LM386 Amp - suggested gain for line level media player input?

[Jack.Straw]

Hi guys. I like to build these little LM386 based guitar amps. Lately people have been wanting them to use with their media players & I want to remove the unnecessary gain control that i typically use on the guitar amps. I know i can set gain from 20-200 by placing the appropriate resistor/cap between pins 1 & 8, but i'm not sure what value would be best for such an application. What gain amount would you recommend for use with an ipod or other media player?

**broken link removed**

Thanks for your time,
-Scott

 

[bountyhunter]

If it is truly line level, the typical gain factor for the power amp would be about 40dB (gain of 100).

BTW: most of those types of cheapie power amps like the LM386 are designed for a specific gain and are not stable at low gain values. The ones we designed were always set up for about 40 dB.

 

[Jack.Straw]

Thanks bountyhunter... i'm not sure if it's truly line level, but i think you understand what i mean... whatever is typical for a ipod/mp3 player. Thanks for the advice, -Scotthttps://www.electro-tech-online.com/newreply.php?do=newreply&p=894430

 

[bountyhunter]

Line level means about 500 mV (RMS) signal level corresponds to 0dB level. It also has a fairly high output impedance like maybe 100 Ohms. The outputs on IPODs are lower impedance because they drive headphones which are pretty low impedance. I'm not sure what the signal level is. You should still use 40dB gain for the LM386 (or whatever gain the data sheet shows is right) and if that is too loud, use a resistive divider at the input until you get the correct full gain setting.

 

[audioguru]

Why not use trimpot volume controls on the inputs of the LM386 amplifier as shown on your schematic? The Fet input is not needed.
I don't think you need more gain than 20 which is what the LM386 has when there is nothing between pins 1 and 8. Add a 10uF capacitor between those pins for 10 times more gain.