Single-Ended Triode vs. Pentode Tube Amps: Which Amp Is Best?
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- Опубликовано: 27 июл 2024
- Tube curious? Want to try a single-ended tube amp? Heard experts trash tube amps with "a lot of feedback" or extoll the virtues of amps without feedback? What the heck is feedback in this context? Are triodes best? What's wrong with pentodes? I modified one of my single-ended tube amps with switches to toggle between triode and pentode wiring and between with negative feedback and without, respectively. In this video, I do listening tests to compare the two and speak upon some of the differences. I use clips by Boz Scaggs, U2, Incognito, The Sunday Manoa, The Stranglers, and Metallica.
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This is a test I needed to hear. Says more then a lot of A/B tests that only use music that doesn't challenge a tube amps ability's under aggressive pace and frequency. Cheer's to You Lancaster! God Bless!
Thanks!
May be not many people knows but adjusting the second grid voltage we can change a 2nd/3rd harmonics ratio. We can add more 2nd harmonic than any triode can provide if you like a sugar. So, we can have a single amplifier for both blues and rock. Those who don't know this trick (and just copy ancient schematics) state that triode is all we need to be happy.
As a relative new tube builder, im curious (understatement!) with your comments. I built the Skunkie kt120 monoblocks and they have such low distortion measurements you would swear your listening to a solid state amp. I also added a switch to go back and forth between triode and pentode but like mentioned in the video burned out lol.. i did enjoy the triode mode and would love to experiment with tuning the 2nd order harmonics.. i plan on replacing the switches but would like to learn more about your comment.. any pointers???
@@AudioFanMan Well.. My comment was exactly about a voltage applied to the second grid of a pentode. From .. I don't know 70 up to 250 gives different 2-nd/3-rd harmonics ratio. And you can even add a switch to set an amplifier into a rock/blues mode I guess -)
PS John Broskie on his tubecad web journal mentioned some other "switches" which can add a little bit of different mood to a sound (however the grid voltage is not from there)
Our hearing deteriorates with age.
I'm almost 69, so, for what it's worth, LOL.
The PC speakers here are not great, so I switched to an external amplifier (Sony), at low volume on JBL ES90 speakers.
The highs seem a bit less with the triode, as was to be expected.
Especially noticeable with the cymbals that appear a bit more muted and therefore seem to roll out less.
The roll off in the low end is less noticeable, since most speakers in this area already roll off.
Not noticeable, but should still be avoided, I think, because when both are added together, you are left with no perceptible bass at all.
For the reproduction of a 78 rpm record, which I also listened to as a child, the triode would be no problem, I think.
But beyond that, the flat curve of the pentode is still recommendable, even for people with old ears like mine.
English is not my native language.
My 2 cents from Belgium.
I'm checking the response curves I made for that amp. In my testing at 0.5 watts per channel, for triode without NFB, the -3 dB points are 30 Hz and just over 10 kHz, so the high-end roll-off is much more noticeable than on the low end. For pentode with NFB, the low-end -3 dB point is just over 20 Hz, and it doesn't roll off at the high end (at least not that I can measure without a real signal generator). There's a slight bump up (less than +0.5 dB) that peaks at 50 Hz, and it's still at nominal gain at 40 Hz--a bit distorted, though.
I definitely prefer the sound of the pentiode with negative feedback with the Metallica songs
Hello Lancaster HiFi, I simulate and build tube amps. To the topic of negative feedback and single ended triode circuit: it depends on the details. Detail one: the Ri of the output triode or pentode in triode circuit. Lower Ri is better. Detail two: the tubes in front of the output tube. Triode or pentode, which tube, which working point. If you do everything right, you need no negative feedback. And yes, you can mask errors with negative feedback. I am happy with low Ri pentode in triode circuit without nfb as single ended and push-pull amp.
As you learned by yourself: don't switch the running amp from pentode to triode. And try the ultra-linear mode. This is output power level wise between pentode and triode and sound wise more triode then pentode. Have fun!
Sadly, I couldn't get much out of this test as the prior one I viewed comparing SE to a Push Pull tube amp. There was some kind of distortion in the mid-bass that was marring the sound of both tracks. However, from what I could pull from this, again the SE triode mode sounded more open with better stereo separation. Pentode = anemic. EDIT: LIstening to it again another day, the distortion I mentioned was gone, so it must have been a RUclips issue. At any rate, I CAN tell the difference between the modes and like before, the triode mode sounded more open, and wider separation of the channels / instruments. Bass was fuller. Pentode mode: overall anemic. It lacked life in the midrange. The only benefit I heard was that the bass extension was deeper. In the end, triode mode wins!!!
Nice video and whilst the comparison was very interesting , I suspect that the big difference in your Pentode vs Triode test was due to the negative feedback present in the pentode case. I believe that the difference between Pentode and Triode would be better served if both were self biased with the cathode resistor well bypassed and no negative feedback loops in either caseI and I would be very interested in the comparison as I described especially for an EL34. I'm a traditionalist and not much into Beam Power tubes, it is claimed that they are very different sonically especially for the class A single ended design but I have no first hand experience with that just yet. Again, very nice video that I thoroughly enjoyed.
Thanks! The cathode resistors on the EL84's are each bypassed by 100 uF, which is about right for an amp that could actually benefit from some roll-off in the bass. I have listened to the amp in pentode mode without NFB. I don't recommend it. Pentodes just distort too much (in pentode mode, anyway) to play nicely without feedback, whether global or otherwise.
As a musician (multi instrumentalist), I gravitate towards the zero feedback sound be it triode or tetrode/pentode. Why? Zero feedback is closer to real/live instrumental sound, warts and all whereas with negative feedback, you get a cleaner, more santinised version which in itself is pleasant and enjoyable, sure but it's not how real/live music sounds like.
Was thinking about this more today and wondering why the SET tube amps are all the rage.? To me the Pentode sounds better.
Thanks for another educational video, among other things I now know what SET stands for
I don't quite get it. I sometimes wonder whether those who pooh-pooh amps with "lots of feedback" actually know what that even means. Morgan Jones refers to "single-ended madness," where single-ended amps are almost assumed to lack negative feedback.
I think using an actual triode like a 300b or 2a3 or 45 etc. goes beyond using switchable pentode/triode as far as sonics go. I think the el84 is a great sounding tube in single ended pentode mode though and this was a good video exploring this triode option is such an amp . I built one single ended el84 and it is a wonderful sounding amp. It's called the RH84. Lots on the net about this circuit.
Pentode sounded better to me on all accounts. Richer fuller sound. Ride the lightning is my favorite Metallica album but not the best recording, but I think I prefer pentode on that as well.
I built my amp to do well in both settings. I can switch from pentode to triode and apply negative feedback on the fly. I usullay find mysel using pentode with feedback 90% of the time. But when I sit down for some special jazz and vocal related stuff triode is where I go to. It sounds livelier then.
My experience is similar. I occasionally think to try out triode mode. I have to actually turn off the amp to make the switch because of the high DC voltage. I found out the hard way by quickly ruining a switch! I suppose I could also switch the feedback on the fly since the voltage is low, but I generally make the change with power off.
@@Lancaster_Hi-Fi Same goes for me with the pentode / triode switch.
I'd be curious to hear how Magnavox wired the 8608 originally
I have a diy built transformer coupled amp with a single ended triode (set) and single ended pentode (sep ) mode. I don’t know what they do but they absolutely demolish the sound of OTL amps out of the water
The higher input capacitance of the triode is going to require a driver with a lower output impedance than your 12AX7, something like a 6N1P or 6DJ8 would work great here. You'd get all the lost HF back, and perhaps some of the low end as well. (You'd have to test)
I ❤️ 6DJ8!
@@Lancaster_Hi-Fi Try the 6N23P from the Voskhod factory with the "rocket" logo, they are really good and somewhat affordable.
Thanks for the tip!
12at7 might be worth trying also. They are cheap too!
Can you record it directly from your speaker wire ?
So that we can hear your system without your room reflection characteristic.
Or
Use resister instead of speaker but I think it is not the way we usually use the amp.
Wow, hello there! Are you in Corvallis OR? I live in Langlois, out on the coast in between Bandon and Port Orford. I’m new to the HiFi community, I started building my system in 2020. Yep, you guessed it, during lockdown. I am currently lacking tubes as my Pro-Ject Tube Box S2 died. Just as well, it was just too bright. I’m using an Solid State Musical Surroundings Phonomena 2+ while I wait for my Decware tube phone pre. I’ve been on the Decware list for about a year, hopefully I’ll get it soon 🙏
Yes, I'm in Corvallis. I started getting into hi-fi again not long before COVID, which then kicked it into high gear 😅
@@Lancaster_Hi-Fiyeah I'm in Portland Oregon . I can learn more perhaps a lesson in person sometime !
Great content , just subscribed.
Researched all the pros and cons of zero feedback v feedback applied and decided to use my ears !
Zero feedback mode sounds more natural with instruments sounding like real instruments and music just flows rather than sounding somewhat forced in pentode setting. Even on the heavier sounding last track , still preferred the zero feedback mode.
Shame you no longer offer the dgse1 with zero feedback option , I’d certainly consider buying one.
Keep up the good work
Triode sounds warmer to me.
I want to see distortion comparison.
Can you do that?
I don't currently have these capabilities.
@@Lancaster_Hi-Fi with FFT you can find harmonic distortion.
After find FFT the ratio between second peak and first peak is a second harmonic percentage and so on.
Better to make ratio between output and input first and give it to FFT to emphasize the analysis.
You make step frequency scan you can plot distortion at any point.
recording waveform allow this analysis.
You might use cheap oscilloscope tap on speaker and input jack then save waveform in a flashdrive.
I have an Idea.
If you have VCO you can supply stairs case voltage to it and it gives a step frequency scan. Then you don't waste time manually scan each step.
If you have 4 channel oscilloscope.
One channel dedicated for recording the stair case step.
You can use programming code to analyze the signal by cutting each stair case step and use FFT for each step to find 2nd 3rd distortion.
Programming allow you to find first second peak separately for distortion harmonic percentage calculation.
The code I recommend is "octave".
In the past we use variable filter with knob. 2nd box, 3 rd box with bridge rectifier at output of it are made. We tied oscillator knob and all the filter knob together. Then meter reading from each box ratio with original output with bridge rectifier is the harmonic distortion percentage.
However the box is difficult to make because you have to have bandpass filter and tuning knob connect with variables inductor.
Then you have to make scale of it comprehend with oscillator.
The modern technology today makes it easier.
Sorry if I make a very long comment.
I know about Fourier transforms. I just don't have the equipment to do it.
Merci, pour la vidéo, seulement il faut inclure la traduction "cc".
Merci encore.
Merci!
Push-pull is best.
First song, diode sounds less restricted
Second song, not much difference, did hear that song too much long ago 😂
Third song triode has it again for me. More swing to it, easier to connect with.
Fourth song, close but diode again
Fifth song diode has is, bit warmer is how I like synths
Sixth song. Intro diode, after that pentode. More speed, this genre needs a quick sounding amplifier.
Now I use planar headphones for most listening to heavy music. My ESL 57 tend to do better with the music I favor the diode for. So guess I will start saving for a SET that can drive those 😂
Subbed to your channel, great content, deserves more exposure.
Thanks!
the pentode sounds brighter
Yes, it is. Pentode + NFB is flat out past 20 kHz; triode w/o NFB rolls off past 10 kHz.
PENTODE.
All day long.
Personally, I would not want to put that much work into building a SET amp if it had that kind of poor performance...
I'm in general agreement. This is the first of four amps I've built with this circuit design, but the three later amps don't have the option of triode mode and no negative feedback.
@@Lancaster_Hi-Fi Nice! I am in the process of researching tube circuit designs and types to build a reference level tube headphone amp. Any suggestions??
@@dmark2639 I don't really know enough about what distinguishes a headphone amp from a normal one. I would think you'd have more options, including OTL (output transformer-less), but I don't really know.
@@Lancaster_Hi-Fi I've been researching the Bottlehead DIY headphone amp kits. They seem like a pretty good place to start for an amateur like me.
A kit sounds like a good starting point, but I can't really say since I've never used/built one. Maybe I'm too cheap or stubborn or both!
The triode is limited by there Output Transformers. If you have the budget for a pair of Great OPT then there’s no comparison triode will win hands down. Most people can’t spend 2k on output transformers or the price of a 300b Tubes. For the best sound for the $ a pentode is the way to go. The negative feedback is just trying to fix a problem that’s already in the circuit. Triode, Pentode really doesn’t matter that much. Once you’ve experiences a single ended tube amp with efficient speakers there’s no going back !!
I've got a DIY Tubelab SE II project on the back burner. See one of my more recent videos, "Why I Must Build ..." My most recent video, about speaker sensitivity, was motivated by my desire to get speakers that can match well with a type 45 SET. I've got some awesome Tamura OPTs, but they're not beefy enough for 300B's or even 2A3's.