Headphone Level to Line Level Circuit?

[Paul Marossy]

I have device that has a recording/headphone out jack. I would like to have an external box that I can plug it into which would convert it to line level so I could plug it into another amp for effects and models. Anyone have a suggestion for what circuit I could use to accomplish that?

[cd]

A simple non-inverting opamp gain stage should do it if your device doesn't have a level control.  Otherwise it should be fine on its own, just crank the level up.  I have a standalone headphone amplifier which works nicely as a preamp this way.

[Paul Marossy]

What about noise? Do you get a lot of noise when you crank up the head phone output too much?

[cd]

What about noise? Do you get a lot of noise when you crank up the head phone output too much?

Not really.  It's about as noisy as a regular line stage.  Depends on what you're feeding it, of course.  If that's already noisy or your device is noisier than usual you may have issues. 

I'll bet you can plug directly from the headphone out to whatever and it will be loud enough.  Line Level is around 2V peak to peak IIRC.  Check the specs of the headphone out on your device.  Say it's rated for 1W into 32ohms.  That's a level around... 5V or more (double check the math since I don't have a calculator handy and I'm doing it all in my head) which is easily line level.

[Paul Marossy]

Thanks fo the help! I'll give that a try. 

[d95err]

I'll bet you can plug directly from the headphone out to whatever and it will be loud enough.  Line Level is around 2V peak to peak IIRC.  Check the specs of the headphone out on your device.  Say it's rated for 1W into 32ohms.  That's a level around... 5V or more (double check the math since I don't have a calculator handy and I'm doing it all in my head) which is easily line level.

I though a reasonable headphone level was typically in the milliwatt range. At least it seems to be a lot lower than line level (but lower impedance of course). For instance, I sometimes plug the headphone output of my laptop into the line-in of an an external multimedia speaker system. I have to crank the laptop volume to insane levels AND the multimedia speakers up a lot higher than normal to get a decent volume.

[cd]

I'll bet you can plug directly from the headphone out to whatever and it will be loud enough.  Line Level is around 2V peak to peak IIRC.  Check the specs of the headphone out on your device.  Say it's rated for 1W into 32ohms.  That's a level around... 5V or more (double check the math since I don't have a calculator handy and I'm doing it all in my head) which is easily line level.

I though a reasonable headphone level was typically in the milliwatt range. At least it seems to be a lot lower than line level (but lower impedance of course). For instance, I sometimes plug the headphone output of my laptop into the line-in of an an external multimedia speaker system. I have to crank the laptop volume to insane levels AND the multimedia speakers up a lot higher than normal to get a decent volume.

Depends on what your headphone out equipped device is.  1W into 32ohms would be a typical DJ mixer.  10mW into 16ohms, a typical MP3 player.  At that level that's only... 0.4V peak (cranked up all the way) which would account for the gain required.