[sdiy] Modeling circuits

[Eric Brombaugh]

On 10/22/2010 12:02 PM, Barry Klein wrote:
> I am wondering if they go and do spectrum analysis/ FFT response
> of say a Fender Twin and then only use their DSP platform to do
> a frequency subtractive overlay on the incoming signal - OR -
> could they also do an analysis of the incoming signal and then
> know better what to do to get it to be a better match to the original
> amplifier output response (that would be actually increasing frequency eq
> gain).

Modeling frequency response is no big deal. Modeling the nonlinearities 
accurately is _really_hard_, and that's a big part of the tube sound. 
The problem is that the best models these days are based on the Volterra 
series which results in huge equations of higher order products and 
delay terms. Then, tweak a volume or tone control knob and all your 
model coefficients change radically. Tough stuff...

Eric (works on RF linearizers & predistortion for the day-job)