• rpnfan
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Topic: effective gain of Babyface Pro FS ? calculating sound pressure level ?

I have a two-fold question:

1) I struggle to understand why the effective gain of the BFP is measured about 58 dB and how that relates to the maximum "Gain" setting of 65 dB in Totalmix?

https://youtu.be/S0sE5mpSLYM?t=421

To calculate the effective gain I would need to calculate 8 dBu - 65 dBu = -57 dBu, right? But than what is the maximum gain setting of 65 dB in Totalmix? It seems to be the gain range!? What is then a gain of 0 dB in Totalmix? A real decrease of 8 dB of the signal?

2) Which values do I need to calculate the sound pressure level from a given microphone, gain-setting in TM and dbFS output?

I want to calculate the sound pressure level (for example with the Neumann Recording app).

Example:
Mic = 15 mV/Pa ~ 36.5 dBV
Preamp - Gain setting in TM = 40 dB    → is that the number I have to use or would I need to calculate the "real gain" by subtracting 8?
AD Converter = 8dBu   (or something else?)
Full scale = -10 dBFS


2b) For best results (to describe a speaker) I would need to measure with pink noise, correct?

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,776

Re: effective gain of Babyface Pro FS ? calculating sound pressure level ?

Too many ads in this video... Does it claim that at the 65 dB setting, there is only 57 dB of actual applied gain?
If so, then obviously that would not mean a "loss" of 8 dB across the board (and no "decrease" or attentuation at 0 dB gain), but a gradual deviation between the setting and the real gain. Like maybe 3 dB at 40 dB gain... I don't know exactly how this was measured and whether the claim is even accurate, so this is partly speculation. If the claim is correct, you'd have to measure the deviation between the setting and the effective gain for several settings.

Regards
Daniel Fuchs
RME

RME Support's Website

3 Reply by rpnfan (edited by rpnfan 2023-05-14 21:52:10)

  • rpnfan
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Re: effective gain of Babyface Pro FS ? calculating sound pressure level ?

I contacted Julian and got an answer from him. For some reason he was (or still is?) not able to login to the forum.

1)
Die Achsen vom Diagramm könnten definitiv besser beschriftet sein..
Die Aussage ist folgende: Ich messe wie viel dBV bei maximalem Gain benötigt
werden um eine Vollaussteuerung (0 dBFS) zu erreichen.
Desto mehr "Gain" ein Interface besitzt, desto niedriger die dBV Werte, die
bis zur Vollaussteuerung gebracht werden können.
 
Beim Babyface sind es ca. -58.8 dBV. Wenn ich also das Gain komplett
aufdrehe und ein -58.8 dBV Signal in das Interface gebe, erhalte ich ein
digitales Signal mit 0 dBFS.
Das Wichtige ist, dass mein "Gain" Wert die AD Konvertierung beinhaltet und
Aufschluss darüber gibt, wie viel dBV in wie viel dBFS resultieren. Das hat
mit dem Gain, auf dem der Preamp eingestellt ist nicht viel zu tun und ist
auch nicht vergleichbar.
 
2)
Interface:
-58.8 dBV = 0 dBFS @ 65 dB (max) gain
-43.8 dBV = 0 dBFS @ 40 dB gain
 
Mic:
-36.5 dBV = 94 dB SPL
 
--> 86,7 dB SPL = 0 dBFS @ 40 dB gain
 
Scheint mir etwas niedrig, aber theoretisch müsste das so passen. Also bei
40 dB gain in TM und einem Mic mit 15 mV/Pa würden 86,7 dB SPL zur
Vollaussteuerung führen. Alles andere ergibt sich dann von dort.
 
Viele Grüsse
Julian

So the mystery seems to be solved. The difference was caused by the AD conversion included in Julian's measurement. So Julian's measurement match pretty close to the specs of the Babyface. Thus I can indeed calculate the sound pressure level from the mic sensitivity, AD conversion (8dBu) and the gain applied with the Babyface. :-)

It is convenient to use the Neumann Recording app for that.

P.S.: I did not understand what "too many ads" meant. Julian does not advertise anything in the video and if one sees ads from YouTube is just dependent on how one watches it (Subscription or not/ AdBlocker or not...)

4 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
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Re: effective gain of Babyface Pro FS ? calculating sound pressure level ?

The manual includes all the info you need:

- Gain range: -11 dB up to +65 dB
- Maximum input level XLR, Gain 0 dB: +8 dBu, PAD +19 dBu
- Maximum input level XLR, Gain 65 dB: -57 dBu, PAD -46 dBu

I have no clue why another YouTube video is needed to extract the same information that is given here already.

Julian's video as such highlights that many other manufacturers do not give such detailed information.

Regards
Matthias Carstens
RME

MC's Website

  • rpnfan
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Re: effective gain of Babyface Pro FS ? calculating sound pressure level ?

MC wrote:

The manual includes all the info you need:[...]

I have no clue why another YouTube video is needed to extract the same information that is given here already.

Der Knackpunkt war, dass das Handbuch dem getesteten Ergebnis zu widersprechen schien und es schien mir unwahrscheinlich, dass die RME-Angaben nicht stimmen, aber auch unwahrscheinlich dass Julian's Ergebnisse so deutlich unterschiedlich sind.

So the mystery seems to be solved. The difference was caused by the AD conversion included in Julian's measurement.