[sdiy] Analog bandwidth

[Rutger Vlek]

I think that many old synths were also designed with the knowledge in mind that we can only perceive sounds up to 20kHz. You'll probably find that the maximum frequency the LPF is capable of doing well never be over 20kHz (and often a lot lower!). In other places in the circuit filters might also be tuned to a maximum of 20kHz (for instance the filters used to kill supersonic opamp oscillations).

Rutger



On 20 feb 2014, at 17:39, Richard Wentk wrote:

> Possibly one of those annoying general questions. ;)
> 
> Has anyone actually measured the true signal bandwidth at the output of an analog synthesizer? Any make or model would do. 
> 
> Obviously in theory there's no need to have much happening above 20k. But I'm wondering how true that is in real circuits. 
> 
> Motivation is to consider how much bandwidth DSP systems need to do a good simulation. 
> 
> 44.1k is clearly a very poor representation of the real thing. But I'm wondering how high you really need to go, and how careful you have to be about modelling features like limited opamp gain bandwidth product and possible single pole phase shifts (etc). 
> 
> If there are real differences the usual abstract models of (say) a four-pole filter aren't going to be all that close to the imperfections of the real thing.
> 
> Richard
> 
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