Joining RCA inputs or splitters and quality

[kirtangl]

Hi all,

So I have a bit of a stupid question, but I am struggling to find any relevant information about it.

I am building a portable speaker box, based heavily on the Boominator floating around these forums somewhere.

However, I am not as focused on battery saving, and as such, I have 4 input sources.

1. External Input (RCA)
2. USB DAC
3. Bluetooth Adaptor
4. RaspberryPi with HiFi Berry

Now as this is my 3rd portable music box, I am trying to make this one as hot swap-able as possible, and so, all of these items output to RCA.

Now all 4 of these inputs will be going into a Pre-Amp first, which controls the volume, and to keep things as simple on the outside as possible (As little switches etc as I can have), I do not want to have a source selector or mixer.

So my question is this, On the inside of the box, there is a 4 way RCA input panel, all 4 sources go into this panel, is there any way to have a single output from this, without causing extra noise, or interference?

I had thought about just literally soldering them all together, than having a single double shielded output, however since I have noticed all splitters have a selector, I assume this must cause noise or something.

My second thought was to use Y-Adapters, but since you cant get 4 into 1, It would be 4, into 2 into 1, which, while I am happy to do this if it's the best option, I want to be certain, this is what is best.

Edit: All 4 inputs will have separate power switches, with the exception of the USB DAC that turns on with the AMP, and the external input, which will just be disconnected when not in use.

Regards
Kirt

 

[DF96]

You can't directly parallel sources, as they will intefere with each other. At best you could get low volume; at worst distortion.

The easiest thing to do is to add series resistors to each source to add some isolation. A few k may be OK.

 

[Speedskater]

At the end of the day, a selector switch is the way to go.
Are all of these sources analog? and at the same amplitude?

 

[kirtangl]

Yeah, they are all analogue output, from digital sources though (from 3 of the inputs).

It sounds like I should just cop it, and look into an input selector... Just going to be a pain to mount the selector somewhere.

Don't suppose anyone knows a decent one that isn't inside a bulky case or anything?

Thanks for the help guys.


EDIT: On second thought, I see all the selector boards use relays, which means I would be wasting power... I don't suppose you'd like yo explain the resistors for me DF96? do I just put them across the positive joins?

 

[sreten]

Hi,

Its a doddle with series feedback, i.e. a mixer.
All the other ideas are just stupid relatively.

rgds, sreten.

 

[kirtangl]

So best bet is a mixer, which would solve the wasted power issue, but would require me to find space for 4x knobs... Unless I just internally mounted it and turned them all to max... But I am guessing that would just cause the same interference issue.

Kirt

 

[kirtangl]

In the interest of keeping things as simple as possible, I am thinking of just using an Elma 2x6 pot, and wiring one up myself. It's still going to create more clutter on the panel, but I can put it on the back at least, and just live with it. It's a small sacrifice to keep the power usage down, and the quality up.

Thanks

Kirt