How to use stereo headphone output to subwoofer mono line input

[vanakaru]

I have powered subwoofer with mono line in. I want to use headphone output to get signal to sub. This way the sub would correspond to the vol. level of the amp. Headphone jack is without muting switch. I want to get combined LR signal to the sub without loosing stereo on speakers. If I just connect headphone L&R channels together speakers would be connected the same way playing mono.
What is the way to do this?

 

[Galu]

Bass frequencies below 100 Hz are mostly recorded in mono, so you could try just connecting to one channel of the headphone out.

Or you could try a stereo to mono converter circuit like the one attached.

 

[vanakaru]

Thanks!
Mostly the one channel is OK as I have it done so far. Only some jazz and experimental music play with stereo effect on bass as well. So I shall try this converter. I did see it somewhere already but was not sure if this works on phones output or was it for line level only.

 

[rayma]

Thanks!
Mostly the one channel is OK as I have it done so far. Only some jazz and experimental music play with stereo effect on bass as well. So I shall try this converter. I did see it somewhere already but was not sure if this works on phones output or was it for line level only.

You likely will need to reduce the headphone jack level back down to around line level, so try two 10k resistors for the series,
and a 1k resistor for the shunt.

 

[Galu]

You don't want the converter to 'load down' the stereo speakers which will be in parallel.

For a headphone attenuator, the 20 k may be more usefully 1.6 k and the 470 ohm resistors may be varied to suit the level you want.