audio pickup in analog x

Hello, sorry maybe this question is already been asked but i cant' find,
i want to read the value from a guitar passive pickup putting it into an analog pin of Arduino, so with this data i would like to move a servo .
Must i put some resistor or capacitor before or can i connect directly to the pin?
something like is already be done maybe?
Many thanx

Yes you need something like a 100K pull up and pull down on the analogue input then you need to attach the pickup through a capacitor.
The odds are that the pickup voltage will be so small it will need amplifying first anyway.

Guitars like to see a higher impedance. A pair of 1 Megohm or 2M resistors would be better. With a 50k load (a pair of 100k resistors) the signal is going to get knocked-down a bit, and your tone will probably be affected.

With a high impedance load and the guitar volume cranked-up, you should get around 1V, which should be plenty of signal to work with.

With audio inputs, I normally use a [u]peak detector[/u] (You'll need to change the 100k input resistor to 1M or more.) A peak detector will work with lower signal levels, and since it's not biased at 2.5V (like the 2-resistor method) you can use the 1.1V ADC reference with weaker signals.

I think I'll measure the out voltage and work accordingly, many thanks Grumpy_Mike,many thanks DVDdoug!