[Ardour-Users] Odd clipping

[Jörn Nettingsmeier]

On 09/24/2012 11:54 AM, Ben Bell wrote:
> I've got an intermittent problem with the snare mic when recording. Initially
> I assumed it was just clipping, but even if I lower the gain on the channel
> significantly so that normal snare hits register -20dB in ardour I still often
> get the spikes. The odd thing about it is that it isn't in the initial
> transient part of the waveform, it's often a little later in.  It's also not
> always on the loudest beats, and it tends to come in clusters where things
> distort for a while, then they're problem free again.
>
> I've superimposed a "good" snare hit over the clipped one, and you can see
> it's slightly odd in that the problem peaks seem to be accentuated:
>
>   http://twitpic.com/ax819i/full
>
> Is this just normal pre-amp or ADC clipping, or have I perhaps got an
> electrical problem with my signal chain somewhere (mic->mixer->interface)?

no, this is certainly not normal. is this a condenser mic?
if not, is the phantom power switched on anyways?

it's odd that the spikes are all positive, so maybe they are induced by 
phantom power - either by a bad cable that has an "almost short", and 
the slight movement caused by the sound does the rest, or maybe a 
condenser mic is not up to the SPL and the diaphragm hits the grid.

the latter problem might also be caused by insufficient phantom power 
(so that the diaphragm isn't tight enough), or - if it's a pre-polarized 
condenser - by loss of electret polarization, perhaps due to heat damage.

so much for shooting in the dark, best


jörn




-- 
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

http://stackingdwarves.net