Single-Ended Triode (SET) Amplifier Revolution of the 1990s. Did it really happen? Was it Successful?

christoph

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christoph

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there are a number of truly great SET amps that will drive great speakers to significant pressure levels and sound amazing.
Can you give some examples, please?
 
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caesar

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Gentlemen, I really appreciate the replies so far. Very informative for those of us who are younger or who have not been in the hobby that long (1990s!!!). Many who are surprised by the question are falling into the "curse of knowledge" cognitive bias, where people assume everyone else has the same knowledge, background, and expertise to understand what they are talking about. Obviously this is not the case, as evident by some of the replies of other experienced individuals in this thread.

Please keep the replies coming!
 

thedudeabides

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Many who are surprised by the question are falling into the "curse of knowledge" cognitive bias, where people assume everyone else has the same knowledge, background, and expertise to understand what they are talking about.
Curse of knowledge cognitive bias? Oh please. Of course everyone does not have the same knowledge, background, etc. Yeah it obviously happened and how do you define "successful" in high end audio? All you need to do is some basic research.
 
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BlueFox

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I never have understood the interest some have in very early 20th century technology. Sure it works, but it certainly isn’t better than current solid state technology. Other than being nostalgic I just don’t see any benefit to tube technology.
 

bonzo75

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I never have understood the interest some have in very early 20th century technology. Sure it works, but it certainly isn’t better than current solid state technology. Other than being nostalgic I just don’t see any benefit to tube technology.

Let me guess, you must be a Magico owner
 

christoph

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morricab

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I never have understood the interest some have in very early 20th century technology. Sure it works, but it certainly isn’t better than current solid state technology. Other than being nostalgic I just don’t see any benefit to tube technology.
Well, your opinion notwithstanding, you clearly haven't heard what is possible from "antique" audio. Most of the life of music is missing from current SS technology that it is even hard to explain with words the difference but once heard a lot of people "get it" even if they don't want to put monstrous speakers and hot running tubes in their homes. It is a difference between gear that makes sounds that tick boxes vs. gear that transports you to a more realistic gestalt of the music.
 

PeterA

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I never have understood the interest some have in very early 20th century technology. Sure it works, but it certainly isn’t better than current solid state technology. Other than being nostalgic I just don’t see any benefit to tube technology.

Bud, surely you knew this comment would be somewhat provocative. I used to own Magico/Pass like you do. It was great sounding and I really enjoyed it. I kept evolving the system with upgrades in electronics and speakers and I always got "more" - more detail, blacker backgrounds, tighter more precise imaging, and what I thought was increased dynamics and realism. I would break the sound apart and appreciate the fragments. Then I started a series of experiments, ultimately ditching my audiophile accessories: acoustic treatments of panels and TubeTraps, audiophile power cords and cables, pneumatic isolation, and current conventional speaker set up.

Some of the sonic attributes I so cherished were systematically replaced by a more holistic and natural sound. I started hearing the music more than just the sound. When I realized I had taken the set up and removal of accessories as far as I thought I could, I heard some vintage SET/horn systems. That is when I realized where audio could really go. I had had no idea.

I replaced all of my Pass gear with Lamm gear and tried the SS Lamm M1.1 100 watt Class A amp because my Magicos were so hard to drive. The sound was completely different, tubes plus SS in general, but Lamm in particular. The system became dynamic and alive like never before in my room. I then tried the Lamm ML2 18 watt SET amp on my Magicos. It certainly did not have the power to drive those speakers, but I heard a type of magic in that sound that I knew I had to change speakers for a pair more appropriate for that specific SET amplifier. Vintage 105dB, 16 ohm corner horns were the answer.

You may denigrate the sound as early 20th century and appealing to our sense of nostalgia, but I was not around during that period, or certainly not paying attention. I had no earlier sound to revive and re experience. I simply knew that this combination suddenly brought me closer to what I hear with live music.

I have no historical perspective to know if there was a SET revolution in the 90s and whether or not it was successful. It does not really matter to me. What matters to me is that I found Lamm SET amplifiers and speakers that work with them. I have learned that the benefit to tube technology is that in certain cases, some people think it sounds more natural. It is really as simple as that for me.

Ironically, a good buddy of mine loves tubes and had a lot of tube gear for years as well as SS. Just as I was switching to tubes from SS, he recently switched back to SS full time and loves his system. He has Magico speakers and his system sounds excellent too. It is just a different sound and presentation.
 

Ron Resnick

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. . . I just don’t see any benefit to tube technology.

You are correct -- there is no benefit to be seen. But, to my ears, there is a big benefit to be heard.

The benefit is sonic -- not visual, and not theoretical.
 

PeterA

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You are correct -- there is no benefit to be seen. But, to my ears, there is a big benefit to be heard.

The benefit is sonic -- not visual, and not theoretical.

And the sonic benefit of some systems can't be seen or heard. Sorry Ron, could not resist. We're all waiting patiently for the completion of your room and the set up of your tube based system. Big turntable feeding big tubes for big panels in a big room.
 
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Atmasphere

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Many who are surprised by the question are falling into the "curse of knowledge" cognitive bias, where people assume everyone else has the same knowledge, background, and expertise to understand what they are talking about.
This is where Google is your friend.
I never have understood the interest some have in very early 20th century technology. Sure it works, but it certainly isn’t better than current solid state technology. Other than being nostalgic I just don’t see any benefit to tube technology.
Here's the benefit: Traditional solid state amps do not have enough feedback at high frequencies to do properly as they do at bass frequencies. This is caused by a lack of Gain Bandwidth Product, which causes the amp's feedback to decrease as frequency goes up. This results in distortion; in particular higher ordered harmonics. There is enough feedback to suppress the lower ordered harmonics. But certainly not enough to suppress the distortion caused by the application of feedback itself!

This is why feedback has a bad rap, but its not that anything is wrong with feedback so much as it gets misapplied and a good number of designers don't know how to design a proper feedback circuit. Since the ear interprets the higher ordered harmonics as brightness and harshness (the ear assigns a tonality to all forms of distortion) and since there are no lower ordered harmonics of enough amplitude to mask the higher orders, you get an amp that is harsh and bright.

SETs don't have feedback and because they are single ended have a quadratic nonlinearity which results in a prodigious 2nd harmonic which is almost inaudible to the ear (but does contribute to the quality audiophiles call 'warmth', ;bloom', 'rich', 'lush and so on). The 2nd order masks the presence of the higher orders and so the amp sounds smoother than solid state, despite having more higher ordered distortion content!

SETs have another advantage which is that when the power is decreased, the distortion drops linearly to unmeasurable. So they can have a very good first watt, where most of the music happens. But to really take advantage of what an SET can really do the speakers have to have enough efficiency that the amp is never asked to make more than about 20-25% of full power- otherwise the higher orders show up on the leading edges of transients, giving the amp a 'dynamic' quality, but its really distortion masquerading as 'dynamics' due to the interaction the higher orders have with the ear/brain system, which uses them to sense sound pressure.

Because the ear has a tipping point where tonality caused by distortion can get more attention than tonality caused by FR errors, the result can be that the presentation, if set up properly, can sound quite neutral and might even sound more neutral than most solid state amps- on the right speaker.
 

PeterA

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SETs have another advantage which is that when the power is decreased, the distortion drops linearly to unmeasurable. So they can have a very good first watt, where most of the music happens. But to really take advantage of what an SET can really do the speakers have to have enough efficiency that the amp is never asked to make more than about 20-25% of full power- otherwise the higher orders show up on the leading edges of transients, giving the amp a 'dynamic' quality, but its really distortion masquerading as 'dynamics' due to the interaction the higher orders have with the ear/brain system, which uses them to sense sound pressure.

Because the ear has a tipping point where tonality caused by distortion can get more attention than tonality caused by FR errors, the result can be that the presentation, if set up properly, can sound quite neutral and might even sound more neutral than most solid state amps- on the right speaker.

Thank you Ralph. This seems an excellent explanation of why my 18 watt SETs sound so good, neutral, and distortion free with my 105 dB/16 ohm load corner horns. It is the right amp/speaker pairing. It also explains some of the sonic characteristics I heard from my former SS amps in the higher frequencies. I appreciate it. I was wondering what you meant by your "dynamic" quality comment earlier. This too makes sense. I have heard HF distortions that seem to make a system sound more dynamic with strong leading edges to transients. Only with various changes did I come to understand that 'dynamic' sound as distortion.
 
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morricab

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This is where Google is your friend.

Here's the benefit: Traditional solid state amps do not have enough feedback at high frequencies to do properly as they do at bass frequencies. This is caused by a lack of Gain Bandwidth Product, which causes the amp's feedback to decrease as frequency goes up. This results in distortion; in particular higher ordered harmonics. There is enough feedback to suppress the lower ordered harmonics. But certainly not enough to suppress the distortion caused by the application of feedback itself!

This is why feedback has a bad rap, but its not that anything is wrong with feedback so much as it gets misapplied and a good number of designers don't know how to design a proper feedback circuit. Since the ear interprets the higher ordered harmonics as brightness and harshness (the ear assigns a tonality to all forms of distortion) and since there are no lower ordered harmonics of enough amplitude to mask the higher orders, you get an amp that is harsh and bright.

SETs don't have feedback and because they are single ended have a quadratic nonlinearity which results in a prodigious 2nd harmonic which is almost inaudible to the ear (but does contribute to the quality audiophiles call 'warmth', ;bloom', 'rich', 'lush and so on). The 2nd order masks the presence of the higher orders and so the amp sounds smoother than solid state, despite having more higher ordered distortion content!

SETs have another advantage which is that when the power is decreased, the distortion drops linearly to unmeasurable. So they can have a very good first watt, where most of the music happens. But to really take advantage of what an SET can really do the speakers have to have enough efficiency that the amp is never asked to make more than about 20-25% of full power- otherwise the higher orders show up on the leading edges of transients, giving the amp a 'dynamic' quality, but its really distortion masquerading as 'dynamics' due to the interaction the higher orders have with the ear/brain system, which uses them to sense sound pressure.

Because the ear has a tipping point where tonality caused by distortion can get more attention than tonality caused by FR errors, the result can be that the presentation, if set up properly, can sound quite neutral and might even sound more neutral than most solid state amps- on the right speaker.
A couple of points Ralf: 1) I have heard some amps (Class D of course) that follow this principal of piling on the feedback to like 80db or more and despite the claims that they are then sonically invisible (not necessarily your claim) it is simply not the case that they make recordings sound closer to the real thing. Things like dynamic contrast (not absolute dynamics), image dimensionality and tonal correctness are nowhere nearly as convincing as even just a good tube amp (never mind SOTA). You can argue objective perfection until blue in the face...as soon as you play a tune you hear the difference.

2) Damage to high frequencies. This is where a lot of the damage is done and distortion rise with increasing frequency is an effect of feedback amps. Increased odd order high frequency distortion has a negative impact on 3D imaging and differentiation in tonality of high frequency instruments. This has a severe impact on realism and soundstage perception and the purest highs I have heard have all come from tube gear and not from conventional SS and especially not class D.

3) How hard a SET can be pushed before it starts to harden up depends strongly on the power supply and it’s ability to instantly deliver current. I have heard ones that harden quite quickly beyond a couple of watts and some seem to have a bottomless well of power.
 

Atmasphere

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A couple of points Ralf: 1) I have heard some amps (Class D of course) that follow this principal of piling on the feedback to like 80db or more and despite the claims that they are then sonically invisible (not necessarily your claim) it is simply not the case that they make recordings sound closer to the real thing. Things like dynamic contrast (not absolute dynamics), image dimensionality and tonal correctness are nowhere nearly as convincing as even just a good tube amp (never mind SOTA). You can argue objective perfection until blue in the face...as soon as you play a tune you hear the difference.

2) Damage to high frequencies. This is where a lot of the damage is done and distortion rise with increasing frequency is an effect of feedback amps. Increased odd order high frequency distortion has a negative impact on 3D imaging and differentiation in tonality of high frequency instruments. This has a severe impact on realism and soundstage perception and the purest highs I have heard have all come from tube gear and not from conventional SS and especially not class D.

3) How hard a SET can be pushed before it starts to harden up depends strongly on the power supply and it’s ability to instantly deliver current. I have heard ones that harden quite quickly beyond a couple of watts and some seem to have a bottomless well of power.
The most I've seen in any class D amp is about 60dB IIRC. 80 would be quite a feat. But the distortion signature is arguably more important than the amount of distortion present; its really important in all cases that the lower orders are in enough quantity that they mask the higher orders. Class D amps can have certain non-linearities in their encoding schemes that result in just that; so if designed with this in mind they can sound surprisingly tube-like natural. But not all class Ds, mind you.

Your point 2) is what I explained regarding Gain Bandwidth Product. It is to feedback what gas is to a car. You run out of gas the car stops, you run out of Gain Bandwidth Product and the feedback has gone to zero. But feedback by itself isn't the problem- the problem is improper use. Think of it as a bell curve; a little feedback does little damage, by the time you get to 20dB its doing a lot of damage (injection of higher ordered harmonics and intermodulations at the feedback node) but when you get over 35dB its pretty innocuous again because it can clean up its own mess. 35dB is no easy task though. Most of the amps that have harshness on account of feedback (which is most amps made in the last 70 years or so) are running 10-25dB- right in the 'trouble' zone!

Your point 3) is false. SETs draw nearly continuous current on account of their class A operation. So it would make no difference if the amp were at full power or not. The test for this is measure the amp's AC current draw and run it up to clipping from idle. The current drawn should not move even a little bit (unless the amp is class A2 or class A3). I don't doubt what you heard though; there are a lot of things that can influence how the amp behaves at full power as opposed to idle. I'm sure you're familiar with them too- tube quality, the competence of the OPT, how well the OPT is loading the power tube, the quality of the preceeding parts like coupling caps, how well the amp is grounded (which is a topic that can consume a book with ease...), how easily its driven and I can go on and on.
 

Tinear1

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Revolution? Well my take is revolution is maybe a bit strong depending on the region of the world you live. In Japan absolutely and continues quite strong today. Here in the US there was some resurgence about every 10-15 years from the 60's to now. I personally have done the entire circular journey of high-power amps and Wilson's / Magico's to SET and horns twice in the last 20 years... so my particular cycle is about 10 yrs. I can say that I have the SET / Horn system now that I will not be further upgrading from... unless... there is a huge technology breakthrough that changes everything which I seriously doubt. I think the type of system you are drawn to is driven by your listening priorities of Speed, Dynamics, Decay, Detail, Tone, and Volume. Various technologies are MUCH better at some and not others. Lastly, remember to have fun in this hobby as you experience various system components... as they say, it's the journey not the destination that is important (as in life itself).
 
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KeithR

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As for companies like ARC, have you heard their products lately? The people who first designed these products are all gone and you have corporate engineers with very limited analog education designing these products.

david
I have and the Ref 75SE is a bargain sonically and 180 degree turn for the company from SS-ish imitation that Bill Johnson loved for a few decades.
 

ddk

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I have and the Ref 75SE is a bargain sonically and 180 degree turn for the company from SS-ish imitation that Bill Johnson loved for a few decades.
I agree fully agree with the SS-ish description, that's exactly what I heard.

David
 

JackD201

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It happened and for me it was truly educational. SETs and Stats (not necessarily together!) remain the benchmark for "purity" as far as I am concerned and thus I still have not divorced myself from SETs. I still support Lamm and KR with passion. Like Peter says, speakers are the challenge when you want dynamics to go with that beautiful purity.

Those who have had the opportunity to have experienced well set up and matched 4 or 5 way true horn designs are lucky indeed. It must be said however that these do come with a caveat. The best I've heard have required multi-amping to go along with the space requirements. I have 7 ft tall "box" speakers but the space they require are small by comparison to true horn sub bass. Add up the electronics, speakers and real estate and one will quickly see that the good stuff in SET and Horn land ain't cheap when we are looking at best vs best. That's when the Best there are are even available or attainable. Suffice it to say, they require more intrepid clientele.

Now if we are looking at mid scale presentation and bandwidth I am happy that all is not lost. PHY with SETs or Ralph's OTLs are an example. Some heavily modded classic oldies too. Let's just not jump the gun that these will approach the WE s and the Bionors of this world. You're looking at 7 figures for the modern offerings and recommended amplification.

No surprise then that it is the DIY community that is really keeping the flame burning.
 

acousticsguru

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You are correct -- there is no benefit to be seen. But, to my ears, there is a big benefit to be heard.

The benefit is sonic -- not visual, and not theoretical.
I've often wondered if, apart from the sound quality, there is any other reason to want to own a tube amp? Seriously.

I know there are people who are fascinated by the look of them, the glow, or have nostalgic feelings about them etc. Some people love tube rolling - I'm not really one of those either, given the choice, I'd be ever so happy to put in the best and leave it at that. What else? Ah yes, the heat. The fear of blowing or setting something on fire - as rarely as that may happen. Let's not even mention minor problems such as spouses, kids, pets…

And yet we love tube amplifiers. It has to be the sound: no sane person would want to own one if it weren't for the sound. I do wonder sometimes how there could be people out there who question that. Although: audiophiles aren't exactly, ahem, sane people… ;)

Greetings from Switzerland, David.
 

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