Cannot change USB levels

C

Champness

New Member
Hi everyone. I'm a newbie. I've searched the forum for an answer, but to no avail.

My AXE FX III is connected via USB to a MacBook Pro M1 running Logic Pro. Everything is fully up to date. The AXE FX III sees healthy input levels (the panel indicators hit orange, and the levels pane also looks good). But the signal coming into Logic maxes at about -24 dB. I would prefer around -12 dB. In the AXE FX III, I've tried changing the output level on the output block, the USB levels in the Settings / I/O / USB/AES panel (which appear to control input USB levels, not output levels), the output knobs (I understand that they just affect analog output levels, but tried it just in case), but nothing works. Logic does not give a way to boost input levels. Is there a way to boost levels in the USB signal in the AXE-FX III?

Thank you!
 
Thanks for getting back to me. But that doesn't work either. The preset leveling window only affects the amps, not the direct signal (e.g. input 2 connected directly to output 4). Also, for the path I have that does use an amp, changing the level so that it's way in the red (as shown in the leveling window) has no effect. Neither does setting the level to -80 dB. In both cases, Logic still shows the same input signal level, at about -24 dB. Nothing I do on the AXE FX III seems to have any effect on the signal level that Logic sees via USB. (Btw the Mac is running Sonoma 14.1.1 OS.)
 
Champness said:
Thanks for getting back to me. But that doesn't work either. The preset leveling window only affects the amps, not the direct signal (e.g. input 2 connected directly to output 4). Also, for the path I have that does use an amp, changing the level so that it's way in the red (as shown in the leveling window) has no effect. Neither does setting the level to -80 dB. In both cases, Logic still shows the same input signal level, at about -24 dB. Nothing I do on the AXE FX III seems to have any effect on the signal level that Logic sees via USB. (Btw the Mac is running Sonoma 14.1.1 OS.)
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Sorry! My mistake. The output leveler does affect the outputs 1 and 2. But I'm also using outputs 3 and 4. Why don't they show up in the leveler?
 
Outputs 3 and 4 aren’t shown in the preset leveling window because those aren’t digital outputs. However, like all output blocks, the output 3 and output 4 blocks have level meters.
 
Ok, thanks. But I'm still mystified. To isolate the problem I set up a preset with input 1 feeding output 4 - and nothing else. I set the inputs in Logic to 7 and 8. Logic does show signal, and I can record it, but the level is about -24dB and changing the level on output 4 block has no effect on this (even though the level meter for the output block goes into the red). I've not been able to find anything in the AXE FX III that changes this. Outputs 1 and 2 work fine.

I'm also seeing even stranger behavior. If I try the same experiment with output 3, then selecting inputs 5 and 6 in Logic shows no signal. But selecting inputs 7 and 8 shows the same -24dB signal!

It's looking like outputs 3 and 4 are just not supported for the USB connection, and I'm just seeing weird edge case behavior? Looking at the Settings / I/O / Audio pane, outputs 3 and 4 show a "boost/pad" option instead of outputs 3 and 4's "Output Level" option. If outputs 3 and 4 are not digital, as you mentioned, they should not be accessible at all in the USB signal, right?
 
Champness said:
It's looking like outputs 3 and 4 are just not supported for the USB connection
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Correct, the manual shows this in Chapter 3's USB Inputs & Outputs section. USB Inputs 5/6 are a copy of the signal at Input 1 (front INSTR or rear Input 1 jack), after unity gain compensation (so your Input 1/Instrument A/D sensitivity setting won't change the level seen/heard), without any further processing by anything in the preset. USB inputs 7/8 can be your choice of the signal at Input 2, Input 3, or Input 4.

To record anything* from the grid you need to route it to the Output 1 or Output 2 block and record USB channels 1/2 or 3/4. The USB Output Mapping parameter can swap the mapping of those 2 outputs to those 2 USB channel pairs.

*If you really need to record more than 4 channels with some type of grid processing via USB, and happen to have some unused inputs/outputs, you could route a signal to the Out 3 or Out 4 block, then cable those output jacks to the Input 2, 3 or 4 jacks, and record USB channels 7/8.
 
Many thanks for your help, Bakerman and GlennO.

[My hoped-for use case was to record voice and guitar, both processed and direct (hence the need for four outputs), using USB into Logic.]
 
Champness said:
[My hoped-for use case was to record voice and guitar, both processed and direct (hence the need for four outputs), using USB into Logic.]
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Maybe I'm missing something but you could use USB 1+2 (Out 1) for guitar, and USB 3+4 (Out 2) for your vocal.

From the manual page 20:

Screenshot 2023-11-29 at 8.09.21 AM.png

For the best SNR you'll want to use a hardware mic preamp in front of the AxeFX since it doesn't have a mic pre. You can get the character of Fractal's mic preamp models in the cab block by loading a null IR and then selecting a mic pre model, so I'd get a very clean and neutral hardware mic preamp, like RNP, DAV BG-1, SCA C84, etc.

Perhaps you're doing a "live recording" thing where you need to record all 4 channels simultaneously, but in general the standard practice is to record the lead vocal mono and dry (i.e. sometimes printing compression and EQ but never wet fx). You could of course record mono and dry while monitoring with stereo wet fx by simply adding wet fx before out1 but splitting the path to out2 before them. Monitor out1 with headphones, record out2.
 
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