AW: Re: external input (again)

[Matt Haines]

>Folks in my band with advanced degrees in electronical engineering
>seem incapable of getting the grounding right.  If your input signal
>finds itself riding on on top of a 115v 60Hz sine wave it's a good
>idea to have reverse-biased diodes to the power +/- supplies as well
>as in input resistor.
>

That's a very good point. Unlike in the 'safe' enviroment of the modular
synth, bringing in outside signal sources could be frought with peril. So
on the power supplies of the op amp, I should have:



+15     ----------------+-------------------- +v op-amp in
                        |
                       ___
                       / \
                        |
GND     ----------------+-------------------- GND
                        |
                       ___
                       / \
                        |
-15     ----------------+-------------------- -v op-amp in


Right? So would a couple of 1w 16v zeners do?



>   Freq response...not crucial, as in not audiophile. I'm going to be running
>   it through horribly mind-twisting processors anyway. 20-20k not necessary,
>   but 200-5k in not good enough.
>
>With opamp circuits it's a good idea to roll of the high end in the
>feedback network to limit the gain in the region where the opamp is
>less able to handle it.

Like a 30pF cap in parallel with the feedback resistor?

>
>   As far as getting a book on op-amps, yes it's something I need to do. I'm
>   much more likely to get answers specific to my problem here on DIY though.
>
>It's important... at the very least it will give you the warm fuzzies
>about how these things work.
>


Hey, I've got the Radio Shack Engineer's Mini-Notebook, the op-amps volume!
That's a start. :)


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