Tube amps and a Stradivarius

If tube microphonics are present, it is a problem not a feature. 

There’s always a degree of microphonics with vacuum tubes.

I have a quad of tung sol kt120’s (2018 m.d.) that are loaded with it.

Same year quad of jj kt88’s that barely sound when I finger flick them.

Im unsure how much it has to do with the “euphonic” sound of tube gear.

I always thought the 2nd order “harmonic distortion “ was most responsible for that…

The Neumann U 87 is still one of the greatest vocal microphones ever (tube). Records have a warm rich rumble that sounds great. Vocals don't have warm and rich rumble. 

Tubes are a physical effect mechanism that have nothing to do with accuracy. They are signal processing. Under Capital Records are 8 rooms, pie shaped with lacquer paint a Shure 88 microphone and a voice of the theater speaker in the corner, these are the most prestigious reverb rooms in the world but the equipment in their is not close to state of the art. 

Whether or not it is high second order harmonic distortion that adds richness or denseness to the sound, or there is something else at work, I like the sound of some tube gear.  I suspect that, in part, it is phase shifting in transformers that is part of the secret sauce.  
I have wondered about tube microphonics too.  I took part in listening to several different Western Electric 310 tubes that were going into a custom build linestage.  All of the listeners agreed on which tubes sounded best in the linestage.  The builder noted that we had picked the most microphonic of the tubes under consideration.  Whether this was merely a coincidence and we liked some other properties of the tubes or whether we liked them because they were microphonic is something that was not resolved.

Among what I've read, Stradivarius used a secret brine to selectively dissolve some of the sap or glue in the lumber he used.  The difference of these instruments is quite real.

You can play any instrument too loud. But sometimes this is necessary to do briefly or not so briefly when it's called for in a performance. In these cases the instrument distorts a bit, giving the sensation of increased loudness and drama. In these cases, the distortion serves the music.

Tubes do the same thing. Unlike SS, they distort a bit more at musical peaks giving a subtle sensation of liveliness. It's just the right amount of wrong. It's not accurate but it's fun. Who doesn't want to have fun...

Yeah, but how are tubes going to work in your powered speakers?

Tube amps are not technically as accurate as solid-state

That's like saying earth is flat.

Proof?  Define accurate.

You ain't heard a Stat like Ray Chen playing his at front row distance.

Another of the great audio myths.

Tubes unlike SS don‘t switch. Unless you go to class D with a high switching frequency that remains audible

Do you want the sound to be accurate or sound cool. There are objective engineering philosophies that clash between flat and good when it comes to sound. The best answer to me is to have the goal of putting the musician in your listening room playing the instrument but then the Stradivarius comes in and says wait you can't design magic. Form will follow function if we demand designers produce accurate equipment and speakers ultimately the end result will be more musical. It is so tempting to add all the flavorings to music and movie that was unintended simply to make the experience more exciting. Is that wrong?

Also if you think tube amps are more accurate you are simply fooling yourself. I use tube amps (hybrid) in my 2 Channel system but I know they are not more accurate they sound better and more musical than SS amps but the audiophile community needs to know the difference if this community is to make a difference in the future of equipment.

I don't care so much whether it's described as accurate or musical, but find that good tube gear does a better job of revealing the other components in the chain, which I simply find useful in building a system that reveals the recording, and that's basically my end game....I want to convince myself I'm there, and experience it.

Triodes are more linear than transistors, which can also make them sound more realistic than solid state.

My tube amps (mono blocks/preamp), CD player and TT are all located outside the listening room (hall closet with a solid door) and the speaker cables run to the listening room through tiny (< 1/4") holes in the speaker wall.

I've also had the tube mono blocks in the  listening room (seeing if short speaker cables made a difference).

In previous settings I've had tube amps in & out of the listening room though I've always tried to keep the TT and preamp/phono preamp isolated (closet or other room).

Never noticed added space/reverb with in room placement, but all my setups since 1976 have used smaller speakers played @ low/medium SPL's.

However, I've experienced slightly microphonic signal tubes in guitar amps that definitely alter the sound.

As long as they were not feeding a reverb tank I actually preferred the sound of them when used with lean sounding Fender amps and guitars using single coil pickups.

DeKay

Triodes are more linear than transistors, which can also make them sound more realistic than solid state

Do you have any articles to back this up, everyone would agree tube sound is more pleasent but any info looking at input and output through a tube as being more accurate than high quality transistors.

Here is an interesting article that kinda supports your view, but looking at input then output with quality transistors there is really no comparison. 

 

Try using transistors without feedback and see what happens.

"Also if you think tube amps are more accurate you are simply fooling yourself."

You have very strong opinions about tubes, considering that you seem to have ZERO stated knowledge on such.

Also, your OT premise is laughable, IMO.

DeKay

All I know is tubes have sounded better than SS amps to me so far.

invalid

You are right, a designer must use feedback that is always a compromise but transistors are still more accurate (don’t sound better) than tubes if you look at them on a scope. Another fare worse aspect is how transistors distort when clipped they sound awful but tubes sound smooth and forgiving. Audiophiles use underpowered amps in general, it takes a lot of power to produce loud sounds from some of our big not so efficient speakers. Tube amps are always way lower power than ss amps but because of the nice distortion it doesn’t matter as much. But physics is physics it takes a certon amount of power to produce a high volume from the speaker and it is very rare that tube amps have even close to enough power in fact it is the exception that even ss amps have enough power to produce movie theater volumes at home. By the way even golden ears have a hard time hearing <15% distortion at high volumes.

Movie theaters use solid state amplifiers, so your point isn't a very good one. I've heard better dynamics in home theater systems than at movie theaters.

Movie theaters use ss equipment because tubes would be a nightmare the tubes would always be sounding not like new and it would be nearly impossible to get the LF response needed to make spec. Sure there are tube amps that can put out a lot of power but the tubes are very expensive, unreliable, and degrade immediately after putting them in the slot they also are about 90% inefficient creating more heat than power. 

My amps are the BHK 300s by PF Audio they make sense to me because the front end is tubes and the power side is mosfet, gives you the best of both. Guitar amps are always tubes they need the ring, warmth and distortion characteristics that tubes can bring, but now guitar amps can be ss and simply be programed to emulate other tube amps, the best of these emulators can fool anyone.

invalid Just asking an honest question, I assume you have tube amps, as I do as well. What sort of system do you use to change all the tubes just change them all each year or 6 months, they start sounding bad very slowly and It's hard to realize the sound is degrading, like a frog being boiled very slowly eventually you have dead sound.

Yes, in the end, it’s about the music. What’s it sound like? Hmmm. 

@donavabdear all guitar amps are not tube. I have a Vox Essex that is SS. Prefer my tube amps but the Eessex was the first guitar amp I bought in 1976. 

I've always heard (and believed) that tubes sound as good as they do for 2 primary reasons:

1 - They better convey the particular harmonic structure of notes from different instruments (accuracy of tone & timbre)

2 - And very often, they overload more gracefully/less abruptly than SS devices, and the distortion byproducts sound more benign (the distortion representing more even-order harmonics and fewer odd-order ones).

But that doesn't really explain the 3D effect one often gets from tubes, where each musical note sounds more tangible, real, occupying real space in a real place. For me, that is the greatest asset of tube audio: how musically realistic the sound is.

@desktopguy Records sound better than CDs everyone knows which format is more accurate. Tubes sound better than ss everyone knows which system is more accurate. I like tubes better also. It just shows that accuracy is not more musical in this state of our technology. No one mixes up a real piano with a recording of a piano in real life, I have a beautiful Steinway B grand its a Spiro /r that plays by way of a digital engine that has 1000 levels or resolution, it plays exactly the way the original player plays it and it doesn't sound like a recording. We have a long way to go to get real accuracy.

That would be a fantastic theory, except that tubes are just as popular with headphone aficionados as with traditional 2ch audiophiles. I definitely agree tubes are doing “something” to the sound (and I like it), but microphony is probably not its primary mechanism for this. And SS isn’t the ideal wire with gain either. 

@mulveling Headphones, yep your right. I have a set of Focal Stellia and a Naim amp that is ok but isn't as good as it is expensive I want to change to a tube amp also. Bigger amps even ss amps vibrate naturally, could it be that the natural field of the amp creates creates microphony in tube amps also? 

@donavabdear

You’re right, self noise cannot be completely ignored. Some even advocate high-end isolation stands like HRS or Critical Mass for headphone amps. However, in my experience while isolation has made a big difference for my turntable & speaker setup, it’s not so much for my headphone setup. I have a very high end T2 electrostatic amplifier (massive tubes & SS hybrid, quad of EL34 and quad of 6922 plus a ton of OOP high voltage silicon), and quite honestly hear no meaningful difference between it on or off a Critical Mass Black Platinum shelf.

Maybe of impact in some cases - but for most cases, the self-noise energy will be a few orders of magnitude below the energy received from some big nearby speakers. But then, who knows - maybe it’s a bigger deal than I’m giving credit to. CMS would probably say I really need their new CenterStage feet (in addition to the shelf) to help defeat self-noise. But feet that purportedly required hundreds of hours burn in (sounding BAD for a lot of the lead-up to that) are just a no-go for me.

I borrowed a Stellia and liked some aspects of its sound, but it’s a bit too bright for me with SS amps. I liked the Utopia better - that headphone also sounded quite good right out of a Naim integrated amp.

I will have to agree that the Stradivarius is a singular instrument. I have been stopped dead in my tracks by it’s sound while walking by a TV with really low end sound.

I have also had the privilege of hearing quite a few Stradivarius’ in close proximity. I also, over the last 50 years of being an audiophile have slowly migrated to an all tube system (see my system under my UserID). Attributing the fidelity of tubes to a single parameter is probably over simplifying thing. I appreciate the thought, but tubes with good electronic design can create a better gestalt of the music than solid-state, but that is because of myriad of reasons. I am sure some folks can come up with the top six reasons. But micro phonics is probably not one of them. 

as we say in the studio and the venue…when you make. your first microphone choice…you picked a distortion….you…like….

SS is also…microphonic….. get yourself an HRS or other competent rack…. or isolation product… and hear for yourself….. 

The NAIM amp…will have a vibration isolator…..on the IEC inlet….. :-)

Tube amps are not technically as accurate as solid-state but they sound more musical, I would submit that they sound that way because of the ring of the tubes just like the reverb of the Stradivarius violin. I believe the vibration of the sound from the speakers excite the tubes and there is a pleasant reverb effect. In mixing vocals there is an important effect in the reverb processor called pre delay and that time delay before the reverb is actuated in the processor is like the time delay of the speakers making the tubes ring. Thoughts?

You are right, a designer must use feedback that is always a compromise but transistors are still more accurate (don’t sound better) than tubes if you look at them on a scope. Another fare worse aspect is how transistors distort when clipped they sound awful but tubes sound smooth and forgiving. Audiophiles use underpowered amps in general, it takes a lot of power to produce loud sounds from some of our big not so efficient speakers. Tube amps are always way lower power than ss amps but because of the nice distortion it doesn’t matter as much. But physics is physics it takes a certon amount of power to produce a high volume from the speaker and it is very rare that tube amps have even close to enough power in fact it is the exception that even ss amps have enough power to produce movie theater volumes at home. By the way even golden ears have a hard time hearing <15% distortion at high volumes.

@donavabdear Most of the last quote is incorrect.

Its more than just looking at the signal on an oscilloscope. The ’scope won’t show you the harmonic content very well at all, and of course its harmonics that cause all instruments to sound the way they do.

Its harmonic distortion and IMD that causes amplifiers to sound the way they do. Based on your comments, my surmise is that the solid state amps you’ve heard don’t have enough feedback. Plus what feedback they do have (which might be 25dB, not nearly enough) was applied at a non-linear spot near the input of the amp (usually a transistor) which caused the feedback signal to be distorted before it could do its job. As a result of the non-linearity, higher ordered harmonics were added to the resulting sauce.

Human ears complicate this in two ways. The first is that the ear uses higher ordered harmonics to sense sound pressure so is keenly sensitive to them (the ear has about 130dB range)! The second problem is the ear converts all forms of distortion to tonality, just as it converts the harmonics of musical instruments to tonality. So you can hear the distortion most solid state amps make quite easily- as harshness and brightness. Its a coloration every bit as much as the ’warmth’ of tubes caused by the 2nd and 3rd harmonics!

The nice thing about the 2nd and 3rd harmonics is they can mask the presence of higher ordered harmonics. This is the sole reason why tubes sound smoother than solid state.

Tubes have traditionally been better at low level detail such as decay of musical notes in a room. This is because the phase of the 2nd and 3rd harmonics help the ear to hear details like this, which includes the 3D sound stage.

It is possible to build solid state amps that sound like tube amps. All you have to do is have the same relationships of lower ordered harmonics to the higher orders (and not get messed up with IMD in the process). This is really hard to do with traditional class A or AB solid state amps, but IME it is possible to do with class D. What I am saying is there are class D amps now that sound like a tube amp- the best way to tell the difference is the class D is slightly better in the detail department.

WRT feedback: Most amps don’t use enough! This is because of two reasons, the first being that adding more feedback might cause the amp to become unstable- that it is more likely to go into oscillation when the chips are down. The second is the amp needs a lot of something called Gain Bandwidth Product, which as you may have surmised is a mathematical number based on how much gain and bandwidth the amp has. If the GBP is too low, feedback will decrease with frequency, meaning distortion will increase with frequency. This is a recipe for brightness and harshness- a ’sheen’ on top of the strings, stuff like that.

All tube amps lack both the phase margins (that oscillation issue) and the GBP to use enough feedback. But they have an advantage: their feedback node is usually a bit more linear than that used in most solid state amps, so the feedback signal gets less distorted, and so does less damage while otherwise doing its job. IOW: smoother sound because less higher ordered harmonics are generated.

Most solid state amps have the same issues I mentioned in the last paragraph, but they usually do a bit better so more feedback can be applied. But as I mentioned the feedback signal is also more distorted so the feedback does more damage doing its job.

In a class D amp you can run a whole lot more feedback and can get around these problems, depending on the topology. As a result there are some class D amps that are as smooth as the best tube amps but more transparent since they have less distortion overall. But like tube amps, not all class D amps are equal!!

I still don't think the best class D amps are as smooth and holographic as the best tube amps, but they are getting better.

I still don't think the best class D amps are as smooth and holographic as the best tube amps, but they are getting better.

@invalid 

IME as long as you have the right amp, class D can be every bit as liquid and smooth as the best tube amps. But you have to hear the right one; like the way tube amps can sound really different from one to another, the same is true of class D (or class A for that matter...).

@atmasphere Thank you for that great post. Your words carry a lot of knowledge and experience in the audiophile world, exactly what I wanted. I did professional sound for 35 years never used a tube amp but I liked them so much after I retired I bought them for my home system. I have a professional Genelec "the Ones" Dolby Atmos system in the same room as my home theater Dolby Atmos and my 2 channel system my home system sounds so much better not more accurate but worlds better, I do think it's because of the tube amps PS Audio BHKs and also BHK preamp. I didn't think there was a technical reason why the tubes would sound better. Very interesting. 

@atmasphere Also I have had my tube amps and preamp for about 3 years I've bought all the cool tubes that are supposed to make the equipment sound better and there has been a big difference, that is really scary to me there is no way I can use my home system to evaluate what's real, I can of course compare it to other music and movies I've listened to on that system. My question is how do you manage the tubes, they slowly get bad I can't take it, I feel like they start going bad the second I put a new one in and I'm just not noticing it because the bad sound happen so slowly, very frustrating. How do I manage tubes?

My question is how do you manage the tubes, they slowly get bad I can't take it, I feel like they start going bad the second I put a new one in and I'm just not noticing it because the bad sound happen so slowly, very frustrating. How do I manage tubes?

@donavabdear 

It sounds to me like you're managing them quite well as you've put your finger on their biggest weakness. Its lovely when they are right and frustrating when they are not; tubes were made to much higher quality standards 60-70 years ago, which is why NOS tubes command higher prices.

My previous SS systems never engaged me like my tube system does now. So, I know I am biased towards tube gear. I am honestly curious about the accuracy claim. How does one measure and judge accuracy of a reproduced recording?  And accuracy against what? Wouldn't it need to be compared against the actual studio recording?  

Nelson Pass did some fancy footwork designing the XA-25 (Eliminated "degeneration" feedback...whatever that means) to make it appeal to tube heads (like me) or maybe just himself, and it seems to do just that in Class A...engaging indeed...

@femoore12 exactly that happened to me a few years ago I worked with a singer everyone knows she and I were on a TV show so I knew her voice perfectly, when she make an album at capitol records I was able to go with her. This was so interesting for me because I knew her voice so well  I used one of the songs on that recording as my reference to test some high end speakers it was very interesting because I didn't like anything I heard until got the top of the line Paradigm beryllium speakers so I bought them. Recently I put in a Dolby Atmos mixing studio with Genelec powered "the one" speakers these speakers showed flaws in the recording I never heard before. My home setup sounds better but definitely not more accurate. The tubes have a wonderful way of covering some of the sins of recording being played back on powered studio monitors.