On 2/10/2019 2:28 PM, James Price wrote:
I was under the impression that the primary difference is that overloading
the front end of the ADC would potentially produce digital hard clipping at
the output, that is assuming the amp sim's volume isn't set particularly low
and the input level is cranked high enough.
Please, exactly what are you talking about? Hardware or software?
Yes, you can overdrive the input of an ADC and you'll get digital
clipping. This clipping occurs at the point where the guitar signal is
digitized, before it even gets to the simulation software. You
definitely want to avoid it.
For example, a 50 dB boost applied
to the input of an ADC vs. an analog amp. Both will clip, but my presumption
was that the ADC would produce digital hard clipping in the form of a square
waveform, whereas hard clipping in the analog amp would produce a waveform
that wasn't chopped.
You can clip an analog stage if you drive it hard enough. Drive it 50 dB
higher than its nominal input level and you'll get something pretty
close to a perfect square wave. When the analog stage reaches its
maximum output voltage, it can go no higher, so as long as any portion
of the cycle is above the maximum output level, it will be clipped at
that voltage.
The same thing happens with an ADC, only its maximum output level isn't
defined as a voltage, but as a binary number - the higher the voltage at
the point along the waveform where the converter takes a "snapshot," the
bigger the number. For a given word length, say 16 bits, the maximum
output, or full scale, as it's called, is when all the bits are turned
on. There isn't a 17th bit so the next successive samples that would
exceed full scale if they could are digitized at the full scale value.
And, yes, that means they're flat on top.
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