Hi all, this is my first guide and it's probably going to be a bit rough, but i'll try my best. Any critcism of the post it's self or the content is very welcome. I'm not an autmobile electrician, just a Sunday tinkerer who likes to play around! If anyone out there knows any reasons why any perticular step isn't such a good idea, please reply to let everyone know and i'll try to change it.

The other option was running the amps audio input from one of the rear speakers. But from what i've read, this was a big no.

Some people out there, like myself, would like to have an amplifier fitted for a sub, higher quality speakers etc, but would like to keep the standard headunit. Whether it be for OEM looks or multi changer intergration etc.

The symphony HU doesn't have RCA preouts like most aftermarket jobbies, so providing the un-amplified sound signal means making your own connections.

On the back of the HU, you'll see 3 plugs, one brown, one black and a multi coloured one (blue, yellow and green) the only one we are interested in is the multi coloured one. Specifically, the yellow section of it.

Before unplugging the HU, be sure that it is the factory fitted headunit bespoke to that car. Alternatively, be sure you have the code to unlock it after, as once you've disconnected the power supply, it will assume "SAFE" mode. If it's the original HU however, plugging it back in and turning the ignition on will unlock it by signal from the ECU confirming the stereo is in the right car.

Providing you meet either of the above criteria, go ahead and disconnect the plugs. You can do the job by only disconnecting the top plug (multi coloured) but you don't have alot of room for movement when it comes to refitting.

Once we have the multi coloured plug off, we want to seperate the yellow section from the blue and green ones. The yellow section should have no wires coming out of it. If it does, then you already have an amp somewhere!

In the picture below, you'll see the the two wires carrying the audio signal and a third wire which provides a swtiched feed to the amp, so the amp is only operational when the HU is on. The switched feed wire is blue, the audio pre outs are red and black. The speaker cable is just standard gauge hi-fi cable. Nothing special is needed as the signal this is carrying is un-amplified.

Remember it is the yellow section we are looking at.

The other connections in that yellow block are as follows. The empty slots at the top and bottom at the right hand side of the plug are another set of pre outs, ideal if you wanted to run 2 amps and not split the feed. The one remining slot in the middle is an earth, which for me is un-needed as I earthed my amp to the body in the boot.

Now comes the problem of attaching these wires into the plug. Ideally, you would source a pack of female connectors for the pins on the back of the HU and wire the plug properly. I suggest you do this, I however took the fast but riskier route...

Although it isn't very clear, what I have done is stripped the cables about 10mm from the end, fed about 5mm of cable through the corresponding hole where the connector should sit then folded the cable over the edge. It is a bit of a pikey mod, but I've been using it for weeks without any trouble so far.

You may find it easier to detatch the yellow section from the the other two sections, I did. Clip the plug back into the HU carefully, ensuring the wires don't slide out if like me you were too lazy to get any connectors. Once clicked in, the wires will be under too much pressure to slip out without a very hard tug. It goes without saying but go careful and try not to pull the wires just incase.

These wires must now be routed through the HU slot, off to where ever your amp is. Slide the HU half the way back into it's slot so it's sturdy but not clicked back in.

When running the main (not switched) live feed to the amp, there is no need to go through the hassle of running a cable into the engine bay to the battery. Under the steering column is a "buzz bar". Get to this by undoing 2 torx screws facing the floor and sliding a black plastic panel out. This panel is literally above the pedals. If you put your head in the footwell, you will see a number of bolts with electrical contacts clamped on. The middle contact feeds the dash and is permanently live, making it ideal for the amp. when undoing the nut on this contact, be sure not to let the ring that's already on there slip off. This will cause the trip computer to be reset. Not a huge problem but if you reset you milage when you fill up etc it can be annoying.

Besides, we should really have disconnected the negative battery terminal as you would before comencing any electrical work in your car which would obviously have the same effect. The reason I didn't was because I was testing the different wires for current to determine their use.

Slip on your amp contact and tighten the nut back up.

Run this cable to your amp too. For this guide, we will assume that it's in the boot. Once there, connect both the switched live feed and the battery live feed to your amp. Connect your amps earth output to grounding point found behind the carpet under the nearside rear light cluster. Once the stereo is turned on, you should have power going to your amp. Next, take either one of the speaker cables and touch it against the outside edge of the RCA input. Providing you have a speaker connected to you amp, at this stage you can determine which cable is left and which is right.

If you are wondering why only one cable per channel is needed, it is because the amplifier it's self is earthed. This common earth used in all cars, completes the circuit and therefore subsitutes the need for a return feed directly to he HU.

Keep the work space clear...

Once you've established which wire is which channel, you can solder some RCA connections to the ends and plug them in. RCA connectors are peanuts from somewhere like Maplin.

Connect up your speakers, check that everything works, fully fit in the HU and you're away! As far as I can tell, this produces just as good results as in my previous Octavia, which had an aftermarket HU with RCA preouts, but otherwise, the exact same setup.

This solution is perhaps not perfect, but it may be of use to somebody!

All the best.

This is an absolutely excellent guide! I was thinking I would have to upgrade my HU to get an RCA output!

Top job!

Have you guys seen the JL audio clean sweep

Very cool piece of kit, sums sorts and balances your oe head unit into a full set of rcas

I don't have the multi coloured plug, only brown and black. Where do i go from here?

There is the open block for where a multi coloured plug should go.

Thanks

Edited 8 July, 201312 yr by gfwc

I don't have the multi coloured plug, only brown and black. Where do i go from here?

There is the open block for where a multi coloured plug should go.

Thanks

You buy it. It should only fit in one hole. The pin arrangemment should be different for each of the mini-block connectors.

http://www.bluespot.co.uk/car-audio.aspx/7607893093-adaptor

 

Shop around £15 is expensive for what it is.

Thank you, ordered one on ebay for £9.00 delivered which i thought was fairly reasonable.