[sdiy] equalizer

[cheater cheater]

On 10/11/05, Johannes Öberg <johannes.oberg at gmail.com> wrote:
>
> (in reply to cheater cheater)
>
> >Why wouldn't an eq made only out of "low-passed" and "high-passed"
> >bands be precise? I think it might feel less "natural", though.
>
> The eq and the filter would have different uses. The filter kills bassdrums
> (etc) while the eq smoothes out "sound differences" from different records
> (some records have too much midrange, others lack a bit of highs, etc) to
> make tracks go better together. You can't make subtle changes to the treble
> with a lowpass filter as it kills everything above its cutoff.
>

no... What I think I'll build would:
1. break up audio into several bands using LP/HP filters
2. set the gain of each of the bands separately (so, as you see, it
doesn't necessarily "kill" those bands, it just separates them much
more sharply)

> I believe the reason professional DJ mixers only have 3-knob eqs with "kill"
> is only that it's cheaper.
>

No, it's because many DJs prefer "kill" over "smooth" EQs :)
Also, I'd think 2 filters per band (and tuning two filters per band)
would be *more expensive* than one (bandpass) filter per band.
And more troublesome to tune and fit in the box.


> I said +- 5 dB only because that gives you more precise control across the
> pot turn range.
>

You need to have precision in your fingers :)

Also, BIG knobs help.

Not that anyone would hear slight differences on shitty audio setups
DJs are forced to play on anyways 8P

> >how steep do you think it should be?
>
> 24 dB/oct was ok to my ears, but of course killing the bassdrum with FFT is
> always better :-)
>
> You wrote in earlier posts that $200 would be too much to spend on a mixer.
> In that case I think 24 dB/oct will be acceptable.

I was talking about a single channel.... 8)

>
> BTW, how are you solving the crossfader problem? Perhaps we should join
> forces and dream up the ultimate DIY DJ mixer, and see if we can harrass
> this list to construct it for us? :) :) :)
>
> /J

I was thinking of a digitally controlled mixer :)

The innards would be CV-controlled. There would be a (pretty fast) uC
to control all of that and take the input from the knobs and faders.

Faders themselves would of course be THE faders.... P&G. no less.
{well, perhaps for prototype, but I won't rest until those are in my
box 8) } Though I cringe at the thought of having 6 of these in a
mixer... or the cost, rather... heh.

Anyways, the digital control would let you:
1. assign any knob to any parameter
2. assign controllers to midi etc (not that I'd use it extensively
really :P nothing like having a separate bank of knobs. but I could
think of e.g. having 3 of the 5 planned channels dedicated to midi
control instead of being "real" mixer channels)
3. set up any, ANY, arbitrary fader curve
4. callibrate the thing mucho easily
5. record movements: I find myself often doing repetitive movements on
a fader or eq knob to e.g. accent a single sound in a pattern. Also, I
don't "do" vinyl, I "do" ableton so you can see my pattern-oriented
noisemakery goes a long way 8). If I could hold a "rec" button, twist
a knob for a bar, and then have it repeat over and over till I turn it
off... that would be just great. greeeaaat. It would be like having an
unlimited number of hands :D


Your proposal of making a mixer together sounds very interesting!
Tell me what you think of my concept.
I could take part of the difficult mathematical aspects of this thing.
I'm a 3rd year maths student :)
Complex calc is yet to come though :/ 2nd semester of 3rd year, though :)

cheers,

D. 8>