Input Voltage/Gain Calibration for Guitar Plugins

[aciddose]

In AmpliTube, the setting of the input gain on your interface has to be made in the same way you would properly set the gain of any preamp in the world (mic or instrument):

Set the input gain so that the acquired signal on the digital recorder or DAW is as close as possible to 0 dBFS without ever clipping. This ensures the best possible dynamic range and SNR.

This is the same thing I've been repeating.

If after that point the signal at 0 dB is "too hot" you can decrease the level ITB and maintain your optimal S/N ratio.

To anyone who doesn't understand: this isn't rocket science.

[aciddose]

Also, when driven under such circunstances, I bet that the Modelling isn't done focusing on a Impossibly Hot Guitar Signal coming in, as a Real Amp would never be profiled that way, so if Amplitube does that, It's not reacting like a real Amp would. It's going outside the envelope of the Simulation, and the sound you get there may sound good, but it's Amplitube's Sound, not the Amp's

Why does that even matter? The programmers likely were intelligent enough to operate one or two brain cells "ping! ping!" and optimized the S/N ratio they were getting before they worried about anything else.

From that point they were able to decrease the level ITB to get the result they wanted. (Why so much opposition to this most simple possible solution?)

Or maybe they enjoyed running the amps "hot" and wanted to accurately model that.

Or maybe they wanted to model plugging a typical guitar into a typical amp and setting it up with the input gain "hot", then passively decreasing the level using the volume pot on the guitar regardless of its effects on S/N ratio because the software would beat the pants off the actual amp anyway. (Software = zero noise.)

I agree with you regarding the "probably not running insanely hot" concept but I'm not certain if you're arguing against running your inputs that hot. If so I absolutely, vehemently disagree. The input should absolutely be as hot as possible at the interface to provide ideal S/N ratio.

I'm sure you could give them advice though on how to model amps or release a successful plug-in due to your expertise. In fact you should start with your own plug-in and put them right out of business.

[Ilya-v]

The input should absolutely be as hot as possible at the interface to provide ideal S/N ratio.

This effectively making a vintage telecaster as hot as a humbacking metal guitar, and that is the true nonsense.
It's exactly what I'm trying to overcome by accurate calibration, understand?
Please stop repeating "play hard, adjust gain, don't clip" in this thread, move on.

I understand what he is trying to say.
That's not how a real Fender Twin would sound in real life,

Exactly!
Boosting the guitar randomly is the very reason I started this thread and want to prevent by accurate calibration.
"play hard, adjust gain, don't clip" completely contradicts the reason I started this thread, it baffles me why aciddose keeps replying in this thread over and over and over again with the very same reason I'm trying to prevent.

The emulated tubes (like 12ax7 etc.) have virtual voltage at their grid input biased by virtual resistors and capacitors like in a real amp.
There is a value of dbFS at the input in the DAW that translated to 1vAC Peak to the simulated 12ax7 tube, usually for most amp sims it's 0dbFS.

Amplitube "realistic" claims mean absolutely nothing if their amp simulation gain stages are completely random and/or if the user applies the "play hard, adjust gain, don't clip" procedure.
If they actually use schematic/component based simulation there IS a dbFS value that the first virtual 12ax7 sees as 1vAC, and I want to know what it is.

[Ilya-v]

Delete duplicate post, KVR is slowish today.

[Burillo]

yeah, right. instead of maintaining optimal signal quality and adjusting input gain in the amp itself to taste, you basically increase noise for no reason, and do the same gain adjustment you would've done anyway, just from a different starting level. great idea!

"play hard, adjust gain, don't clip" completely contradicts the reason I started this thread, it baffles me why aciddose keeps replying in this thread over and over and over again with the very same reason I'm trying to prevent.

the reason he "keeps replying" is because you keep making the same mistake. if you bring down your levels, you increase noise. simple as that. if you then increase your levels by whatever amount you've calculated, you're bringing noise up by the same amount.

in addition, you keep making assumptions and assertions about other modeling software when you have no way of knowing "how it's done". this has also been repeatedly pointed out to you, both by acid dose and by IK representative (for some reason you have a particular vendetta against Amplitube), and yet you keep insisting that everyone else is incorrect and you're the unsung genius, while having nothing more than assertions to back up your claims.

[Ilya-v]

adjust input gain in the amp itself to taste...
...you basically increase noise for no reason,

"To taste" comes after proper calibration, this is the reason for this thread, it's in the topic title.
Turning the gain knob in the amp sim will increase the noise in equal amount as boosting volume before the plugin.
If the amp is too gainy after proper calibration you can lower the gain control in the amp sim and the noise level will be the same as in the random "to taste" way.


It seems people don't understand the reason I started this thread.
This thread is about preserving the voltage output of your guitars so they react with the simulated amp like a real amp would.
The Axe-Fx has an Input gain control to maximize SNR, when you raise the input gain axe-fx internally lowers the input volume to compensate so that 1V at input always stays the same internally for accurate amp simulation.
Using an Audio Interface and Amp Sim plugin in your DAW does not have internal compensation like the Axe-Fx has that's why we use a reference 1vAC Peak and do it manually.

We want to preserve that behavior with "realistic" DAW plugins and audio interfaces and NOT use random or "to taste" input gain adjustment.

if you then increase your levels by whatever amount you've calculated, you're bringing noise up by the same amount.

Correct.
But aciddose assumes that raising the input gain on the audio interface is quieter that raising the gain in DAW, which is not true unless the audio interface has some unique anti-noise circuitry.

in addition, you keep making assumptions and assertions about other modeling software when you have no way of knowing "how it's done".

Actually at the bottom of page 4 of this thread there are direct replies from very respectable and accurate amp simulation authors about the 1vAC Peak = 0dbFS in their plugins, this is also true for most freeware amp sim plugins like Ignite Amps, LePou, etc.
I have nothing against Amplitube, in fact, this is one of my favorite amp sim plugins.
Amplitube claims "realistic" simulation, yet at the same time encourages a procedure of input gain adjustment that makes all guitars equally as hot.

Can't you really see the flaw in adjusting the input gain to make all guitars equally as hot?

[Burillo]

Correct.
But aciddose assumes that raising the input gain on the audio interface is quieter that raising the gain in DAW, which is not true unless the audio interface has some unique anti-noise circuitry.

no it doesn't. rather it points to the fact that you can't get away from thermal noise no matter how hard you try, and lower input gains bring you closer to that minimum noise amount that you're going to get. you're not "adding noise", but you're raising the noise floor.

Actually at the bottom of page 4 of this thread there are direct replies from very respectable and accurate amp simulation authors about the 1vAC Peak = 0dbFS in their plugins

...which only holds true for those plugins.

Amplitube claims "realistic" simulation, yet at the same time encourages a procedure of input gain adjustment that makes all guitars equally as hot.

so? if you don't like your guitar sounding that hot, you lower the input level, and voila - it's no longer as hot. that's what the input gain knob is for!

Can't you really see the flaw in adjusting the input gain to make all guitars equally as hot?

no, i do not see the flaw, because i don't care whether it's "realistic" (according to some made up standard of "realistic"), i care if it sounds good. and in my world, less noise is better than minutia of input gain adjustment.

[Ilya-v]

Can't you really see the flaw in adjusting the input gain to make all guitars equally as hot?

no, i do not see the flaw, because i don't care whether it's "realistic" (according to some made up standard of "realistic"), i care if it sounds good. and in my world, less noise is better than minutia of input gain adjustment.

Okay, then this thread is not for you.

[Burillo]

the reason i (and probably aciddose) am replying is not because "it's for me", but because it's bad advice and i'm cautioning everyone against doing this, as that is a surefire way to increase noise.

[Ilya-v]

I repeat, adding gain at the analog stage before the ADC adds the same amount of noise as boosting in software after the ADC if not more.
The ADC process itself has much lower self generated noise than the op-amp/fet before it.
It's easy to test and I already explained how.

I'm starting to get tired of repeating myself and the purpose of this thread.
No, it's not about maximizing SNR.
It's about keeping the difference between guitars and feeding the amp sim the correct/realistic volume of a particular guitar.

[Burillo]

I repeat, adding gain at the analog stage before the ADC adds the same amount of noise as boosting in software after the ADC if not more.
The ADC process itself has much lower self generated noise than the op-amp/fet before it.

that's the point. when your source is quieter, you're closer to that "self-generated noise", thereby effectively increasing noise.

I'm starting to get tired of repeating myself and the purpose of this thread.

it doesn't matter what "the purpose of this thread" is when you're giving out wrong information.

No, it's not about maximizing SNR.

yet, your initial post indicates that it is, in part, about that. here, let me quote it for you:

1. Set you audio interface to High-Z and keep the gain pot on the audio interface at minimum, this maximizes headroom and minimizes noise floor.

this is demonstrably not the case, as quieter signals are closer to the noise floor.

It's about keeping the difference between guitars and feeding the amp sim the correct/realistic volume of a particular guitar.

the "correct" volume is one that has the least amount of distortion (i.e. not too loud) and noise (i.e. not too quiet). anything past that you can adjust with a digital gain. that's what DAC's are for, and that's how they work.

tell me, what is preventing you from doing the same process on a well-recorded sound? i.e. calculate the difference between current gain and unity gain and add that as your "pre-amp sim boost", rather than doing it the silly way (i.e. with minimum gain)?

for example, if your "calibration" method needs 10dB of boost till you hit -0.1dBFS, but your "ideal" level is 6dB higher - it's pretty easy to figure out that you now need only 4dB of pre-ampsim boost, not 10dB. that way, you get best of both worlds - you get "calibrated" input (whatever that means) and are happily masturbating to voltages and "realism", and you get the lowest SNR and distortion you can get. as aciddose said, it's not rocket science!

[michaeltn86]

Hi Ilya-v, I think ur efforts are remarkable and u did a lot a research and shared ur findings, and that's great.

but I fear that ur claims are not healthy for the community nor for the guitar players.

It's very easy to check if what u claim is healthy or not.

try to set the level the peak levels or average level (based on ur research) of ur guitar to 0 dbfs. then route an output to ur amp.

u are more likely to blow the amp than to get a good sound from the "real deal".

if u are going to experiment on that, please start with at least -30 dbfs and level it up until ur amp behaves the same way than plugin it directly.

In my experience and findings, I found that -30dbs to -12 dbfs peak level brigs the most out of amp sims.

the biggest problem is that the developers don't state "recommended start levels" in their manuals. every pick up and guitar have different levels, but they should at least explain and make videos about it.

I think the will to share knowledge that u are showing is remarkable. but please try it for urself in a "real" amp to see if that is really true or not before making big claims.

I'm no PRO, and would be very happy to be corrected and be enlighted.

I do think it's healthy to discuss, ask for help, and rethink the more knowledge u have.

For instance, more than ten years ago, I used to put my pick ups very high and close to the strings because the "gain was much higher". In the digital era of amp sims, my pick ups are so low that's aesthetically unpleasing.

cheers

[michaeltn86]

did quick examples for clean guitars.

my guitar is a heavily modified Squier classic vibe
3 guitars example
https://www.dropbox.com/s/msnnuf57b11lm ... s.mp3?dl=0
1 guitar example
https://www.dropbox.com/s/t2vvc7sexu6zc ... p.mp3?dl=0
logic project
https://www.dropbox.com/sh/1et5vybi5ifr ... 3pxua?dl=0

my guitar skills are average at best. I didn't edit (and u can hear some clippings in the examples depending on where u play). but if u have the time check the input levels.

I didn't tweak anything, just used presets and what the plugins opened with it. the project is to easily see the input levels recorded.

hope my playing doesn't hurt ur ears ;p

[Ilya-v]

Michael you seem to completely ignore or didn't understand the calibration procedure.
Did you understand the reason why I'm trying to calibrate to external 1vAC Peak?

Burillo:
Yes you are right about optimizing the gain control on the audio interface and then adding more in software to reach 0dbFS.
But that means you have to calibrate each and every time you change a guitar and that is not ideal.
My Focusrite interface has 8dBu headroom and my EMG guitar clips the input with hard playig, these two reasons are why I suggest keeping the gain at minimum.

[Burillo]

Yes you are right about optimizing the gain control on the audio interface and then adding more in software to reach 0dbFS.
But that means you have to calibrate each and every time you change a guitar and that is not ideal.

that's the point. you have to re-calibrate your input every time you plug in a different source, be it a different guitar or a different mic or a different this or a different that. that's what you do to minimize noise and distortion. that's what everybody does, and that's what you're supposed to do. it's called gain-staging. if you don't want to do that, buy an interface with more ports (like i did) and leave them on ideal levels all the time.

My Focusrite interface has 8dBu headroom and my EMG guitar clips the input with hard playig, these two reasons are why I suggest keeping the gain at minimum.

yes but those are applicable to you, because on your guitar with EMG pickups, minimum gain is minimum noise. it may not necessarily be the case for others (or guitars with passive pickups), which is why you have to adjust the input gain to be ideal first, and then do your voodoo gain adjustments to match the "virtual" reference levels.