How does amp modeling work?

RyanD

Member
Not looking for specifics or any secrets as I'm not planning to model anything, nor do I have the skill. But I'm interested in the process simply out of pure curiosity.

I know some people put out free amp models like LePou that are pretty amazing given they're free. I assume a lot of work goes into it though.

It is just math? How would someone make a program that can process a guitar signal like a real amp?

Do hardware modellers like the Axe FX use actual components in the box to process the tone or is it all software based? Like could a VST with the same algorithms sound 100% like the Axe?
 
What a question! Hardware modellers use a different type of processor than desktop computers that specifically process a signal. There are also several other components in the hardware that helps reduce noise and latency. From hanging around here for a few years it seems that apart from the hardware design its pretty much all research, measurement, math, imagination and most importantly, very sharp minds
 
From what I have been led to understand the problem with going with a pure VST is that a CPU doesn't have the same basic code or instruction sets that a full blown audio DSP has. Add the overhead of the operating system and variations in system configurations and you end up having to write code that just isn't as optimized or streamlined and that all increases latency while reducing overall quality. A lose/lose situation.

As far as the "math" or code it really comes down to the person writing it. Much of the older stuff kind of approximated entire sections of a circuit with a static filter of sorts which is why a lot of times when you roll the volume back on the guitar it doesn't really react like a real amp does, i.e., clean up. It just changes in volume. Some of it's kind of fizzy and of course the further back you go in time the more inferior the technology was so they had to make do with what they had. A lot of different amps sounded very similar in gain structure and just had different EQ characteristics (at least to my ears).

The FAS stuff is based on the actual circuits where each component is actually modeled and then the circuit is constructed in the code. There are some other apps that do that now on PC (Peavey's ReValver comes to mind) and I know that there is at least one other one that is out there, but then we start talking about the quality of the virtual components. Things like how accurate the code for a capacitor from one manufacturer is vs. another one...it's really interesting. I know that Cliff has had what seems like a thousand different "ah-ha" moments when studying the finite details of components and recreating that in the virtual world.

I don't know if any other company has delved to that sub-atomic level of nuance or if they even have the desire to based on cost vs. profit margin and the simple fact that their product lifecycle is so short. The way that I look at the AxeFXII is that it is a dedicated computer for all of the math and crap that Cliff comes up with. The fact that it was built for bear from the beginning that enabled him to continue developing and further refining the sound to where it is today. There's no other amp modeling product on the market with the sheer audio processing power of the AxeFXII even a few years after it's release.....that should shed some light on how important those audio DSP's are to what he's doing.

Of course I could be completely wrong so hopefully someone much smarter can chime in. This is all just how I understand it.
 
Fun to read inputs and speculations from people. I would never have had the balls to ask this question ;) Its like asking "how high is up?"
 
Not looking for specifics or any secrets as I'm not planning to model anything, nor do I have the skill. But I'm interested in the process simply out of pure curiosity.

"Fractal’s underlying technology uses sophisticated behavioural models of electronic components to model amps and effects. The electronic schematic is the key essential component here, as that determines how the circuits are put together. It is doing realtime circuit simulation."


http://www.modernmojoguitars.com/digital-modeling-of-amps-kemper-vs-fractal/
 
The way I understand it is .... someone spends most of their youth indoors learning stuff .... they eventually build a box ..... you plug in your guitar and good shit happens.
 
Back
Top Bottom