external audio input module

[Matt Haines]

>     I remember countless hours spent trying to characterize non-electronic
>     real-world audio waveforms.  I too concluded that most signals will
>     average about 1 Vpp.  But what was really difficult was characterizing
>     the exceptions.
>
>     Microphones and especially guitars can give some really tiny and
>     really large signals (read that: large dynamic range).  Of the
>     electronic instruments I tested, I found that the dynamic range was
>     somewhat limited and tamed probably because of the output stage that
>     has a max output voltage.  Their outputs were more predictable and,
>     hence, easier to process externally.
>
>     So I would like to offer my 2 cents about your circuit.  I would think
>     about putting some kind of dynamic (or maybe hard) limiter on the
>     input or output because, if you are processing audio through an
>     amplifier with more gain than you need (just in case), you will
>     probably drive the signal way beyond the clipping threshold of the
>     amplifier.
>
>     John Speth - johns at oei.com



Thanks for the input. I don't actually want to put a *real* limiter in
front of the circuit, 'coz that costs money and could be used elsewhere
anyway. Should I put a zener diode in, just for emergencies? If so, where?
(before the op-amp I would assume) And what value?

Realistically, I'm going to be taking the output of samplers and other
synths, which are usually in the same range. No mics, no guitars, no
bassoons. :)


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Matt Haines  haines at apc.net         .       .       .       .
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Moonlight, Muzak, Knick-Knack, Paddywack