simple high pass filter question

[werewolf831]

My mixing board has a low cut switch (high pass filter) on every channel. I keep this emgaged whenever I record most of my tracks, ok, all of my tracks. Now then, When I monitor what I've recorded and make my stereo mixdown, I still have all of these engaged...should I not? Am I putting my tracks through a low cut twice? BTW I'm using a Mackie 1604 and an adat, mixdown to the PC.
Thanks in advance.

[roman]

I would record blank and use the high pass on mix down. If it needs that!
just listen and decide if there's too much low rumble on the track... it's also just a matter of EQ taste.

[Fletcher]

Anytime you add a filter you're adding a "phase shift" to the signal. The cumulative effects of this 'phase shift' may lead to a "smaller" sounding overall event.

FWIW, I'm from the "when in doubt, leave it out" school of engineering... especially when things like Mackie desks are involved.

Best of luck.

[moley]

Like Fletcher said, filtering causes phase shifts (EQ in general does, but filters in particular) - so perhaps you shouldn't do it needlessly.

If you have the facility, look at the waveform of a square wave, before and after you've applied a high pass filter (make sure the cutoff frequency is well below the frequency of the square wave).

Even though the filter is well below any frequency present in the square wave, what you'll see afterwards don't look much like a square wave

Granted, you're unlikely to hear the difference with just a squarewave...

[werewolf831]

Thanks for the replies.
I'm not too familiar with phase shift. Can this make things seem slightly off key? Also, how do you make a square wave form?
Thanks,
werewolf

[moley]

Originally posted by werewolf831
Thanks for the replies.
I'm not too familiar with phase shift. Can this make things seem slightly off key?

It's a change in the phase relationship between the different frequencies that compose a signal.

If you imagine that every sound can be made up from sine waves at particular frequencies and relative volumes - then what filtering does is to shift those sine waves "sideways" by some amount, so the phase relationship between the constituent sine waves (frequencies) is different. This happens with filtering, even with the frequencies that aren't directly affected by the filter. If you're filtering out all frequencies below 20hz, that still causes phase shifts with the rest of the frequency spectrum.

Unless, you have the facility to do linear phase filtering.

Also, how do you make a square wave form?

With a tone generator. I presume from that question that you don't have the facility to, or if you do you've never found it

Here's what it looks like (second one down):