So I have had a pretty hard time figuring out how to correct what almost sounds like high end phasing when using my quad cortex. Here’s what I have found and I hope it helps:
Many cab sims and IRs have an inherent high frequency “shift” or something like that. It might be caused by the SM57 or combining 2 different mics in the capture process and I’ve heard that it’s worse on the closed back cabs but I still am finding it an issue with open backs… in any case, I have found this same problem using pretty much every modeler I’ve tried and high cuts haven’t really helped me in this area. With the quad cortex I have found a method that gets most of it out of the signal:
1- global input volume- I’ve found that helps right off the bat, and I’m not talking about the input block. It’s got to be the global input gain stage so that you have a nice strong signal coming into the quad cortex. I’ve got mine set to 14.1 dB of gain and that has worked pretty well, but it all depends on your guitar’s output. Start at 9.4 dBs. I’ve read that internal software raises the noise floor after 9.3 dB of input gain which gives you more headroom but I don’t know how to test that “fact” for sure. Either way, it’s worked me… in any case once you have a good strong signal coming into the unit itself long press the input block where you can set up your input gate and post input gain stage and turn the gain down as many dBs as you tuned it up on the global input gain stage. (ie. If you had to turn up the master global input to 9.4 dBs to get a strong signal, turn the input block gain section to -9.4 dBs to even everything back out to unit volume).
2- use an EQ block before any pedals and tweak to taste, but make sure to adjust the volume (either up or down) before you start messing the frequencies. The OD and distortion virtual device blocks also “want” a certain input volume for optimal tone.
3- another EQ block after the OD/distortion pedals right before the amp sim. EQ to taste, but before you EQ, again, lower or raise the volume so that it’s hitting the amp section at the “sweet spot” volume. You’ll notice that the amp’s tonal response will drastically change as you lower and increase the volume. Just play around with it until you find that “right tone” you’re looking for.
4- you guessed it- another EQ block after to amp block and before the cab. Slight EQ tweaks and slight volume tweaks… I’ve found that sometimes I’ll turn the volume up on the amp block and lose my tone, but if I turn up the volume on an EQ block afterward my tone stays the same, just louder (which is what I want).
5- Download a bunch of tube driven power amp captures and place one right before the cab block, then cycle through them to find what you’re looking for. The addition of a power amp worked wonders once I tried it. I’ve landed on a Fryette LXII Power amp capture but I tried a whole bunch of them before I found what I was looking for.
6- and of course- another EQ block after the cab for some final tone shaping.
7- what has also helped is running my guitar into a tube driven preamp before the quad cortex. I tried multiple tube driven pedals that I DID NOT like and was a waste of money, but what finally did the trick was a $175 Art Tube MP StudioV3 on the “valve” or “multi” setting. It has absolutely helped warm my tone up and give it that real amp feel.
8- I put a T-Rex roommate deluxe pedal in the effects loop. It is a tube driven stereo reverb pedal which also warms up the tone and helps give it that real amp feel.
Final thoughts: I was really surprised at how much the volume going into a virtual device made such a huge difference, whether it’s an OD, Distortion, Amp, or Cab. I’m guessing that it works like that with real equipment in much the same way, but I’ve never found a Boss GT 1000, or Helix to be so “touchy” when it came to the input volume going into each stage of the virtual pedal board. The biggest positive changes I noticed as I was figuring all this out was initial input volume, and then input volume going into the amp capture. These 2 will absolutely help you eliminate much of that “artifact” stuff that’s so hard to get rid of. I suggest you get these 2 parts close to where you want them before you do any of the surgical EQ stuff.
I hope this helps someone. Peace out