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
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Received on Mon Jul 18 20:15:02 2016
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