Calibrating Input Level for Plugins

valimaki said:
I mean that the maxium input level refers to the highest analog signal level (dBu) the preamp can handle without clipping (in the analog domain) before being converted to digital, that doesn't mean that it will match 0dBFS (digital domain) at that level.

So you need the pream specs + the DAC reference level to exactly calculate the signal level in the digital domain, or measuring the dBFS you get using a reference signal.

One audio interface may have a reference value (analog to digital) of +4 dBu = -18 dBFS and another one may have +4Bu = -20 dBFS. So if I am not terrible mistaken, using the maxium input level of an input is not enough to get a proper calibration.
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I’m not really following. All of these specs would provide the information you need.

+4dBu=-18dBFS is the same way as saying 22dBu of headroom, or 0dBFS=22dBu. The highest signal level it can handle before clipping is 0dBFS, and everything scales down from there.
 
MirrorProfiles said:
I’m not really following. All of these specs would provide the information you need.

+4dBu=-18dBFS is the same way as saying 22dBu of headroom, or 0dBFS=22dBu. The highest signal level it can handle before clipping is 0dBFS, and everything scales down from there.
Click to expand...
Lets say we have two interfaces, both have preams capable of handing a max input level of 14dBu, The first one has a DAC calibration of +4dBu = -18dBFS, the second one uses +4dBu = -20dBFS. Whats the amount of gain needed to reach 0dBFS with a 1Vp signal at minimum preamp gain for each interface?
 
valimaki said:
Lets say we have two interfaces, both have preams capable of handing a max input level of 14dBu, The first one has a DAC calibration of +4dBu = -18dBFS, the second one uses +4dBu = -20dBFS. Whats the amount of gain needed to reach 0dBFS with a 1Vp signal at minimum preamp gain for each interface?
Click to expand...
This is separating the preamp and the A/D which is not really relevant for built in preamps (where its typically not possible to route the preamp anywhere other than straight to the A/D.

The specs for JUST the preamp aren't relative to the converters, thats just analog headroom before they overload. You'll find this on standalone DI boxes and mic preamps but it has nothing to do with calibration for digital levels. All we care about is what digital level a known analog signal is represented as. Mic preamps can add 70-80dB of gain, and output a lot of signal before overloading. Converter specs are designed to accomodate this, so its rare you'll be in a situation where you have a problem unless its a creative choice.

For interface one, the converters can take 22dBu before clipping. Anything before it may well have less headroom and might distort sooner (say like a 9V distortion pedal) - that would be analog clipping though and have no bearing on the dBFS level that hits the DAW.

Interface two has 24dBu=0dBFS. Same thing applies. Typically analog gear will have plenty of headroom before distorting them becomes an issue. And for the average home studio guitarist using an Audient/UAD/Focusrite/etc the specs are provided for the instrument input which includes BOTH the preamp and A/D, so its a solved problem that is all accounted for.
 
MirrorProfiles said:

Nice guide from Two Notes about calibrating, including some nice copy and pasting from a certain spreadsheet (all cool because that information is there to be shared),
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They linked the table though:

1732716846588.png
 
Chromatizm said:
I have an RME interface. So this means I should be increasing the input by 2.8dB for every plugin I'm using?
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It also depends on which RME interface you have ! The specs of the Instrument input varies between devices :
  • UCX II: Maximum input level, +19 dBu, Gain 0 dB: Inst +13 dBu
  • UFX III: Maximum input level, Gain 8 dB: +21 dBu
  • UFX II: Maximum input level: +19 dBu
  • FF 802: Maximum input level, Gain +6 dB: +21 dBu
It looks like their +2.8dB in the table for RME refers then to the UCX II.

Amazing how an article made to clarifies things can confuse people even more :bonk
 
I have a UFXIII. I'm pretty sure the minimum gain on the preamp when set to instrument mode is 6 or 8dB, I'll have to check when I get a chance. Been ill the last few days so haven't been in the studio much.
 
Last edited:
The accuracy of the published numbers in the table can also be questioned. If you follow their step-by-step guide* and apply it to the UAD Volt interface (https://help.uaudio.com/hc/en-us/articles/4409522227092-Volt-Specifications):
  • UAD Volt Maximum Input Level: +12.5 dBu
  • 12.5 - 10.2 = 2.3 dB
The value is 2.1 dB in the table. Not a huge difference but still... my confidence level shrank by 0.2 dB.

Also, why do they say to remove 10.2 dB when they have calibrated 1 Volt Peak to -11dBF ?

* Step-by-step guide :
  • Look for your Audio Interface’s Specifications (usually available on the related manufacturer’s product page)
  • Find the “Maximum Input Level” for the Hi-Z/Instrument input; this value is usually sits between 10 and 20 and is expressed in dBu
  • Remove 10.2 from this value and set this figure as the GENOME “IN” Input Gain Value.
    1. For Example: Maximum Input level = 12.5dB equates to 12.5 - 10.2 = +2.3dB in Genome
 
Melodioso said:
The accuracy of the published numbers in the table can also be questioned. If you follow their step-by-step guide* and apply it to the UAD Volt interface (https://help.uaudio.com/hc/en-us/articles/4409522227092-Volt-Specifications):
  • UAD Volt Maximum Input Level: +12.5 dBu
  • 12.5 - 10.2 = 2.3 dB
The value is 2.1 dB in the table. Not a huge difference but still... my confidence level shrank by 0.2 dB.

Also, why do they say to remove 10.2 dB when they have calibrated 1 Volt Peak to -11dBF ?

* Step-by-step guide :
  • Look for your Audio Interface’s Specifications (usually available on the related manufacturer’s product page)
  • Find the “Maximum Input Level” for the Hi-Z/Instrument input; this value is usually sits between 10 and 20 and is expressed in dBu
  • Remove 10.2 from this value and set this figure as the GENOME “IN” Input Gain Value.
    1. For Example: Maximum Input level = 12.5dB equates to 12.5 - 10.2 = +2.3dB in Genome
Click to expand...
Which value is 2.1dB?

10.2dBu is the same as 1Vp=-11dBFS

The difference between 12.5dBu (your interface) and the plugin (10.2dBu) is the amount you calibrate by.

Tolerances might vary a bit but if you are concerned about anything you can always measure your own rig. I doubt most people will be able to head much difference if it’s 0.3dB in either direction. Even a dB either side of the target is probably good enough for a realistic response.
 
MirrorProfiles said:
Which value is 2.1dB?
Click to expand...
The first entry in the table provided by Two Notes on this page for the UAD® Volt Series interface says: +2.1 dB.
If you apply their formula (step-by-step guide on the same page), you'll find +2.3 dB.

I agree it doesn't make any real world difference, but find it disconcerting that the first value in the table doesn't follow their own logic.
 
Melodioso said:
It also depends on which RME interface you have ! The specs of the Instrument input varies between devices :
  • UCX II: Maximum input level, +19 dBu, Gain 0 dB: Inst +13 dBu
  • UFX III: Maximum input level, Gain 8 dB: +21 dBu
  • UFX II: Maximum input level: +19 dBu
  • FF 802: Maximum input level, Gain +6 dB: +21 dBu
It looks like their +2.8dB in the table for RME refers then to the UCX II.

Amazing how an article made to clarifies things can confuse people even more :bonk
Click to expand...
Yeah, honestly I'm just more confused now. I have the Babyface Pro (non-FS) model, btw.
 
Chromatizm said:
Thanks! Set the instrument input to +4dBu in the RME software or with whatever plugin I'm using?
Click to expand...
There’s a setting in the RME that’s either +4dBu or -10dBv. Set it to +4dBu mode and gain all the way down. Now you have 13dBu of headroom and you can adjust accordingly for whatever software you are using
 
hey there, long time listener first time poster here. just wanted to say how great it is that i found this forum thread. im sure there many people like me using plugins who have said 'i just can't get it to sound right'. they've gone onto read user manuals, watched youtube videos (full of misinformation) and tweaked and tweaked until they're blue in the face but no closer to fixing their problem let alone understanding it.

For me im a career IT guy (now in my late 40s) so bits & bytes are home and im not scared of code & electronics. i took up guitar in 2015 and been (trying) to use guitar sims since not long after that but since forever (as my guitar teacher can attest) ive never been able to get it to sound right. FINALLY i found this thread and i've read every goddamn post in it (over the course of 3 days). The lightbulb moment was:

'1 Vp = 0.707 VRMS = -0.79 dBu equals -13 dBFS in the digital domain' regarding the neural amp model.

i bought the Fortin NTS amp sim a few years ago but as i mentioned it was never able to get it to sound even close to all of the vids that i saw online. I followed the process on calibrating my audio interface to -13dbfs that all of the sudden it sounded perfect. not even just close but PERFECT.

just wanted to say thanks to James Freeman & MirrorProfiles (i assume you're EdS on YT). so anwyays i wanted to try & help in my own way. i've done the calibration thing with an Irig HD2 (my first ever audio interface purchase) as well as an an apogee jam+. I calibrated them against -13dbfs as I have a few of the Neural plugins so that just seemed like a natural choice.

i used my hx stomp to produce a 1khz sine wave with a voltage of .707v RMS (it's a bit out but is close enough)
20241214_144858 copy.jpg



i then plugged that into my irig hd2 (on minimum gain) and looked at how many dbfs that is on 0 gain (it was -13.6dbfs). turns out it needs +0.6db of gain to bring it to -13dbfs (i dont have a screenshot offhand but if people want it i can repro).


irig-hd2 +0,6 db gain.png


This is for the apogee jam+. it has a cool feature where you can see the amount of interface gain in the audio/midi app. 0.707v RMS on the apogee jam+ -is -21dbfs. so needs +8 db of gain to bring it to where the Neural amp sims expect it. i hope my understanding of whats needed (and how to measure it) is correct and this info helps someone.
jam plus plus 8db.png



You may see it above but i also have an FM3 but ill leave that to another post. its got killer tone once you get it right but holy crap was it unneccesarily hard.
 
Fwiw, I looked around in this thread but couldn't find any info about leveling Amplitube properly (unfortunately I couldn't resist, so I just got IK's Studio 4 Max in the recent sale). I'd only need to know how much the input level would deviate from what HX Native likes to see, because I have that covered pretty well. The Amplitube presets are of zero value to at least get a "ballpark" idea as their levels are all over the place (I have hardly ever stumbled across worse presets). It does however seem as if it needs somewhat less input gain as HXN because many amps start to compress noticeably (might as well just be their settings or questionable modeling, though).
Anyhow, in case anyone knows the difference between the input levels of HXN and AT, I could just see whether I'm getting along.
 
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