Help in designing an input selector switch

**bcw55** · 03-11-2005, 12:11 PM

I originally posted in another thread - however I think my question really has more to do with the specific details of creating an input selector switch - any help or advice would be appreciated.

I have the following set up:

Eclipse 54400 head unit - no aux input.
Eclipse Model 3640 4/3/2 Channel Power Amplifier
Dell MP3 player

I, like many others in this forum, would like to patch my mp3 player into the sound system. After contacting my local Eclipse dealer, they confirmed that there is no aux input on this older head unit, nor does it support a CD changer. They mentioned RF modulators or doing something custom. I've heard output from RF modulators and they really do, in my opinion, compromise the sound. Having the dealer do anything custom would be cost prohibitive - at that point I might as well purchase a new HU that has an aux in.

I'd like to keep the Eclipse HU, and don't really need to have a "full" integration of the mp3 player - just the ability to plug it in to the system. I can happily control the volume and song selection from the mp3 player itself.

I thought that since I have the external amplifier, I could either buy or build an input selector switch that would allow me to toggle between the head unit and the MP3 player.

I've attached a diagram of what I think I need.

I've seen some existing switches/selectors available, but almost all are designed for video - red, white and yellow RCA - with only two audio inputs per position, and only two audio outs.

The head unit has four RCA outputs, the amp has four RCA inputs. The MP3 player has a single headphone (mini 1/8") out with which I can use an RCA Y adapter to get two RCA outs.

It seems, that to build something, I would need a small box with four inputs for the head unit, and two inputs for the MP3 player, and then four outputs to the amp - with a switch to select which input source to direct to the amp.

Can someone help provide a novice with information about the appropriate parts and the wiring info I would need to build such a thing? While I don't have any real experience with this sort of project, it seems like it should be simple enough with some basic parts (a box, RCA jacks, a switch) and a soldering iron.

Ideally, I could run a wire from the box to a switch that I put into an open slot in my dashboard.

Or if this set-up is available for purchase somewhere (again, I can't seem to find much other than video switches) I'd appreciate a tip.

OR let me know if there is any reason this is not an appropriate way to do this.

Thanks very much.

**Zebelkhan** · 03-11-2005, 06:18 PM

I built a box similar to what you want to do:

I got a relay from allelectronics.com , a project box and a set of RCA connectors from Radio Shack (you can get them also from the above place which is probably better and cheaper. and after about 1/2 hour of soldering I was done. I did not even install a switch. Whenever my HU is powered on, the relay automatically switches the audio from HU to the amp, and if HU is off, MP3 is connected.
I even switched the cable shields this way! You can use two relays to accomodate all rca plugs (each RCA has a main lead and a shield) or you may be able to connect all sheilds to the ground and use one relay. I don't know enough about electronics to say which is the correct way. I just decided to switch mine just in case I was not supposed to ground them. You fit all of these in a box and you are done!
Here is a rough drawing of the connections:

**bcw55** · 03-11-2005, 07:15 PM

Thanks - the idea of no manual switch is great. One issue is that my amp gets powered on when the HU gets turned on - I guess I could just run some additional wire from that contact to the new switch box.

Another thought came to me after reading your post (again, emphasizing again that I know nothing about electronics), and I found a schematic for an "Audio Activated Switch" that is powered by a small lithium camera battery:

http://www.discovercircuits.com/PDF-...DIODETECT1.pdf

While my project just got more complicated - I'm actually in over my head, but I suppose it'll be a good learning experience - I think I'm going to look further into this "switchless" solution - thanks again for steering me in this direction!

**Zebelkhan** · 03-14-2005, 05:29 PM

I have "zero" knowledge in electronics. Heck, a good solder job is a big accomplishment for me! So I get a huge kick out of doing these little projects, stuff that some others on the forum may even laugh at.

**Altimat** · 03-14-2005, 05:34 PM

For $26 you can't waste your time building one:
http://www.davidnavone.com/detail.asp?PRODUCT_ID=N-806

**Zebelkhan** · 03-14-2005, 05:39 PM

Good find. Thanks. Will it switch a 4 and 2 channel input?

**bcw55** · 03-15-2005, 12:07 PM

From the photo of this device (http://www.davidnavone.com/linedrivers.html) it appears that there are only two RCA outs and four ins - two per channel.

Much interesting stuff on that site, though.

I did find a less elegant solution - picture attached.

While not perfect, this allows me to have all four inputs from the HU go more or less direct into the amp. I then split the two from the mp3 player into four. Not ideal, but as long as the volume is off from the HU, all is well.

I think I'll likely invest in a new HU that actually has an aux in.