Hello,
I just unboxed and started using my Quad Cortex today and have been watching videos on capturing VSTs. It all makes sense to me for the most part and I was able to sorta capture a VST to test, but where I’m having a little confusion is on setting the input level of my secondary interface. I was just using a little Scarlett 2i2 so I connected the left monitor output to the input of the QC. When I play my guitar as hard as I can and set the input on the QC just below clipping and set it just below clipping on the Scarlett as well, when I go to capture, the Scarlett starts clipping. I imagine this is because of the various signals the QC sends to capture the responses but is this normal/will it result in a bad capture? When I turned down the gain on the Scarlett so it was no longer clipping at all, the resulting capture was rather low gain for an otherwise high gain VST. Just wondering what the best way to do this “correctly” is. Many thanks in advance!
Hi @sunny-mittal and welcome to the community! I use a Presonus interface when capturing my plugins and for the most part, capturing plugins works the same way you would capture a live amp, drive etc. Each interface is different in how you would set the input levels but essentially you would set your QC capture INST/IN levels to just under clipping and make sure you are set to Instrument instead of MIC input etc. You will need to adjust your Scarlett levels to just below clipping and play with the gain until you don’t see any clipping on the QC. The other alternative is to try AUTO-SET on the QC if you can’t find the right gain-staging for the captures. You definitely do not want digital clipping as your captures either won’t work or will not sound correct so you will just need to find the right spot so that clipping does not occur on the QC. If you still have issues, reach out to support@neuraldsp.com and they might be able to walk you through if someone is familiar with the Scarlett etc.
I’ve used Slate and Presonus interfaces and it’s a pretty mysterious process- it’s hard to say exactly what settings are best. As long as you’re sure there are no extraneous gain stages involved (plugins, gates, comp etc) it’s mostly a game of balancing input vs output levels. Have fun experimenting
Hey, I have the same issues with my scarlett 2i2 3rd gen. If you solved the problem please let me know!
Maybe this helps: Capture Techniques - Quad Cortex Wiki
EDIT: I’m just guessing but the clipping of your audio interface input could be due to the QC probing the captured device with hotter signal peaks than what is sent during level adjustment before capturing. We know that every captures includes a gain parameter. In order to be able to increase the gain of the capture later on, QC has to know how the real device reacts when it’s driven with a hotter signal compared to the hottest signal during level adjustment, right? It’s less of an issue when capturing analog devices but with VSTs it might be problematic when the input gain is set just below clipping related to the pure guitar signal.
Therefore, theoretically, you should avoid leveling your VST/audio interface input to be at 0dB when just the guitar is connected. Instead, try setting the input level lower (e.g. -12dB) and compensate for the lower gain by adjusting the VST’s virtual gain parameter post input. This way, there should be more headroom for hotter signals when capturing. Imagine setting your audio interface and VST so it doesn’t clip when you connect a boost pedal between your guitar and audio interface. Does that make sense?
also, keep in mind that the guitar signal is not actually involved in the capture process; setting it below clipping will not affect the capture at all. It’s only there for comparing the capture to the reference source when you’re done. Don’t worry about adjusting that level.
Concentrate on the other input level. I tend to start high, and lower it a bit each time if it fails the ‘sanity check.’ It’ll tell you if it’s too hot. Then keep experimenting till you get just below that fatal level.
This is very helpful, I haven’t played around much with capturing yet. I did read or hear that you can damage the QC if the signal is too hot, though. Is that inaccurate? That’s the main reason I’ve been reluctant to ply around too much.
No, you will just get digital clipping which will make your capture useless etc.
what’s more likely, though I haven’t heard of it actually happening, is that the QC capture signal would be too hot for the gear it’s being sent thru. In the case of plug-ins, support doesn’t officially recommend it because of that slight/remote risk