I understand this argument, but I choose to treat it lightly it in real life because I am mostly interested in the sound I get in my own living room with my own real equipment making sounds for my skeptical human ears. There is a large and creative cohort of audiophiles generating and repeating numerous claims about audio. I cannot really credit many of these claims because they cannot to be reproduced in blind ABX tests, much like the spirits of the departed or the spoon-benders of yore. In truth, the presence of a side-table for my refreshments has a far larger and more measurable effect on the sound I hear than many of the possibly apocryphal sonic indecencies of the electronic components in front of me.

To address your point directly, equalization (the feature of the Behringer DEQ 2496 I am using and discussing) does change the incoming signal, or it would not be a very useful audio component. My hands-on experience with oscilloscopes and digital audio analysis suites indicates that equalization does induce phase changes in the signal – you can see that by comparing input and output signals, or alternatively by doing the simple math that creates band equalization in the digital domain. These phase changes are pretty much unavoidable by-products of the audio filtering process, whether analog or digital.

Better ears than mine sometimes claim to hear the effects of phase retardation, and I can conceive of extreme situations where this might be plausible. Those with golden ears can test themselves by doing a controlled blind ABX test with a conventional EQ system (as I am led to understand the Behringer implements) and a linear-phase EQ system, and publish results from which we all may learn. But I cannot hear phase retardation effects with current audio equipment and I would be interested to see the blind ABX tests that showed them to exist at all in normal human hearing. Ethan Winer has addressed the real-world impact of phase shifting in high fidelity audio on several occasions – for example:

“More to the point, phase shift occurs naturally and unavoidably in all speakers and crossovers, and in every EQ circuit, with no obvious detriment as far as I can discern. Phase shift can be an important factor in speaker and crossover designs, but only because a tone whose frequency is near the crossover point is radiated by two speakers at once. In that case phase shift could cause the two acoustic outputs to partially cancel each other as they combine in the air in front of the speakers. But any time you stand in front of a loudspeaker and then simply take one step backward, you are inducing a large amount of phase shift at the higher frequencies.” [1]

As to the more general implication that the Behringer DEQ 2496 introduces distortion, specifically the kind of distortion I would hear and dislike, this claim may still be argued. I will say that I have not yet run the full suite of digital audio analytics on the signal coming out of the Behringer DEQ 2496, and it may (against the general practice and standards of commercial audio equipment) distort the heck out of the incoming gunshots, explosions, and piccolos. You cannot prove it by me, and if I live up to my responsibilities I will check the manufacturer’s specifications with a digital audio reference suite some quiet week in the future.

I would note, however, in case anyone else is concerned about the capacitors that may be magnifying harmonic distortion in the Behringer signal path, that its EQ process in my setup is conducted entirely in the digital domain, from SP/DIF digital input to TOSLink output. Only the infinitely delicate fingers of the Fourier transform and its ilk have touched those bits, and the reputedly foul influence of capacitors appears, if at all, downstream in the amplifier.

References

[1] From “Dispelling Popular Audio Myths” (http://ethanwiner.com/myths.html, retrieved 2015-05-11).