1 (edited by Jojo434 2010-11-29 17:40:02)

Topic: Babyface : Enough power via Phones Out ?

Hi,

I would like to know if my headphones will deliver sufficient sound pressure level when connected to the Babyface. I'm totally lost in converting V/mW/Ohms/dBu... Could you please help me ?

Babyface :
DA Phones 3/4, as DA Line Out, but:
Output impedance: 30 Ohm
Output level at 0 dBFS: +7 dBu


My Headphones (AKG K-702) :
Efficiency:       105 dB SPL/V
Max. input power:      200 mW
Rated impedance:      62 ohms

Q1. What's the max power (in mW) the Babyface is able to deliver via the Phones Out?
Q2. What will be the max sound pressure level (in dB) reached by my headphones connected to the Babyface Phones Out?
Q3. If the max sound pressure level is too low for my taste, can I connect without any risk (except for my ears) my headphones to the DA Line Out to get more power?

Thank you in advance.

Re: Babyface : Enough power via Phones Out ?

This might help:
http://www.sengpielaudio.com/Calculations03.htm

The Line Outs will not be louder. You could connect them to an external headphone amp, though.


Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

3 (edited by Jojo434 2010-11-29 19:47:20)

Re: Babyface : Enough power via Phones Out ?

Thanks for your quick answer.

If I refer to the convertor (http://www.sengpielaudio.com/calculator-db-volt.htm), then +7 dBu = 1.734105937 volts RMS.
So my headphones will deliver 105 dB SPL/V  + (3 dB x 0.734105937) = 107,2 dB
If it's right, then how is it possible that the Line Outs will not be louder when you consider:

?  Maximum output level: +19 dBu
?  Output impedance: 75 Ohm
?  Output level balanced at 0 dBFS: +15 dBu

Is it because even if the output power is +/- the double, in the same time the impedance is also +/- the double ?
If not, I'm lost.

Sorry, but I'm not an physicist nor an engineer nor even an electrician. I'm just an hoobyist who need a good portable soundcard and a simple an clear answer to my question : What will be the max sound pressure level (in dB) reached by my headphones connected to the Babyface Phones Out?

Thanks for your understanding.

4

Re: Babyface : Enough power via Phones Out ?

The line outs of the BF have +15 dBu and only in balanced mode, so with phones you get +9 dBu. Where does it say +19? Outdated manual?

Regards
Matthias Carstens
RME

5 (edited by Jojo434 2010-11-29 21:26:22)

Re: Babyface : Enough power via Phones Out ?

P 66 from the downladable manual : https://archiv.rme-audio.de/download/bface_e.pdf

DA, Line Out 1-2
?  Resolution: 24 bit
?  Dynamic range (DR): 112 dB, 115 dBA @ 44.1 kHz (unmuted)
?  Frequency response @ 44.1 kHz, -0.5 dB: 5 Hz - 22 kHz
?  Frequency response @ 96 kHz, -0.5 dB: 5 Hz ? 45 kHz
?  Frequency response @ 192 kHz, -1 dB: 5 Hz - 80 kHz
?  THD: - 104 dB, 0.00063 %
?  THD+N: -100 dB, 0.001 %
?  Channel separation: > 110 dB
Maximum output level: +19 dBu
?  Output: XLR balanced
?  Output impedance: 75 Ohm
?  Output level balanced at 0 dBFS: +15 dBu
?  Output level unbalanced at 0 dBFS: +9 dBu

DA, Phones 3/4
As DA Line Out, but:
?  Output: 6.3 mm TRS jack, unbalanced
?  Output impedance: 30 Ohm
?  Output level at 0 dBFS: +7 dBu

Okay, so is it now possible to answer to my question please ? :
"What will be the max sound pressure level (in dB) reached by my headphones connected to the Babyface Phones Out?"... 105 dB, 107 dB, less, more ?

6

Re: Babyface : Enough power via Phones Out ?

100 points! A left-over only in the english manual. Thanks. So your calculation was correct, and the line outputs will be less loud as they loose 6 dB already due to their higher impedance.

Regards
Matthias Carstens
RME

7 (edited by Jojo434 2010-11-30 03:47:31)

Re: Babyface : Enough power via Phones Out ?

First of all, thanks for your patience.

Now I'm sorry to bother you but... if I refer to your statement "The line outs of the BF have +15 dBu and only in balanced mode, so with phones you get +9 dBu.", then the german manual gets also a left-over, as he says :

DA, Line Out 1-2
?  Ausgangspegel symmetrisch bei 0 dBFS: +15 dBu
?  Ausgangspegel unsymmetrisch bei 0 dBFS: +9 dBu

Or did I missed something like "If headphones are connected to a balanced output, they will operate as if the output was unbalanced and you will lost 6 dBu (15 - 9)"?

Btw, I think it will be more convenient (and time saving) to specify the phone output power in mW like most headphones manufacturers do for their max input power, so we can easily compare which is comparable...