[PD] dac object question

[Mathieu Bouchard]

On Thu, 8 Jul 2004, Frank Barknecht wrote:

> first: thanks a lot for explaining the DC effects to you and to Lex. I
> did however ask my question slightly ambivalent. I also would be
> interested in why and how a [hip~ 5] filter removes a DC offset.

why: because DC is, in some way, a 0 (zero) Hz wave, and by definition
"High Pass Filter" means something that cuts off low frequencies, which
would include 0.

how: I don't know how [hip~] works, and that is implementation-dependent,
that is, there are many kinds of high-pass filters.

> And related to that: What would be the best way to make sure you get
> no DC offset?

Filter out the DC whereever it is where you don't want it, and don't
filter it where you don't care about it. How you do it exactly is your own
business.

> I normally don't use sound input, so are there other possible sources
> to watch out for in purely algorithmic patches, which might generate a
> DC offset without intention? I see that a phasor introduces a DC
> offset, but should I watch out for less obvious offset sources, maby
> filters and the like?

Depends what you call "without intention"... squaring a signal (e.g.
[expr~ $v1*$v1]) always introduces some DC. It is useful, too. The RMS
volume is defined as the square root of the DC of the square of a signal.

For other filters I don't really know. If you want to probe for DC, you
can do it, using something like [lop~ 1] -> [snapshot~].

Makes sense?

________________________________________________________________
Mathieu Bouchard                       http://artengine.ca/matju