Why tube amp sound better than solid state?

[Alan0354]

You are right, many SS circuits like the Marshall Lead 12 etc. don't have any emulation of the tube's transfer curve.

There are other circuits that do, but they usually use diodes or BJTs which both have an exponential law, or FETs which have roughly a square law. Neither is quite the same as the two-thirds power law of a vacuum tube, but I'm not sure how much the difference matters in practice.

When using transistors, a bit of negative feedback from an emitter or source resistor messes up the math and produces a whole spray of harmonics. To my ear, this works well with FETs, and makes them sound more tubey. Without the degeneration, the distortion is almost pure second harmonic, and that sounds a bit sweet and bland.

I remember one guy who owned a Vox AC30, and using measurements from his amp, he modelled every tube stage using op-amps for the gain and zeners for the non-linear elements. The result worked well enough that Korg bought the design from him, and he had to take the schematics down.

Teemuk has written an entire book on these circuits. If you want to get into the subject in this kind of depth, it's worth reading. I picked up a lot of useful information from it.

http://www.thatraymond.com/downloads...ttala_v1.0.pdf

The relevant bit to this discussion is around page 268.

I really appreciate all the information you gave me. This is very helpful. I started the post not to have a debate on tube vs SS. They sound different, not necessary better or worst, just very individual. I am more interested in the quantitative aspect of it. I have been using LTspice to simulate BJT and JFET and look at the distortion characteristics. Too bad there is no model for tube available for simulation.
I downloaded the book, it'll take a while to read through it. You said the person use zener to simulate the distortion, do you have the circuit how he did it?

Again, I really appreciate your information.

[teemuk]

I have been using LTspice to simulate BJT and JFET and look at the distortion characteristics. Too bad there is no model for tube available for simulation.

I'm not going to cover this in any greater extent since it gets too off topic but let's just say that while LTspice doesn't include tube models by definition there's an abundance of such models (including various types of diodes, triodes, tetrodes, pentodes, etc.) made for SPICE, that including LTspice. Google is your friend: A bit of searching and you'll find a handful of sites and even entire discussion groups dedicated to the issue.

[MarkusBass]

Teemuk is right. On LTSpice yahoo group there are examples of several valve amp simulations including great simulation of Fender 5E7.

Mark

[kleuck]

Nobody mentioned the damping factor of power stages ?
Give it a try : build a cheap LM380 amp, plug it in a good guitar cab, what you will hear when playing will be a tiny "Hi-Fi" or radio sound.
Then, solder a power resistor of 1/4 the impedance of your speaker, play, and enjoy a guitar amp sound.

For me, one of the more important differences between SS and Tube amps, ALL SS amps have a huge nfb as aforementioned, as it's almost impossible to have them simply working without, and certainly not for cheap ; where tube amps have low or no nfb at all.
This leads to very different output impedance, therefore damping factors.
Why do amp builders put "good" speakers only in tube amps ? Cost ? Not at all, but because they know it would make little, if no no difference in a SS amp.

Not the only reason for the "better" tone of tube amps, but one very important, and usually forgotten.

[walkman]

This link presents a good summary of the differences (including damping factor) Lenard Audio - Education - Valve Amps

[kleuck]

This link presents a good summary of the differences Lenard Audio - Education - Valve Amps

[Enzo]

What a great discussion, it is the same every time we have it. it very quickly devolves into the same camps presenting the same arguments. Oh well.

In defense of SS I always see "the list." Yep, bunch of guys have used SS amps, some even mostly use them. Get 1000 guys on that list if you like. That alone tells us little. How about a context. Make the same list up for tube amps. My instinct tells me it is a longer list, but that is just an opinion. But even if it is 5 times longer, that tells us nothing, other than that more recording pros use tubes. Well McDonalds sells more beef than Outback. Kraft sells a lot more Velveeta than all the nice Jarlsburg in the world. Jello sells a lot more instant pudding than all the creme brulets in the world. The numbers don;t tells us what is "better."

Some generalized objection to some aspect of something and instantly there is some contrary example. "The odds are against you getting bit by a shark." "Oh yeah? Tell that to the kid who was bit by a shark." Well what does that have to do with odds?

I remember a SS can do anything tubes can discussion where it was announced someone had exactly emulated a tube with only 17 op amps, or something like that. HArdly a head to head comparison then.

No absolutes, and no resolvable argument.

[J M Fahey]

Well, there´s this KMG guy from St Petersburg who has made definitely his homework, and developed a series of *IMPRESSIVE* preamps and Power amps.
For one, he feeds his fets 200V DC, not puny 9V.
Not that complex, he replaces each triode with a single Mosfet, to which he adds a simple buffer to avoid external loads altering the working point he so carefully chose, and another bipolar stabilizing the bias point (the real curse of Fet stages).
As an example:
Fet version of the SloRectoTwin
Be certain to hear the sound samples:
http://milas.spb.ru/~kmg/files/proje..._srt_clean.mp3
http://milas.spb.ru/~kmg/files/proje...g_srt_lead.mp3
Enjoy.

[GregS]

This link presents a good summary of the differences (including damping factor) Lenard Audio - Education - Valve Amps

Good read. Thanks for posting that. It also got me re-thinking speaker cabinet design.

[anthillrich]

Maybe slightly off topic, then again maybe not, but Id like to share an experience.

we as musicians, technicians, what have you, have an ear that almost nobody else has.

a friend of mine once asked me what the "little switch" on my guitar was for. he was pointing to the blade switch on my strat, so i thought i would demonstrate for him.
i went thru each position playing with a clean tone, trying to describe the "in between" tones and out of phase funky virtues of the pickups.

he blankly said to me "one just sounds more dull than the other". how could he not hear the difference? the detail? these were good pickups thru a nice amp, how did he not get it?

I think the same is tru for SS/Tube amps.
almost nobody can tell, even us "dog ear" musicians, what someone is playing from a studio recording.
"It sounds like a gibson thru a marshall", when in fact it might be something completely different. with the twist of a knob on a console, the sound can be altered significantly enough to fool some of us. most of us.

In a live band setting, it's even harder to tell. as was mentioned earlier by another poster.

for me, why I prefer tubes (and I do prefer them), has alot less to do with sound and much more to do with "feel".
there is a difference, a noticable difference, especially at stage volume with how a good tube amp feels.
I cant tell you exactly why or what that feel is, certainly not in technical terms, but it is very real.

I have "HEARD" many great amps both SS and tube, but I have only played thru tube amps that "FELT" right.

my 2 cents.

[Enzo]

I would maintain that whether someone else can hear you and tell what kind of amp you are playing is irrelevant. If you can hear or feel a difference in the amp while you play, that is the issue. I don't care if the drunken fools dancing in front of me can hear the nuance I appreciate.


I am sure Yo Yo Ma can tell the difference betwwen formualtions of bow rosin. I am sure it doesn't matter if I could touch the bow hair and tell any difference.

[Chuck H]

I don't care if the drunken fools dancing in front of me can hear the nuance I appreciate.

+1
But the guitar players are always wanting to know this or that about what you play through. And also usually CAN'T hear the difference. I build really good sounding amps (pulled shoulder patting self on back) but there are A LOT of really good sounding amps out there. I certainly don't need to build amps to have a good sounding one. Still, when I played out I always used my old Marshall. Which was basically a Marshall box and chassis with my amp stuck inside. And I used a franken strat I made from Warmoth parts with custom pickups and series wiring switches. I always got a kick out of the guys who would ask "How do you get that tone?" And I'd answer "Don't know what to tell ya. It's just a strat through a Marshall."

Sorry JM but I think the clips sound more like typical SS pedals than tube amps. No offense intended. Just one guys opinion.

[anthillrich]

ah, yes. Yo Yo MA. and Eric Johnson can hear the difference between Duracell and Energizer batteries in his effect pedals. Can anyone else.
Which one sounds "better"?

It also makes little difference to me what the drunks in the front row think sounds better. but, the question is why tubes sound better. I contend that they dont necessarily sound better.

my other point being......most people couldnt tell the difference anyway.

why do we sweat it?
I think its because we like the way tubes "feel".

It always amazes me when someone (always another guitar player) looks at the "made in USA" label on my strat and says "thats a nice guitar".
like they had to see that first to say it was a nice guitar. as if a mexican made strat wouldnt sound as nice. silly.

I think the same also applies to Tube amps. "oh, you have a Marshall ? " and then they look at the back to see if it has glowing tubes in it.
listening in a blind test they wouldnt know the difference. I probably wouldnt either. but in a blind test I could tell you if I was PLAYING thru a tube amp.

I dont know if its compression, speaker dampening, the way a tube amp "tracks" the guitar.......I dont know, but I know its different, different in a way I like.

[jmaf]

ah, yes. Yo Yo MA. and Eric Johnson can hear the difference between Duracell and Energizer batteries in his effect pedals. Can anyone else.
Which one sounds "better"?

Wow I was thinking of this piece of myth just minutes ago. What a coincidence to click through here and see this. Reason: I was messing with an amp, where I added this tiny capacitor in parallel with another bigger cap. I thought "I know what I did, I can hear the difference, but less than 1% of humankind will ever notice this, except Eric Johnson who can tell between battery brands" LOL!

I think the origin to EJ's battery myth was something like this: one drained battery was installed, it sounded brown, then a newer battery was installed, it sounded shiny. Interviewer concludes: Eric Johnson can tell between brands of batteries. I can tell between Coke and Pepsi, I won a prize for that at a park 30 years ago.

[walkman]

Well this morning I had a chance to crank it up at home , so i go out the yamaha g100 2x10 with celestion clone speakers and maxed it out on the volumes. Now while it sounded good , what really made a difference was the shear volume. With a pedal i was easily getting lots of nice feedback and guts. You know guitar to amp interaction. Now while there were some problems with the yamaha at that volume (perhaps filter caps need replacing and the speakers really flap on the low strings) I felt as if i was getting some subltle compression and sag too.

Now I get my other yamaha , a pe-100 preamp head and plug that into the reverb return of the yamaha ( so it bypasses the g100 pre and uses the reverb return as a master vol) and there is a whole different tone and vibe going on. Much more compressed, in away slightly more dynamic lighter feeling going on ,with a nice soft brownfaceish overdrive, and i could still crank it through the g100. I used to have another early 70 SS amp head that had a similar vibe too it. They are much more tube like in one way but then again not the same by any means.

Playing the amp really loud and the feel of the amp is always going to make a difference. At that point some of the subtle differences may fade away, or show that some amps, even if they are rated at a wattage just don't sound good played at anything else but medium to lower levels ( that you might hear in the shop for instance ... deville? hotrods? , and hence all the modding craze. )

Even my stock Boss SD-1 sounded better than one i'd modded to get back some of the bass that is usually dumped in these pedals. And you know what The SD1 sounds pretty average a low volume but really loud it really does what it needs ( i'd forgotten that).