About amp "immediacy"

[netfences]

I've often heard about the feel and immediacy of tube amps compared to SS and I've never understood it. Is this just another way of describing the slew rate of your input signal or is there more to this that I need to understand?

[Chuck H]

I always interpreted it as slew rate. Which is typically slower in tube guitar amps than in SS guitar amps. In fact reducing slew rate is one thing some SS designs do to sound more "tubey". And it's just a subjective and vague term people toss around anyway. It's usually best to ignore any reference to an amp being "fast" or "slow". Likewise, one guys "harsh" (used negatively) might be another guys "bright" (used positively). Further, I think it's possible to misinterpret a "bright" amp as a fast amp or one with "immediacy" because of the HF assault on the ears. Again, subjective.

[netfences]

Thanks for the response but I'm still confused. Why would a lower slew rate sound more immediate than a higher slew rate? You would think just the opposite were true. A higher slew rate makes it easier for a amp to reproduce higher frequency transitions. That means more presence and presence can be interpreted as immediacy, psycho-acoustically speaking. What I guess I'd like answered is why bother with tube maintenance if you don't have to? The natural question that follows it is, what quantifiable attribute is missing from SS amps that make less preferable to tube designs?

[uneumann]

Thanks for the response but I'm still confused. Why would a lower slew rate sound more immediate than a higher slew rate? You would think just the opposite were true. A higher slew rate makes it easier for a amp to reproduce higher frequency transitions. That means more presence and presence can be interpreted as immediacy, psycho-acoustically speaking. What I guess I'd like answered is why bother with tube maintenance if you don't have to? The natural question that follows it is, what quantifiable attribute is missing from SS amps that make less preferable to tube designs?

So, slew rate is only one of dozens or hundreds of amp behaviors and psycho-acoustic effects that impact how someone "hears" an amp. If you're trying to say a high slew rate makes one amp better than another, I'd suggest you reconsider. If you're asking which parameters (besides slew rate) make one amp better than other, that is unfortunately a harder question that no one has fully answered as it varies for everyone playing and listening. If you are asking what makes tube amps different than SS, there are some quantifiable parameters that people here and in many publications have measured or described. Seek and you will find plenty on that front. The technologies and circuits are so different that measurable differences are not really surprising. What is maybe more surprising is that both technologies can produce good tone. Another way to answer the tube/SS question is to suggest you play a bunch of both and then decide what's different and what's preferable for yourself.

[Enzo]

Well one reason is that "immediate" has no particular definition here.

Another problem is trying to define an amp in terms of one variable. Chuck said he thought slew rate might be a factor, that is a far cry from slew rate being the whole deal.

Another problem is trying to define amps as tube or solid state, rather then just as individual amps. And your question assumes there is already agreement that tubes are "better" than solid state. A lot of us prefer tube amps, but certainly not all. And that also points out that we love the tube amps we play. I never heard an old Gibson/Epiphone amp I thought sounded worth a damn. All tube amps. And there are plenty of SS amps I just hate.

But if you try to compare a Lab Series amp and a Hot Rod DeVille just on the basis of tubeness or solid stateness, you are missing the boat.

I like a Fender Twin Reverb, and I put up with tube maintenance because that is what it takes to keep a Twin Reverb running. One of my all time favorite amps is the Fender Princeton Stereo Chorus. That is a totally solid state amp. I like it too. I also really like my GK little MB series solid state head.

And the bottom line for me is asking me to boil it down to some defined characteristic that controls my tastes. It might be there, but I don't know what it is. At a restaurant, I much prefer crab to lobster. Can I tell you specifically what it is about the taste? NO, I can't. As technician, if someone brings be a GX40 Crate and asks me to make it sound like a Blues Junior, I'll give him a blank stare.

[Chuck H]

Thanks for the response but I'm still confused. Why would a lower slew rate sound more immediate than a higher slew rate? You would think just the opposite were true. A higher slew rate makes it easier for a amp to reproduce higher frequency transitions. That means more presence and presence can be interpreted as immediacy, psycho-acoustically speaking. What I guess I'd like answered is why bother with tube maintenance if you don't have to? The natural question that follows it is, what quantifiable attribute is missing from SS amps that make less preferable to tube designs?

Once you dissect this^^^^^^^^^^^^^^^^^^^^^^^^^^

There's a lot of questions in there and even more answers needed to address them.

First, a slower slew rate doesn't sound more immediate than a faster slew rate. That's just something someone said somewhere at some time. Entirely subjective and with potential flaws in the reasoning.

You followed with the all time great question. No, not "What is the meaning of life?" The other question. Why and how do tube amps sound different from SS amps? Well guess what.?. I'm not going to answer that. Not because I don't know, but because the web is already chock full of tomes on the subject ranging from guru flavored lore to technical discussions. If you just search "tubes" "SS" you won't even be able to go any further without tripping over a discussion on the matter. That and the whole answer would take entirely too much time to write. Just look a little bit. You'll find answers.

I will say that your quandary is also steeped in subjectivity. Especially in todays world of digital amps that sample many tube amps. A lot of players are perfectly happy with the digital simulations. Not a tube in sight. And who say's tube amps are better than SS amps? Players who like tube amps, that's who. Which is admittedly most of us. But that doesn't mean the boutique dirt box industry doesn't thrive on many of the same players lining up to buy the new flavor of the week. Not a tube in sight.

I'll also say that you're on the right track to wonder about this. It's pretty easy to go browsing at TGP and come away thinking they're all just drinking the Kool Aid. But consider that in the amplifier market the top of the line models and any pro series products use predominantly, if not entirely tube signal paths. That didn't happen on it's own. Tubes do indeed make better guitar amplifiers than silicooties... Subjectively

[Pedro Vecino]

I´m sorry. I could not avoid it

[Chuck H]

I'm a cake and rug guy myself Not that there's anything wrong with bread and tiles

[Leo_Gnardo]

"Immediacy" another meaningless term to me. For over 20 years some of the hi fi geeks have been going on about "PRAT," which stands for pace, rhythm, um... something else that starts with A maybe articulation, something else that starts with T maybe timing? To describe amps, preamps, even wires. Hell, it sounds good or it doesn't, that's all that should matter. Music has pace, rhythm, articulation, timing and so much more. How the #### does a piece of equipment? Might as well use it to describe a car. Or a toaster.

Slew rate, though a measurable quantity, also does not correlate with listening pleasure. Or much of anything else. Some gear with the slowest slew rates on the planet sounds perfectly good, so having a super duper slew rate isn't a guide to good sound. And it can be very misleading if used to decide which gear to buy. A local music venue called me in years ago to repair their PA system. The problem was all in their power amps, some fly-by-night brand "Time Square" made in Alabama, that were supposed to be the hot ticket - because they had a whomping stomping slew rate 200V/microsecond. Inside, they were built like $#!+, and of course no schematics nor tech support because the company had already folded. Clearlyh, fodder for the scrapyard. The venue grabbed a couple cheap used reliable old Crown DC300A's and went on to have another decade or two of successful shows, no further problems.

Whenever possible use your own ears to find out if sound quality is good. When the so-called experts start throwing around terms like "immediacy, PRAT, slew rate" and other such malarkey, you know they're trying to snow you, move on.

[galaxiex]

Completely subjective of course...

... but I have a toob amp that the notes seem to "jump out at you" immediately ...almost before you play them!

I would call that amp "fast" if I were looking to describe it that way.

I have other amps (some SS, some tube) that don't have this "immediacy" of what you play.
Those I would call "slow" for lack of a better term. Not bad, just not "as immediate" as the first one.

In the case of the "fast" amp, maybe it's more of a presence thing. IDK...

For the "slow" amps, they sound good, they make sounds I like,
they just don't have that "in your face" seemingly quick response.

I have no idea how you could measure something like this... sorry, not much help.

[Leo_Gnardo]

... but I have a toob amp that the notes seem to "jump out at you" immediately ...almost before you play them!

- - -
In the case of the "fast" amp, maybe it's more of a presence thing. IDK...

For the "slow" amps, they sound good, they make sounds I like,
they just don't have that "in your face" seemingly quick response.

Could be a speaker phenomenon, some of them do that for me. The ol' "Blue Bulldog" also Weber's F150's from 15-20 years ago.

[galaxiex]

Could be a speaker phenomenon, some of them do that for me. The ol' "Blue Bulldog" also Weber's F150's from 15-20 years ago.

Hmmm, interesting...

I have played some of those "slow" amps thru the "fast" amp speaker cab.

Did not get the same fast response.

Leads me to believe there is something about the fast amp circuitry that makes it so...

Here's the schem of the fast amp.
Not that it will help....

Edit; FWIW the speaker is a Celestion G12H

[g1]

Here's the schem of the fast amp.
Not that it will help....

Edit; FWIW the speaker is a Celestion G12H

[ATTACH=CONFIG]50636[/ATTACH]

Does the NFB switch have an effect on the 'fast' feature of this amp?

[galaxiex]

Does the NFB switch have an effect on the 'fast' feature of this amp?

Doesn't seem to.

It certainly changes the loudness and tone, but the notes still jump out at you.

[Leo_Gnardo]

Hmmm, interesting...

I have played some of those "slow" amps thru the "fast" amp speaker cab.

Did not get the same fast response.

Leads me to believe there is something about the fast amp circuitry that makes it so...

Here's the schem of the fast amp.
Not that it will help....

I've worked on a couple of those YGL-3 lately, very similar to a Twin Reverb. Last one was a 2x12 combo. Had a rare follow up call from its owner, he was really lovin' it - in spite of very rattly 6CA7 output tubes he decided to keep in place for now. Had Celestion G12-80 speakers. Heavy rig, but a big "in your face" sound all right.

Would be interesting to A/B it with a healthy Twin sporting a pair of JBL's.