[sdiy] The annual I/O impedance/protection thread! (bumped)

[Justin Owen]

-----Original Message-----
From: Harry Bissell [harrybissell at wowway.com]

>>Q:...and if Yes to the above - were would the AC coupling cap go? Between Input and 100K (formerly 100R) or between Zeners and inverting input?
>>

>ugly any way you slice it. The cap should go between the inout and the zeners imho, with ANOTHER resistor to ground right at the input, so both sides of the capacitor have a bleed-off path to ground (no pops when you jack in) AND the non-inverting input can get bias current (or the opamp runs to the rail and stops working.
>

Harry,

For an AC Input - can you clarify the order for the components you've suggested above?

Input Socket, Resistor to Ground, Cap, Zener protection Resistor in Series, Zeners?

What value would you give the resistor to Ground - or what would dictate the value?

Much appreciated,

J