Why tube amp sound better than solid state?

[tedmich]

Thanks JM! His stuff is very impressive!

Check his FET version of an Engl530 and V30 speaker sim !!
http://milas.spb.ru/~kmg/files/proje...0_SIM_V30R.mp3

it rages!

Well, thereīs 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.

[J M Fahey]

Don't thank me, thank *him* !!

[guitician]

I'm sure you've all heard this quote from Dumble regarding what makes tube amps better than solid state...
"The more fragile harmonics can survive in a vacuum tube, were they seem to be eliminated, or squashed, in a solid state crystal lattice. It just comes down to that. The physics of it, electrons can survive in a free space vacuum, where they have trouble in a crystal lattice. I think that's the best, and simplest, I can put it."

I wonder how well those free electrons survive crossing the transformer windings?

[J M Fahey]

Excellent poetry. Somebody should give him some kind of prize.
Now, for technical writing .......

[hasserl]

Listening to the dirty KMG clip now, sounds like a sick (ummmm, meaning not well) JCM800, way too much fuzz IMO. Not a good example IMO. Instead of a 5E3, have him emulate a plexi. What I'd like to hear is his emulation of a tube amp set to "edge of breakup" range (around 6 - 7 on the amp volume), with the player rolling back and forth with the guitar volume to demonstrate between cleaning up with the vol rolled back and breaking up with the vol rolled up; and I think a plexi circuit does that about as well as any amp. In that JCM clip it doesn't seem to do it very well, but that just may be his interpretation of a JCM. The plexi circuit is pretty well known around these parts, let's see how well he nails it. If he can do that, that would be impressive.

[Steve Conner]

Well, here's his solid-state Plexi.
Fet version of the Marshall Superlead Plexi 40W

Unfortunately the samples are all reamps again. I bet if it was actually played by someone who understood the concept of using the guitar volume to clean up, it would sound pretty good.

[Alan0354]

Well, here's his solid-state Plexi.
Fet version of the Marshall Superlead Plexi 40W

Unfortunately the samples are all reamps again. I bet if it was actually played by someone who understood the concept of using the guitar volume to clean up, it would sound pretty good.

Does this sound like a Plaxi? I read the schematic. I did similar design using a diode at the source Q2 to get a little more even harmonics. I use BJT though. I don't understand why he use such a complicated scheme with Q1 to create biasing as the whole circuit is bypassed with big caps C3 and C4. I don't see any added advantages. You can easily ground the collector of Q1 and do away with the whole bias circuit. Then put the bias at the gate of Q2 and let R7 to set up the current. Or if you insist on using a negative supply, pull R7 to negative rail. If you put larger voltage across R7, you can even ignore the gate source voltage variation and get rid of the trim pot. You can still put the trim pot at the gate side of Q2 to adjust the tail current and get the right gain of the stage. But it is more effective to put at the drain side like the few schematics you posted.

I still don't see Q3 and D1 how it is better in clipping than the good old diode to AC ground.

I absolutely do not see the point of having C10//C11, C12//C13 and C14//C15 as the value is close enough and you don't need to worry about the ESR of the big cap. This practice only apply for higher frequency circuits.

The whole circuit is basically a few stages of what is described above. I think the few circuits you posted make more sense to me. But bottom line is whether this one sounds better or not.

[J M Fahey]

I don't understand why he use such a complicated scheme with Q1 to create biasing as the whole circuit is bypassed with big caps C3 and C4. I don't see any added advantages. You can easily ground the collector of Q1 and do away with the whole bias circuit.

Q2 is an enhancement type FET, meaning it needs a positive voltage at its gate .... or negative voltage at its source, which he did.
Although he *might* have used a plain trimmer there, Q1, an emitter follower, gives better regulation.
Grounding Q1's collector would kill the negative source voltage needed.
What you suggest would work with a normal FET, which is simpler to bias.

[Alan0354]

Q2 is an enhancement type FET, meaning it needs a positive voltage at its gate .... or negative voltage at its source, which he did.
Although he *might* have used a plain trimmer there, Q1, an emitter follower, gives better regulation.
Grounding Q1's collector would kill the negative source voltage needed.
What you suggest would work with a normal FET, which is simpler to bias.

I under enhancement FET, all he need is to pull the R7 to negative rail. The rail has better regulation. What I meant ground collector of Q1 is to put that point to ground and totally eliminate Q1 circuit. If ground that point, you will need to bias the gate of Q2 and AC couple the input. Doing that will save a negative supply which is $$$. I don't see you need a whole negative supply just for that.

As I said, how does it sound?

[jmaf]

Excellent poetry. Somebody should give him some kind of prize.
Now, for technical writing .......

You should see the top comment on the YouTube video where he was quoted saying this

[J M Fahey]

As the Cinese said "Vely funny!!"

[harry]

I too found the KMG site through Steve Conner's link - sorry if I missed it, but I'm surprised that nobody has posted the samples that have a comparison between the FET JCM800 and a valve version, as on this page:

Fet version of the JCM800 using LND150 mosfets

What is it that sounds different? I don't have headphones here at the moment, but I remember the valve version having a more "swirly" quality, and the FET being more static. Could this be the FET circuit's solid bias compared to the valve circuit's less-rigid bias giving a variable duty cycle ratio?

[Chuck H]

Could this be the FET circuit's solid bias compared to the valve circuit's less-rigid bias giving a variable duty cycle ratio?

Good call. Almost surely. The valve is self biasing which both reduces the harsh dynamic and causes the buckle which creates swirl. How the heck do we get transistors to do this? Even if we simulate it via external response based circuits (which has been done to some degree) it tends to sound like "orange drink" instead of "orange juice" (if you've read some of my other analogies). Not that that's entirely bad. Certainly some people like orange drink better. And I don't think I would like a world where there was no distortion pedals (for example). But it seems to me that wherever there is a great tone some tubes are involved somewhere in the formula. Just sayin'. There's a reason for every stigma or stereotype. That doesn't make it the rule but you'd have to be ignorant to ignore it.

[Steve Conner]

I thought the KMG circuit was supposed to simulate the duty cycle shifts too. Maybe he didn't get it quite right.

It's done by using a JFET (which draws "grid current" when overdriven, just the same as a tube) or by adding a diode to an op-amp or MOSFET circuit. I've tried both approaches, and I prefer the second one. Lateral MOSFETs like the LND150 are more consistent and more thermally stable than JFETs.

I don't believe that all stereotypes have a reason, either. Or at least, I doubt they have a valid reason. Maybe there was one famous example 20 years ago, and everyone got tarred with the same brush ever since. The stereotype of solid-state guitar amps is formed by the cheap, nasty practice amps, since those are the majority of solid-state amps sold. But (IMO) they're not a fair representation of what solid-state technology can actually do.

[J M Fahey]

Hey !!! The orange juice example is MINE !!!
Iīll see you in Court !!!!
KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK <-- drooling blank eyes blood curling laughter.
KKK
Well, when customers ask me to build a Tube amp for them, my usual answer is: " tube amps are like just crushed orange juice; most SS amps are like Fanta or Mirinda or one of those "orange flavored" Vitamin C pills; mine are like Tang or better"
And why donīt I just build the tube one?
Short answer, most canīt afford it.
Or to put it another way, I limit my sales too much.
I much prefer building 20 cheaper SS amps a month than a single expensive tube one in the same period.
And thatīs the realistic ratio.
As somebody said once: "when you ask people: What do you *prefer* for lunch? most answer Steak .... when then you ask: Ok, what *did* you have for lunch today? .... most answer Hamburger"