NAM calibration: find audio interface unity gain level

jle

Newbie
Messages
3
Hi everyone,


Ive been testing NAM lately and Ive been interested in the calibration feature. My understanding (correct me if im wrong) is that if an amp was captured at 12 dbu and my audio interface input max headroom is 20dbu i should basically setup my interface at unity (+0db gain) and set NAM input gain at +8db.


Thats basically what the code of the client is doing here: https://github.com/sdatkinson/Neura...b8/NeuralAmpModeler/NeuralAmpModeler.cpp#L653


Im using an old audiobox 44vsl interface with -30/+50db gain range control. My problem is that unity position (+0db gain) is not marked clearly on the interface knob, so im wondering, is there a simple way to establish it with certainty using some calibrated test signal somehow? Ive searched the web and thought about it but i cant figure it out, am i missing something obvious here?

At first i was thinking about generating some sine wave at a certain dbfs level (lets say -30dbfs) in my daw (ex: tone test in ableton), get it out of the interface with main output volume at max position (+0db), plug it back in and find the knob position where I have the same -30dbfs input level in daw.
But im not sure that this makes any sense, since to my understanding different interfaces will produce different outputs for -30dbfs depending on interface output level (+10dbu in my case).

Any help/explanation will be deeply appreciated.
 
Last edited:
@MirrorProfiles has a few vids on his YouTube channel that walk you through finding out your instrument input "maximum input gain " / headroom if you don't have a spec sheet for the unit.
 
I have the specs of my audio interface, maximum input gain is 21dbu. What i dont know is where the gain knob should be positioned to be at +0db.
 
Hi everyone,


Ive been testing NAM lately and Ive been interested in the calibration feature. My understanding (correct me if im wrong) is that if an amp was captured at 12 dbu and my audio interface input max headroom is 20dbu i should basically setup my interface at unity (+0db gain) and set NAM input gain at +8db.


Thats basically what the code of the client is doing here: https://github.com/sdatkinson/Neura...b8/NeuralAmpModeler/NeuralAmpModeler.cpp#L653


Im using an old audiobox 44vsl interface with -30/+50db gain range control. My problem is that unity position (+0db gain) is not marked clearly on the interface knob, so im wondering, is there a simple way to establish it with certainty using some calibrated test signal somehow? Ive searched the web and thought about it but i cant figure it out, am i missing something obvious here?

At first i was thinking about generating some sine wave at a certain dbfs level (lets say -30dbfs) in my daw (ex: tone test in ableton), get it out of the interface with main output volume at max position (+0db), plug it back in and find the knob position where I have the same -30dbfs input level in daw.
But im not sure that this makes any sense, since to my understanding different interfaces will produce different outputs for -30dbfs depending on interface output level (+10dbu in my case).

Any help/explanation will be deeply appreciated.
You can set your gain to minimum, run a sine wave into the input, and then increase the gain knob until the sine wave dBFS level is 30dB higher.

Or if you have a multimeter you can do things more accurately.
 
I have the specs of my audio interface, maximum input gain is 21dbu. What i dont know is where the gain knob should be positioned to be at +0db.
Well then with the gain knob at minimum your interface Hi-Z input should be able to take in about 8.691 Vrms until you see 0 dBFS in the DAW.

I used this to convert the dBu rating to Vrms:

 
If you just want to play through NAM profiles but are worried about the best experience, look for profiles which have calibration metadata embedded. Tone3000 has a filter that you can use to only display those profiles.

You can then use NAM plugin player 0.7.12 or later as it has the logic for using the calibration metadata and with your interface's gain knob at 0 (where you know you have 21 dBu headroom) just type in "21" in the "Input Calibration" textbox within the NAM plugin.

More info here & example here:

 
  • Like
Reactions: Elf
You can set your gain to minimum, run a sine wave into the input, and then increase the gain knob until the sine wave dBFS level is 30dB higher.

Or if you have a multimeter you can do things more accurately.

You can set your gain to minimum, run a sine wave into the input, and then increase the gain knob until the sine wave dBFS level is 30dB higher.

Or if you have a multimeter you can do things more accurately.
Fuck, of course. I know that with minimum gain im at -30db, so yeah, whatever the input signal, i just have to turn it up till i reach "original value + 30db" and i know im at +0db.
Sorry guys, i feel stupid now, i guess i got lost in complicated scénarios. Thanks a lot for your answers.

Just for my knowledge, what would be the more accurate version using a multimeter?
 
@jle have a look here. I had a very similar conversation with a few folks yesterday & decided to put together a quick vid to help make the most out of NAM & the new cablibration metadata:

 
Last edited:
Back
Top