sound but it's more enjoyable. I believe for the bulk of my listening it will be done in the Pentode setting.
I was sort of surprised as well. Before I purchased the amp I expected I'd use triode for acoustic/vocal music, and perhaps UL for electronic/rock/etc.
Silly me, I've reversed what I discovered. The Triode setting is what I switched back to and found it more musical and not as analytical, therefore for most of my listening it will be in the Triode setting. This setting is extremely musical to my ears.
Yes the the Pentode (Ultralinear) sounded not as musical to my ears as the lower powered Triode. The Pentode was great with well recorded music, very accurate, however if the music was compressed and without DR it became more fatiguing and music where the highs were more etched it exaggerated this. I found the Triode setting much more forgiving and musical.
The Ultralinear setting (Pentode) is 75 watts per channel. The Triode setting 33 Watts per channel. My speakers are rated at 91 dB so they play plenty loud in both settings. I do notice a slight, very slight difference in the impact that the music comes across, less in the Triode setting, but there is plenty of impact for my tastes. The sound has a warmer tube sound which I like and the highend is more pleasing. The trade offs, which there is in my case favor the Triode setting.
