I'm probably preaching to the choir with some of this but maybe a few folks find it helpful if they're into "Neural Capture" and aren't getting good enough results.
May not work for all use-cases but found some of these definitely helped in mine.
Tip #1:
Before starting the Neural Capture, ensure the input impedance on the instrument is set to what your amp has.
Most amps have a 1Mohm input so getting IN 1 and IN2 to 1M will help (I know if you goin into IN2 with an XLR cable, it makes no difference as the input flips to another value for MIC signals)
Tip #2:
After the "Neural Capture" guide / connection diagram screens, you end up at the point where you can start the Neural Capture process and/or adjust levels.
Do NOT boost the "IN 1 LEVEL" - just leave it as is. Don't go for peaking at -6dB or any other value - leave it as is.
Bump the IN2 (coming from the Mic or Loadbox) if you need it / the capture to be louder.
Tip #3:
Unless you have a good quality USB cable with ferrite choke between your PC and Quad Cortex (ex:
https://www.thomann.de/gb/udg_ultimate_usb_2.0_cable_s2bl.htm), remove the USB cable from the Quad Cortex to the PC.
I was getting some annoying interference / noise that messed my captures & found out by accidentally disconnecting the USB cable while at the Neural Capture screen.
It's a good idea to have the bare minimum of cables connected to the QC for the Neural Capture process; I'd leave everything else disconnected aside from the stuff you're told to hook up during the "Connection Diagram" screen.
Tip #4:
For folks using the
vanilla (non-IR) Suhr Reactive Load, don't use the XLR-out on the Suhr to go into the Quad Cortex.
The Suhr RL has a high output impedance (probably too high for the QC's XLR input to work well with the non-IR Suhr Reactive Load XLR's output).
Use an unbalanced cable if you're shooting "direct" / loadbox-only (no cabinet) profiles of your amp if you must (pick a good quality cable like the Sommer LLX stuff).
What I found out last year shooting NAM profiles is that the output transformer on the Suhr hypes the highs and has a sharp attenuation from about 100Hz downward (too sharp for my liking). It does the same thing even if you use the
THRU port with a real cab hooked
up.
I got a Behringer GI-100 DI box (very cheap) and connected it between my tube amps and the Suhr Reactive Load for silently shooting direct captures.
The Behringer GI-100 can also go between the amp and a real cab, it'll apply the impedance curve of the real cab to the capture but the "reamping" phase will not be silent
(ie. you'll hear the alien sounds coming out of the cab
)
Tip #5: DISREGARD not needed (seems to only affect the output volume!)
This one's important for consistency of captures & that they play well on other folks' QC units if they use them.
After the Neural Capture finishes and you're at the "Cortex" / "Reference" page, apply a 5.5 dB boost to the level / gain of the capture right before you hit "Save" and put a name on it.
The Quad Cortex' "Capture Out" port used to pump the training signal / sequence into the amp is rated at 9.5 dBu (confirmed by NDSP support);
The QC IN1 is rated at 15 dBu (also confirmed by NDSP) when plugged in with an unbalanced cable and set to 1Mohm.
Saving the capture this way will help it behave as close as possible to your gear; in essence you're not applying any boosts before the capture process starts but are somewhat calibrating / making up for the delta between the maximum gain of the QC's input and "capture out" ports to help the capture fidelity.
Tip #6:
If noise is still present when you have stuff hooked up, try putting an iso-box like the Palmer PLI-01 or the Palmer PLI-05 between the QC's "Capture Out" port and the tube amp's input (or pedal etc - depending on what you're trying to profile).
I had some pretty aggressive settings on my Ceriatone King Kong 100W where the profiles didn't turn out as the amp and throwing the PLI-05 in between the QC Capture Out and the Input jack of the Ceriatone helped get good captures.
Sorry for the wall of text but since I got another Quad Cortex recently, Neural Capture was on my mind and wanted to try and apply some lessons learned from the time I sold the first one & moved to exclusively using NAM (neural amp modeler) to profile my gear and present day.
All in all, I like the way the Neural Captures turn out; even the "direct ones" that are shot using a loadbox.
