What's the deal with SET? (Single-end Triodes)

[MothAudio]

Very well said. Craig makes superb and brilliant amps. I am honored to own one of his ultimate 2a3 headphone amps, (only three were made). Not sure what kind of financing you are finding for the 45's though! Does it involve a first born child? :)JC

 

I'm currently using the JJ 2A3-40 which is 1/2 the cost of the Emission Labs 45. I'll get another pair next year. Thanks. Where is the rectifier mounted on your amp, inside or top side?

[Melvin]

Very interesting. Being new to high-end audio I went to every single room and listened to every set of speakers at the last audio show here in SF. The one that was absolutely unforgettable was a high-efficiency speaker driven by SET amplifiers. I was smitten. But I was not sure which component I was listening to, the speakers were very very nice, the DAC was world class, and the SET amplifier was very expensive, at least by my standards. I will say that what you are describing here is what I heard. I guess I'll have to look more into it. question though what are the best reasonably priced high efficiency speakers?

 

 

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Prices for Omega Loudspeakers start at $695. Just last week my Super 3i's (94.5 dB at 8 ohms) arrived and are now breaking in. I've wanted to try a SET amp and high efficiency speakers for years and finally decided to go the Omega single driver route. My next acquisition will likely be a Decware Zen amp. The pairing is reported to be terrific, especially at this price-point.

[mordante]

I have never heard a SET or any low power tube amp that can play louder stuff still Slayer/Mahler/Tchaikovsky/ Dead Can Dance etc. Sometime you want to crank up the volume over 90dB maybe just for 1 minute. Make the glassware shake and the speakers rumble.

 

To move a "lot" of air you need power. Not talking about 100's of watts. But I think most good (integrated)amps need between 50 and 250 watts and the best power supply for those watts.

[jabbr]

Here is an explanation of the desirable characteristics of the "triode": FIRST WATT SIT INTRO . Bottom line, the triode acts as a voltage variable resistor while MOSFETs and power jFETs act as voltage variable current sources. In this case the silicon carbine SemiSouth SIT device (as well as the Sony VFET) have characteristic curves that match "triode" behavior.

Regarding the concordance of measurement and listening:

We can try this with Pentodes or Mosfets, but the results don't measure well, and they don't sound as good. This is a clear-cut case where measurements and subjective performance agree.

[YashN]

Moth Audio s45

 

If unclear, I LOVE THIS AMP! This speaks more of what the Moth does right than a lacking on the part of my old amp. With the prior grouping there was just a nagging feeling that something just wasn't "right" that I attributed to the VAC and now with just this one [1] change, there is a feeling of "rightness" with it. IMS/room, with my music (coupled with my replay preferences), this amp mated to my Sonatinas I could easily live with THIS setup for awhile, * it satisfies - Me!

* 15 years later I still own it.

Very cool write-up and impressions.

[YashN]

I have never heard a SET or any low power tube amp that can play louder stuff still Slayer/Mahler/Tchaikovsky/ Dead Can Dance etc. Sometime you want to crank up the volume over 90dB maybe just for 1 minute. Make the glassware shake and the speakers rumble

What were the efficiency of the speakers that were used with the SET and the power rating of the latter?

 

I play Dead Can Dance - "The Serpent's Egg" and "Spiritchaser" all the time here and my speakers aren't even that efficient.

[mordante]

What were the efficiency of the speakers that were used with the SET and the power rating of the latter?

 

I play Dead Can Dance - "The Serpent's Egg" and "Spiritchaser" all the time here and my speakers aren't even that efficient.

 

I thought it was a SET amp, turns out to be a 300B push pull amp. My bad. The Nagra 300 was the amp, speakers had 100dB efficiency. I prefered the Zanden mono blocks, the Octave amps, Jeff Roland Integrated and Aavik integrated amp over the Nagra.

 

You can have a good sounding audio set for 4k. (speakers, turntable, amps etc). But trying to get a "low" budget tube system to sound good is much more of a challenge. Even 2nd hand. I'll admit tube can sound great, best tube amps I've heard are Zanden and Octave. But it comes at (steep) price.

[phusis]

I have never heard a SET or any low power tube amp that can play louder stuff still Slayer/Mahler/Tchaikovsky/ Dead Can Dance etc. Sometime you want to crank up the volume over 90dB maybe just for 1 minute. Make the glassware shake and the speakers rumble.

 

To move a "lot" of air you need power. Not talking about 100's of watts. But I think most good (integrated)amps need between 50 and 250 watts and the best power supply for those watts.

 

The missing link here is high to not least very sensitivity, moving instead the "power" into the impact of the speakers. 106dB/1watt sensitivity speakers will do with 1 watt that an average 86dB variant requires 100 watts to equate SPL-wise. A single watt through pro drivers means tremendous ease - like a walk in the park, whereas 100 watts through typical hifi-drivers translates into the beginning of (or already being well into) thermal stress. More so, moving a lot of air can be done differently (and heard accordingly): one approach is to generate air movement with limited radiation area through higher excursion (requiring lots of "power" - that is, many watts), or through a big radiation area with limited (more gentle) excursion, preferably via few watts. With very high sensitivity easy-load speakers 5-10 watt SET's are suddenly transformed into small monsters, where less than 1 watt can generate in the vicinity of 100dB's at listening position - thermal compression not even hinted at.

[Ralf11]

any SETs with > 100 W into 4 ohms?

 

The Pass designs at 1st watt seem to top out at 50 W

[mordante]

The missing link here is high to not least very sensitivity, moving instead the "power" into the impact of the speakers. 106dB/1watt sensitivity speakers will do with 1 watt that an average 86dB variant requires 100 watts to equate SPL-wise. A single watt through pro drivers means tremendous ease - like a walk in the park, whereas 100 watts through typical hifi-drivers translates into the beginning of (or already being well into) thermal stress. More so, moving a lot of air can be done differently (and heard accordingly): one approach is to generate air movement with limited radiation area through higher excursion (requiring lots of "power" - that is, many watts), or through a big radiation area with limited (more gentle) excursion, preferably via few watts. With very high sensitivity easy-load speakers 5-10 watt SET's are suddenly transformed into small monsters, where less than 1 watt can generate in the vicinity of 100dB's at listening position - thermal compression not even hinted at.

 

Where can you buy 106db affordable speakers? I know that audionote UK, Blumenhofer, Tannoy Prestige etc sell these kind of speakers but none of these are exactly affordable. In other words they cost more than a average person earns in a year.

 

It's also not just spl but also the ability to deliver power in an instance. I had an Octave integrated tube amp to test for a week or so. Even though it came with a super black box it lacked the punch my simple SS amp delivered. It has strengthened my idea that I prefer SS amps with high class A bias and when needed about 100 watts of a/b backup.

[phusis]

Where can you buy 106db affordable speakers? I know that audionote UK, Blumenhofer, Tannoy Prestige etc sell these kind of speakers but none of these are exactly affordable. In other words they cost more than a average person earns in a year.

 

It's also not just spl but also the ability to deliver power in an instance. I had an Octave integrated tube amp to test for a week or so. Even though it came with a super black box it lacked the punch my simple SS amp delivered. It has strengthened my idea that I prefer SS amps with high class A bias and when needed about 100 watts of a/b backup.

 

It's true very high sensitivity speakers (100dB+) aren't cheap nor that frequent, but less (>95dB's) would do to still take advantage of lower powered SET's while providing SPL-headroom (perhaps not with less than 5-8 watts).

 

Your experience seems to go contrary to many in this thread (see earlier replies) with regard to "instant power delivery," my experience as well (albeit SET is not yet realized in my own setup), but your own context appears not to be that of SET's? I believe that's vital in light of the discussion here, not least also considering the pairing of speakers. Not to streamline any opinion, but more to hone in on the dependence of context.

[YashN]

You can have a good sounding audio set for 4k. (speakers, turntable, amps etc). But trying to get a "low" budget tube system to sound good is much more of a challenge.

 

It's not that hard if you're handy with some woodworking and electrical/electronic work: DIY open-baffles with high-sensitivity drivers are easy to do.

[Kimo]

At times, I wonder how much of the SET magic is really speaker magic. They don't work with many speakers that work well with more powerful amps, so there is no point of comparison there. As I understand it, more efficient drivers move less, so they should have an advantage with respect to playing cleaner. Maybe much of the magic lies within the 15" woofers and horns.

 

When we compared solid state Pass gear was compared with SET and push/pull tubes on relatively efficient Tannoys, the pick was the Pass gear. 30 class A watts was clearly better in everyone's opinion.

 

Big clean power on big efficient speakers remains as one of the few approaches that I haven't tried, but am curious to hear.

[YashN]

They don't work with many speakers that work well with more powerful amps

 

You mean, the inefficient speakers that need powerful amps to make them have good sound?

 

Doesn't that sound like a truism?

 

SETs are best with high-efficiency speakers, that's all.

 

And you don't go to the Oscars dressed in rags.

[Kimo]

You mean, the inefficient speakers that need powerful amps to make them have good sound?

 

Doesn't that sound like a truism?

 

SETs are best with high-efficiency speakers, that's all.

 

And you don't go to the Oscars dressed in rags.

 

I would just like to hear the Pass amps compared with a couple of SETs, on a nice easy to drive load, say a Klipsch horn. Of course this won't likely happen. I am not going to haul those suckers over to the horns and no one is bringing the horns to my house.

 

We tried a 2a3 on the Tannoys, but I don't think it was a good match.

[esmit]

You mean, the inefficient speakers that need powerful amps to make them have good sound?

 

Doesn't that sound like a truism?

 

SETs are best with high-efficiency speakers, that's all.

 

And you don't go to the Oscars dressed in rags.

Do you use SET with your Totem Mites? I would expect them to be too inefficient (my Model One Signatures will be).

 

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[semente]

Me: "But most of those high sensitivity loudspeakers have problems of their own"

 

Him: "You asked me about amplifiers, not loudspeakers. A SET amp, operating within its linear range, is one of the best amps you can buy. The major problem, as you pointed out, is how to make sure it stays within its linear range ..."

 

Operating linear range and loudspeaker sensitivity are the operative words for using S.E.T. amplification.

I would add easy load to sensitivity.

 

Which of you S.E.T. users is actually abiding to the "rules"?

 

You @Keith_W (Acapella High Violon, Rythmik subwoofers x4) are good to go.

 

But I see that @YashN is running his S.E.T. full-range with a pair of Totem Mites.

 

How about @MothAudio's Silverline Sonatinas, probably also used with S.E.T.s running full-range?

 

@accwai is using Ocellia speakers and amplification so we would assume that they partnership is viable.

 

But I find that the single-driver topology is overly crippled and globally under-performing for music playback (the same could be said for mini-monitors).

Ocellias with tweeters might have a bit more potential but my guess is that you'd really need to be able to accept some very significant trade-offs.

 

 

I think that S.E.T.s should only be used with horn, band passed, in an active configuration.

And you'll probably have to use sub-woofers or PP amplification if you want some extension in the lower end.

such systems are complex, extremely expensive and require a lot of floor space (mostly the speakers).

 

 

I really enjoyed listening to a pair of Avant Garde Duo Mezzo speakers run by a flea-power S.E.T. some years ago.

 

R

[zackthedog]

Twenty years ago I heard a Cary 300B amp with a pair of ProAc Tablettes and that, as they say, was that. I now use a pair of original ProAc Response 2's, and they respond very well to 300Bs. I've spent the last 15 years building my own SET amps and enjoying them on the ProAcs. I listen to jazz, classical and some pop. I've played some pretty demanind stuff that friends have brought along to listen to and while you can't get head-banging volume, they do some pretty cool things in terms of hearing the instrumentation and colors. "Wow, I've never heard that part of the mix before."

 

A robustly-made 300B SET will drive a surprising number of ordinary speakers to listenable levels, provided they're relatively efficient and don't use complex crossovers. A friend of mine drives his bookshelf PSBs with a homebrew SET and they sound very nice. But he has a smallish room and doesn't play Mahler. :-) Grant Fidelity makes multi-driver speakers that mate well with their SET amps. If you ask around the options are greater than you might think. And it's also tricky because some SET amps are punily constructed, with inadequate driver stages, weak power supplies and mediocre output transformers. Hence my "robustly-made" comment. The Grant 300B was a good example of this, using as it did a triode-wired EL34 as a driver for the 300B.

 

I've never found Tannoys to be particularly good match for SETs, don't know why. They should work but they don't seem to.

 

I've spent two years working on a PP 300B amp and I now prefer it to SET. It has the transparency and attack with more power and a more 3D presentation of instruments and voices. I don't know why there aren't more commercial PP 300B amps available. They're not that difficult to build. The few I know of, like Nagra and Border Patrol, are fantastically expensive. I built a little pair of PP 300B monoblocks for a friend for well under $2K.

 

Regarding "measurements," as I commented on the other thread, you've got a dead-linear output device, no feedback, no crossover distortion, minimal components, soft clipping characteristics and a few other nice things going for you. Yes, you're going to roll off at the extremes, and get some highish THD at full power. But those first few watts look and sound pretty damn sweet.

 

As for perceived power, I just bought my daughter a 300wpc Pioneer Elite receiver because it was on sale. Nifty gadget, lots of fun features for her. I thought I'd try it on the ProAcs. It sounds more like 2 watts. Not unpleasant but thin and bright. My 16wpc triode amps sound much, much fuller and more powerful, as someone else has pointed out.

 

At any rate, hope the OP can get a chance to listen to some quality SETs and judge for himself.

[accwai]

I have never heard a SET or any low power tube amp that can play louder stuff still Slayer/Mahler/Tchaikovsky/ Dead Can Dance etc. Sometime you want to crank up the volume over 90dB maybe just for 1 minute. Make the glassware shake and the speakers rumble.

 

So which SET or low power tube amps have you heard? So far none of the ones you listed in here are SET or low power tubes...

 

As for playing Mahler, Tchaikovsky etc, it has to do with both loudness as well as dealing with complexity. For loudness, I don't see how playing above 90db can be a problem. Even with relatively modest 95db/w/m efficiency speakers, a stereo pair can give you 95db from 6ft away with 1w input per channel. As for staying completely together in orchestral crescendos, that is not a tube vs SS problem. Very few amps can be completely unflinching under extremely complex music, tube or SS. It's just the quality of the particular amp.

 

I thought it was a SET amp, turns out to be a 300B push pull amp. My bad. The Nagra 300 was the amp, speakers had 100dB efficiency. I prefered the Zanden mono blocks, the Octave amps, Jeff Roland Integrated and Aavik integrated amp over the Nagra.

 

You can have a good sounding audio set for 4k. (speakers, turntable, amps etc). But trying to get a "low" budget tube system to sound good is much more of a challenge. Even 2nd hand. I'll admit tube can sound great, best tube amps I've heard are Zanden and Octave. But it comes at (steep) price.

 

Are you saying Zanden and Octave come at a steep price while the Rowland and Aavik on the SS side do not? Hmmm...

 

Where can you buy 106db affordable speakers? I know that audionote UK, Blumenhofer, Tannoy Prestige etc sell these kind of speakers but none of these are exactly affordable. In other words they cost more than a average person earns in a year.

 

I believe the speakers you mentioned are mostly around or slightly below 100db. Plus the Tannoy might not be as SET friendly as spec says--the Westminster Royal that I heard isn't all that alive with 25wpc SET amp.

 

There is a rather significant difference between 100 and 106db. Reaching the latter normally requires horn, which does add a level of complexity. But in the 100db or so category, Omega Speaker has been mentioned in the thread. They certainly affordable. And there are other small outfits like it.

 

It's also not just spl but also the ability to deliver power in an instance. I had an Octave integrated tube amp to test for a week or so. Even though it came with a super black box it lacked the punch my simple SS amp delivered. It has strengthened my idea that I prefer SS amps with high class A bias and when needed about 100 watts of a/b backup.

 

At the end of the day, SET is pretty much at the fringe of the fringe. It's perfectly fine to prefer SS. But if you want to argue with SET-heads, understand that they are rather passionate. Make sure you get your story straight before you start

[mordante]

So which SET or low power tube amps have you heard? So far none of the ones you listed in here are SET or low power tubes...

Like I said before. I thought the Nagra 300 was a set amp, its a 300 push pull. I have heard a SET amp at a show once with Avetgarde speakers but these speakers are bad so I quickly walked away.

As for playing Mahler, Tchaikovsky etc, it has to do with both loudness as well as dealing with complexity. For loudness, I don't see how playing above 90db can be a problem. Even with relatively modest 95db/w/m efficiency speakers, a stereo pair can give you 95db from 6ft away with 1w input per channel. As for staying completely together in orchestral crescendos, that is not a tube vs SS problem. Very few amps can be completely unflinching under extremely complex music, tube or SS. It's just the quality of the particular amp.

Are you saying Zanden and Octave come at a steep price while the Rowland and Aavik on the SS side do not? Hmmm..

These SS amps are bloody expensive. Never said otherwise. But you can buy a great to decent SS amp for 500 to 1500 euro. Try finding a SET or any tube amp at that price that sound decent.

I believe the speakers you mentioned are mostly around or slightly below 100db. Plus the Tannoy might not be as SET friendly as spec says--the Westminster Royal that I heard isn't all that alive with 25wpc SET amp.

 

It is not only how efficient the speakers are its also about the impedance curve.

There is a rather significant difference between 100 and 106db. Reaching the latter normally requires horn, which does add a level of complexity. But in the 100db or so category, Omega Speaker has been mentioned in the thread. They certainly affordable. And there are other small outfits like it.

As far as I can tell Omega speakers are not sold outside the US, and even they "cheat" on some models by making powered speakers.

At the end of the day, SET is pretty much at the fringe of the fringe. It's perfectly fine to prefer SS. But if you want to argue with SET-heads, understand that they are rather passionate. Make sure you get your story straight before you start

 

There is no story. I'm sure SET can sound nice. But I've never heard it do so.

I think it would be a challenge to go to a audio shop spend less then 5k and walk away with a SET audio set. That includes speakers, amps turntable streamer etc.

[accwai]

[...] Ocellias with tweeters might have a bit more potential but my guess is that you'd really need to be able to accept some very significant trade-offs.

 

Frederic Beudot at 6moons has been testing a variety of frontends with Ocellia speakers and writing quite extensively about these combos. He's been complaining about all kinds little things but nothing serious about the speakers themselves. So apparent we both missed these significant trade-offs

[manisandher]

I've posted this quote on a couple of other forums and thought it'd be relevant here too. This is what Nelson Pass has to say on the subject, which I personally find fascinating:

 

"Given the assumption that every process that we perform on the signal will be heard, the finest amplifiers must employ those processes which are most natural.

 

There is one element in the chain which we cannot alter or improve upon, and that is the air. Air defines sound, and serves as a natural benchmark.

 

Virtually all the amplifiers on the market are based on a push-pull symmetry model. The push-pull symmetry topology has no particular basis in nature.

 

Is it valid to use air's characteristic as a model for designing an amplifier? If you accept that all processing leaves its signature on the music, the answer is yes.

 

One of the most interesting characteristics of air is its single-ended nature. Sound traveling through air is the result of the gas equation:

 

PV1.4 = 1.26 X 104

 

 

where P is pressure and V is volume. The small nonlinearity which is the result of air's characteristic is not generally judged to be significant at normal sound levels, and is comparable to the distortion numbers of fine amplifiers. This distortion generally only becomes a concern in the throats of horns, where the intense pressure levels are many times those at the mouth, and where the harmonic component can reach several per cent.

 

We can push on air and raise the pressure an arbitrary amount, but we cannot pull on it. We can only let it relax and fill a space as it will, and the pressure will never go below "0". As we push on air, the increase in pressure is greater than the corresponding decrease when we allow air to expand. This means that for a given motion of a diaphragm acting on air, the positive pressure perturbations will be slightly greater than the negative. From this we see that air is phase sensitive.

 

As a result of its single-ended nature, the harmonic content of air is primarily 2nd order, and most of the distortion of a single tone is second harmonic. Air's distortion characteristic is monotonic, which is to say its distortion products decrease smoothly as the acoustic level decreases. This is an important element which has often been overlooked in audio design and is reflected in the poor quality of early solid state amplifiers and D/A and A/D converters. They are not monotonic: the distortion increases as the level decreases."

 

I've recently switched to SET mono amps and ultra-high efficiency speakers (109dB/W@1m) and wouldn't go back to any other config now (tried many, many over the years). But it's proved an expensive endeavour and the results may not be to everyone's tastes.

 

Mani.

[YashN]

Do you use SET with your Totem Mites? I would expect them to be too inefficient (my Model One Signatures will be).

 

They are. I am fortunate enough to be sitting rather close to them and the room is small in that distance.

 

Doesn't mean I am satisfied: I am designing and building my own Open Baffles with high-efficiency drivers for the SET.

[YashN]

I've posted this quote on a couple of other forums and thought it'd be relevant here too. This is what Nelson Pass has to say on the subject, which I personally find fascinating:

 

"Given the assumption that every process that we perform on the signal will be heard, the finest amplifiers must employ those processes which are most natural.

 

There is one element in the chain which we cannot alter or improve upon, and that is the air. Air defines sound, and serves as a natural benchmark.I've recently switched to SET mono amps and ultra-high efficiency speakers (109dB/W@1m) and wouldn't go back to any other config now (tried many, many over the years). But it's proved an expensive endeavour and the results may not be to everyone's tastes.

Yay, Mani!

 

Well said, well said.

 

NB: DIY with high-efficiency drivers in Open Baffle cost far less than the expensive commercial offerings. Ditto for the SET Tube Amp, I've built my own.

[YashN]

There is no story. I'm sure SET can sound nice. But I've never heard it do so.

 

But which speakers have you heard them on, apart from the Avantgarde in a show?

 

Have you actually listened to one in extended periods of time in your listening room?