• Registered: 2016-10-13
  • Posts: 9

Topic: Babyface Pro instrument input calibration

Hi,

There is some talk on several guitar and music software related forums about audio interface input calibration to achieve the most realistic results with amp modeling software.

It has been said that a 1kHz sine wave 1VAC peak / 0.707 RMS test signal should be fed into the audio interface’s instrument input. Then gain should be raised digitally on the corresponding input channel of the DAW until it reaches just below 0 dBFS. Some guitar modeling software developers confirmed that their software is indeed optimized for that input level.

I became curious and would like to test this approach with my RME Babyface Pro but unfortunately do not have a function generator. There also seems to be a way to calculate the required digital gain boost depending on the audio interface’s technical specifications (related to the instrument input’s dBu level / headroom, if I understood it right).

Perhaps there is someone with more technical or mathematical knowledge than myself who can kindly help me out and tell me how much gain should be applied to achieve a level of 0 dBFS with a 1 KHz 1VAC signal on the Babyface Pro’s instrument input?

Cheers :-) Sven

2 Reply by MC

  • MC
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  • Registered: 2007-04-06
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Re: Babyface Pro instrument input calibration

Your instrument/guitar doesn't care about 1V AC or whatever at all. Every instrument/guitar has a different output voltage.  And even the same guitar will be differently loud when different people play it. Guitars provide up to +15 dBu output signal in peaks, so you need to choose the correct ANALOG refence level to avoid clipping the analog input stage. And which one is correct you see immediately when playing your instrument and trying them.

This is all so screwed up that I expect something was quoted wrong or out of context.

Regarding the BF Pro:
Maximum input level @-10 dBV, Gain 9 dB: -5 dBu

-5 dBu = 0.44V RMS, only 4.2 dB below that obscure reference. So a gain of only 5 dB will match 0.7 V for 0 dBFS.

Regards
Matthias Carstens
RME

MC's Website

3 Reply by GrabtharsHammer (edited by GrabtharsHammer 2017-08-27 06:56:07)

  • Registered: 2016-10-13
  • Posts: 9

Re: Babyface Pro instrument input calibration

Yes, I know it sounds screwed up. But honestly I don't have the theoretical background to judge if this 1 kHz 1VAC @ 0 dBFS thing really is complete BS or if there is at least some truth to it. That's why I wanted to get some more information about the topic.

Here is a link to one of the forum threats I was relating to:
https://www.kvraudio.com/forum/viewtopi … p;t=482600

4 Reply by MC

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Re: Babyface Pro instrument input calibration

I read this thread and understand the idea. You have to use the +4 dBu Ref Level with 0 dB gain in the BF Pro to prevent clipping. Then in the DAW (NOT in TotalMix!) you raise the gain digitally by 13.2 dB. As a result the emulation of an AC-30 (example) will have the correct amount of distortion when played with low level or very hot guitars respectively.

The question here of course is: does that make any sense in real world usage? Don't you adjust the volume / input level so that it sounds like YOU want it anyway? And why did not a single of those famous plug-in providers came up with such kind of calibration instructions? Maybe they think the same, you adjust to what you like anyway...

Regards
Matthias Carstens
RME

MC's Website