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Comment by wintermutestwin | Hacker News Reader

It is my understanding that capture based emulation of a given sound seems like a better idea than it really is. Say you capture a given amp or pedal sound - even if you get the latency down to acceptable #s, what if you want/need to turn a knob? Tweaking knobs is an essential part of the process of dialing in a sound relative to your guitar and output environment.

Contrast with the Fractalaudio approach of modeling each component of a device. Fractal's AxeFx is the gold standard and any geek would gush over the HW and SW engineering. The best part is that the company owner keeps improving his algos and pushing out updates for free. This device costs the equivalent of a good amp head and is loaded with more amps and effects than any of the competition.

Sorry if this sounded like an ad, but I am always surprised how little airtime this amazing product gets in hacker circles.

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The AxeFX is old news when it comes to guitar modeling. The newest Kemper firmwares do a much better job, and NeuralDSP's Quad Cortex does an even better job still along with the ability to capture distortion pedals.

Modeling real gear is all fine and dandy, but what really has potential is being able to replicate circuits that aren't viable in the real world, like a tube amplifier on the edge of occilation or one run way over the rated TDP of it's tubes, situations that might provide sonic possibilities that aren't viable long term can now be stable and replicatable long term. Additionally, being able to modify a tone stack in software to provide extra flexibility is very handy.

The Quad Cortex is also slated to receive updates that will allow it to capture modulation effects, and will undoubtedly get better with time as the Kempers did.

>he newest Kemper firmwares do a much better job, and NeuralDSP's Quad Cortex does an even better job still

Umm. You and I are just random people on the internet. I have spent a lot of time trolling the places pro musicians talk about the leading devices and I have found that Fractal is very widely considered to be the best of the best as far as sound quality goes. Kemper is known to be easier to use and Neural is the new kid on the block that has bluetooth, touch screen on device and footswitches that act as knobs. For the limited # of tones you get, it is supposed to sound great. None of those features are advantageous to me at all.

>being able to replicate circuits that aren't viable in the real world

That is definitely something that Fractal does. Considering the two devices you are talking up are based on capturing actual tones from real world devices, I am unsure of your point here.

>capture modulation effects

Modulation and time based effects have been modeled to perfection in the digital realm for a long time now. See the ubiquity of Strymon, etc. Fractal has equally good algorithms and allows incredibly intricate and signal paths as it is an all-in-one device. I have four expression pedals and 10 switches that can be programmed to control any parameter I would desire with a couple clicks of a mouse. No other multi effects device brings this degree of controllable complexity.

The knobs can be included in the emulation. So that is to say, you model the unit as something having an audio input, and several controllers, such as knobs or switches. You then capture the behavior for all combinations of controller values, as part of the model. ("All combinations", for a potentiometer, might mean stepping it from 0 to 11 in increments of 1.)

The emulation ased on the model runs on a piece of hardware which has some generic controllers on it: some rotary encoders, a couple of switches and whatnot. These get assigned to the parameters of the model.

You could have a MIDI input on it, and use MIDI controllers, which would be cool. There are MIDI foot controllers that you can tilt with your foot to vary a parameter.

The different models could be assigned to MIDI program numbers. You could change the patch number with the foot controller, and vary the parameters with it also.

The foot controller might have, say, only two pedals, so you have to assign which ones you want: if the patch has five parameters, you have to fix the values of three of them and map the two important ones to the foot pedals you have. For the others, you can bend down and tweak the knobs on the unit itself.

the problem with this approach is you need to have knowledge about the circuit to make it happen, not only that, but you also need people, who can reconstruct the circuit digitally

this approach is not scalable (that's why the high cost)

the ML approach doesn't require any knowledge about the system (black-box) to produce the result

> this approach is not scalable (that's why the high cost)

It may be opposite, most of the amps follow some classic schematic (e.g. jtm, plexi, princeton) with insignificant changes, so after building digital copies of some limited number of classical amps they can add new one rather fast.

As result, fractal has about 100 high quality models already (average guitarist probably uses 5?).

> the ML approach doesn't require any knowledge

ML approach requires you to capture training data: which is different sound samples with all possible knobs positions (8 knobs per amp in average) + different types of speakers and mics, which is very huge number of variations.

> that's why the high cost

cost is driven by market, ML profiling competitors (kemper, neuraldsp) charge about the same for their devices.

sure, but can it model my amp? i doubt they will ever add it!

correct, ml requires data, but you don't need to capture every possible position to do a good prediction

only a handful would suffice and let's be honest, how many presets do you really need (average guitarist probably uses 5?)

> sure, but can it model my amp? i doubt they will ever add it!

This is very different and more narrow use-case.

Also they have tone match like forever, you build signal chain close to your amp, then add tone match block, which applies ML to voice your digital signal chain close to recording.

Here is example: https://www.youtube.com/watch?v=hZnZ1nJODLo

Also in this example he didn't profile actual amp, but actual AC/DC recording, and result is very good I think.

> how many presets do you really need (average guitarist probably uses 5?)

But how you find this preset for your signal chain (guitar + speakers)? That's one of big points of frustration with kemper: one needs to go through hundreds profiles (not necessary good quality) to find one which will sound good with his signal chain.

With fractal: you take some basic preset, and change knobs to your tastes and goal as with real amp.

>sure, but can it model my amp?

I believe you can already create your own impulse responses (from your personal amps).

This is exactly what Fractal has achieved. They took actual amps and modeled the actual circuits. Basically, this work was done for a massive number of amps by one dude. And he sells this device for $2k - which is ~ the cost of a single good tube amp head.

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