Why is solid state more popular when tubes are better?

however for hologram sound nothing beats TUBES and not old crap from the 80’s but modern made gear.

@luvharbeth That used to be true- no longer. You can now get that from class D if the designer did his homework, and just as smooth and relaxed in the mids and highs as well.

Are there any class a/b amps in your opinion that have gotten it right? Thanks 

Zero feedback is one way to get it 'right'. The problem is its very difficult to get the Gain Bandwidth Product needed to support both the gain of the amp and the amount of feedback used and also have the amp be stable; the goal being that distortion does not rise as frequency goes up.

Zero feedback is one way to get around that problem. On top of that though, there is always distortion. IME its important to be pragmatic about that fact so a savvy designer will see to it that as best as possible, the primary distortion is the lower ordered harmonics.

That's a bit of a trick! The topology of the design has enormous influence on the kind of distortion created.

I think there are some solid state AB amps using feedback that meet this criteria. Ayre makes a zero feedback amp that has gotten good comments and Pass Labs has done well too. I think there are others, but not many of them, maybe five or six! I've not done any kind of study in this regard.

@inna I think you're looking at this the wrong way.

Tubes sound the way they do because of the distortion they make. If you can make something else to make distortion of the same kind it will sound the same for that reason.

There are lots of things out there you can loosely call 'transistors'. Some are meant for linear operation and some are meant for switching. No-one these days would take germanium transistors seriously except for repairing some old thing. These days GANFETs have lots of buzz around them. Amps that use them have garnered a lot of praise. But in ten years or so there will likely be something else that is better. Maybe someday people will laugh when GANFETs are mentioned. All that you really need to do when looking into this sort of thing is seeing if the manufacturer made some effort to sidestep obsolescence. If class D, is the module easily replaced? If yes, it might not matter if GANFETs are obsolete. 

Tubes are fun to play with because they are so simple. But from a designer's point of view, they come with lots of limitations. Right now is an interesting time in audio history; class D has taken over everything but high end audio. Its making inroads there too but its taken about 50 years to be taken seriously. IME once you get an amp to play and sound like real music, you stop caring about whether it glows in the dark.

Ralph, I hope you are wrong about tube power amps becoming obsolete soon enough. It pains me. I am a traditionalist of a sort and don't want to hear it.

@inna Seriously I wouldn't worry about it. There are tubes for now and I think you'll find that if the amplifier is really making music like it should that it will not matter to you if its tube or solid state. You find that if the music is right, the glow of tubes or the glow of a single LED is just as calming. At least that's how it worked out in my case.

I concede that the tubes have an arcane, perhaps Gothic look to them but once you hear the music that sort of thing is no longer important. Its nice knowing you have the music and its there without a warmup or worry about a rare vintage part failing 5 minutes to 5PM on a Friday afternoon.

Ralph might partly disagree, but tubes are like tape - there is currently no substitute. 

@inna You're correct in that I 'might' disagree. There are class D amps now that have the same distortion signature as a good tube amp and so unsurprisingly sound like them in that they are smooth and detailed, lacking harshness, with organic mids and highs. But more detailed owing to lower distortion. It took 60 years (since tubes were declared 'obsolete' back in the 1960s), but class D has made power tubes obsolete. I am not saying that all class D amps have done this as they clearly haven't. IME class D amps vary in sound quality more than tube amps do. But class D does offer a way to make an amp that sounds very musical- in the way that some tube amps sound musical. But better.   

Well, some will say that transistors are not worse, they simply sound different.

There are engineering reasons why tubes and traditional solid state sound different. As a result, most solid state amps generate unmasked higher ordered harmonics that are interpreted by the ear as harsh and bright while most tube amps have these harmonics masked. This is what has kept tubes in business for so many decades- now longer as 'obsolete' than when they were the only game in town.

In the paragraph above is a clue as to how to make a solid state amp that does not sound like traditional 'solid state'. FWIW its very difficult to do that with class AB designs- the problem you run into as a designer is getting enough Gain Bandwidth Product is tricky, as is obtaining adequate Phase Margin so the amp is stable. If you don't know what those terms are, look them up. Class D offers solutions for both. This allows you to run a lot more feedback without running into some of the problems it causes (such as unmasked higher ordered harmonic generation)- it can more effectively do its job.

Any amplifier manufacturer should be on notice at this point that tube power amps are on life support/borrowed time because of the tools offered to the designer by class D. If they don't get a handle on it they will be left behind. In ten years, tube producers will be dealing with a vastly reduced market due to the incursions class D is making in the guitar amplifier world- in case you don't know it, guitar amps are the bread and butter of tube producers as they use more 100x more 6L6s, EL34s and KT88s than home audio does.

My speakers require a lot of power, so a set tube amp may not be the best choice.

@emergingsoul Speakers that need a lot of power have a lot stacked against them! There's something called 'thermal compression' which is a reduction of dynamic contrast caused by heating in the voice coils. The more efficient the speaker is the less you have this problem.

In addition its not good to make any amplifier work hard for a living. The harder they have to work, the more distortion they make so less detail and likely harsher sound is the result, both due to increased distortion.

Speaker cables also become more critical. This is especially true if the speaker is harder to drive due to a low impedance; all other things being equal an 8 Ohm speaker will always sound better than a 4 Ohm speaker on this account (but of course all other things are never equal).

So you might consider getting speakers that are easier to drive. In the old days when tubes were the only game in town, speakers were a lot easier to drive because the simple fact is that tube power is expensive.

A 300 Watt tube amp will not have hifi bandwidth. The limitation is the output transformer- its very difficult to make one that is capable of full power and 20Hz to 20KHz response (and it really should have 10Hz to 50KHz response to minimize phase shift) at that power level.

Tubes are not better.  As a technician/engineer that started my career in the days of mil-spec tubes that you can no longer purchase, I can tell you no Class A tube amp can match solid state for linearity.  They all produce non-linear amplification to one degree or another.  However, some people prefer their sound to have the coloration produced by a non-linear amplifier because the non linear output sounds warmer.  

@barjohn There is far more to it than just this. What is being ignored here is the simple fact that two decades into the 21st Century this is still a conversation. In any field, when a superior art appears (such as solid state), the prior art vanishes. As an example, no car manufacturer makes a flathead side valve engine anymore- overhead valves offer greater reliability and performance. But for some reason, even though tubes were declared 'obsolete' in the 1960s, they have persisted for over 60 years. That's longer than when they were the only game in town.

Its not just that 'people like the distortion of tubes'. There is far more to it than that. What is keeping tubes around is that people don't like the distortion of solid state (which manifests as harshness and brightness).

I've explained all of this, plus a solid state solution (because this really is all just engineering; there's no 'magic'), earlier in this thread.

Although I must claim total ignorance, as I didn't past the comment that tubes are warm because they produce harmonic distortion.

@pedroeb To be clear, all amplifiers produce harmonic distortion. In general there are two kinds of harmonic distortion- the lower orders (2nd and 3rd) and the higher orders (5th and above). The lower orders are well-known to be innocuous to the human ear. The higher orders are well-known to be unpleasant if audible. This fact has been known to the audio world for some 90 years or so. If you want a reference see the Radiotron Designer's Handbook, 3rd edition, which was published in the mid to late 1930s. I think its available on CDROM.

The 2nd and 3rd harmonics contribute to what audiophiles call 'warmth'. If not masked, the higher ordered harmonics can cause an amplifier to sound harsh and bright, clinical, sterile and other such audiophile terms.

"Seems many comments above are talking about artificiality of solid state. Tubes introduce a more realistic Sonic impression versus scientifically created solid state transistor stuff. Tweaking all those electronics to get sound suitable for listening.

It’s no wonder why solid state has such a harsh reputation."

What a bunch of unsupportable nonsense.

@jumia Actually its easily supported if you understand how distortion interacts with the ear. If you lack that information, then solid state appears the winner hands down.

FWIW, tubes have been around a long time since being declared ’obsolete’ (which was the 1960s- imagine that idea in the face of germanium transistors 🤣). They’ve actually been around longer than when they were the only game in town. So there is an economic ’support’ as well- if tubes were really inferior they would have been gone 6 decades ago!

So you don’t really need to know the engineering about why solid state has had troubles ending tubes in audio. The economic reality is enough.

I outlined what the engineering problem with solid state is in prior posts so will not repeat myself here.

Despite all this I’m not saying that tubes are superior at this point, as you will see if you read my prior posts.

Could you please enlighten us, not as to brands or products so much as to what traits those solid state amps have and what ICs/transistors they use? e.g., are there transistors that introduce the rich mellow sounds of even harmonics without other distortions? that provide the damping as to tubes? what other traits in the sound are you referring to? And what transistors/ICs are you referring to that must be at the heart of your systems? Any SS manufacturers that are generating a tubey sound must have at the core of their pre-amps and their power amps some unit that is identifiable across the board. Can you please help us with this?

I can, but you have to promise to follow along.

Here are the traits a solid state amp needs to have to sound nice and smooth like a tube amplifier:

1) it needs to have enough Gain Bandwidth Product to support the negative feedback the amp employs across the entire audio band. Depending on the gain the amp has, this value might be 10MHz to 20MHz.

In terms of what is measurable, this will result in distortion not rising with frequency, which is something at which most solid state amps fail.

2) the feedback must be applied in such a way that the feedback signal doesn’t get distorted before it can do its job. To this end, the base of a transistor or gate of a MOSFET isn’t a good place to apply feedback. For more on this see the writings of Norman Crowhurst. If the feedback is properly applied it won’t add higher ordered harmonics of its own, which is part of what makes solid state amps sound bright and harsh.

3) The non-linearities that cause distortion in the circuit should have either a quadratic or cubic nature, so distortion product tends to be lower orders.

This is obviously all engineering. Its doable. There are amps like this and unsurprisingly, sound a lot like a really good tube amp (actually a lot like real music). If you have any in-depth questions about the 3 topics I brought up, none of it is trivial and might require some study to sort out.

If someone here can point me to a SS Amplifier that will sound EXACTLY like my AUDIO NOTE VINDICATOR SILVER 2A3 Amplifier...I'm all ears!!! 😎

@voodoofunk You can't even find another 300b or 45 based amp that will do that- for that matter probably not even another 2A3 based amp.

do you have distortion measurements that you can share with us comparing your tube and class-D amplifiers?

In general our class D makes about 1/10th the distortion of our tube amps at full power. At lower power levels its much lower, since the distortion of our tube amps decreases linearly as power is decreased, whereas with our class D the distortion increases dramatically just before clipping.

The distortion spectra of our tube amps favors the 3rd harmonic with the 2nd slightly less- the better matched the tubes are the lower the 2nd becomes. In any event that distortion is plenty to mask the higher orders. Our tube amps are fully balanced and differential so the distortion spectra is based on a cubic non-linearity rather than the quadratic nonlinearity you see in an SET. Conventional tube amps that have a single-ended input and push-pull output have both non-linearities in the design so tend to feature a more prominent 5th harmonic (see Norman Crowhurst). SETs and fully differential push-pull amps like ours avoid this problem.

In our class D the 2nd harmonic is more prominent and in that respect the distortion spectra looks more like that of an SET. Again the lower orders are prominent enough that they mask the higher orders. But the distortion is essentially about an order of magnitude lower and most of that is the 2nd.

More important than the actual distortion values is the fact that in both kinds of amps we make, the distortion does not rise with frequency.

Atmasphere manufactures Class D amps to so he's invested in the technology (I haven't heard his Class D mono amps but I imagine they sound fine) so there's that, and although he claims they measure like tube amps, I'm not sold.

😀 In the past there have been so many outrageous claims in the audio world that I doubt anyone takes printed claims as gospel in the audio world. We all have to take the equipment home and play it. I think this is because there's been a really big disconnect between the printed specs and what we hear for since the 1970s at least, since solid state began to dominate the market.

BTW, to add to my outrageous claims there is a review published in last month's Hifi+. So you can see what an allegedly independent reviewer thinks.

@phusis I can't speak for other class D amps although I've heard a few that are really quite good. Class D amps vary in sound more than from the worst to best tube amps. Some really can't be taken seriously. Some are really boring. And some are amazing. 

The amp we designed worked out to have a distortion signature that looks for all the world like a tube amp when you have it on the bench. The distortion of any amplifier is its 'sonic signature'. What so many people don't realize is how audible distortion really is since our ears assign tonality to all harmonics (that is after all how musical instruments sound unique too...). So if you have an amp that has a distortion signature that looks like that of another amp, it will sound like that other amp too.

We were lucky in that the non-linearities that exist in our design tend to generate lower ordered harmonics. So very similar to a tube amp in this regard. Of course we have a lot lower distortion so the amp is more transparent.

I sincerely doubt that we are the only ones to be able to do this!! So tube amps are on borrowed time.

Many people like solid state. It happens to be more convenient. But that's not why everyone likes it better.

Not everyone agrees. I'm glad not everyone agrees.  Leaves more tubes for me.

The problem is there is plenty of S. S. and plenty of tubesc amplifier all different which one another...

Then it does not make sense to compare tube and S.S. in general...

It makes plenty of sense to compare tubes and solid state! Tubes have pointed to a failing in solid state designs since the inception of the transistor.

I explained exactly why this is so and the solution in my prior post above.

@emergingsoul 

Tubes are better for multiple reasons and yet the world and the trade prefers solid state.

IMO, for audio this used to be true. Not because of anything other than the distortion tubes made was innocuous to the human ear so they tended to sound smoother and more real in the mids and highs.

There are engineering reasons for this. IME the big disconnect for engineers has been their understanding of human hearing perceptual rules and how that intersects with the circuit they are designing- most are looking for specs on paper rather than how the ear actually perceives things.

This is why tubes are still around- they obey human hearing rules better.

Until recently.

There are now class D amplifiers that can deliver all the musicality that used to be exclusively the domain of tube amplifiers. Because of that I really think tube power is on borrowed time. When people find out the first statement of this paragraph is true, they will be wondering why they have to seek special tubes to make their amp really sing and then deal with the simple fact that a little ways down the road they will have to do it again. They will also wonder why they are dealing with the weight, size, heat and the simple fact that tube power is expensive. 

You have to admit that solid state is easier to live with. But now you don't have to sacrifice anything in the sound quality department either. Your call.