[LAU] Mackie Onyx like channel strips?

[David Kastrup]

Folks,

it would appear that Mackie puts up the circuit diagrams of a number of
its mixer models up for download.  That's something that I very much
appreciate.

Now the EQ section of the Onyx mixers has been designed by Carl Perkins
and is liked by a few people.  Since it has to get along with not too
many elements and uses opamps, the actual equations for the various
sections (shelved low-pass, parametric mid pass(es), shelved high-pass)
are comparatively simple and basically amount to comparatively simple
transfer functions yielding themselves reasonably well to bilinear
transforms and consequently low-order IIR filters.  There is frequency
warping, of course, but at least for higher sampling frequencies like
96kHz the effect should be reasonably contained since the filters are
shelved and thus the warp at higher frequencies becomes irrelevant.  And
it probably makes sense to transform the filters such that the
transition frequencies remain the same in analog and digital filters.

So it should be possible to offer emulations of the various mixers'
channel strips.  Bonus task, of course, would be to recover
automation/settings of physical channel strips including EQ by recording
the analog complete mix as well as the pre-fader pre-EQ signals and then
reconstruct from there.  But that would be a lot more complex than
providing the digital equivalents of the channel strips including EQ.

Now if one did this, what would be the most defensive way to go about
it, and how would one try getting Mackie to be ok with it?  I don't know
if there would be legal repercussions unless one used trademarked terms,
but stuff like providing the circuit diagrams is a great service from
them that I would not want to see stopped.

Obviously, the "recover automation" bit would help a lot since it would
work best if you owned a physical mixer with the exact channel strips
being emulated.  Certainly more appealing than "now your Behringer
BCF2000 can be used for producing the same mix digitally as a Mackie
analog mixer, and you get a full automation record in the process".

That would not sound exactly like a driver of enthusiasm.

Of course, an analog mixer beats a DAW in terms of signal delay and
hands-on-ness and reliability, so one could consider the digital version
"training wheels" for "the real thing": if you like the digital version,
you'd quite likely get along with the analog version.

-- 
David Kastrup