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

[D. Sen]

Ok, so the gain option quoted by the device isnt the gain quoted by the 
conventional pre-amps. However, you are assuming a lot here. In essence, 
you are assuming that just because you dont see "60 dB gain", the device 
is not amplifying the signal to line-level when in-fact, even at x1 
gain, the device is producing line-level and the extra 20 dB gain using 
the x10 setting is beyond what is required for line-level inputs.

The gain does not tell you anything about the voltage at the output. The 
  pre-amp from RME quotes an output of 21 dBu max. This converts to 
about 24 V p-p. The device I am using produces an output of 10 V p-p. 
This is a difference of slightly above 6 dB.

If at the end, the gain was the root of the problem, I would surely see 
the same kind of low level recording on other digital recorders (namely 
a FOSTEX and a SONY line-level input recorders), and I dont.


Fernando Lopez-Lezcano wrote:
> On Sat, 2006-05-13 at 06:00 +1000, D. Sen wrote:
>> Look at the specs. The output is definitely line-level. The function of 
>> a pre-amp is to produce line-level output and this does it. 
> 
> Not really. Please compare to the specs of a real mic preamp, please,
> for example:
>   http://www.rme-audio.com/english/micpreamps/quadmic.htm
> (which would be an appropriate companion to the multiface)
> 
> In particular: "Amplification can be set between 10 and 60 dB". 60dB of
> gain expressed as a voltage ratio would be amplifying the signal by
> 1000. I would imagine you would need to use 40 to 60dB to amplify a mic
> to line level so you are at least a factor of 10 below what would be
> needed. 
> 
>> It is sold by B&K and they swear by it.
> 
> (they can swear all they want but that's not gonna make it amplify the
> signal more :-)
> 
> The key here (as outlined before in the thread) is gain. This signal
> conditioner's gain is too low (probably by a factor of at least 10) to
> act as a mic preamp _unless_ your line input has additional gain you can
> dial in (which is probably why you can use it with other equipment). 
> 
> -- Fernando
> 
> 
>> Paul Winkler wrote:
>>> On Sat, May 13, 2006 at 04:16:28AM +1000, D. Sen wrote:
>>>> This is what is being used between the microphone and the multiface:
>>>>
>>>> http://www.bksv.com/pdf/4416B.pdf
>>>>
>>>> This is providing line-level output to the multiface.
>>> What you have there isn't really a microphone preamp.  Max gain of 10
>>> isn't very much at all, it's what, 20 dB?  
>>>
>>> Commercial mic preamps typically have at least 60 dB of gain available.
>>>
> 
> 
>