AXE FX instrument input and A/D conversion (help me understand)

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Xbuk

New Member
Something I have never understood about the AXE FX digital conversion, let me explain. From my guitar into the AXE FX is obviously instrument level. I understand that the unit uses A/D sensitivity levels to adjust the noise floor. My question is, what is exactly going on here?

For instance, if I plug my guitar into a DI box the DI must go to my pre-amp to boost to a line level for my Lynx Aurora A/D converters.

How is the AXE FX skipping the instrument to line level boost and going directly to the A/D Converter?

How is this any different than me plugging my guitar directly into the Aurora's converters?

Thank you.

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Why would your DI box need to boost to Line Level?

A true DI should be the same Output level as sent in.

Edit:

Sorry, I see you are saying DI->preamp.

Fractal is basically a preamp...
 
Assuming Fractal uses converters that are calibrated for pro audio line level signals, I'd wager the range of the Input Sensitivity setting corresponds to the amount of analog signal boost before the converters in order to maximize the converters dynamic range and provide the best signal to noise ratio. The key difference is that once the signal is converted to digital, the virtual signal level is then padded back down an equal but opposite amount to ensure a relative unity gain setup through the conversion. That ensures that the virtual amp models respond naturally to any given guitar's output level in the same way the real amp would with the same guitar. There's no normalization of the input signal so natural level differences between various guitars and pickups are preserved regardless of how the Input Sensitivity is set (assuming you are not clipping the input of course).

In other words, Fractal likely does boost the DI signal level up for the conversion, but then digitally compensates for that boost to maintain unity gain through the conversion.
 
mr_fender said:
Assuming Fractal uses converters that are calibrated for pro audio line level signals, I'd wager the range of the Input Sensitivity setting corresponds to the amount of analog signal boost before the converters in order to maximize the converters dynamic range and provide the best signal to noise ratio. The key difference is that once the signal is converted to digital, the virtual signal level is then padded back down an equal but opposite amount to ensure a relative unity gain setup through the conversion. That ensures that the virtual amp models respond naturally to any given guitar's output level in the same way the real amp would with the same guitar. There's no normalization of the input signal so natural level differences between various guitars and pickups are preserved regardless of how the Input Sensitivity is set (assuming you are not clipping the input of course).

In other words, Fractal likely does boost the DI signal level up for the conversion, but then digitally compensates for that boost to maintain unity gain through the conversion.
Click to expand...
What you say sounds logical. I wonder if someone from Fractal would be willing to elaborate on this?
 
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