Why Am I getting phase issues? [Chorus EQ trick]

[isuckatproducing]

Hi,

So I saw some video I think from UAD where they put EQ on AUX with a massive cut, and their chorus after it. I've tested in before on some random sound and it did widen it nicely without phasing issues.

I'm now messing with trance lead, when I do it the way you can see on a screenshot, I seem to be getting phase issues. The more I cut with the EQ, the worse it gets.



Thanks

[Zeisner]

Use a linear phase EQ.

[kernaudioio]

the phase issue comes from the EQ itself, not the chorus. when you put a minimum-phase EQ on a parallel/aux send and mix it back with the dry signal, the EQ's phase response interacts with the original and creates comb filtering. the bigger the cut, the more phase rotation, the more cancellation -- and it gets worse in mono.

zeisner's answer (linear phase EQ) does fix the EQ side of it. but your chorus is still adding modulated delays that will cause their own mono issues when summed, which is a separate problem.

what this technique is doing is decorrelation widening: making the aux sound slightly different from the dry signal so they spread apart in stereo. it works, but DIY versions tend to be hard to control because you're stacking two sources of phase manipulation (EQ + chorus) without knowing what your mono sum looks like.

if you want reliable widening on a trance lead without the mono headaches, purpose-built allpass decorrelators handle this a lot more cleanly -- they spread stereo without introducing audible cancellation on summing. i built one called WIDE that uses this approach (disclosure: i'm the developer, kernaudio.io). there are also free options worth looking at, like the Mid/Side matrix trick in most DAWs or Voxengo MSED.

if you want to stick with your EQ + chorus approach: switch to a linear phase EQ, keep the cut shallow (under 6dB tends to behave better), and check your mono sum regularly as you dial it in.