[LAU] [Music] Sans titre - Without title

[Len Ovens]

On Sun, 17 Jul 2016, Robert Edge wrote:

> If you don't believe me, do this simple test:
> 
> feed a 1kHz tone in to the input
> 
> set 'analog volume' control in software to 0dB
> 
> connect to ardour or your choice of recorder with decent metering.  set meter
> point to 'in'
> 
> increase volume of test signal until you are getting 0dBFS.  no matter how much
> you increase the level of the test signal from here it will continue to read
> 0dbFS.  turn the signal generator up a good few dB so you are well in to
> clipping.
> 
> record a bit of this.  you will see a squared off wave.
> 
> now turn down the 'analog volume' control until you are seeing a nice comfortable
> level.  do not change the level of the test signal generator.
> 
> record again.
> 
> the result will still be clipped.
> 
> in fact it will be identical to the first signal you recorded, just scaled down.
> 
> I mean, you guys do whatever you want, but that is what is actually happening in
> your signal chain.

How do you know this is digital and not analog clipping? The result would 
look the same.

signal path:

AC -> resitor -> buffer -> digitally -> ADC
in    pad on     amp       controlled
       card                 analog gain

if the input signal after the input pad has p-p higher than amp's power 
rails allow, the signal will be squared off, just as you are seeing. The 
gain stage would be a part of the ADC chip BTW. The buffer amp is probably 
not, but rather a gain stage added to allow the use of mic level inputs. 
(M-Audio advertise it as a Mic Pre)

--
Len Ovens
www.ovenwerks.net