I need help choosing the right potentiator for limiting volume

[GoldenMole]

I am currently making a device which connects two .25W speakers (http://www.electronics123.com/s.nl/it.A/id.2847/.f?sc=11&category=12) to an mp3 player. The device is associated with babies and I need to ensure that the volume is unable to get too loud. Having the volume limited would prevent ear damage, regardless of what volume setting the mp3 player is set to. I was wondering if a potentiator is the best way to adjustably limit the volume, and if so, what specifications would work for this kind of use.

[davenn]

any variation of the MP3 player volume is still going to result in a change of volume in the speakers even with a potentiometer (variable resistor) volume control in between
ie if the MP3 player level increases then the pot level will need to be manually decreased correspondingly to maintain the required output level from the speakers.

To maintain a constant output to the speakers regardless of the input level to the controller cct. You would require some sort of active cct, along the lines of an AGC Automatic Gain Control system

PLEASE tell me you are NOT going to put head (ear) phones on a baby ???!!!
dont even consider that unless you want to cause permanent hearing loss to the child at a very young age

Dave

[GoldenMole]

hahaha no I'm not making headphones for a baby.

I see what you are saying about how the volume is ultimately dependent on the device producing the audio signal... Could an AGC be powered by the mp3 player? If so, would it have a pretty significant draw on the batteries?

[davenn]

hahaha no I'm not making headphones for a baby.

I see what you are saying about how the volume is ultimately dependent on the device producing the audio signal... Could an AGC be powered by the mp3 player? If so, would it have a pretty significant draw on the batteries?

Thats good to hear :) haha

would be difficult to power it from the MP3 player directly, more likely you could power it from whatever you supply the MP3 player with ... it its a long term arangement

[GoldenMole]

hmmmm I think that I am going to go the route of using a pot, and calibrating the resistance to the most common mp3 players, since most mp3 players have roughly the same output levels anyways.

Do you have any ideas for what type of pot I should use? Or how I could go about calculating this?