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