Digital Guitar amps

[neilford]

This thought occurred to me while I was playing through Amplitube into my headphones. A digital amp models an amp. This is created essentially in software. In tube amps, there is an analog process between guitar pickups and speaker, so that construction, perhaps through microphonics of pickups or feedback, would show a difference in sound between solid or hollow body guitars. With headphones on, none of this back and forth would occur. Therefore, would it make a difference in the sound playing a solid or hollow body guitar in this manor?

 

I hope this question makes sense.

[capmaster]

This topic is rather complex due to the latencies of digital systems. Given an emulation doing its work including A/D and D/A conversions within five milliseconds, this is equivalent to circa 1.735 meters or 5 feet 8 inches air travel of sound.

 

When you use headphones, there will be no interaction no matter if the sound processing is analog or digital. Using digital systems, the latency will delay the signal that much that the acoustic attack tone will reach your ear before the headphone signal does. This is the reason why I use exclusively closed headphones for that. Perhaps I should add that I practice 100% through digital and circa 97% through headphones.

 

The reaction of digital systems driving speakers is different, too. The above mentioned delay will add to any real distance between guitar and speaker. I play 100% digital through speakers, too, but never really use feedbacks. Next to all of my guitars are solidbodies.

[neilford]

Is it safe to assume that if I have guitar A and B, playing through analog or digital amp into headphones, that the only contributor to the sound I hear is the string interacting with the magnetic coils of the pickup(s) and electronic circuit connected to pickups and little to nothing, to do, with the composition of the physical guitars?

 

This seems very nerdy, but I am trying to put my head around what I am hearing as related to equipment used to produce that.

[capmaster]

Is it safe to assume that if I have guitar A and B, playing through analog or digital amp into headphones, that the only contributor to the sound I hear is the string interacting with the magnetic coils of the pickup(s) and electronic circuit connected to pickups and little to nothing, to do, with the composition of the physical guitars?

 

...

The sound delivered at the output socket of your guitar will be the same as with using amp and speakers at moderate levels. The build of the guitar, that is design, woods and construction, contribute to tone as they always do. The speaker's sound pressure will affect strings, body and pickups, in particular single coils or some prone to microphonics, not before you increase gain and/or volume to a level inviting comb filtering and finally feedback howl.

[badbluesplayer]

I'm not 100% sure what the exact question is, but the answer is probably yes. Play through a halfway decent tube amp and see if you like it for what your trying to sound like. Certain amps have a reputation for sounding good with different kinds of music, whether they're solid state amps or tube or whatever.

 

If you want your amp to sound like, say, a Vox AC15, then playing some modelling amp with a "Vox AC15" setting isn't going to really sound completely like an AC15. But it might be close enough.

 

But if you're asking if modelling amps can create the same sound at high volume as a tube amp, no way. Just totally different.

[JayinLA]

Diital Amps are getting better, faster and more realistic all the time. With Headphones on you are still going to run into the old cliche. The sound does not decay naturally in a digital amp. For example, if you turn you digital amp up all the way, and pluck the harmonic on the 7th fret, with or without headphones on, listen to the note decay into feedack. Do the same with a good (mediocre even) tube amp, and then tell me what you hear.

 

Then you will start hearimg those natural harmonics and colors all over the spectrum.

 

What I find remarkable from a scientific standpoint is....we (supposedly) sent a man to the moon with 1960's computing. The fact that in 2016 we still cant make a digital amplifier and/or rectifier that is fast enough to correctly mimic a natural tube amp tonality is crazy when you think of the stuff we can do with computing.

 

But the things Kemper is doing, Line 6 as well with thier new Helix line is getting there. I'd say we're still a good ways off. Like an alt energy car. We have em, their just not really doing it yet.

[capmaster]

It's a matter of time and therefore the frequencies affected in application.

 

Digital is very slow on principal. It always creates a delay, if wanted or not, known as latency due to conversions and calculations.

 

A/D and D/A conversions have to take place and together take minimum 1.36 milliseconds. This equates to 0.472 meters or 1 ft 6,6 inches at the speed of sound in air, responsible for any sound-pressure reaction. It's also 408 kilomters or 254 miles at the speed of light, critical for any electromagnetic interaction between speaker coil and pickup for instance.

 

Calculating the instructions needed for emulating a complex amplifier and speaker transfer function as close as possible takes usually around 3 milliseconds, depending on EQs, distortion, output transformer and speaker of the amp set-up to be mimicked. Other digital effects added take much less time but will add into the whole thing, too.

 

All in all, the sound will be delayed about circa 1.735 meters or 5 feet 8 inches of air travel as I mentioned in an earlier post, and 1,500 kilometers or 932 miles of electromagnetic travel.

 

Thus an exclusively analog signal path is a rather different and much faster thing. Remember that analog is not far from the speed of light within electronics.

[stein]

I think one thing people miss with the subject is the "fidelity" of the amplifier, the whole chain.

 

While amps can and do color the sound, there is still the aspect of how much of the original signal is being passed, colored or not colored. THAT ability to let details and signal through is why "better" amps seem to have more touch, dynamics, harmonics, all of it.

 

Tubes also, are very good at this. All things being equal, tubes let more info pass than solid state devices and op-amps. The more switches, caps and resisters, wire, amp stages are added, the less "fidelity" and original signal is lost.

 

When one goes digital, all the same rules apply, except there is an added problem that you are completely breaking down the original signal, and reproducing it again. MUCH is lost with the current technology. It would take a very powerful computer to capture all of the origonal signal in the first place, which current musical digital tends not to have.

 

The advantage of digital, is it is easy to control and program. So simulations can be made, using what little of the original signal is taken, to "replicate" signal that isn't present in the first place. But what lacks, or what most seem to experience, is lack of the original signal this is all based on. It's a more generic representation.

[capmaster]

An amp doing anything but amplifying will severely alter the original signal. Valves/tubes are good in signal handling on principal, but transformers are critical, several hundred times more critical than capacitors. All in all solid-state is superior in any respect, but lots of players like the way valve/tube amps deteriorate the original signal. Finally there are the speakers, typically woofers only, and due to the lack of control through poweramps with lots of linear and non-linear distortions, the latter also caused by the "Power Speaker" design to increase efficiency. Lots of odd-order harmonics there as well as with push/pull output stages.

 

Pure guitar tone is obatinable with an all-analog acoustic guitar amp built to stringent HiFi specifications. I love all of my guitars most this way, including all EQs flat.

 

The DSPs used for digital audio are way faster since over twenty years than any computer of today. The very problem of digital is the principal impossibility of real-time operation.

[vangoghsear]

There is a slight bit of the back and forth you describe happening just by the action of strumming the strings on a hollowbody or semihollow that I feel is translated to the pickups. If this translation did not happen, then feedback would not occur because what difference would that resonance make if it was not picked up by the pickups to continue the feedback loop?

 

I am sure the difference is slight, but I think hollow and semi hollow sound different than solid bodies when recorded direct to digital.

 

You should post a blind test and see if anyone can tell the difference.

[stein]

An amp doing anything but amplifying will severely alter the original signal. Valves/tubes are good in signal handling on principal, but transformers are critical, several hundred times more critical than capacitors. All in all solid-state is superior in any respect, but lots of players like the way valve/tube amps deteriorate the original signal.

Transformers, very true. They are at least as important as anything, and a big part of the cost and the difference between SS and tube designs.

 

However, I disagree with SS being superior, and also the "myth" that what makes tubes "superior" is the way they distort and we like that. The truth is, a tube will GENERALLY let more pass through it than a SS device will.

 

Comparatively, a tube amplifies with more clarity than a SS because the electricity is going through a vacuum, where electricity through a SS device goes through silicone or whatever materiel it is made of. It is figuratively, and literally, more "electrically transparent"

 

Where a SS DESIGN will come in a superior is in the care of the parts and transformer. Tubes designs require more of a transformer, where SS devices could be designed and made that require less in the way of a transformer. So, when using cheaper or inferior transformers is part of the design, a cheap transformer effects tube designs more than cheap trannies in SS stuff because more is being "transformed", so to speak.

 

This is why MOST of the best "audiophile" amps are tube. The myth is that audiophiles prefer the "effects" or softening of the tube "distortions", but the truth is, they are more accurate, and most of the difference in sound between tube and SS is the result of SS adding more "distortions", or clouding the signal more. (There are great designs in both, though).

 

Where this relates to guitar amplifiers, is in using tubes, we benefit a lot more because of the "fidelity" of tubes than we give credit for. It IS true we all pretty much prefer distortion from tubes, and we also prefer our signals "altered" both in EQ and frequency response. But: BEFORE the signal is altered, there is more clarity and signal that originates from the guitar in a tube design, especially when in a SS guitar amp, more is lost in the distortion/overload effecting fidelity compared to tube designs. Especially in amps that aren't designed to preserve fidelity.

[Pin]

Cap is right insofar as it is the latency that lets digital down. When people say they can hear a difference between Kemper simulations and the real (tube) amp it is the latency they are hearing for the most part.

 

However, there is another aspect that solid state modelling can't replicate so well in my view and that is the almost random aspect of tube sag that derives from valve rectification. The valve rectification is a de rigueur option for me when considering any amp. No tube rectifier and I'm not interested.