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Old 27th February 2008, 23:57   #1
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Default 3.5mm / RCA signal coupler type of thingy?

Hello Musical Gurujis,

I have a problem (that i dont think i have seen addressed in any other threads).

I have a two sources (laptop & cable-box), and only one set of speakers (typical computer speakers - 2.1 type).

I would like to be able to use either which one over the speakers, without having to unplug / replug or flip a switch. There is no need to play both at the same time (so if some kind of auto switching device/circuit exists, thats cool too).

Is there a solution??

I know that back in the day when walkmans were all the rage i had a 3.5mm audio splitter (1male into 2female) kinda plug so that two people could plug in their headphones at the same time. I'm looking for something similar, but the opposite (2male to 1female).

Whats the best way to do this with the least drop in signal / no(least) damage to the audio components?
Is there some kind of circuitry, or is it just like connecting them in parrallel ??

Thanks,
R
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Old 28th February 2008, 00:06   #2
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There is an AV splitter in the market for 150 bucks, should solve your problem. You can connect 3 devices into it & give the output to one device. I have one, but have never used it, my brother does since his TV has only one AV in.
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Old 28th February 2008, 00:33   #3
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hmmm am sure there's such an adapter.. else do it the dirty way

For only $1.00 each when QTY 50+ purchased - 3.5mm Stereo Jack/two 3.5mm Stereo Plug cable - 6 inches | 3.5mm Audio Cables

Look for other cables/adapters and you can do a DIY thing

Last edited by mohit : 28th February 2008 at 00:39.
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Old 28th February 2008, 05:01   #4
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Hi Esteem_lover,

I think i know what you are talking about, but what i am thinking about has a switch with which you have to select your input?

Mohit,

Thanks. Thats pretty much what i wanted but had to luck finding it, so i presumed there must be some reason they dont make them.... hence all the questions

So looks like its just a parrallel connection.
Any chance of harming either of the inputs?
And what are the negatives of something like this... will there be a drop in the volume level, or is that only in the case of 2 headphones being pluged into 1 walkman?

Thanks,
R

EDIT : Mohit, thanks a lot for re-introducing me to monoprice! Someone had suggested it a long time ago (i was looking to buy a HDMI > DVI cable) so i just bought a whole bunch of cables and stuff from there. Thanks.

Last edited by Rehaan : 28th February 2008 at 05:25.
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Old 28th February 2008, 06:20   #5
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imo this can be achieved by doing it at home, get a three way switch a branded one, you can connect the ends to two different ends of the switch solder it, there is always the neutral one to make it stay off! the one end should connect it to one output while the other should connect it to the other!

just the switch used for the horn the three way switch this can be done!

navinji should throw some light on this!
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Old 28th February 2008, 07:29   #6
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Hi Rider,

Sounds like that would need a dual or triple throw switch if im not mistaken?

However, i did mention that i did not want to have to flip a switch.

Thanks,
R
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Old 28th February 2008, 07:40   #7
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if you dont mind getting your hands dirty with some soldering, something like this is what you need. but if you turn both of the sources on, you'll hear both of them

I think you can even leave the op amp bit,but use higher value resistors, I think, because the Speaker input should be high impedance anyway.

Last edited by greenhorn : 28th February 2008 at 07:44.
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Old 28th February 2008, 08:02   #8
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You get the splitters in SP Road, Bangalore, so guess it should be easily available in Mumbai as well. The outputs are parallel, but because of the switch, only one output will be connected at a time. This should be your solution. As esteem lover said, it should cost in the region of Rs 150.
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Old 28th February 2008, 09:56   #9
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Rehaan-bhai, if you are in Mumbai you can go to Lamington Road (Navin can tell you where exactly) and ask one of the road-side electronics technicians to make you two Y cables (2 RCA sockets going to one RCA plug, joined with screened cables). No switch needed (but make sure only one of the boxes is on at a time; otherwise you will get your hip-hop with "Ba, Bahu aur Baby" dialogs in the background and vice versa)

You should be able to get the same from ICE-wala shops - ask for Y cables that split the HU pre-out for 2 amps. If you don't have the EP (3.5mm headphone jack) to RCA cable, that should also be available there.
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Old 28th February 2008, 19:18   #11
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Quote:
Originally Posted by Rehan
EDIT : Mohit, thanks a lot for re-introducing me to monoprice! Someone had suggested it a long time ago (i was looking to buy a HDMI > DVI cable) so i just bought a whole bunch of cables and stuff from there. Thanks.
You are welcome! I have ordered a bunch of stuff from there and can vouch for the high quality and low prices. Amazing value.
Quote:
Originally Posted by Rehan
So looks like its just a parrallel connection.
Any chance of harming either of the inputs?
And what are the negatives of something like this... will there be a drop in the volume level, or is that only in the case of 2 headphones being pluged into 1 walkman?
I really don't think there should be a very perceivable loss in audio quality. There should not be any drop in volume levels as in case oh headphones, you are putting double load on a puny amp and power supply. In this case, the sources are independent so its just a matter of bridging the output. Since you are talking headphone output, you can not generate enough power to damage the speakers anyways!

Navin can probably shed more light on the pros and cons.

Last edited by mohit : 28th February 2008 at 19:21.
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Old 28th February 2008, 19:55   #12
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Quote:
Originally Posted by Rehaan View Post
I have a two sources (laptop & cable-box), and only one set of speakers (typical computer speakers - 2.1 type).
Quote:
Originally Posted by mohit View Post
I really don't think there should be a very perceivable loss in audio quality. There should not be any drop in volume levels as in case oh headphones, you are putting double load on a puny amp and power supply. In this case, the sources are independent so its just a matter of bridging the output. Since you are talking headphone output, you can not generate enough power to damage the speakers anyways!
Rehaan I asume you are using the headphones out of the laptop and the RCA out on the cable box. Correct me if I am wrong.

If you connect both outputs to one high impedance input in parallel things will be fine as only one of the 2 devices is on. Since only once device (laptop) has a low impedance if both devices happen to be on at the same time you will at get a mixed output as Der Alte stated.
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Old 29th February 2008, 01:15   #13
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Quote:
Originally Posted by navin View Post
Rehaan I asume you are using the headphones out of the laptop and the RCA out on the cable box. Correct me if I am wrong.

If you connect both outputs to one high impedance input in parallel things will be fine as only one of the 2 devices is on. Since only once device (laptop) has a low impedance if both devices happen to be on at the same time you will at get a mixed output as Der Alte stated.
Technically, all outputs should be as low impedance as possible , and all inputs should be as high impedance as possible. The laptop out will just have higher current capacity as it has to drive headphones ,while the RCA output will try, and may end up clipping/ output going into protection if called upon to drive loads like headphones. Most Op amps don't have difficulties driving headphones though.

Connecting two low impedance sources in parallel is highly NOT recommended. thats why i suggested the circuit in my previous post , with resistors to buffer the outputs. While the mode of operation you have mentioned may work, it is certainly not recommended

what Rehaan needs is a simple mixer, Its the hardware equivalent of the windows advanced volume control But unless he is willing to make one himself, a 3 input switcher should be the easiest solution

Last edited by greenhorn : 29th February 2008 at 01:26.
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Old 29th February 2008, 04:48   #14
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Dinu2506 & Navin's first post,

Thanks, but as i mentioned, i do not want to have to flip a switch. (i have explained why below)

Der-Alte, sadly i do not have the luxury of lamington road at the moment! I guess i am stuck with monoprice.com instead From your post i take it that it is a simple parrellel connection.

Mohit, thanks again, but i wasnt worried about damaging the speakers, but instead was worried about damaging one of the two sources if they were on / connected / played together.


Navin's 2nd post - Okay i guess i will get a bit more specific now. When i said "laptop" i actually meant "wireless music bridge". (this is also the reason flipping a switch is not something im keen on, since i wont always be nearby).


As you can see, it has a RCA out, 3.5mm out, SPDIF, & optical out :


Greenhorn - as you mentioned, do you think the 3.5mm out will have higher current capacity than the RCA out in this case ?? Ie do i have to make sure i use RCA on this as opposed to the headphone out? (since i am using RCA on the cable box).


The cable box only has RCA out :



And the speakers i need to connect them to :




Quote:
Originally Posted by Navin
If you connect both outputs to one high impedance input in parallel things will be fine as only one of the 2 devices is on.
So are the RCA & 3.5mm out both high impedance ?

And even if they are both plugged in (connected in parrallel) and turned on at the same time, and only one of them is outputting audio, is there any chance of damaging the other?


Also, could someone please explain to me the differences between RCA and 3.5mm.... (these are called line level outputs/inputs???) i always assumed that it was the same thing with a different plug (same wine, different bottle), but it seems i am mistaken.

Thanks,
R

Last edited by Rehaan : 29th February 2008 at 04:53.
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Old 29th February 2008, 08:03   #15
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connecting them together will not work
please read this to understand why it wont work
the link also contains the simplest solution for your problem

Yes , you understood it correctly. Line level inputs are the same whether the connectors use RCA or 3.5 mm jacks. tha latter happens if you dont have space for 2 full size RCA connectors on the equipment. Line level output means a high quality output to be fed to the line level input elsewhere. If the 3.5 mm connector has been mentioned to be headphone capable , then it is a bit more general purpose in nature. slightly less quality, but higher power output, enough to drive headphones(~16 Ohms). it can also be plugged to line level inputs(~47K Ohm) as well

Last edited by greenhorn : 29th February 2008 at 08:15.
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