[Ardour-Users] Removing hum from track

[Al Thompson]

On 04/30/2017 02:19 AM, anahata wrote:
> On Sun, Apr 30, 2017 at 02:00:00AM -0400, Al Thompson wrote:
>
>> Trying different combinations of tracks to phase reverse
>> should get a substantial reduction in hum.
> There's a massive assumption going on here (and in previous posts along
> similar lines),  which is that the same hum waveform is beng picked up on 
> all or several channels.
>
> In my experience, a typical hum problem occurs on ONE channel, or it
> might be on two different channels but with quite different sound quality
> and level so nothing would cancel at all.
>
> Even if you are getting very similar hum on two channels, inverting one
> and delaying to get a null would also need the relative levels of the
> two channels to adjusted to a particular ratio to cancel the hum. What
> happens if that makes the relative levels of the actual instruments/vox
> etc. wrong in the mix? Adjust for correct sound balance and your hum
> comes back!
>
> It's certainly not the simple and obvious procedure some people seem to
> think it is.
>

It's not a fix-all, and it certainly won't work in every situation, but
I'd certainly try it first in an attempt to maintain low end and
fidelity as much as possible, before resorting to steep notch filters,
with their phase weirdness and ringing.