Why do tube amps often subjectively sound more powerful than SS ?

Tubes can have more headroom, softer clipping, and their harmonic distortion adds to the perception of loudness. And they’re just more awesome.

Perhaps it is simply more sensitive at input voltage and just sounds louder?

Maybe because the particular tube amp you are enjoying has a great transformer....;0)

It's not really about loudness, it just feels more powerful at the same volume.

But I would say that in my case it is an excellent amp/speakers electrical match, the amp drives them with effortless grace at any sane level.

It’s the low-order harmonic distortion which makes tube amps sound "full" and satisfying at the same SPL levels. Never sterile, lean, or bright. It’s also probably the fact that their front-ends give a lot of gain (6SN7, 12AT7, 12AX7 etc), so often lower powered tube amps will actually give you more SPL output at the same preamp / control volume setting, versus solid state amps with even higher power ratings (@mikhailark pointed this out via senstitivity). In these cases, you have to raise the volume dial to tap into a SS amp’s power reserves - past the point that would be safe for the tube amp.

Gain is NOT power - when it comes to the limits, power is power and you will hit clipping all the same, at the amps’ actual limits of power, whether SS or tube. Tubes might be polite and give you a "warning" first - compression and then a soft-crunchy garbled distortion before the hard, nasty clipping.

@inna - how do you calibrate "same volume"? Literally 1% of sensitivity difference makes it well audible. And yes, tube distortions add to the sound.

I have always heard that tubes were more powerful. But until I got one I had no idea how night and day they can be. I went from 350 wpc solid state to 70 wpc tube and the difference was not at all in power, not even a little bit. If I had gone to a 70wpc solid state it would have been night and day. In many respects the tube watts were more powerful in the richness of the midrange and the bass was much more articulate. What it lacked was the artificial quick (very fast rise and very fast fall) in the bass. The bass sounded like what I heard at a real rock concert or symphony… not that quick wall of bass usually called slam. But the bass is much better, more real.

It sounds like all the bass and midrange is sustained as opposed to cut short as solid state often sounds. This makes details stand out, but is often unnatural.

Why… as in technically. I have no idea.

You might find this article interesting!

https://medium.com/collectors-weekly/could-an-old-school-tube-amp-make-the-music-you-love-sound-better-a35574739c45

Not all tube amps do, but good ones tend to have excellent micro dynamics, great midrange clarity and harmonic structure, and ample headroom.

Maybe it’s just easier to say that they’re "magic"!

I'm with @noromance .  Tubes are more awesome.

You guys know I try to understand everything going on in audio, and I don't always achieve that.  And understanding tube power vs ss power is one of the things I want to understand better.  

I have very successfully driven full range 96dB 4ohm floorstanders with a 2 wpc Decware EL84UFO.  

I'd like to compare a first watt sit-4, but there is very little chance I would leave tubes.

Jerry

 

Mostly due to soft clipping if so.  “Subjectively” is the key word.  Check actual SPL with a sound meter to know for sure. 

I’m not really sure why that is. But my tube amps have huge power supplies and oversized capacitors. That doesn’t hurt.

i tend to find, particularly with lower powered tube amps, the sound tends to be more full and rich sounding and more lively at any given volume level than is the case with solid state.  Solid state tends to sound a bit dead and less engaging which prompts one to turn the volume up more.  That one tends to be satisfied at lower volume levels with tubes, I suspect, makes one feel that tubes are delivering more power than they are actually delivering.  Also, most people don't come close to actually using up the massive "reserve" of power from their amplifiers.  So, something that sounds rich and lively at low power is not disadvantaged as much vis-a-vis much more powerful solid state amps; the advantage of extra power in reserve tends to be more theoretical than practical. 

As long as the tube amp is working at or below about 1/3 or 1/4 of its rated output it will sound sweet and uncompressed.  While that power level might see, really low, it is probably a limitation that is breached for only short periods for most listeners not requiring head-banging levels.

 

Nelson Pass wrote an interesting paper on this and I think this is it.

It doesn't directly say tube amps but rather amplifiers with high impedance.  Worth a read. 

Contrary to popular opinion, I greatly appreciate how much Nelson Pass does for the audio community, and this is an example of why.

All of the above true, and the biggie for me is tube's special way of delivering micro dynamics, Brits call them valves which brings to mind human lungs and breath, tubes give breath to performers.

It's not really about loudness, it just feels more powerful at the same volume.

@inna, Mapman has it right. The reason the tube amps sound like they have more power is because of how they make distortion when approaching full power. Unless its an SET, with most tube amps the higher ordered harmonics start showing up in greater amounts near overload. This interacts with the ear which imparts the impression that its louder- more powerful. This has given rise to the false notion that tube power is more powerful than solid state.

But like @mapman pointed out, if you have a sound pressure level meter, you'll find that its not louder- and in fact might be quieter.

I mentioned the caveat of SETs- they take this to an extreme by producing those higher ordered harmonics at a much lower power level- perhaps only 20-25% of full power, which is why many people talk about their 'dynamics' (since power is used the most on transients). But what they are really talking about and also in this case is distortion and how it interacts with the human ear (the ear uses higher ordered harmonics to gauge sound pressure).

Tubes make it an enjoyable experience since there's plenty of second order harmonics to go around too.

I mentioned the caveat of SETs- they take this to an extreme by producing those higher ordered harmonics at a much lower power level- perhaps only 20-25% of full power, which is why many people talk about their 'dynamics' (since power is used the most on transients). But what they are really talking about and also in this case is distortion and how it interacts with the human ear (the ear uses higher ordered harmonics to gauge sound pressure).

You've mentioned this before, and I finally got to experience & hear this phenomenon for myself. Spot on. Push-pull amps are better for me, especially since I like to listen loud. 

Put simply and without a lot of technical detail, as other have noted, many solid state amps sound downright nasty when they clip, while tube amps don't. That allows you to leave the tube amp at the higher volume even though it is still clipping versus a clipping solid state amp that sends you running to turn the volume control down.  That's one of the big reasons many electric guitar players greatly prefer tube amps.

I swap in a 250watt/ch ss amp with my 45watt/ch tube mono blocks. I leave the volume control on the preamp at exactly the same setting for both amps, as the volume in the room from the speakers is identical. 

I listen mostly at moderate levels, not much distortion besides the one coming from the recordings themselves and some from the speakers that I do hear.

The impression is that tube amp does have more power in reserve, and you can feel it.

Tubes are superior to transistors, anyway, and that's a true explanation ! I agree with many others here.

How does anyone hear "power" from an amp or anything else? Volume, sure. power, not in the least.

Just thinking out loud. Tube amps also tend to boost the mid bass and mid range (from about 1 kHz to 2 kHz or ao) due to their low damping factor interacting with speaker impedance. This could be part of the explanation for differences in ound versus solid state.

On the other hand, if you talk Gryphon SS power..This can be bloody hell. I didn't compare directly Gryphon and, say, VAC or ARC amps. Now, this could be interesting in terms of power and it's perception.

 

@mapman suggested a spl session, which I second.  You phones ought to have one as a matter of course imho....  Quit guessing how loud is loud.... ;)

Having grown up ( years-wise, anyway ) with tubes, I kinda developed a recalcitrance to rolling and trolling for ones that would keep the TV up, later with early 'audio' about.

For sure, the early ss stuff had issues....it's typ with anything new, like D.....
D amplification has improved rather quickly, a lot faster than the early ss did.

But what they are really talking about and also in this case is distortion and how it interacts with the human ear (the ear uses higher ordered harmonics to gauge sound pressure.  

Add in the noting of impedance variables, the different characters' of pre's, amp's. cables, ic's. source types....

...and the room you're in and the chair under you.

All that said, if I stumble upon a tube amp I recognize from y'all that can be stolen for a pence or three, consider it bagged.  I'm curious about how my Walsh will react to a different sort of feed.... ;) *G*

For the way I listen, a crucial part of any audition is how softly the gear can be played and still sound full and engaging.  How loud it can go is largely irrelevant if it gets loud enough.  It’s like the old horsepower rating on Rolls Royce—“sufficient.”

Generalised distinctions between tube and solid state amplifiers are meaningless - it totally depends on the particular amps being compared.

I started with tubes growing up, than switched to SS ie Hafler pre and amps in the early eighties.  While they worked great, there was something i was missing.  Later in the eighties, I went back to tubes and have never left, well kinda.  The rig downstairs is hybrid. The preamp and the amps are IC chip input with tube output and the main system is tube input and transistor output on both the preamp and amplifiers. 

Tubes are transformer coupled and have more power on a wpc basis 

tubes are voltage based ,Solid state is current driver , better image and for sure more defined Bass ,if both are quality products,, that too is why Loudspeaker efficiency and  matching is critical .

In my experience, tubes tend to highlight the lower part of the spectrum, where s/s favors the upper. 

Tube amps also tend to boost the mid bass and mid range (from about 1 kHz to 2 kHz or ao) due to their low damping factor interacting with speaker impedance.

@dynamiclinearity This is only true if the amp is unable to act as a Voltage source on the speaker in question. Many tube amps are perfectly capable of such a thing. You only need about 15dB of feedback to achieve that in many cases.

In my experience, tubes tend to highlight the lower part of the spectrum, where s/s favors the upper.

@stringreen That is on account of how the amps in question make distortion. Once you understand that, its then possible to design a solid state amp (including class D) that doesn’t sound bright.

How many tube amps have a damping factor of even 10 into 8 ohms, especially with 4 ohm speakers(halving the damping factor) that are so common today? I can only think off the top of my head of one tube amp with a high damping factor, the old Melos amps that had a damping factor of 20(unpublished Atkinson test). Every published Atkinson test of a tube amp I've seen(and I've been a subscriber since before Atkinson) shows substantial frequency variance with frequency.

@dynamiclinearity I'm going with 'a fair amount'.

The venerable Dyanco ST70 has a damping factor of about 15. This does not change with a 4 Ohm load since you'd be using the 4 Ohm taps. It would be cut in half if you ran a 4 Ohm load on the 8 Ohm tap.

ElectroVoice made a number of tube amps (such as the A30) that had a damping factor of 15 back in the 1950s. It was EV and MacIntosh who came up with the idea of the amplifier being a Voltage source and the speakers being Voltage driven; this to enhance plug and play.

Prior to that speakers had adjustments on the back (midrange and tweeter level controls) to allow the speaker to be adjusted to the unknown output impedance of the amp.

The Mac MC275 had about 15:1. The Marantz 8b amplifier had a damping factor of 16:1.  The famous Fisher SA100 was 20:1.

FWIW no speaker made needs a damping factor of over 20.

Then why do almost all the damping factors measured by Streophile fall below 10 and usually well below. And mor observationally why isn't the frequency response of amps shown by Stereophile into a simulated speaker load so far from flat?

High damping factor in my opinion gives artificially tight bass, or one note bass 

This has been my experience as well in terms of tube amps sounding more powerful, at least for their wattage.  Maybe not all but certainly some that I have used. 

 

Conrad Johnson premiere 12 tube mono blocks - 140w side.

 

I’ve had a very large variety of loud speakers in my room over the decades since I’ve owned those amplifiers , and they have been able to easily drive every single one of them, always sounding powerful.  That includes even tough to drive Thiels and MBLs.

 

But once in a while, I try another solid-state amplifier in my system  “ just to see.”

 

The last time I did it, I borrowed a Bryston 4B3 solid state amp (300 W into eight ohms, 500 into four ohms).

 

Just to take one example 1st :  before I borrowed the Bryston amplifier one of the tracks I’ve been playing quite a bit was Basil Poledouris’ incredibly dynamic score for Conan the barbarian.

Especially the opening track The Anvil Of Crom.

 

It’s performed by an augmented symphony, Orchestra , extra instruments, especially extra horns, and Timpany, and it’s just a massive, powerful charging sound.

It had been blowing me away on my system .

 

So when I got the Bryston amplifier, I thought, since it was more powerful, put on really powerful music that will take advantage of it like the Conan soundtrack.

 

I put in the Bryston, cranked it up and…huh?  Where was that power?

Why did it actually sound thinner? 

Less impactful?  

 

The Bryan did have better grip from the upper bass on down - it unravelled some of the in their power range down there, that were a little bit more muddy on my CJ amps.   And it was perhaps a tiny bit cleaner on the horns when playing their loudest.

 

But otherwise , it just sounded actually weaker and thinner, and it didn’t have the punch and drama I was used to.

 

I put this down to the type of distortions from the CJ amp - less damping factor probably allowed for a little bit rounder sound in the power region.  And that little bit of tube distortion over the whole thing, thickening out the sound.

Essentially, I think the tube was acting something like a mild bit of compression, at least in Sonic analogy terms.

 

The Bryston did better on some other stuff.  But most often the CJs sounded richard and fuller, and I often liked even the bass better. 

It was a little bit more round and had more feel, without being slowed down or losing any pace or snap.

 

So anyway, every time I do this comparison, I go running back to my CJs.  Which is why I’ve had them for like 25 years.

Then why do almost all the damping factors measured by Streophile fall below 10

@dynamiclinearity I don't read Stereophile so I've no idea if this is actually true and if so, what amps to which you are referring.

It might be a better question to ask who the designer was and what was their intention. Did the designer have a degree? FWIW, most of the tube amps designed in the old days were designed by actual engineers. That's a lot less common these days. Not saying you need a degree to know what you're doing but it helps!

Some speakers, for example some open baffle designs, really don't do well if the amp has a high damping factor. Nelson Pass demonstrated this about 15 years ago a RMAF using a set of open baffle speakers and a solid state amp he built that was constant current rather than constant Voltage, so its damping factor was fractional since the amp's output impedance was about 50-60 Ohms. It sounded just fine and made good bass despite the small size of the OB speakers. 

So intention is a big variable here and Stereophile does not recognize that certain speakers need a higher output impedance from the amp to sound right. They just have their standard simulated speaker load and that's that.

Basil Poledouris’ incredibly dynamic score for Conan the barbarian.

Especially the opening track The Anvil Of Crom.

@prof I really like that LP. I think Poledouris did a great job on that.

Actually you don't need a degree to design tube amps. I winder if Bill Johnson had a degree. I'm lazy so I won't do the research but I'd bet a significant number of tube amps were designed by people who learned on the job. And I bet that includes a lot of well regarded tube amps. Most reviews for tube amps are positive.

Your example of open baffle speakers is a very small niche area and on top of that many open baffle speakers are designed to be used with higher damping factors.

I've used and loved tube amps. They have their pluses and minuses. In an imperfect universe like audio properly used they sound good. I'm just throwing out the idea for discussion that they may seem louder than a comparable solid state amp due to their high output impedance(low damping factor). I don't disapprove of tube amps.

When I bought some Alexia 1 a couple years ago, I took my Audio Research REF 75SE with me to pick up the speakers and to listen to them with my amp.  There was much written about those speakers being hard on amps due to the impedance dips.  That guy had a McIntosh MC452 so we compared his 450 solid states wpc to my 75 tube wpc.  We did not have to adjust the preamp volume...they had the same output volume and the REF 75 sounded better to both of us.  

So when I got the Bryston amplifier, I thought, since it was more powerful, put on really powerful music that will take advantage of it like the Conan soundtrack.

 

I put in the Bryston, cranked it up and…huh? Where was that power?

Why did it actually sound thinner?

Less impactful?

Man, I love that soundtrack. And film.
Yeah, another way I can put my experience with various amps - push pull tube amps tend to sound "good to the last drop". I listen loud and I’ve pushed hard on some vintage PP tube amps in the 20 - 35 Watts / ch range. Until you hit hard clipping, they sound amazing (euphonic) all the way through. Sweet, fat tone.

With solid-state there’s more of a phenomenon like: when you crank it up, you start hearing stuff presented in a way that makes you want to back down the volume again. This can occur even when theres’ still AMPLE power reserves left before approaching hard clipping limits. With tubes, you may keep wanting to crank it up until you actually hit hard clipping.

Probably due to a combination various factors - like harmonic distortion spectrum (which Ralph has educated many of us on), and possibly some dynamic compression with tubes (as another poster mentioned) that can actually work toward the presentation’s favor in some instances. "Loudness wars" with regards to digital mastering gave dynamic compression a bad name, but it’s not all bad.

@mulveling 

 

yes, that’s been exactly my experience!

I have sensitive ears, And I have always found that my tube amplifiers give a sense of ease and relaxation, So that I can crank the sound much higher and still enjoy it.  Whereas when I have a solid-state amp, I find myself turning the volume down.

tube amps typically have much higher current which is more important than watts in several ways (but marketing won't tell you this).

It’s because they’re old school sound, from the days when tubes were all there was.  Some of us were born in the days when SS didn’t sound so good. SS has gotten much better. But then again, so have tubes. Today’s tube amps aren’t your Great-Grandfather’s tube amps. 

Actually you don't need a degree to design tube amps.

@dynamiclinearity That is certainly true. But it helps, especially if the amp in question has a feedback loop. Designing a good feedback loop is a bit less trivial if you want to get it right.

My point was there's been a resurgence of SETs since the early 1990s, most of which don't use feedback. They tend to have a high output impedance and so speakers that expect the amp to behave like a Voltage source (which is most speakers made) don't work right with them. Hence along with SETs we have more horn and open baffle designs meant to work with low power tube amps with high output impedance.

If Stereophile was measuring such an amp it wouldn't measure well by their standards but might sound pretty decent.

Some tube amps I would expect to have a higher damping factor are those made by Roger Modjesky.

Futterman made some OTLs with quite high feedback and had damping factors as high as 40:1. You can put more feedback on an OTL since you don't have the poles created by the output transformer; you can have a greater phase margin. Khron Hite made some laboratory amps (UA-101) in the early 1960s that had as much as 80dB of feedback (and hence had very sophisticated feedback design) which had a damping factor of 100:1.

Primarily to only add to the discussion. I had demonstrated to me by my friend Murray Zeligman and David Berning that full loop negative feed back was deleterious to linearity(a Berning amp with variable feedback and as the feedback was reduced to zero what I heard sounded better to me).

And just to add to things I've always wondered about more use of feed forward. If done right it wouldn't have the phase problems of feed back.

I had demonstrated to me by my friend Murray Zeligman and David Berning that full loop negative feed back was deleterious to linearity(a Berning amp with variable feedback and as the feedback was reduced to zero what I heard sounded better to me).

@dynamiclinearity  If the feedback isn't set up right you will get exactly this sort of result. One of the problems is the feedback is sent to the cathode of the input tube. The tube isn't linear of course, so the feedback signal is distorted. This causes additional higher ordered harmonics. Norman Crowhurst wrote about this problem nearly 70 years ago but its rare that anyone has done anything about it. 

The solution to that problem of course (one we've used for decades) is to apply the feedback to the grid of the tube rather than the cathode, in a manner similar to how its done with opamps. The feedback is thus mixed with the audio in a resistive divider network which is far more linear than any tube or transistor. This reduces the harmonic and intermodulation distortion generation you otherwise get. Of course you have to sort out how to get the phase right but if an output transformer is involved its easy.