Hello gentlemen. I am the new owner of an AxeFX II XL+. I through read the manual, but it doesn't seem entirely straightforward in some regards. I plan to use computer speakers through the headphone jack until my active monitors, mixer, and audio interface comes in. I've watched some intro videos, but not really anything describing how to set the amp so it can be used with its FX return as a power amp for the AxeFX. What settings need to be changed in the AxeFX to make it sound good? What are some other practical things I should know about the AxeFX got get a good start? Thanks in advance.
Fellow Newby!! (I've had mine less than 30 days...)
I run my XL+ into two tube amps through the each amp's effects loop RETURN, like you are planning. Biggest three things (that I have found so far) to adjust on the Fractal is the "Power Amp", "Cabinet" modeling and the "OUT 1" tab's EQ. All three are in the Global button on the front panel. For a real amp, I turn cab modeling OFF (for sure!). I've had mixed results with the Power Amp modeling. Some I like better with it ON, others I like a little more when it is OFF. While you have the Global open, hit PAGE > to get to the "OUT 1" tab. From there, you can fine tune the EQ to bring out the best in your real cab. Although, it IS a Global EQ - the perfect EQ on one preset isn't the best on another. So, a better way is to go into Axe Edit and EQ each amp (or deep-dive from the front panel), but the Global EQ works great and quickly.
I've been changing my hook-up method every couple of days until I settle-in to a favorite. I've been a little reluctant to save a lot of changes until I figure out the long-run set-up, hence playing with the global EQ. Today was XL+ into a Crown XLS2000 stereo power amp into a Marshall JCM900 4x12 cab and it was awesome! I go through headphones quite a bit, so I've gotten familiar with tweaking the amp/cab settings to match the hook-ups. Favorite so far is XL+ into effects loop RETURN only of two tube amps (with power amp and cab modeling OFF). Great amp-in-the-room sound from every preset. The 10-band EQ on the Global Out 1 tab makes for excellent "quick tone tuning." The thing I missed initially was using the NAV buttons to "move" the ABCD knobs to the different sliders for quicker tuning.
If you end up running two real amps for a stereo rig (or if you get hum with a single amp), I recommend a Radial Engineering ABY pedal to kill the inevitable 60-cycle hum. They are reasonably priced (new and used!) and widely available. They have three switches for an isolation transformer, ground lift and polarity 180. I'm sure there are several other brands that have a similar function, but the Radial pedal is what I use. And: no power required! You can leave it hooked up without worrying about batteries or wall warts. Newer ones have LEDs that do require power, but if you don't need the lights, it works fine without power.
My tube amps (Lee Jackson-modded Ampegs: VL-series) both have attenuators on them. Running those definitely lowers the "idle" noise and hiss. With the effects loop RETURN only method, usually only the volume and maybe presence or reverb controls on the amp will function, so there's not too much to adjust on the amp. Caution: the amp volume will be extremely touchy! Everything else is "usually" (some amps are different) in the pre-amp, which you are bypassing. I ran it into the PRS Archon (no attenuator) and it got a little "woolly" with the noise and sensitivity of the XL+ volume. If you feel like the effects loop RETURN is a little out of control on your amp, try the four-cable method (4CM) instead. Or, spend $200 for a used class-D (very lightweight) stereo power amp and run it into a stereo guitar cab! Most guitar 4x12s are 300-watters, so you don't need a massive power amp. Quick note: most power amps you find are rated for the "bridged mono" wattage when used with a certain ohm-value speaker(s). Splitting them into stereo 'normally" cuts that number by half and then is further decreased by the ohm of the speakers. I think the higher the ohms of the speaker, the less power is put to them. So, a 1000-watt power amp might be 500 per side in stereo, but only 200 (or less) per side if you use 16-ohm speaker cabs. That's a HUGELY simplified explanation and is probably more "concept" than fact. But it gives you more questions to ask... Ha!
It sounds like you have a pretty good handle on this stuff, but I always post a "spelled out" version for other newby users who may not have your knowledge or skill. I know I've picked up stuff from posts that were YEARS old. Ha!