S&S D Duplex

[Sarah Fox]

I prevously wrote

> 6 dB

Hmmmm....  I pulled out my SPL meter and tried timing a couple of decays on
my Knabe (*without* any sort of bandpass filtering, admittedly), and I must
say I was surprised by the rate of decay.  (It fools the ear.)  A decay of
20 dB (1/10 amplitude) might be more measurable.  I also think that this
sort of experiment would be impossible without bandpass filtering.

It would be greatly facilitated, by a storage/digital oscilloscope or
analysis of a digital waveform.  Ron suggested a digital spectrum analyzer.
That would work fine if it does digital bandpass filtration or if it does
FFTs and then *inverse* FFTs with phase information preserved, so that the
FFT can be multiplied by a filtration function to achieve the same thing.
This is all avoided, I think, with electronic bandpass filtration on the
input, rather than "computational" filtration on the output.  In any event,
whether on a storage or digital scope or on a computer running a digital
spectrum analyzer, it would simply be a matter of examining the waveform
over time and identifying the relevant start and stop times -- probably
across a 20 dB decay.

Peace,
Sarah