Using my headphones with my computer is frustrating. Whenever I want to use my headphones, I have to move my computer so I can access the back panel, unplug my computer speakers, and plug-in my headphones. Okay, maybe it isn’t that difficult, but it should be easier. How about a device that allows you to select between headphones or computer speakers?
Solution
After some careful thought, I realized such a device could be implemented using three 3.5mm jacks and one dual-pole dual-throw (DPDT) switch (see the schematic below).
As you can see, the DPDT switch simply selects whether the input is connected to the headphones or the computer speakers.
Other Possibilities
A similar device can be implemented using two dual-pole single-throw (DPST) switches. This would allow the user to select headphones, computer speakers, or both. A much more sophisticated implementation might include operational amplifiers allowing the user to adjust the gain on each output.
9 comments
Sam says:
October 22, 2009 at 7:18 pm (UTC -7 )
jackpot. this is so cool!
Jared Huntington says:
October 23, 2009 at 12:48 am (UTC -7 )
You can always adjust the gain passively by just using a potentiometer. An op amp would be nice for boosting signals though. You could also just use a SPDT and leave the grounds connected together at all times. Nice work! I need to make one of these.
kris says:
October 23, 2009 at 9:18 am (UTC -7 )
@jared
I like the idea of using a potentiometer to passively adjust the gain. Usually I have the maximum gain at the output of my PC which is good for my computer speakers, but bad for my headphones. The potentiometer would allow me to passively lower the gain for the headphones while delivering the maximum gain to the speakers.
Unfortunately you have to use a DPDT switch because it is a 2-channel stereo signal. Even with the DPDT switch, the grounds are connected together at all times. Thanks for the comment!
roochie says:
June 28, 2011 at 9:28 am (UTC -7 )
I’m trying to build my own audio switch which is essentially exactly the same as this one. Problem is when testing my TRS sockets, I get mono sound (i.e. audio is only coming out from my left speaker) I’ve checked my wiring over and over so I doubt its that. Could it be that my TRS socket only plays Mono? I just need clarification on whether there is are mono only sockets and stereo sockets.
Kris says:
June 29, 2011 at 11:40 am (UTC -7 )
Roochie, check your audio cable. You might be using a cable with TS jacks (mono). You can tell by looking at the jacks. The link below has a picture of 4 jacks. The jacks from left to right are: 2.5 mm TS, 3.5 mm TS, 3.5 mm TRS, and 6.35 mm TRS. All of your audio cables must have TRS jacks for stereo sound. Thanks for the comment!
http://en.wikipedia.org/wiki/File:Photo-audiojacks.jpg
Patrick says:
January 14, 2012 at 11:57 pm (UTC -7 )
What program did you use to make the drawing? I looking for a real simple cad type program for drawing such as this.
Kris says:
January 15, 2012 at 8:26 pm (UTC -7 )
I used Cadsoft Eagle which is fairly easy to use if you intend on making a printed circuit board. However, if you just want to make a simple drawing, it probably isn’t the best solution.
Trevor says:
January 25, 2012 at 12:26 pm (UTC -7 )
This is EXACTLY what I was looking for. Didn’t want to spend $20 + $20 shipping on a device I could make for a few bucks. Question: When you mention, “Even with the DPDT switch, the grounds are connected together at all times”, are the grounds for the jacks connected TO anything within the box (like, each other), or are they taken care of by the male connectors?
A little new to electronics.
Thanks
Kris says:
January 25, 2012 at 6:50 pm (UTC -7 )
Thanks for the comment. Yes, all of the ground connections are connected together. The 3.5mm jacks should have 3 solder lugs: 1 for left audio, 1 for right audio, and 1 for ground. All of the ground lugs should be connected together.