DIY "mixer" question

[Ofek Deitch]

hey everybody

I wanna build this kind of "mixer" inside of an Altoids box or something similar. The "mixer" is pretty much a lot of inputs and one output, and a switch on each input which turns it on/off.
The problem is that all the cables I use are, if that's the right name to call them, "Mini PL cables" (Like the regular PL cables you use with your guitar, but smaller. Just like the ones in your earphones and speakers..)
Their size is the same size as the cable that goes from that green output jack at the back of your computer to the speakers..

I have to use those because I wanna connect my TV + PC to the same set of speakers, and both have inputs and outputs with these "mini" cables.

The problem is that I can't find these kind of sockets anywhere ! I'm not sure what their proper name is, which makes my search of them much harder, and I'm not sure these kind of sockets even exist..


I'm looking for these sockets (image below..) - but smaller




Any help would be excepted !
THANKS!
Ofek 

[joegagan]

mouser used to stock these in 1/8". it has been 10 years since i bought them tho. they were mono, just like the 1/4" you show here.

[Ofek Deitch]

Thanks I'll check Mouser out..
I need Stereo though...

[Ofek Deitch]

I found this:
http://www.taydaelectronics.com/3-5mm-mono-enclosed-socket.html

Do you think it's the size of the mini PL cable?
what size are the mini cable and what are the normal ones?


Thanks

[artifus]

3.5mm is the standard size for mini headphone jacks on mp3 players and what have you. the picture you posted is of the 'skeleton' variety rather than 'enclosed' and are still commonly available in both mono and stereo. 2.5mm also available but are not used so much. guitar jacks are 6.35mm - quarter inch.

[Ofek Deitch]

So are these gonna work or not?
Ofek

[Tubebass]

The jacks would work fine, but it would be a bad thing to connect the outputs of two amplifiers together!

[Ofek Deitch]

What does it mean to connect the outputs of two amplifiers together? Like what will it cause?

What will connecting the output of my computer and my tv to the same set of speakers cause?

[hooya]

You'll be effectively plugging the output of one into the output of the other as if it were a speaker. You can't just wire them up and have them join, you need some kind of buffer/directional circuit that pushes the circuits together correctly, or you could blow one or both of the power amps you're setting together.

You should really get a commercial product for this. It'll probably be cheaper to be honest...

[Ofek Deitch]

Ok.. didn't know.. 
Thanks for warning me !

[haveyouseenhim]

I know radioshack has em. but i doubt there's any radioshacks in Israel    check their site maybe they will ship there

[PRR]

Usta be called "mini" (when 1/4" was "normal").

Nowdays called 3.5mm.

Normal on computer sound-cards and Walkman headphones, stuff like that.

Made in mono, stereo, and up to 3 rings for cellphones, iPods, and video-cameras which need more signals in the same small space.

Tayda calls mini stereo jack a "3.5mm Stereo Enclosed Socket Chassis Jack"

I have no idea why the stereo is half the price of the mono jack.

You only need 3 of the 5 pins on the jack. It has a switching function you do not need. The center pin is probably common ground. If one side of the jack is clear you can see what-touches-what. Otherwise stick a cable in and use your buzzer/meter to figure what jack pins go to a cable.

> connecting the output of my computer and my tv to the same set of speakers

Mix signals with resistors. For strong outputs like TVs and sound cards, 1K per input is fine (any Watts). For stereo TV and stereo PC, that's four 1K resistors.

[Ofek Deitch]

If I'm getting right what you're saying I'm suppose to connect everything like this:

TV Left ------- > 1KR    \
TV Right ------- > 1KR   \
                                    \

                               ------- >  Speakers

                                    /
PC Right ------- > 1KR   /
PC Left ------- > 1KR    /

Are all Grounds to be connected together?

And nothing will blow up or something.. ?  

[Ofek Deitch]

Are the jacks "Panel Mounting"? Doesn't that mean that it doesn't have the nut and that little round thing I'm not sure its name is? which means that I can't mount it directly to the enclosure?
Do 3.5mm stereo jacks that look like normal 6.5mm(I think..) with the nut and everything exist?

[hooya]

If I'm getting right what you're saying I'm suppose to connect everything like this:

TV Left ------- > 1KR    \
TV Right ------- > 1KR   \
                                    \

                               ------- >  Speakers

                                    /
PC Right ------- > 1KR   /
PC Left ------- > 1KR    /

Are all Grounds to be connected together?

And nothing will blow up or something.. ?  

You'd like it to be that simple, but without a buffer or circuit pushing the signal in one direction you don't get a signal flow like the arrows are pointing. You get this instead:

TV Left ------- > 1KR <<<   \
TV Right ------- > 1KR <<<  \
                                    \
                                    /
PC Right ------- > 1KR <<<  /
PC Left ------- > 1KR  <<<  /

The TV is going to send the signal to the PC and the PC is going to send the TV. So you're going to connect output to output. Yes they will also connect to the speaker, but you'll also be connecting the outputs together. NOT good. Maybe they have circuit protection, but I highly doubt it and wouldn't take that risk.

Panel mount is like what you pictured. The jack isn't mounted directly to the circuit board, it's locked to the "panel" only, and requires wiring. This is opposed to PCB mounting, which is where the legs of the jack connect to the PCB directly.

[PRR]

> connect everything like this



> TV is going to send the signal to the PC and the PC is going to send the TV

No harm results.

No "push" buffer needed.

The 1K resistors prevent the possible harm (mostly distortion) if two active sources face each other directly.

If the TV sent +1V, and the PC sent -1V at the same instant, with zero resistance the current would be 2V/0 or infinity. In fact the TV and PC chips will self-limit at a few dozen mA, clipping distortion.

With 1K in series with each output, the cross-current is 2V/2K or 1mA, a value any TV or PC chip can manage easily.

Yes, there will be some PC sound at TV's output jacks. In complicated systems where each output may feed multiple sub-buses, this matters; not when they all only go to the same place (one set of speakers).

The main drawback of this un-buffered mixer is that signal levels are about half of what they are without the mixer. In nearly every case, you can turn-up the TV or PC a bit, turn up the speaker-amp a bit, and arrive at happy loudness.

I used this trick to add CD/DVD decks to classroom amps which did not have enough inputs. Direct, happy loudness was about 3 to 4 on the volume control. With the mixer, 4 to 5 gave happy loudness.

[newperson]

just out of curiosity, one the top left drawing why do you use the > marking for both/only of the "L" channels?  does it mean anything other than you are pointing output signal?

[PRR]

> does it mean anything

Lazy, sloppy.

[mth5044]

These are stereo:

http://www.taydaelectronics.com/3-5mm-stereo-enclosed-socket-chassis-jack.html

[Jdansti]

Rat Shack has the 3.5mm (1/8")stereo jacks too.

http://m.radioshack.com/radioshack/product/detail.do?itemId=2103452&op=%22http://www.radioshack.com/product/index.jsp?productId=2103452%22