Fractal Audio Systems AM4 - Amp Modeler

AlbertA said:
Latency measurements

Using firmware v1.02 public beta 2

TL;DR
  • Empty chain => 1.33ms
  • Drive only
    • Esoteric RCB => 1.98ms
    • Two Esoteric RCBs in series => 2.63ms
  • Amp only (seems to depends on the amp)
    • Texas Lonestar Clean => 1.92ms
    • Plexi 100W Normal => 2.11ms
    • Deluxe Verb Normal => 1.88ms
  • Cab with unit impulse user IR => no extra latency as expected
  • Drive (Esoteric RCB) -> Amp (Texas Lonestar Clean) => 2.58ms
  • Drive (Esoteric RCB) -> Drive (Esoteric RCB) -> Amp (Texas Lonestar Clean) => 3.22ms

Legend
  • Yellow => AM4 Input
  • Purple => AM4 Out L

Empty chain => 1.33ms
View attachment 56654

Drive Only (Esoteric RCB) => 1.98ms
View attachment 56655

Drive (Esoteric RCB) -> Drive (Esoteric RCB) => 2.63ms
View attachment 56656


Amp (Texas Lonestar Clean) => 1.92ms
View attachment 56659

Amp (Plexi 100W Normal) => 2.11ms
View attachment 56658

Amp (Deluxe Verb Normal) => 1.88ms

View attachment 56657


Drive (Esoteric RCB) -> Amp (Texas Lonestar Clean) => 2.58ms
View attachment 56660

Drive (Esoteric RCB) -> Drive (Esoteric RCB) -> Amp (Texas Lonestar Clean) => 3.22ms
View attachment 56661
Click to expand...
Amp only is 2 ms. Linear systems have "latency". We call it "phase response". If you pass a sine wave through a filter it will have some amount of delay that I suppose you could call "latency" but it's not latency in the traditional sense.

If you pass a sine wave through an analog tone stack the output will be delayed relative to the input. How much delay depends on the transfer function of the tone stack and the frequency of the sine wave.

This is one of the problems with this latest obsession with latency. The vast majority of people don't understand enough about electronics and signal theory to even measure it correctly. All but a few don't even understand what causes latency and the trade-offs involved in minimizing it.
 
Should probably also clarify, that phase shifting is near enough impossible to avoid in circuits where you want an analog response - by that I mean a causal frequency-selective analog circuit.

There are filters that preserve phase response. But they are not appropriate for a heck of a lot of DSP processing. Most DSP audio processing aims to emulate causal analog behavior, where low latency is usually required, pre-ringing is often undesirable, and typically minimum-phase behavior is perceptually more natural.

So filter latency is necessary, and latency is not always an inherently bad thing. What people are often calling latency, is actually that the algorithm(s) in question are stateful; meaning they have memory, and they can track measurements and data over time. For this, you need buffers; which very quickly leads you to an inherent latency in order to collect and analyse enough data on the fly.

True zero-latency processing implies no memory and no frequency selectivity, which is rarely what anyone actually wants.

The bottom line is - as long as it is perceived as real-time, then the eggs are goosey golden ratio happy fun fun time.
 
Orvillain said:
Should probably also clarify, that phase shifting is near enough impossible to avoid in circuits where you want an analog response - by that I mean a causal frequency-selective analog circuit.

There are filters that preserve phase response. But they are not appropriate for a heck of a lot of DSP processing. Most DSP audio processing aims to emulate causal analog behavior, where low latency is usually required, pre-ringing is often undesirable, and typically minimum-phase behavior is perceptually more natural.

So filter latency is necessary, and latency is not always an inherently bad thing. What people are often calling latency, is actually that the algorithm(s) in question are stateful; meaning they have memory, and they can track measurements and data over time. For this, you need buffers; which very quickly leads you to an inherent latency in order to collect and analyse enough data on the fly.

True zero-latency processing implies no memory and no frequency selectivity, which is rarely what anyone actually wants.

The bottom line is - as long as it is perceived as real-time, then the eggs are goosey golden ratio happy fun fun time.
Click to expand...

The only thing I understand from this is eggs, the rest is way above my head but it's fun to read and learn lol.
 
Ed DeGenaro said:
This is getting silly I’m must be getting old.
Either the modeling is so much better than the one in the Ax2 or Ax8.

I mean I didn’t care for my big MkV and dig the lil one. But the Patrucchi 2c+ is just maddening cool.

Hmmm. I’m gonna live with this for a bit longer but I might just ditch my UA pedals and get an Axe3 or maybe wait for next gen.

Oh sometimes GAS feels just right.
Click to expand...

Man, there’s nearly a decade of updates since the 2 or the AX8! I got my III right before Cygnus first came out and that was pretty damn big as that’s the one that allowed me to stop using the multiband comp and additional EQ to get the amps sounding how I wanted them to, now it’s just amp and cab blocks and the only additional EQ is getting things to sit in a mix, in Logic.

I love all the Mesa’s in there, while I’ve never played a real IIC+, it’s still my favorite amp in there next to the Mark IV.
 
Steve Harvey Judge GIF by ABC Network
 
DrewJD82 said:
Man, there’s nearly a decade of updates since the 2 or the AX8! I got my III right before Cygnus first came out and that was pretty damn big as that’s the one that allowed me to stop using the multiband comp and additional EQ to get the amps sounding how I wanted them to, now it’s just amp and cab blocks and the only additional EQ is getting things to sit in a mix, in Logic.

I love all the Mesa’s in there, while I’ve never played a real IIC+, it’s still my favorite amp in there next to the Mark IV.
Click to expand...
As I said in a previous post, I’m a dumbass.
 
Mine was supposed to arrive between 10:50am and 1:50pm today. It showed up at 9:40am this morning which tells me the AM4 has a pretty good dollop of negative latency. Like, more than an hour's worth.

This is my first foray into the Fractal-verse and it's very slow going. I did manage to figure out how to play a few of the factory presets/scenes. The hardest part was figuring out how to update to the newest firmware. The editor must only look for "full releases" because it kept telling me I was up to date although I was running 1.01.

I suppose I had some unrealistic expectations. I thought the things I checked out sounded good but after a couple of weeks of daily visits with Helix Stadium I didn't feel like anything I tried on the AM4 stood out as decidedly superior to what I was used too. This evening I might try building a patch from scratch to see how readily I can get something going that I like.

Even though it's a bit like tackling something in a foreign language so far, I don't think it'll be too unwieldy to use once I get used to it, and will likely be a outstanding solution for my situation (a small rig to use while I stay in a tiny cabin over the summer). I just want to get around a dozen good sounds that cover my usual fare (so maybe 3 presets with 4 scenes each) that I can navigate between using my feet without it being a headache. I've been using a POD Express in that role and while I got by with it, I think I'll be more satisfied with the AM4.
 
Anyone know off the top of their head where SIC is adjusted. I was looking for it in the amp block last night and came up empty. Perhaps it’s tucked in expert mode somewhere?
 
EOengineer said:
Anyone know off the top of their head where SIC is adjusted. I was looking for it in the amp block last night and came up empty. Perhaps it’s tucked in expert mode somewhere?
Click to expand...
Yep, expert mode in the amp block (page right a few times… should be after the output compressor page but before the speaker cabs page)
 
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