Custom video/audio switcher thing - Page 1
Forum section: electronics / beginners

author: Dan9550
author_rank: Contributor
timestamp: September 19, 2013, 09:39:38 am
content: So i'm looking for a way to connect a bunch of my devices together to the same speakers and monitor, i can't find much readily available that meets my requirements or that isn't insanely expensive. I thought maybe i could make something custom! Although i'm not really sure where to start with this and i only have a relatively basic knowledge of electronics. I will now begin to describe what i want and be ready to be told hows its probably not going to work how i vision it.What i want to do is connect 5 VGA inputs and possibly 3 (but definitely 2) HDMI inputs to my computer monitor, which shouldn't be too hard, i could get a VGA switcher off eBay or something and connect its output to the VGA port on my monitor, the same goes with the HDMI. I'm guessing for that part its easiest to do that, although if anyone has any nice ideas of how i could make some kinda of device that will take that to a HDMI out and let me switch between it all that would be cool.Next is the audio i want like 8 audio inputs simple RCA / 3.5mm stereo that i can easily switch between, so the idea here is i have a mystery box which has all the inputs connected and the output goes to the Line-In on my PC so i can control the volume and have it output to my speakers or headphones from there. There much be some kinda chip of some kinda out there that would let me do this i assume but with my knowledge i have no idea.Alright so i hope this all made sense ill sum up though, i want a solution to switch video and audio inputs i don't care if these devices are a few separate boxes, but the dream would be some all in one unit. Which is most likely a bit far fetched, if anything at all what i really want is the audio switching part if someone could help me designing something i can make myself or show me something out there i could buy that is not to expensive that would be awesome (i'm going to say this right now, i don't want to stack a bunch of those $2 RCA input switchers together :S).I appreciate any feedback and ideas on the issue, Thanks.

author: fcb
author_rank: Super Contributor
timestamp: September 19, 2013, 09:56:59 am
content: Assuming you want to go down the DIY route (which is VERY unlikely to be more cost effective), you'll get a lot more help from this forum if you can draw a rough schematic of what you want (i.e. inputs, signal types, outputs).

author: Dan9550
author_rank: Contributor
timestamp: September 19, 2013, 10:14:35 am
content: Alright here is a rough idea of what i want, i'm sure it wouldn't be too hard to make something.Hope this makes sense

author: kizzap
author_rank: Unknown
timestamp: September 19, 2013, 10:43:47 am
content: Looks relatively easy, but in regards in audio quality could get quite complicated very quickly.First question, are the RCA inputs line level inputs, or something higher?If they are line level, I would then go about using two 4051 paralleled together, one side dealing with the Left Channel, and the other doing the Right. This would mean having dual rails, and some form of controller to ensure that the correct channel is selected, which I would probably use some form of MCU.The other option, which would work at either signal levels, would be to use relays. the benefit would be having a single voltage requirement, and a clever design with 8 latching switches could have no IC design incorporated into the box at all. The downside would be that the design could be kinda large, but with 18 RCA connectors it always was going to be large anyway.-kizzap

author: fcb
author_rank: Super Contributor
timestamp: September 19, 2013, 05:50:14 pm
content: I'd use relays if your building a one-off. Even the humble <$1 BT47 will out perform a 4051. If you want to avoid spikes, then use another relay to temporaily short the audio-out whilst you switch.

author: kizzap
author_rank: Unknown
timestamp: September 20, 2013, 12:39:37 am
content: Quote from: fcb on September 19, 2013, 05:50:14 pmDepends on how you set it up I guess, I did hear of one option where you use the 4051 in the feedback section of some inverting op-amps toimprovepreservethe audio quality.-kizzap

author: Dan9550
author_rank: Contributor
timestamp: September 20, 2013, 03:00:51 am
content: Everything i'm dealing with will be line level signals.

author: kizzap
author_rank: Unknown
timestamp: September 20, 2013, 03:53:23 am
content: what you are asking for is extremely simple...can you be truthful with us here, what sort of electronics background do you have?It just seems that you want someone here to design the circuit, and lay out the board for you.-kizzap

author: Dan9550
author_rank: Contributor
timestamp: September 20, 2013, 01:42:46 pm
content: I don't have much of a background designing my own circuits, my main area of expertise is computers and such. What i have done before is soldering really, uhh latest thing i did was add a VGA port for a Dreamcast, just a simple circuit with 3 capacitors, couple of resistors and diodes. Easy to put together, found the schematic for that online.Off the top of my head for this i was thinking it would be possible to do this with a bunch of SPDT switches, but even i know that would suck. Never have done much with ICs and i really have no idea what kind of stuff is out there. BY no means do i expect someone to spit out a design, although a hint in the right direction and some feedback to make sure im not going to do anything horribly wrong would be nice.

author: Zero999
author_rank: Super Contributor
timestamp: September 20, 2013, 05:54:19 pm
content: Quote from: kizzap on September 20, 2013, 12:39:37 amYes, a simple multiplexer is all that's needed.Here are the datasheets:http://www.jaycar.co.uk/images_uploaded/CD4051BC.PDFhttp://www.nxp.com/documents/data_sheet/74HC_HCT4051.pdf

author: envisionelec
author_rank: Frequent Contributor
timestamp: September 21, 2013, 04:17:14 am
content: About 20 years ago when I was 18, I built a switcher for a high end McIntosh audio display. The line levels were switched by 4066's on 2VRMS line level outputs. The sound quality was not diminished in any perceptible manner. If it had been, the store's owner would not pay for it and hundreds of customers would have never bought a thing.I'm still designing audio equipment and still look back on that project with fondness.