enjay Posted February 6, 2008 Posted February 6, 2008 I'm trying to get the audio feed from a PC and a DVD player into one set of speakers without having to buy £60 dual-input speakers. So, I bought the necessary converter cables, BUT... the sound from either of the devices is almost inaudible while both other are connected, but fine if they are on their own. I have other 2-into-1 PC audio adapters which work fine, so I'm wondering if the problem is my RCA-to-3.5mini converter. Other than giving up and buying the £60 speakers, has anyone got any suggestions? Might I have more luck if I bought speakers with RCA inputs on them and converted the PC signal than the other way around? Whatever solution I find will need to be done to quite a few computers, so needs to be as cheap as possible.
Domino Posted February 6, 2008 Posted February 6, 2008 hmmm, have you tried a little pre-amp or similar to boost the signal before sending it to the speakers?
mattx Posted February 6, 2008 Posted February 6, 2008 Sounds a bit daft but won't a simple audio switch do ?
rhyds Posted February 6, 2008 Posted February 6, 2008 The way I did it was to connect the output from the DVD player in to the Line-In on the PC and the PC's Line-Out to the speakers. You can then use the volume control on the PC to control the DVD level, it might not be perfect but it's cheap!
enjay Posted February 6, 2008 Author Posted February 6, 2008 Sounds a bit daft but won't a simple audio switch do ? Possibly; ideally I'd like something passive though, as I suspect I would quickly get sick of people saying "the DVD player is broken" when they just needed to flick the switch. It is hard enough getting some people to learn how to re-scan the projector to the video input without adding another step to the proceedings!
enjay Posted February 6, 2008 Author Posted February 6, 2008 @rhyds - is that using a fancy soundcard or just the regular mic in port on the PC?
mattx Posted February 6, 2008 Posted February 6, 2008 Possibly; ideally I'd like something passive though, as I suspect I would quickly get sick of people saying "the DVD player is broken" when they just needed to flick the switch. It is hard enough getting some people to learn how to re-scan the projector to the video input without adding another step to the proceedings! Thats true, I setup audio switches on all our PCs / DVD / TVs in our classrooms - in the end I ended up putting VERY LARGE STICKERS on them stating which switch did what and how to use it, what a volume control actually does and how leaving the volume control right up on the speakers is not a good idea....
western Posted February 6, 2008 Posted February 6, 2008 The problem is that there is slight power coming from any PC sound card/on-board. If you are playing a DVD on the separate player if you turn the PC of the sound will be ok! That is how we got around it.
rhyds Posted February 6, 2008 Posted February 6, 2008 @rhyds - is that using a fancy soundcard or just the regular mic in port on the PC? Regular onboard HP soundcard. I used the line-in rather than the mic input and used the windows volume control to set the levels etc. right
Andrew_C Posted February 6, 2008 Posted February 6, 2008 Your problem is an impedance mis-match. The output of the DVD will be something like 10k ohm, but the PC is 600 Ohm. This results in the PC sinking the voltage that should be going to the speakers. You can use a matrix of resistors to get over this problem, or a variable resistor. I can look up the values I used (if I can find the scrap of paper...)
mac_shinobi Posted February 6, 2008 Posted February 6, 2008 (edited) can't find what I mean on maplins ( and however I do agree with the amp before connecting to speakers ) but just as a thought. Not sure what they are called but will try and explain anywho ( these type of things ) http://www.tlc-direct.co.uk/Images/Products/size_3/TLCON15.JPG those electrical block things where you get a screw driver and it has copper inside and you take a wire in at each end and screw the wires in at each end and it connects the wires together and then you use electrical tape around them If you take the left wire from the left audio output from the dvd player and the same again from the pc and screw that in one end and do the same for the right side audio cable and then connect both speaker cables into it to combine it . will have a look later on ( probably sounds like a bunch of cr4p at the min lol ) Gotta run for now though you will have to chop the wires for the speakers and the dvd and pc outputs but will use the above to re connect them that way you dont have to use a switch but obviously if they try and use both together it will most likely distort. Edited February 6, 2008 by gecko
ICT_GUY Posted February 6, 2008 Posted February 6, 2008 Possibly; ideally I'd like something passive though, as I suspect I would quickly get sick of people saying "the DVD player is broken" when they just needed to flick the switch. It is hard enough getting some people to learn how to re-scan the projector to the video input without adding another step to the proceedings! Yes you do, it gets old very quickly.
mattx Posted February 6, 2008 Posted February 6, 2008 Not sure what they are called but will try and explain anywho ( these type of things ) I call them choc boxes
mac_shinobi Posted February 6, 2008 Posted February 6, 2008 I call them choc boxes thats what I thought but when I came to search for them it took me a while to get that image and I still can't find it on maplins or else where - unless im just being a numpty like I usually am when it comes to finding stuff on sites like dabs and misco etc. would be nice to know the official name
powdarrmonkey Posted February 6, 2008 Posted February 6, 2008 We do the same as rhyds, push all the audio through the PC at line level. It's the best solution we found, totally transparent to the user (as long as the PC's switched on!). Make sure you connect the DVD to line in (blue) not mic in (pink) or you'll blow up the sound card in the PC. Chocblock will still give you the impedence problems, ie all the PC being greedy and absorbing the DVD's audio before it reaches the speakers.
Andrew_C Posted February 6, 2008 Posted February 6, 2008 would be nice to know the official name Choc BLOCK will find it anywhere they know what they're talking about. Terminal strip is a bit more formal. But joining the wires together as described, will give the problems that I described above.
john Posted February 7, 2008 Posted February 7, 2008 I call them choc boxes Choc blocks actually, Choc Boxes are these - http://www.tlc-direct.co.uk/Images/Products/size_3/CHOCBOXA.JPG a plastic box that you put the connecting strips AKA choc blocks in to protect them and meet IET Code.
enjay Posted February 7, 2008 Author Posted February 7, 2008 Sounds like the line-in option is my friend; I'll give that a go and report back...
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