Idea for a case mod, but i need some help with the electronics

[Bignate603]

Ok, i want to put a switch on the fron of my computer that lets me switch back and forth from my computer speakers to my stereo speakers. However, I don't have a huge amount of knowledge about electronics.

My first question is, has anyone ever done this and if so can they just give me a simple layout of the circuit?

Second question, if no one has done this, does anyone know if the current through a headphone wire oscillates in direction or does it only move in one direction?

Third question, I'm probably going to resort to using transistors to route the audio, what kind should i get for this application and can i use the -5v from my PC to run them?

Any ideas would help...

 

[Bignate603]

Bump

 

[pbrain]

i think you need to be clearer in your description. aren't computer speakers stereo speakers? i really have no clue what you're trying to do.

 

[Bignate603]

sorry, i meant a shelf system, i like my labtec surround sound for games but prefer my mp3s on my shelf system. The music just sounds better on it and it fills the room a little better so i can hear it well away from the computer. Right now i have to reach backand sway wires from computer to shelf system, so i want to make a flip switch so i don't have to.

 

[pbrain]

why don't you plug the two systems into a stereo y-splitter and turn off the system you aren't using (so they both don't get weakened signals)?

 

[smp]

Someone correct me if I'm wrong.. but there are three way switches.. on-on-off. I think that if you got one of these, you could route your stereo input through one, comp speakers through two, and the third would be off. I don't know if you actually want to mod your sound card as well.. I'm pretty sure that there is a how to at virtual hideout about something similar.. yeah.. this one is for RCA inputs.. but I'm sure that with a bit of imagination you could put something together to your liking based on this tutorial.
Hope this helps..

 

[ericd]

This could be done and unless I am thinking incorrectly it could even be done without loss of signal integrity. What you would do is use a DPDT switch with one set of poles operating each channel and then one universal ground that everything runs into. This universal ground would not be wired through the switch at all. I can picture how it all would have to work but unfortunatly I am horible at describing things. But I can tell you with a pretty high level of confidence that it is possible. Hope this helps.

Eric

 

[pbrain]

smp, the link you posted is to a guide on how to add audio inputs. and i think i know what you're suggesting ericd, and shall take a stab in trying to describe it. it seems similiar to what i suggested, except putting a switch on the y-splitter to have it switch between the two sound systems instead of turning off the unused system. this way is fairly simple and low tech, don't know if it's what you're looking for. one downfall to this set up is that it only works with one stereo output. a 4 pole 4 throw switch would be required for a front/back stereo output. don't know if you could find those.

materials:
1 male stereo plug (or male to male, or male to female cable with one end cut off)
1 dpdt switch
2 female stereo plugs
wire/stereo wire

procedure:
1. ::10 minutes pass as i draw up a purdy sketch, and as i ponder on how to describe the procedure::

ok. this would require a bit of time to properly explain. so i'm just going to link to a scan of my sketch and let you figure it out. if anybody's actually interested and/or needs help, message or mail me and i'll take the time and write some instructions.

 

[ericd]

Yes if there is two outputs involved either a Quad throw switch (if such a thing exist) or two double throw switches would be needed.

Eric

 

[Bignate603]

ericd you landed on my problem, if i had just one output i wanted to switch, i could do it with a simple 3 position switch. However, my computer speakers use two outputs. I may have to have 2 switches, but i was really wondering if somebody knows how i could wire so when i flipped a single switch it turned it from my computer stereo to the shelf system.

I would need basically a switching system, I was thinking of it basically as a train interchange because it was easier to picture.
Line out one would need to go through a switch with two options, computer speakers or shelf. Line two would need to go to computer speakers or nothing, and just be turned off. Now, i was thinking for these switches i would use a transistor.

I would have to split line one into computer speakers and shelf system and then put a transistor on each. Line two wouldn't need to be split because it's on or off. The three position switch would then switch which transistors would allow current and which won't. Position one would allow the transistors on line one and two to pass the signal to the computer speakers. Position two would change so it opened the transistor on line one to the shelf system, line two would be off. Position 3 wouldn't open any transistors, turning off the sound, or i could switch it so it went to a headphone jack on the front of my case...

I don't know if anybody understands that but that's what i'm thinking.

 

[Bignate603]

ok, my understanding of transistors is that if you apply a charge to one leg of it, it will allow current to flow through in one direction, no charge on that leg, no current. Now, I don't know if the current going through a headphone wire switches directions. If it does, then i would have to double the transistors, one opened in one direction and the other opened in the other. Now is this right or am i whacked?

 

[ericd]

It sounds as though you have it about right. To my understanding line out stereo is DC so no two way transistors are necessary.

Eric

 

[Bignate603]

hmm, i would need to figure out the direction. Thanks

 

[kponds]

wrong. The line out signal is a low level AC signal desinged to be fed into a pre-amp. It is designed to be fed at a certain voltage independent of of the volume setting you have set up on the computer. Primarily, I use the line out jack to feed the signal into a tape deck or other recording device. You could also feed the line out signal in the the line input jack onto your stereo receiver and ultimatley control the audio with the receiver controls.

If I understand what your wanting to do, you want to take the speaker output (higher voltage that adjusts its voltage with the computer volume control and be able to switch it between your labtecs and a set of home stereo speakers. Essentially, you have three conductors coming out of the speaker level output of your sound card. The are a left channel positive, a right channel positive, a a universal ground. In the switching scheme your talking about, the gound would not need to be switch but could be common between all four speakers (use a big old wirenut). You need to use double throw (DT) switches (has three wiring connections. Generally the center connection is the signal feed and the two otehr connections are the signal out dependant on the switch lever setting. You would need two switches, one for the left positive and one for the right positive wiring. You could also buy a double pole switch (DP) that is essentailly two switches in one mechanical package with both switches controlled by one lever.

The ultimate switch for you is a DPDT (double pole, double throw)

 

[ericd]

But when 4 channels....not 2 are involved a DPDT don't cut it (if you look that's what I suggested originally untill I realized that he has 4 channels to deal with). With that in mind do you have any other suggestions?

Eric

edit: I think that he was wanting to use the speaker outputs, not the line out.

 

[Bignate603]

you're right, speaker output. i think i'm going to try doubling up on the transistors because i guess it's light AC. I got to start working on the layout, anybody know what the maximum voltage the speaker connection would put out?