Why tube amp sound better than solid state?

[Alan0354]

I am referring to scientific reason. I know the I/V curve at the flat region is slanted more than the transistor implying that di/dVp slope is steeper. Seems like tube produce more even harmonics than transistors. What other reason?

[Steve Conner]

We just had two good threads on that in "Theory and Design". Read those.

Executive summary: The subjective sound differences are systems effects, the actual choice of devices hardly matters.

If you understand these systems effects, you can easily make a transistor amp that sounds like a tube one or vice versa.

And it doesn't matter anyway because both tube and transistor sounds are musically useful. (For example, everyone loves the Ibanez Tube Screamer, even though it has no tubes in it.)

[Enzo]

And a steam caliope has neither, yet it sounds so goo...


oh wait, nevermind...

[Chuck H]

I think Enzo spent to much time at a "Pizza and Pipes" or something like that. Maybe an old amusement park with a real carousel? This is his second mention of a caliope in a week I think.

IMHO there are soooo many little nuances to how tube and transistor amps are different that it's almost impossible to quantify. Some biggies in favor of tubes are the fact that they respond favorably to variable voltages, which happen a lot in tube amps, with changes to their dynamics. This can be useful for an amplifier that acts more like an instrument. Tubes handle intermittant flurries out of their operating range gracefully adding another set of dynamics. All the variables in how tubes amplify, or fail to amplify, a signal because of just these two things is part of what defines the feel and sound of a tube amp compared to transistors. That said... It is plausable that these variables can be simulated with some success using transistors. I don't know if it can ever be done so well as to be indistinguishable. But that doesn't mean these properties can't be simulated well enough to create some desireable properties in transistor amps. I only touched on a couple of differences. The list is a mile long. Companies that have tried to simulate tube amp properties in transistor amps seem to have picked their battles in what differences they choose to simulate. Some are better than others. I do like the idea of "analog modeling" tube amp character A LOT better than digital though. I think Steve raised the issue of time constant in another post regarding this and it may be one of the more valid arguments against digital modeling that I've read. I am very interested to try out a Peavey TransTube.

Once we start to find out what desireable properties about tubes sound and feel best when simulated in transistor amps I think any inhearent tonal "quality" differences will vanish. As noted, tubes aren't inhearently better, just different. There are a ton of transistor devices used to generate tones that players love. It turns out that for now the difference tubes make IS better for the amps themselves and a combination of transistor devices and a good tube amp is the current "best" for most players. I'm exited, if not intimidated, by the idea that SS amps will become as good as tube amps. Like I said before, analog modeling is much more appealing to me than digital.

[Steve Conner]

Chuck, I think your beloved Peavey Bandit was probably a Transtube amp. All the stuff we're talking about now, Peavey figured out in the 70s or 80s. I think they were already using the circuit before they stuck the Transtube name on it.

Digital vs. analog is a whole other debate.

[olddawg]

Ya know....I use almost exclusively tube amps. I choose the amp for the venue, always bring a spare, and I can maintain them. However, a lot of working musicians i know arent technically inclined and use exclusively SS amps. They tell me it seems that no one in the audience but other guitar players can tell the difference. They are more reliable. They weigh less. They scale better with the volume control so one amp is good for different sized venues. Basically they do everything that they want an amp to do better for a series of clubs or cruise ships, don't break their backs doing it, and dont need constant maintainance. Did I mention that that they say only the guitar players in the audience can tell the difference.

[Chuck H]

Did I mention that that they say only the guitar players in the audience can tell the difference.

It's funny that you mention that because most guitar players DON'T know the difference until they look at the amp. Then they can't wait to smack about how crappy that guy's tone is. I've seen live shows where I could have sworn the amp was a SS turd and it turned out to be a classic Fender. And I've seen shows where a guy was playing through a SS amp and was impressed by the good guitar tone.

I've played some good SS amps and built some great tube amps (strain to pat self on back) and I must say that tubes win in several key areas. Mostly in the natural distortion tones, And especially in the "just breaking up a little" tones. For obvious reasons. That region is where all the differences between tubes and transistors are really apparent.

Most attempts to simulate tubes with SS seem to try copying the distorted wave form and ignore that there are all kinds of voltage sags that change almost every dynamic. Some try to emulate the compression effect of the voltage sags but don't emulate what happens to the wave form under those conditions. This is all going to get sorted out soon enough though. I think. With digital showing some limitations and tube amps being so expensive I think analog tube emulation is going to be the next wave in market demographic guitar amps. Just intuition. Before I started rolling my own tube amps but after I discovered what an expensive proposition they can be both in purchase and repair I was heard to say "If they ever come up with a SS amp that sounds as good as a tube amp I'll buy it and never look back." Well... It's too late for me now. But I'll bet there are a whole bunch of players who won't ever get into building amps that are thinking that same thing.

I'll need to dig around for schems and see how much of the TransTube tech was already being implemented in the Bandit 65. I mentioned on another thread that after I sold my Bandit I strugled for two years with tube based rack gear trying to get a good tone. Often lamenting having sold my old Bandit. I even heard a rumor once that Neil Schon used a Bandit for several parts in the studio. Can't confirm that though.

[Enzo]

Bandit 65 and Bandit 75 even are plain old op amps, no transtube.



The Transtube preamp circuits are essentially a bunch of transistor pairs - darlington pairs - in a circuit that resembles a tube circuit. The way a JFET circuit resembles a tube circuit. SO adding a bypass cap to the emitter resistor acts similarly to bypassing a triode cathode resistor.

[Alan0354]

Anyone has schematic of analog simulation circuits?

I think there are more to it than just different cabinet, speakers. A Marshall Plexi still sound like Marshall even you plug into a Fender speaker cabinet or even just into the Fender Twin speaker setup. I tried that before.

Most big name players use tube amps. The distortion is where it make the biggest difference.

I looked at Peavey, Marshall and Fender SS amps, all use op-amps. Marshall and Fender use LED for clipping. I have the Marshall JCM900 with LED clipping and I don't like the distortion sound at all.

[Steve Conner]

Ewww... Chuck is an opamp lover!

The most advanced "analog modelling" work I know of in the public domain is this:
Main page

The various "Fetzer Valve" based circuits at runoffgroove.com are also worth studying.
http://www.runoffgroove.com/articles.html

I have my own "12AX7 simulator" based on a LND150 MOSFET, and I've heard some surprisingly positive emails from people who just tried subbing it for a tube in random locations.
LND150 tube emulator attempt.

It was inspired by KMG's work and also the "Trioderizer"
http://www.radiomuseum.org/forum/the...te_triode.html

KMG's circuit is more accurate, but it needs several supply rails. I sacrificed some accuracy for simplicity, on the grounds that it might be more likely to catch on if it could be tried out easily by dropping into an existing amp.

I also have a transformer-driven transistor power stage which sounds somewhat tubey, and you doubtless all have seen before.

[Chuck H]

Yupper... Op amps and diodes in the Bandit 65. Pre TransTube tech. I guess I'm dating myself with this one. I used to run mine with the post gain up high, 7 to 10, and then use the pre gain as the volume control. I didn't use the "saturation" circuit on the amp (always on 0) or the "normal" channel (how anti rock n roll would it have been for a fourteen year old to use a channel called "normal"). With the post gain around seven and the pre gain up a little the amp did get a very acceptible grit. After that it was up to my '84 RAT pedal.

[nashvillebill]

Here's the Peavey distortion circuit used in the early to mid 80's..... Circuit for distorting an audio signal and this patent http://www.freepatentsonline.com/4439742.pdf also pertains to the VTX design

[tedmich]

Jeez I loved that PV Backstage Plus I borrowed in college, cranked the "Saturation" right up... at least I thought I loved it, must have been mistaken as I know I have better taste than that...

"They said, 'I thought I had better taste than that!" Hartley Peavey

[GregS]

Jeez I loved that PV Backstage Plus I borrowed in college, cranked the "Saturation" right up... at least I thought I loved it, must have been mistaken as I know I have better taste than that...

The PV Backstage Plus was my first guitar amp. I remember liking the way it sounded too and I used it for many years. I liked it's distortion a lot better than the PV Express 112 that I got later which I found very buzzy. Although I have always hated to sell things I ended up trading in both PV's so I could get a Fender Blues Deluxe.

[J M Fahey]

*Excellent* analog tube amp simulation?
Jusy have a hard good look at Sansamp GT2
Even better, build one and experiment.