[linux-audio-user] Recording Level using Audacity and a Multiface card

[D. Sen]

Actually, after Sampo's hint, everything does indeed work fine (without 
the 10x gain of the power-supply/conditioner, I might add).

Cheers,
DS
Asbjørn Sæbø wrote:
> On Sat, May 13, 2006 at 08:03:48AM +1000, D. Sen wrote:
>> Yes, sure.
>>
>> Here are the relevant links for the 4189 + 2671 microphone housing in 
>> our setup, that connects to the Deltatron power supply.
>>
>> http://www.bksv.com/pdf/Bp1380.pdf
> 
> That is a microphone, indeed.  A B&K measurement microphone, that is.  
> (A note to those not familiar with B&K measurement equipment: These are 
> not quite like "normal" microphones.  But they are of very high 
> quality.)
> 
> According to your linke, this microphone has a sensitivity of 50mV/Pa. 
> 
> 
>> http://www.bksv.com/pdf/bp2111.pdf
> 
> And this is the preamplifier.  (Which would, in audio, normally be 
> considered part of the microphone.)
> 
> This one has, according to the link, a peak output of 7 volts, 
> corresponding to an SPL of 138dB for a 50mV/Pa microphone.  Your 94dB 
> signal is 44 dB below that.  Which means that the output level after the 
> preamplifier will be
> 
> l = 7 * 10^(-44/20) = 0.044
> 
> And 0.044 volts is quite a bit below full scale line-level.  However, 
> adding the 10x gain of your amplifier you should be at 0.44 v, which is 
> certainly in the ballpark of consumer line-level.
> 
> 
> After looking closer at it, your setup actually seems to make some 
> sense.  Your amplifier (the 4416) is not one normally used for 
> amplifying microphone signals, but rather accelerometers and the like.  
> (As your links says: "conditioner for use with ISOTRON(R) or other 
> piezoelectric voltage mode transducuers.")
> But the preamplifier (the 2111) _seems_ to be of a special kind intended 
> just for interfacing microphones to this kind of amplifier, so you are 
> probably right in that it should work.
> 
> 
> Asbjørn
> 
>