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Author Topic: 3.5mm jack: resistors to use to avoid ear damage  (Read 1565 times)
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Hi folks, I'm working on a white noise machine.  I'm having a hard time finding documentation on what resistor values to use with a 3.5mm jack in order to avoid ear damage due to excessive decibels.  I don't want the white noise to drive me deaf!  Any suggestions or references? 1000 Ohms seems to get the signal down to a reasonable volume, but I'm afraid to put it too close to my ear until I can find out some facts.  Thanks for any help!
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Just adding a resistor won't work right.

The voltage (and hence volume) dropped by the resistor is dependent on the current flowing through it.

What you need is a resistive voltage divider http://en.wikipedia.org/wiki/Voltage_divider.

The simplest one is a potentiometer.  Apply your signal to one end of the potentiometer, and connect the other end to ground.  The ear piece then goes between the wiper of the potentiometer and ground.

Turning the pot then gives a volume between 0% (ground) and 100% (full input).

Start with the volume at 0% and increase it until it's loud enough to hear without deafening you.
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And a pot with an audio taper (logarithmic) will give better results for your application then a standard linear pot.

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Awesome, thank you very much for these replies!  Time for a trip to Radio Shack!

Have a great weekend!
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I am literally attempting to solve the same problem as this guy was, but I just have a super quick question guys:




wtf are those things on the bottom of the pot????
smiley-sad

I soldered some wires to the knobbies on the front of it and it's not giving me the results I'm hoping for...I'm getting a lot of noise just from touching it smiley-sad((
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What you have there is either a switched pot or a stereo pot.

The connections on the back of the unit (the bits with red) will either be one of the pot channels, or a switch.

The connections on the underside (the ones bent at right angles) are definitely a pot connection.  The center one is the wiper.
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What you have there is either a switched pot or a stereo pot.

The connections on the back of the unit (the bits with red) will either be one of the pot channels, or a switch.

The connections on the underside (the ones bent at right angles) are definitely a pot connection.  The center one is the wiper.

Oh, so they're just the same as the other ones? This has 2 of each type of connection?

Thank you, very helpful stuff smiley
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If the pot goes "click" at one end, or you can pull or push the shaft, then it's a switch.  Otherwise, it's just 2 pots.
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If the pot goes "click" at one end, or you can pull or push the shaft, then it's a switch.  Otherwise, it's just 2 pots.

Very helpful, thank you! :3
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