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

[Addicted to hifi]

set amplifiers can sound stunning.

 

[PeterA]

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.

David, I think you could ask the same thing about vinyl. It is more hassle, more inconvenient, more work, more adjustments and maintenance. Yet there is something about the sound, and perhaps some intangibles, that make people want to own it. For me, it is the sound above all else.

 

[jeff1225]

I would say there was definitely a revolution that began really in the 1990s. Just look at the sheer number of available SET amps now, from Europe, from Asia and yes even from America. Horns were kind of kept alive in Asia but have now really caught on in Europe and this seems to be slowly seeping into the US as well.

You see several makers of horns in Germany, some in Greece, Cyprus and Eastern EUrope. THere are also an increasing number of high sensitivity "conventional" speakers where maybe the tweeter is horn loaded but the rest is high sensitivity cones. Single driver speakers have also gone through a revival.

While still not "mainstream' there are far more options than ever before, which suggests a much stronger customer base than ever before as well.

THe 80s was the rise of the great panel speakers (Magnepan, Apogee, Acoustat, Infinity etc.). Every serious audiophile had big panels...because they simply sounded better (they still sound great if you use an appropriate amp). The 90s moved away from big speakers (although that has somewhat reversed in the 2000s) but not big amps. The last 20 years has shown a serious growth in the SET amp and the increased acceptance of horn/high sensitivity speakers...as people start to realize what was missing in the previous paradigms. This also has led to an awareness of what was lost from the distant past (western electric, Altec, JBL etc.). Of course there were some who never lost sight of this era that produced some fantastic speakers and amps but they had definitely faded from the general public consciousness. Now; however, an audiophile might not like SETs/horns but they have definitely heard or heard of them...something that was not really true before the 90s.

Evidence of this can be seen with the escalating prices on used horn speakers. You used to be able to buy Altec speakers for nothing, now they’re quite expensive.

 

[bonzo75]

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.

Tube rolling apart from the itch to try out anything that can be changed in the audio chain, is required to optimize. Once you hit the right tubes you don't need to roll further except if you find new tubes. There are clear differences in sound with different tubes and some sound quite superior on all aspects to others, some are just changes in characteristic

Also, low watt SETs are much easier to maintain, service, and simpler than the push pulls or the big SS

 

[acousticsguru]

David, I think you could ask the same thing about vinyl. It is more hassle, more inconvenient, more work, more adjustments and maintenance. Yet there is something about the sound, and perhaps some intangibles, that make people want to own it. For me, it is the sound above all else.

Exactly, that was the point I was trying to make: people look upon tube or vinyl lovers (may want to add open reel tape recorders to this short list also) as in some way irrational (why would anyone want to own old-fashioned technology, in particular if it's so high-maintenance?), partly because they choose to ignore the obvious, that it's for the one reason they think most unlikely, which is that it must be doing something better.

Greetings from Switzerland, David.

 

[bonzo75]

I don't see a common factor. I don't view SETs as inconvenient compared to SS nor are they more expensive.

 

[acousticsguru]

I don't see a common factor. I don't view SETs as inconvenient compared to SS nor are they more expensive.

Never said a word about cost, but they're running hot for one thing (huge problem depending upon room and climate - believe me, I know from personal experience), need to pay attention to pets, the output transformers make many back-breaking to lift etc.

Also, ask Moni, Christoph's wife: she's reached the conclusion tube amps are just like horses, feeding on hay (tubes - her reply to his claim that in contrast to her horses, his amps are low-maintenance).

Greetings from Switzerland, David.

 

[Hear Here]

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.

Plenty of truth in you last sentence!

It took me 15 years using tube amps (SETS plus one OTL) to realise that I'd listen to much more music if I wasn't burning fuel to power for my amps (and having to pay for it along with the Environment), checking and replacing expensive tubes from time to time and general tube hassle. I thought that if (and only if) I could find as good or better sound from an SS amp, I'd switch. I home auditioned a dozen and jumped ship 3 years ago. Regrets? None, I'm relieved to say.

 

[Rob181]

Also, ask Moni, Christoph's wife: she's reached the conclusion tube amps are just like horses, feeding on hay (tubes - her reply to his claim that in contrast to her horses, his amps are low-maintenance).

Now that is a cracker of an analogy - I agree with Moni they - tube amps ARE just like horses feeding on hay

 

[acousticsguru]

Plenty of truth in you last sentence!

It took me 15 years using tube amps (SETS plus one OTL) to realise that I'd listen to much more music if I wasn't burning fuel to power for my amps (and having to pay for it along with the Environment), checking and replacing expensive tubes from time to time and general tube hassle. I thought that if (and only if) I could find as good or better sound from an SS amp, I'd switch. I home auditioned a dozen and jumped ship 3 years ago. Regrets? None, I'm relieved to say.

If you're happy, that's all that counts. I like and own both, the reason being, I'll listen to anything that sounds great (I don't have "principles" in this regard as some of the guys here do). Also, I don't mind owning more gear than I need, or indeed will simply use it for different purposes and/or music, including in summer (directly under a roof) and winter, as long as I can fit it somewhere. As I'm getting older I'm trying to avoid buying heavy components to go easier on my back, but that's another resolution I just broke again (pun intended), what can I say, guilty of being an audiophile, not sure that'll serve as an exucse. Curiosity killed the cat?

Greetings from Switzerland, David.

 

[JayV]

I would suggest listening to Robert Koch’s new Koda power amps. Sound like SET’s but the power of solid states required to drive low impedance big speakers. Horns not to my liking personally but can understand why others might.

 

[JayV]

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.

 

[oldvinyl]

Was there really a SET amplifier and horn speaker revolution in the 90s? Was anyone around in this hobby in the 1990s to witness it? Was it successful? What was the outcome and impact?

My impression of the recent history is that we have had some expensive hard to drive box speakers , like Wilson and Magico, that are thriving. (On the other hand, companies like Magnepan, and others that produced larger panel speakers, are on the ropes.)

To complement these hard to drive box speakers, the industry has had a solid state amplifier revolution with new brands like Soulution, Consoulation, CH Precision, etc., come around in the last 10-15 years. (Tube companies like audio research, on the other hand, seem to be on the ropes. and other tube brands are known only to experienced audiophiles and are not easy to find for those not in the know.)

Seems like these days audiophiles are older, deafer, and richer. They are after "hyper- details" and "accuracy", although most don't know what accuracy is and can't define it. And the hifi industry seems to be fighting for this segment.

An average person walking on the street will find a wilson, magico, sonus fiber, and McIntosh. But they will be hard-pressed to find a horn with SET.

Other than a few passionate SET - horn aficionados on this site, who have experienced the subtlety, delicacy, flow, aliveness, and emotional connection to the music these types of systems can deliver, what was the effect of this SET revolution?

From my understanding, there was a resurgence of SET amps in the late 1980s and 1990s. I purchased several different amps from Cary audio in that time frame. While I do not use horn speakers, I have selected fairly efficient and tube friendly speakers that work well with SETs. I still have the CARY 300-SEI for my office and headphones and the 1610 monoblocks for my 2 channel system. These amps have endured well over the last 25 years.

Cary 805 started in 1993: Cary 805 amps
Cary 300-SEI 1995 review: 300-SEI review
Cary also produced 300B and 2A3 monoblocks in the late 802/early 90s.
Their last SET in the late 1990's was the 1610 based on a KR 1610 tube: Cary 1610 review
The 300-SEI and 805 amps are still in production.

Speculation on the effect of SET revival - more interest in tube amps, the NOS 300B and 845 tubes got scooped up, manufacturers revived replica 300B and 845 tubes, speaker manufacturers made more efficient speakers. In general, interest in overall sound quality since the SET was such a stark contrast to the solid state amps of the day.

 

[G T Audio]

I don’t remember any great SET amplifier revolution in the mid 1990s despite being a major part of the SET/Horn movement here in the UK during that time. Having said that there was a number of companies that made SET amplifiers, most when out of business quite quickly when SET amplifiers became less fashionable. Credit must go to Joe Roberts and his Sound Practice magazine who was certainly instrumental in those times to reintroduce the sonic benefits of horns speakers and SET amplifiers.

Also, Jim Smith and his partner (Avantgarde USA) did some great marketing for Avantgarde Acoustic horns and did something unique, in that they got Avantgarde Acoustic a seriously well established high-end brand within a couple of years. Whereas this normally takes many years, even decades to get a brand this well established, they did it within 2 years. This also helped me as I was importing Avantgarde Acoustic into the UK at the same time (1998) and I carried on representing them for a further 17 years. I remember quite a few Uno’s and Duo’s being sold through 2 of my dealers in London to Americans working in the City as a direct result of Jim’s marketing in Stereophile Magazine. The benefit of this was to offer great horn speakers to a wider audience so that SET amplifiers could be used in main stream domestic audio.

Typically, when there is any sudden interest generated in something “new” or “interesting”, everyone wants a piece of the action, or a slice of the pie, so some manufacturers started to design SET amplifiers and like in all things commercial, there was a strive to the lowest common denominator, as in the “price”. Unfortunately, you cannot make a good SET amplifier cheaply, as the parts required cost large amounts of money, as in transformers, valves/tubes etc, and poor design cannot be covered up using feedback, as SET amps are feedback free. These manufacturers striving for market share cut corners with poor designs and poor parts and poor build quality to the point that they measured poorly, performed poorly, and got a bad rap from the magazines, who in their infinite wisdom reviewed them with conventional loudspeakers!!! Ironically, the only speakers you could use with a SET amplifier were high efficiency types like Horns. But nearly all SET amplifiers at the time were just too noisy and poorly designed to use with speakers of such a high efficiency. I regularly measured less than 4 watts from a quoted 8 watt SET design. It’s really no wonder SET amplifiers got a bad reputation. I have been designing and building SET amplifiers for 30 years and I know of no better amplifier topology to use with high efficiency loudspeakers that offers the same natural audio performance as a live musical event.

 

[ddk]

I don’t remember any great SET amplifier revolution in the mid 1990s despite being a major part of the SET/Horn movement here in the UK during that time. Having said that there was a number of companies that made SET amplifiers, most when out of business quite quickly when SET amplifiers became less fashionable. Credit must go to Joe Roberts and his Sound Practice magazine who was certainly instrumental in those times to reintroduce the sonic benefits of horns speakers and SET amplifiers.

Also, Jim Smith and his partner (Avantgarde USA) did some great marketing for Avantgarde Acoustic horns and did something unique, in that they got Avantgarde Acoustic a seriously well established high-end brand within a couple of years. Whereas this normally takes many years, even decades to get a brand this well established, they did it within 2 years. This also helped me as I was importing Avantgarde Acoustic into the UK at the same time (1998) and I carried on representing them for a further 17 years. I remember quite a few Uno’s and Duo’s being sold through 2 of my dealers in London to Americans working in the City as a direct result of Jim’s marketing in Stereophile Magazine. The benefit of this was to offer great horn speakers to a wider audience so that SET amplifiers could be used in main stream domestic audio.

Typically, when there is any sudden interest generated in something “new” or “interesting”, everyone wants a piece of the action, or a slice of the pie, so some manufacturers started to design SET amplifiers and like in all things commercial, there was a strive to the lowest common denominator, as in the “price”. Unfortunately, you cannot make a good SET amplifier cheaply, as the parts required cost large amounts of money, as in transformers, valves/tubes etc, and poor design cannot be covered up using feedback, as SET amps are feedback free. These manufacturers striving for market share cut corners with poor designs and poor parts and poor build quality to the point that they measured poorly, performed poorly, and got a bad rap from the magazines, who in their infinite wisdom reviewed them with conventional loudspeakers!!! Ironically, the only speakers you could use with a SET amplifier were high efficiency types like Horns. But nearly all SET amplifiers at the time were just too noisy and poorly designed to use with speakers of such a high efficiency. I regularly measured less than 4 watts from a quoted 8 watt SET design. It’s really no wonder SET amplifiers got a bad reputation. I have been designing and building SET amplifiers for 30 years and I know of no better amplifier topology to use with high efficiency loudspeakers that offers the same natural audio performance as a live musical event.

Unfortunately the Trio was never really SET friendly and Duo was only borderline. Further bass quality of their active boom boxes didn’t and don’t sound natural and never heard them adequately mesh with high end SETs or any good tube amplifier. I agree that Jim did a fabulous job marketing AVs.

david

 

[morricab]

Unfortunately the Trio was never really SET friendly and Duo was only borderline. Further bass quality of their active boom boxes didn’t and don’t sound natural and never heard them adequately mesh with high end SETs or any good tube amplifier. I agree that Jim did a fabulous job marketing AVs.

david

Hi David,
Please elaborate on why they would not be SET friendly. At about 109db and easy loads seem to be the very definition of SET friendly. Are you also meaning tubes in general or just SET? Do you think SS works better because it integrates more with the bass modules?

Having heard LOTs of AV speakers over the years the two best setups I heard were a setup with Thomas Mayer SET amps (with Avantgarde Duo (Omegas?)) and with AudioPax amps (also Duos of some sort). The worst I have heard them sound is with their own SS amps.

 

[ddk]

Hi David,
Please elaborate on why they would not be SET friendly. At about 109db and easy loads seem to be the very definition of SET friendly. Are you also meaning tubes in general or just SET? Do you think SS works better because it integrates more with the bass modules?

Having heard LOTs of AV speakers over the years the two best setups I heard were a setup with Thomas Mayer SET amps (with Avantgarde Duo (Omegas?)) and with AudioPax amps (also Duos of some sort). The worst I have heard them sound is with their own SS amps.

Hi Brad,

The Trios require power and some current to come to life that sensitivity figure is deceiving. I tried them with Lamm ML2 and Nagra HD on several occasions and they both struggled with it, strangely the Nagra even more, DUOs are an easier load and ML2 can drive them. I must mention that I haven’t heard any of the current generations and don’t know if they made changes, my comments to @G T Audio were regarding the era he was talking about.

david

 

[morricab]

Hi Brad,

The Trios require power and some current to come to life that sensitivity figure is deceiving. I tried them with Lamm ML2 and Nagra HD on several occasions and they both struggled with it, strangely the Nagra even more, DUOs are an easier load and ML2 can drive them. I must mention that I haven’t heard any of the current generations and don’t know if they made changes, my comments to @G T Audio were regarding the era he was talking about.

david

Sorry David that doesn't make sense and is counter to my experience with these speakers. Even if AV overrates their sensitivity by an extreme amount (let's say 100db instead of 109db) they would still be very SET friendly speakers. I am not sure what you heard that you call "struggling" but it couldn't have been running out of power...unless the room was literally a ballroom and you were like 10 meters away from the speakers playing at AC/DC levels. I have a smallish SET from Ayon (Spark) that is nominally 20 watts (about what Lamm rates the ML2s) but in reality it is more like a 5 watt amp that has a lot of dynamic headroom. I have zero problem with it driving my 97db Odeons to quite loud levels, without obvious struggling. This same amp also does just fine on my much less sensitive Dynamikks speakers (91db). The ML2, if anything, would be overkill in a domestic setting for AV speakers. It think the Thomas Mayer amps that drove the Duos so well were a couple of watts or so (can't remember the output tube anymore).

Based on measurements, the Lamms are one of the more powerful SETs in terms of what they actually deliver vs. distortion, unlike most SETs, so I really can't see how they didn't work...maybe you just really don't like the sound of the speaker and then it is irrelevant what amp is used...this I could understand because I find the Trio to have coherence issues and so prefer the simpler, but better integrated, Duo.

 

[ddk]

Sorry David that doesn't make sense and is counter to my experience with these speakers. Even if AV overrates their sensitivity by an extreme amount (let's say 100db instead of 109db) they would still be very SET friendly speakers. I am not sure what you heard that you call "struggling" but it couldn't have been running out of power...unless the room was literally a ballroom and you were like 10 meters away from the speakers playing at AC/DC levels. I have a smallish SET from Ayon (Spark) that is nominally 20 watts (about what Lamm rates the ML2s) but in reality it is more like a 5 watt amp that has a lot of dynamic headroom. I have zero problem with it driving my 97db Odeons to quite loud levels, without obvious struggling. This same amp also does just fine on my much less sensitive Dynamikks speakers (91db). The ML2, if anything, would be overkill in a domestic setting for AV speakers. It think the Thomas Mayer amps that drove the Duos so well were a couple of watts or so (can't remember the output tube anymore).

Based on measurements, the Lamms are one of the more powerful SETs in terms of what they actually deliver vs. distortion, unlike most SETs, so I really can't see how they didn't work...maybe you just really don't like the sound of the speaker and then it is irrelevant what amp is used...this I could understand because I find the Trio to have coherence issues and so prefer the simpler, but better integrated, Duo.

What you say about the Lamm's capabilities is true but IME they're not enough for the Trio, my experience is in average US rooms. Duo is a different speaker and easier to drive, I don't know anything about the Odeons.

david

 

[Atmasphere]

Please elaborate on why they would not be SET friendly. At about 109db and easy loads seem to be the very definition of SET friendly.

The problem was the impedance curve which I think was fixed in later examples. The designer used a solid state amp, and so only had caps to keep lows out of the smaller drivers. So it started at a nice impedance in the lows but as you went higher in frequency the impedance dropped as each additional driver was rolled in and thus in parallel with the LF driver. This is bad for SETs. Later I suspect he was convinced to put in a real crossover, which included coils and fixed the problem- resulting in a much flatter impedance curve.