About amp "immediacy"

[g1]

'immediate-sounding' versus ...whatever the opposite is?

Tardy. As in "I prefer an amplifier more on the tardy side but with a pinch more than medium-rare 'torty ".
One of the previous posters submissions seemed to be going for the record of non-quantifiable adjectives with respect to sound, so I doubt I am any where close but at least I'm trying.

[DrGonz78]

You get snow in Scottsdale?

Of course!! Snow Cones!!

[netfences]

Will this be a self contained guitar including a pre amplifier intended for guitar exclusively? Do you plan to used processed or digitized modules and use this project as a power amplifier? Is this even for a guitar? Are you going to build this amp OR have you ever built an amplifier OR is this just casual rumination on the matter?

Some answers:
Limited experience building amps (3 kits of varying sophistication and 1 built from schematic (successful), adequate science background and equipment (scope, a few 5.5 digit meters, sig gen, etc.). Ten years as a sound engineer and twenty as a mostly amateur player. No FX on amp except for maybe tone and presence controls. Yes, I want to really try and build a good combo instrument amp that takes pedals well. Maybe having buffered and unbuffered inputs.

That is not what happened at all. There was nothing wrong with the GNF used in nearly all amplifiers. The TIM people pointed out a potential problem as if were an actual common problem; it never was in all audio power amplifiers. GNF leads to the lowest distortion and should be used when you want to use an amplifier in the linear range.

I'm sorry, I've been around too many amps that measure great and sound like a hospital death bed. I've been convinced that GNF takes more than it gives in most circuits. Perhaps my opinion is in the minority but there are only a few HiFi amps with GNF that I've been able to tolerate over time. GNF is like bitters in my drink, a little can sort it out but too heavy a hand spoils it. If we're going to do signal correction and time alignment, I prefer it to be early in the circuit. When you understand electrical circuit feedback from an advanced physics perspective, you begin to understand its nature as an iterative (ie: damping) process. A little on the output is tolerable but it's too easy to go overboard.

[Malcolm Irving]

… . When you understand electrical circuit feedback from an advanced physics perspective, you begin to understand its nature as an iterative (ie: damping) process. ....

Sorry to disagree, but electrical circuit feedback does not require 'an advanced physics perspective' to be understood, just electric circuit theory and some control theory. It is not 'iterative' but is simultaneous, provided you are prepared to ignore the pure time delay of about a nanosecond in the feedback loop wiring. Also, it is not a 'damping process'.

EDIT: the best way to understand feedback is to read a suitable engineering textbook, not to rely on the Web.

[Mike Sulzer]

I guess they were able to get away with it because it was designed to amplify music not 20kHz sine waves. With a music signal the lower frequencies would be hitting the rails well before the high frequencies so it wouldn't need to be able to produce a +/-15V 20kHz sine wave.

True, it would be rare for it to actually hard slew limit, that is, hard current saturation in the first stage, but distortion can be expected to rise before the limit is hit. Amplifiers with a lot of GNF must designed properly, and of course, the 741 op amp was not designed for audio.

[Mike Sulzer]

I'm sorry, I've been around too many amps that measure great and sound like a hospital death bed. I've been convinced that GNF takes more than it gives in most circuits. Perhaps my opinion is in the minority but there are only a few HiFi amps with GNF that I've been able to tolerate over time. GNF is like bitters in my drink, a little can sort it out but too heavy a hand spoils it. If we're going to do signal correction and time alignment, I prefer it to be early in the circuit. When you understand electrical circuit feedback from an advanced physics perspective, you begin to understand its nature as an iterative (ie: damping) process. A little on the output is tolerable but it's too easy to go overboard.

Are you listening to these amplifiers in their linear range, or are you clipping on peaks? GNF is a disaster if you clip, but there is no reason to do so since powerful SS amplifiers are readily available.

[yldouright]

@Malcolm Irving
I think what @netfences is referring to is the erratic nature of an electrical signal through a conduit. Most people are under the mistaken impression that electricity through a conduit is an organized system running at light speed, it isn't, it's a chaotic series of starts and stops running at ~35mph. Feedback is a method used to control the voltage variations that are a natural consequence of electrons moving through a wire. The problem with feedback is that it creates momentum of the signal which result in residual signal aberrations. Lots of these are incorrectly blamed on the distortion in the drivers when the feedback is on the outputs. That would explain his preference for NGFB amps. I've never had the opportunity to hear such an amp but I know a few fans of these. I'm sure he'll correct me if I didn't get this quite right but I think I'm close to what he meant by his physics comment. I've said this before in relation to another less popular topic but you have to be willing to unlearn some stuff to get a better perspective of reality.

[Mike Sulzer]

@Malcolm Irving
I think what @netfences is referring to is the erratic nature of an electrical signal through a conduit. Most people are under the mistaken impression that electricity through a conduit is an organized system running at light speed, it isn't, it's a chaotic series of starts and stops running at 35mph. Feedback is a method used to control the voltage variations that are a natural consequence of electrons moving through a wire. The problem with feedback is that it creates momentum of the signal which result in residual signal aberrations. Lots of these are incorrectly blamed on the distortion in the drivers when the feedback is on the outputs. That would explain his preference for NGFB amps. I've never had the opportunity to hear such an amp but I know a few fans of these. I'm sure he'll correct me if I didn't get this quite right but I think I'm close to what he meant by his physics comment. I've said this before in relation to another less poplular topic but you have to be willing to unlearn some stuff to get a better perspective of reality.

You are confusing the drift of electrons along the conductive path, which is slow, with the flow of the current, which carries the signal information and is fast (near light speed). The consequence of individual electrons as charge carriers is noise, very low in level and properly treated as additive to the signal.

[Chuck H]

Yes, I want to really try and build a good combo instrument amp that takes pedals well. Maybe having buffered and unbuffered inputs.

The desire for buffered and unbuffered inputs implies "to me" that you may want to use this with plain ol stomp boxes but sometimes use digital preamps that might more commonly be for direct patching or digital recording media input. But I can only guess. And to my reasoning that's still a pretty tall order because anything designed for direct input would likely have the patch EQ'd for a reference, reproduction or sound reinforcement amplifier. In this regard I think it's the speakers that are the biggest issue because patched samples would already have cabinet simulation designed in. Going through anything resembling a normal guitar speaker cabinet would double the effect giving unpleasant results (subjectively). There may be some digital options that allow you to bypass any cabinet simulation. I think I saw a *outube recently that kind of pissed me off because it sounded pretty damn good and it offered A LOT of flexibility WRT what you might plug it into. Just something to keep in mind.

"takes pedals well" is a tricky one. It can imply that the amp is capable of handling pedals with grace OR that it responds to them in desirable ways. Using well known vintage examples for the purpose of familiarity I'd qualify Fender BF type amps as being a little pedal touchy. They don't seem to like being boosted at the input (subjectively) While Marshall type amps respond more favorably to being pushed at the input. Of course this generates distortions withing the amplifier itself. So that's not a clean amp anymore. As to "instrument level" effects like dirt boxes that are NOT turned up for boosting, chorus, delay, most digital modules, etc. I don't know what sort of amp wouldn't take them well. So if you do indeed plan to keep the amp part of the signal chain clean I don't think you need to worry about this.

Not sure if you need to play jazz, metal, country and blues through the same rig, but the cabinet design is going to be a critical issue. A 1x12 combo is fine for a lot of country, rock, blues, indie, etc. But you're not going to thunder any 7 string metal through it. If you want a bigger sound in a do-all cabinet you might consider a 2x12 sealed cabinet and make the amp a head. Or if you want more portability maybe one of those detuned EV loaded single 12 cabinets. They really do make a remarkable noise. That's also a sealed design so you're still stuck with the amplifier being a head design. Just so's to not leave out the obvious... If you're playing mostly metal get a 4x12 cabinet and if you play mostly blues then just use a 1x12 open back combo amp design.

Maybe the biggest part of why tube amps are preferred by so many players is the way they deliver the power. Because of the high voltage supplies and the actual nature of how tubes respond to signals. Simple SS designs tend to sound flat and bland. No bounce or response interaction to the player. Even when played close to the clean headroom limit tubes compress some due to voltage sagging with current. This is mostly a power amp phenomenon but because the preamp voltages are typically on the same rail there is some affect in the preamp too. When tubes do distort they do so less sharply initially than transistors do. This is a very audible difference. There is a lot less difference between them when clipping hard, but it's the onset of distortion where tubes get their reputation for being more "musical". As a tube begins to clip the waveform is sort of elastic. Like you're pressing a clay peak down. Whereas transistors tend to clip more like the signal is rising into a slicer. There are other differences too, like how either device responds to signals relative to shifting gain and interelectrode capacitance, but I think it's mostly the reactiveness of the power supplies used for tube circuits and their smooth transition into distortions that are most noteworthy. So... Tubes get their good rep because they transition smoothly into distortion and the power supplies sag voltage at their higher current levels. I don't get the impression you plan to have your amp clipping or stressing it's headroom limits. So there's no reason I can see for you to hassle with the expensive, hot, fragile tubes and their heavy transformers. Sound right?

And I want to reiterate, and am open to correction if anyone thinks otherwise, that I don't believe you need to trouble too much about distortion components and their balance because their contribution in this case is going to be such a small addition to the overall sound. Assuming there will be signal processing and the power amp is intended to be transparent your distortion figures would have to be grossly bad to have any noticeable influence on the overall tone. Remember that this will still be acting as an instrument amplifier and not a stringently reproduction amplifier. To put it another way, why fuss about 2% harmonic distortion when the pedal, patch, pod or pad generated tone going into the input will likely be several times higher than that. Even the distortions caused by guitar speakers and different room acoustics when you set up in different places will likely be more noticeable. Save the high end audio ideology for the play back amp you'll listen to your recorded track on.

[nosaj]

It sounds like a pipe dream. Limited experience building amps. Its most likely gonna have a PCB involved, which he'll have to create. Might be better to go play some amps and find one you really like then work with that.
I keep thinking audiophile guitar player on atone quest.
I have a friend like that, his perfection gets in the way of progress.
nosaj

[Chuck H]

It sounds like a pipe dream. Limited experience building amps. Its most likely gonna have a PCB involved, which he'll have to create. Might be better to go play some amps and find one you really like then work with that.
I keep thinking audiophile guitar player on atone quest.
I have a friend like that, his perfection gets in the way of progress.
nosaj

Yep, I have a friend like that too. Can't get to an end game or enjoy anything. Too distracted by being critical. Great voice, always has a problem with the mic or the patch and has to stop in the middle of a practice song to make adjustments. Again, always letting dissatisfaction distract him from doing his personal best in any of his talents.

Glasshoppa, go up on mountain and find focus. Try to snatch pebble... from my pants.

[yldouright]

You are confusing the drift of electrons along the conductive path, which is slow, with the flow of the current, which carries the signal information and is fast (near light speed). The consequence of individual electrons as charge carriers is noise, very low in level and properly treated as additive to the signal.

I'm pretty sure I'm going to get some howls for the following blasphemy but here goes:

Measure an operating amp circuit in live time that would normally require feedback, without the feedback. Have a switch that introduces feedback to the circuit and watch the meters. As expected, the voltage readings are erratic without feedback. Now switch in the feedback. If the signal was truly light speed, you would see an instantaneous settling of the voltage but it takes a second or so depending on the signal path. We have been taught (conditioned) to believe its the meter taking the time but even analog meters exhibit the same behavior. More fuel for the fire? The time is takes to settle the voltage is repeatable and matches the estimated time it would take at 35mph! This is just one of the many examples we witness in real life that we dismiss without further thought about it. Is it possible that signals through a conduit are not really traveling at near light speed? I'm going to introduce one more blasphemy, voltage potential is commuted at nearly light speed to all points connected to the source but current is limited to 35mph through a wire. Put another way, voltage is NOT a signal. This is part of the electrical science that some applied physics is experimenting with. That whole body of physics has to deal with high voltage fields and frequencies and how they relate to dimensional phasing. I hinted at some of these in a prior post when I referred to the relative nature of mass and speed.

[uneumann]

@Malcolm Irving
I think what @netfences is referring to is the erratic nature of an electrical signal through a conduit. Most people are under the mistaken impression that electricity through a conduit is an organized system running at light speed, it isn't, it's a chaotic series of starts and stops running at ~35mph. Feedback is a method used to control the voltage variations that are a natural consequence of electrons moving through a wire. The problem with feedback is that it creates momentum of the signal which result in residual signal aberrations. Lots of these are incorrectly blamed on the distortion in the drivers when the feedback is on the outputs. That would explain his preference for NGFB amps. I've never had the opportunity to hear such an amp but I know a few fans of these. I'm sure he'll correct me if I didn't get this quite right but I think I'm close to what he meant by his physics comment. I've said this before in relation to another less popular topic but you have to be willing to unlearn some stuff to get a better perspective of reality.

OK - so now you claim that some sort of quantum electronics influences the audio amp circuit in my Fender Bassman ... this is really getting far out there and becoming a laughable discussion. We crossed a line here and I suspect there is no return. Pls refer us to a credible source about this erratic momentum and 35 mph phenomena. Until you can do that, I'm just left with no alternative but to treat this as "fake" theory that you're making up.

[Dave H]

Electrons are sneaky. If you put one in one end of a wire it pops out the other end as if it had travelled at 0.6 times the speed of light but it hasn't because it's a different electron and they all look the same so you can't tell the difference. The first electron is still lazily drifting along and will arrive in its own good time.

[Enzo]

And that is the difference between electrons and current.