Whats going on with my sound?

[paulrockliffe]

Long shot I know, but maybe someone will be able to tell me what's gone wrong with my wiring.

I've got a distributed audio system setup in my house, 6 pairs of speakers run from 6 amplifiers with a distribution amplifier feeding the amps. I have a couple of inputs to the distribution amplifier, so I have a 4-pole On-On switch to select between the inputs.

RCA connections. If I connect the first RCA connector up between source and switch the left speaker works perfectly. When I connect the second connector the right speaker works perfectly, but the left speaker goes quiet. It's still working, but quietly.

I've tested all sorts and the issue appears to be at the 4-pole switch. My first thought was that I've not soldered the wires tot he back of it very well, but I can't find anything out of place. It feels like an earthing issue to me, but I don't know enough about it to work it out.

I have managed to 'fix' the problem, but I don't understand how. Connecting the central pin of the RCA connector to the outer pin of the RCA plug, without connecting the second pin to anything, lets both speakers work.

Anyone any ideas what's going on?

[h0b0]

The "Left"/white plug carries the mono sound and should output the same sound from both speakers. The "right" carries the right signal only. So, if you connect the white plug only you should still get sound out of both speakers. It sounds like you my have something funky going on with the stereo settings

[TheInternet]

paulrockliffe said:

It feels like an earthing issue to me.

Yep

paulrockliffe said:

Connecting the central pin of the RCA connector to the outer pin of the RCA plug, without connecting the second pin to anything, lets both speakers work.

Not quite sure what you mean by this, sounds like you're deliberately shorting it out. Draw a diagram maybe.

[paulrockliffe]

TheInternet said:

paulrockliffe said:

It feels like an earthing issue to me.

Yep

paulrockliffe said:

Connecting the central pin of the RCA connector to the outer pin of the RCA plug, without connecting the second pin to anything, lets both speakers work.

Not quite sure what you mean by this, sounds like you're deliberately shorting it out. Draw a diagram maybe.

Right, thanks for your replies. This:



Is the setup. You can see the amplifiers and the distribution amplifier. The bank of switches with the amplifiers selects whether the input to each amplifier comes from the distribution amplifier, or from either a source in the room or from the patch panel above. Rear looks like this:



The patch panel above has a pair of RCA sockets for each amplifier and also two RCA socket pairs for the distribution amplifier. These two are at the top and there's a 4-pole switch to select between the two inputs in between them:



The rear of this patch panel looks like this:



I have tested every aspect of the wiring and confirmed that the only time there is this problem is when the sound is passed through this switch.

The wiring diagram is like this rough sketch, though I've not included the bank of switches on that one:



When I said I'd connected the central pin of the RCA plug to the outer pin of the RCA socket I meant this:



Three of the four wires are connected, the fourth is disconnected completely. I had to bodge the connection as you can see.

I had assumed that both pairs carried each channel exclusively so left was + and - for left and right was + and - for right. Is this not correct? I didn't pay any attention to which wire is + and which is -, which might have caused a problem if the left and right channel are different.

[h0b0]

Nope. Left is everything and produces mono through both speakers. Right is where the stereo comes from

[TheInternet]

paulrockliffe said:

I had assumed that both pairs carried each channel exclusively.

You can think of the L and R as two independent mono channels.

paulrockliffe said:

so left was + and - for left and right was + and - for right. Is this not correct?

Yes, but your sources may well have both negatives connected, as is the case for a headphone jack (i.e. your Raspberry Pi):

paulrockliffe said:

I didn't pay any attention to which wire is + and which is -, which might have caused a problem if the left and right channel are different.

Well worth checking, I'd make sure all the negative connections are correct from source and through to the DA, if nothing else it'll verify the channels aren't out of phase.

Edited by TheInternet on Friday 21st March 21:44

[paulrockliffe]

TheInternet said:

Well worth checking, I'd make sure all the negative connections are correct from source and through to the DA, if nothing else it'll verify the channels aren't out of phase.

Edited by TheInternet on Friday 21st March 21:44

Thanks, the Bluetooth source has a headphone jack too which is connected to the RCA outputs, so from what you say it must combine the earths inside.

I figured the easiest way to check was to cut the end off one of the RCA leeds to the distribution amplifier and fit another one with the wires swapped over. This has solved the problem, so that's made my morning, cheers!

I have another issue that I'll describe below....

[Morningside]

Please can you describe your system as it looks very clever. I also like the use of your Raspberry Pi. What software etc. are you using? I purchased one for media use but to be honest its been sitting in the cupboard since Christmas.

I would like the idea of controlling it all via a mobile phone using a web browser.

[paulrockliffe]

Morningside said:

Please can you describe your system as it looks very clever. I also like the use of your Raspberry Pi. What software etc. are you using? I purchased one for media use but to be honest its been sitting in the cupboard since Christmas.

I would like the idea of controlling it all via a mobile phone using a web browser.

Hello, it's not really very clever, it's quite simple in principle. It's a little complicated by the number of bits of kit, and little quirks like the earthing issue that this thread has identified.

Clever would have been replacing the various switches with something controllable from my phone, but I couldn't find anything that wouldn't have ended up very expensive, ie using Sonos for everything. Best thing about this setup is that the speakers were £10 each and the amplifiers about £15. The distribution amp was £10.50 on eBay, after failing to secure new units for £40+ and the next 6 way option being priced at over £100. The bluetooth receiver was £25 and the RPi was £55.

Anyway, the principle is a pair of speakers in the ceiling, wired back to the cupboard. Each pair has it's own amplifier, which is fed from either the distribution amplifier or a local input. There's a bank of switches that control this for each amplifier, so you can have different stuff in any room, or the same across any combination of rooms.

What you can't see is that in the dining room, kitchen and two bedrooms there are local RCA sockets that let you plug the TV etc sound in. These are wired back and connected to the panel of RCA sockets that you can see above. So for the dining room for example you can connect a TV in on the chimney breast or in the corner and have the sound come out of the speakers. The RCA sockets in the cupboard mean you can install a local source such as the bluetooth receiver or an RPi to supply sound to the bathroom or the landing where I haven't installed a local source. The local sources are only necessary where there would be a TV.

All those inputs are connected using choc-bloc connections, in a sort-of-manifold, so you could connect any source to any speakers if you had a reason. The only cock-up has been not wiring back from the living room. I did this as I've wired local 5.1 surround behind the skirtings, with a local amplifier. I should have added the option to bring stereo back to the cupboard to distribute around the house as the XBMC on TV is great for setting up playlists etc. No big deal, I just need to frig XBMC to output over bluetooth and this can then be done wirelessly and I think without causing 5.1 vs 2.1 issues.

The RPi is setup with XBMC using the OpenElec version, which is the best option for running XBMC on the Pi I think. It's connected to the net and also to the server you can see. There's no head or controls connected, but I use Yatse on my phone to control it instead. This works perfectly for using it as a sound output as the the problem with the Pi is that it struggles to run the XBMC menu system perfectly. You use the Yatse menu system to go directly to the files or add-on streams, by passing the XBMC menu system. It works supperbly, but I was struggling to get a consistent Radio stream with it, as it would cause it to crash with the iPlayer plugin. I'm sure this can be sorted, but I've a lot on with the house, so haven't got round to sorting it yet.

To get round this I added the second input to the distribution amplifier and connected the bluetooth receiver. This basically plays anything from any bluetooth device, so it's connected to my phone and I use TuneIn radio for radio, which works really well. This is actually a really good way to go and compares well to the RPi as all of the XBMC add-ons are for things that you can stream on your phone anyway. However, I can't find a decent Android music player that streams from my server. I've got as far as using ESFile Explorer to find the folders and to play the music from it, but I need something that will catalogue the tracks instead. I've got XBMC on my phone, which will do this, but it's a full-screen application so not compatible with using the phone while the music plays in the background.

You might find the best solution is to get a cheap tablet, such as Tesco's Hudl and install XBMC on there, and have that talk to a bluetooth receiver. I've still not worked out the best setup. The bluetooth is good as it's very easy for anyone to connect in an d play too.

BTW, the web browser access to XBMC works well, but is very basic compared to the app access you can have Yatse is the best and worth paying for. Only thing the web access is best for is if you want to clean or rescan your libraries as it has shortcut buttons that the apps tend not to have.

HTH!

[paulrockliffe]

Right, my other issue is this:

If I switch the selector away from the distribution amplifier to take sound from a local source and there's nothing connected to those sources I get noise from the amplifiers. The noise is a load of static with a chirp.....chirp.....chirp laid over the top.

I've had all the wiring to bits and traced it back to the amplifier. If I connect an RCA lead directly to the amplifer and hold one of the wires the noise appears.

What is going on?

[TonyRPH]

If your diagram is accurate - then I don't know why you have used a double throw switch.

I would use a simple double pole changeover switch, as you do not need to switch the earth.

ETA: A switch like this:




Which would be wired thus:

Bluetooth to: NC-1 / NC-2

Raspberry Pi to: NO-1 / NO-2

Output to dist. amp: C-1 / C-2




Sorry - I did this post in installments - had a momentary distraction.

Edited by TonyRPH on Saturday 22 March 11:44

Edited by TonyRPH on Saturday 22 March 11:47

[paulrockliffe]

Simply because I wasn't sure if that was the case or not and wanted to make sure!

[TheInternet]

paulrockliffe said:

Right, my other issue is this:

If I switch the selector away from the distribution amplifier to take sound from a local source and there's nothing connected to those sources I get noise from the amplifiers. The noise is a load of static with a chirp.....chirp.....chirp laid over the top.

I've had all the wiring to bits and traced it back to the amplifier. If I connect an RCA lead directly to the amplifer and hold one of the wires the noise appears.

What is going on?

How loud is the noise? Sounds like it's just interference.

[TonyRPH]

paulrockliffe said:

Simply because I wasn't sure if that was the case or not and wanted to make sure!

See my updated post.

You would simply take all the earths to a common point, and this should reduce any possibility of noise.

I suspect the noise you are hearing is oscillation, especially if you are using those cheapie Ebay amps.

Try and pull all your commons (earths) to a common point (*only* for the inputs).

[paulrockliffe]

I've disconnected all of my inputs at the amplifier, I can then replicate the noise by touching one of the input wires of a connected lead. So the issue isn't related to the wiring I've used

I presume when I touch the wire I'm earthing it through my body?

They are cheap chinese amplifiers, but they seem to be well regarded, they're Lepai something or others that were recommended as the best of the cheap options.

If I connect a source to the RCA socket (that isn't playing anything) the interference disappears completely.

Can you explain what's happening here for me?

Is there anyway of replicating what the input source does so that the interference is eliminated all the time?

[TheInternet]

paulrockliffe said:

Can you explain what's happening here for me?

Your long unterminated cable run is acting as an antenna.

paulrockliffe said:

Is there anyway of replicating what the input source does so that the interference is eliminated all the time?

Stupid question perhaps, but why would you want to switch to a disconnected source?

[paulrockliffe]

TheInternet said:

paulrockliffe said:

Can you explain what's happening here for me?

Your long unterminated cable run is acting as an antenna.

paulrockliffe said:

Is there anyway of replicating what the input source does so that the interference is eliminated all the time?

Stupid question perhaps, but why would you want to switch to a disconnected source?

It's next to the boiler, the server, TV/Satellite distribution, network switch, various power adaptors and the boiler, so I guess there's probably a lot of potential transmission sources to pick up.

Not a stupid question, I wouldn't but if all the amps are on and someone turns off the sound in a room they might flick the switch to change sources without realising it's better to turn off the amplifier. If they do that they get all the interference, which isn't very professional. Would just prefer to eliminate it if possible.

Could I earth the inputs somehow without interfering with the sound from any connected input?

[TonyRPH]

It sounds like you're picking up hum (50hz mains).

Does it make a 'bzzz' type of sound?

You should be using screened csble (which you don't appear to be) for all the input connections.

The screened portion of the csble should be connected to the common ground / earth point I referred to in my previous post.

[paulrockliffe]

Sounds like it could be that. There's background noise then a buzzy/chirpy sort of noise, a bit like a heart beat that oculd be about 50Hz frequency.

Bit late to be screening cables now, but it's good to learn these things.

Any retro-fit solutions?

[TheInternet]

paulrockliffe said:

Could I earth the inputs somehow without interfering with the sound from any connected input?

Buy some of these and put them on the unused inputs (or make your own):
http://www.russandrews.com/product-Noise-Reducing-...