ICONS accurate input calibration

Is Gibson 498T an edge case? It can absolutely produce more than 14 dBu.
My 490T is one of my loudest pickups - I get a stronger signal from that than my of my Seymour Duncan’s.

EMG’s clip internally before you get to 12dBu. Most 9V pedals will also clip before then. I’ve been recording DI’s with different bands for decades and I can’t recall anything coming in louder than my own pickups.

Well, digital clipping is always bad, I don’t think there’s any context where it’s beneficial. And we’re talking about interface specs, exactly where this digital clipping occurs.
I’m not saying it’s beneficial, but often it’s benign. Many pedals will clip with these stronger peaks, and as soon as that signal hits the 1st gain stage of an amp, the peaks is getting shaved off. Often clipping is quite transparent for very short peaks. I wouldn’t recommend clipping as a matter of course but it’s not always going to be your biggest problem to look out for.
Guitars are dead quiet when properly shielded. Interfaces produce noise which, when going through a higher gain amp/ampsim, gets boosted with compression and you can only defeat it with a gate which in turn kills the attack unless you use some lookahead stuff.
You’ll do well to get much more than 100dB of dynamic range from a guitar. You just need to mask the interface noise below your background noise. Hasn’t been an issue for a long time, modern interfaces are generally very low noise.

I thought you solved your headroom and noise issues? There’s plenty of gear out there that can accommodate you if either is an issue. It’s just about choosing the right gear and moving on.
 
You’ll do well to get much more than 100dB of dynamic range from a guitar. You just need to mask the interface noise below your background noise. Hasn’t been an issue for a long time, modern interfaces are generally very low noise.
I did test that hypothesis, it's wrong. Interface noise with all the amp gain and compression is very loud and unpleasant, and the difference between interfaces is huge, it's very easy to check. Guitar by itself doesn't produce noise. And if it does, it's all on top of interface noise. Most interfaces, modern or not, are very bad.

I thought you solved your headroom and noise issues?
I use the FM3 as the interface right now and don't record these days, so yes, you may say I solved it. :)

But it's not so much about myself, rather to bring the point that low noise interface matters a lot when you use plugins.
 
I did test that hypothesis, it's wrong. Interface noise with all the amp gain and compression is very loud and unpleasant, and the difference between interfaces is huge, it's very easy to check. Guitar by itself doesn't produce noise. And if it does, it's all on top of interface noise. Most interfaces, modern or not, are very bad.


I use the FM3 as the interface right now and don't record these days, so yes, you may say I solved it. :)

But it's not so much about myself, rather to bring the point that low noise interface matters a lot when you use plugins.
hmm.

FM-3 specs are good but many interfaces are equivalent or better noise wise.

A/D CONVERSION

Bit Depth: 24 bits
Sample Rate: 48 kHz
Dynamic Range: 114 dB
Frequency Response: 20 – 20kHz, -0.01 to +0.01 dB
Crosstalk: 110dB (typ.) Interchannel Isolation



For instance SSL’s consumer grade stuff is 116dB dynamic range, 15dBu headroom. A lot of consumer grade stuff is in that ballpark. I can’t say I agree that it’s going to present an issue to most people.

https://solidstatelogic.com/product...LeQ-ro0KLrHFzKSy2rGAJu24zICgB0ohoCtM0QAvD_BwE

Same goes for MOTU:

https://motu.com/en-us/products/m-series/m4/specs/
 
FM-3 specs are good but many interfaces are equivalent or better noise wise.
Some do, most don’t. I never said Fractal interfaces are the best, or that decent interfaces don’t exist. I’m arguing with the statement that all modern ones are good and that it doesn’t matter.

Fractal input specs aren’t stellar but they have noise shaping that masks the noise (“secret sauce” they call it).
 
Some do, most don’t. I never said Fractal interfaces are the best, or that decent interfaces don’t exist. I’m arguing with the statement that all modern ones are good and that it doesn’t matter.

Fractal input specs aren’t stellar but they have noise shaping that masks the noise (“secret sauce” they call it).
You’d really have to have significantly worse performance to notice a problem. Most 2i2 or UA volt or audient users are going to face bigger issues than noise. They’re all very close in performance and many people are using them daily on recordings with no issues (think of how many recordings have been made with Kempers and check their specs against all these consumer units). Not really sure what to say if you think the FM-3 is quiet enough but 1 or 2dB more noise is a problem.
 
You’d really have to have significantly worse performance to notice a problem. Most 2i2 or UA volt or audient users are going to face bigger issues than noise.
Those are very bad indeed

But I do notice the problem even with better ones very easily, it’s the amount of gate I need to apply. With low noise inputs I can have very little or even turn it off completely if I’m playing a bit away from the monitor and other stuff. With bad ones it’s impossible to play without a gate.

Fractal devices mask noise by some shaping filtering stuff so there’s not so much in the audible range that matters. So the end result is much more than 2 dB.

Also, 2 dB at the input, after going through a lot of gain, compression and distortion, is a lot in the end.
 
Just out of curiosity, how did you arrive at this number? I've been trying to learn some of this stuff so I'd be interested to see the math :)
Just by measuring a sine wave’s voltage, running it into the axe fx input, noting the DI level. The plugin tells you that it needs 18dB of boost when using this specific input.

You can then use that information for other inputs. If an input has 5dB less headroom than Fractal (the same sine wave signal is 5dB closer to 0dBFS - in other words louder) then that input would only need 13dB of input boost to reach the same level.
 
What's the issue exactly?
Isn't the common issue with other plugin amp sims that: if the author has not published a reference plugin input level based on which the model reacts as the author intended (hopefully to faithfully reproduce what the physical reference amp would do), then there is no way for any user (even more tech savvy ones) to determine what that plugin reference input level should be to represent the sim as intended (separate from the goal of getting an unclipped signal to the plugin and having sufficient range within it).

This is why I mentioned above that I appreciate the authors who do publish that reference level (or provide a calibration tool as is the case here) - because without either of those, there is no way to know what level the plugin expects as input based on the author's design/intention, and therefore no way for users to run the plugin's input accurately to the author's intention. Maybe I misunderstand something here?

And of course, without any way to calibrate (if I understand correctly) in such cases, one can always set input level to taste and intuitively set up for any plugin amp sim by ear, BUT, if I have purchased a plugin suite of many amp sims which I intend to use extensively and which I may have purchased on the basis of their accuracy to the physical reference amps, then I would think most users (even the most adamant "just use your ears" folks) would want to calibrate such that the plugin's amp sims react fairly accurately and as intended for any given guitar at the get go (otherwise, what's the use of authors striving for such accuracy and users clamouring to get it). To add insult to injury 🤣, apparently, some plugins that contain many amp sims, don't even have a consistent unpublished reference input level across the plugin's included amp sims! - seems crazy to me - just publish the input reference level number if not wanting to go thru the effort of creating a calib tool for users as Fractal has done here, and for pete's sake, at least keep that unfortunately unpublished reference input level consistent across various amp sims within a plugin (I can't think of any reason this would need to vary other than that maybe some plugins containing many amp sims have different authors working independently on the different included amp sims). A primary goal of amp modelling since the beginning has been to give users a realistic starting point: when I plug guitar X into amp sim Y, the sim reacts as realistically as possible to what the physical ref amp would do with that same guitar as input as the user proceeds to tweak the amp. Why many plugin authors work all the way to attaining that level of accuracy as demanded by their user base, and then not provide users any way (even with a simple published single value known to the author) to calibrate, if desired, at the outset of using the plugin (leaving users open to being possibly wildly off the mark wrt using the amp sim accurately as intended) is beyond me, but again, maybe I misunderstand something as basement hacker tech nerd
🤓
 
Last edited:
Isn't the common issue with other plugin amp sims that: if the author has not published a reference plugin input level based on which the model reacts as the author intended (hopefully to faithfully reproduce what the physical reference amp would do), then there is no way for any user (even more tech savvy ones) to determine what that plugin reference input level should be to represent the sim as intended (separate from the goal of getting an unclipped signal to the plugin and having sufficient range within it).

This is why I mentioned above that I appreciate the authors who do publish that reference level (or provide a calibration tool as is the case here) - because without either of those, there is no way to know what level the plugin expects as input based on the authors design/intention, and therefore no way for users to run the plugin's input accurately to the author's intention. Maybe I misunderstand something here?

And of course, without any way to calibrate (if I understand correctly) in such cases, one can always set input level to taste and intuitively set up for any plugin amp sim by ear, BUT, if I have purchased a plugin suite of many amp sims which I intend to use extensively and which I may have purchased on the basis of their accuracy to the physical reference amps, then I would think most users (even the most adamant "just use your ears" folks) would want to calibrate such that the plugin's amp sims react fairly accurately and as intended for any given guitar input at the get go (otherwise, what's the use of authors striving for such accuracy and users clamouring to get it). To add insult to injury 🤣, apparently, some plugins that contain many amp sims, don't even have a consistent unpublished reference input level across the plugin's included amp sims - seems crazy to me - it's easy to just publish the input reference level number as a plugin author if not wanting to go thru the effort of creating a calib tool for users as Fractal has done here, but for pete's sake, at least keep that reference level consistent across various amp sims within a plugin (I can't think of any reason this would need to vary other than that maybe some plugins containing many amp sims have different authors working independently on the different included amp sims). A primary goal of amp modelling since the beginning has been to give users a realistic starting point: when I plug guitar X into amp sim Y, the sim reacts as realistically as possible to what the physical ref amp would do with that same guitar as input as the user proceeds to tweak the amp. Why many plugin authors work all the way to attaining that level of accuracy as demanded by their user base, and then not provide any way (even by simply publishing a known single value) for users to calibrate to once at the outset of using the plugin if desired (without which leaves users open to being possibly wildly off the mark wrt using the amp sim as intended) is beyond me, but again, maybe I misunderstand something as basement hacker tech nerd
🤓
I agree - thankfully its getting more common for manufacturers to provide specific levels (or the means to work it out).
 
IK Multimedia doesn't provide this for their Tonex hardware. Which is bananapants if you ask me.
Fyi, this is not what I was referring to in the post he responded to, which is the intended input level to the plugin itself that will facilitate using the plugin accurately (wrt input) to the author's intention, and which is not user determinable in the absence of published info or a calibration tool.

The maximum input level (headroom) of Tonex hardware is a bit if a different topic, and tho I agree that should be published also for clarity, it is at least user determinable without published info (I measured my Tonex and Tonex One pedals both at 8dB of headroom - am guessing Mr Vangrieg won't like that number at all 😳). The actual Tonex captures on the other hand can be difficult to use accurately either in plugin form or via the pedals if the author has not published a reference input level for their capture as Jason Sadites and a very few others do (hence prob why capture users often express difficulty getting the gain in the ballpark of what the captured amp would be with the same guitar as input). Even NAM captures which afaik provide ability to enter some sort of compensating reference input level factor cannot mitigate for that compensating value being unknown / undeterminable due to the reference input level being unpublished by the author of a given capture.
 
Last edited:
Just by measuring a sine wave’s voltage, running it into the axe fx input, noting the DI level. The plugin tells you that it needs 18dB of boost when using this specific input.

You can then use that information for other inputs. If an input has 5dB less headroom than Fractal (the same sine wave signal is 5dB closer to 0dBFS - in other words louder) then that input would only need 13dB of input boost to reach the same level.
Ah ok that make sense.

So what about the Axe-FX III?

The manual says it has a max input level of +16dbu.

Does this mean the Axe-FX is actually outputting a DI of about -2dbu?
 
I appreciate that folks are taking this topic way more seriously and methodically on this forum than on equivalent forums for other guitar plugins. And I'm not surprised.
What can I say, sometimes I feel like I might be on the spectrum lol
This is the kind of stuff that makes me love this forum haha
 
  • Love
Reactions: KFF
Isn't the common issue with other plugin amp sims that: if the author has not published a reference plugin input level based on which the model reacts as the author intended (hopefully to faithfully reproduce what the physical reference amp would do), then there is no way for any user (even more tech savvy ones) to determine what that plugin reference input level should be to represent the sim as intended (separate from the goal of getting an unclipped signal to the plugin and having sufficient range within it).

This is why I mentioned above that I appreciate the authors who do publish that reference level (or provide a calibration tool as is the case here) - because without either of those, there is no way to know what level the plugin expects as input based on the author's design/intention, and therefore no way for users to run the plugin's input accurately to the author's intention. Maybe I misunderstand something here?

Correct, an amp modeler needs to relate a physical voltage level to the resulting level in the digital domain. For H/W modelers, since they know their own input frontend design, they know this relationship and it's not a problem.

For amp modeler plugins, given that audio interfaces are all different (due to their converters and the circuit design driving the converters), then they have to assume some relationship - this is the "spec" you a referring to.

I believe for example NeuralDSP plugins assume a relationship of 12.2 dBu => 0dBFS. In other words, this relationship assumes, that if you present a 12.2 dBu signal at the input, it results in a 0dBFS signal in the digital domain. If my interface instead has a relationship of 16dBu => 0dBFS, then I adjust the plugins digital input gain control to +3.8 dBFS to calibrate.

The NAM plugin is neat because it just lets you specify directly this relationship directly by just inputting the dBu value that corresponds to 0dBFS for your interface. Then captures that contain proper metadata work accurately because everything is calibrated.

The Fractal plugins could offer something like that for us nerds, because we already know this number for our audio interfaces.
 
Last edited:
^On the front input. +20dBu on the rear.
I measure 17.6dB headroom on my Ax3-mk1 (sending a measured 0dBu signal (0.775V) to Ax3 instrument input from an external source, I get -17.6dB peak popping out in my daw via Axfx USB with no processing in between).
 
  • Like
Reactions: KFF
I measure 17.6dB headroom on my Ax3-mk1 (sending a measured 0dBu signal (0.775V) to Ax3 instrument input from an external source, I get -17.6dB peak popping out in my daw via Axfx USB with no processing in between).
Is that the front Input? Have you tried the rear one?

Actually... I haven't checked the MK I specs. MK II definitely listed as +20dBu on the rear instrument Input.
 
Back
Top Bottom