S40 (New) Electrics : Aux In DIY - Wiring Instructions

[kane]

The amp in the boot requires an analogue signal to be "boosted" as you can't amp a digital signal. All you do is find two solder points on the board after the DAC (digital - analogue converter). The only downside is that you cant use the EQ settings in the car or the steering wheel controls.

Personally I don't mind this and much prefer the option to use the mp3 files on my phone.

I did try using the relay method but gave up on it. Too much hassle tbh. All i do is turn my stereo off plug in my phone and use the EQ and volume control through the phone. If I then want to listen to a CD or the radio I unplug the phone and turn on the stereo.

This mod is cheap and relatively easy to do I think people just have a phobia about electronics and possibly damaging things. But meh. A sensible head and taking precautions make this doable for most people.

It's been some time since I did this mod but here are my own experiences and steps for performing this yourself. I did rush this slightly and there is a chance I have missed something but please be grateful and don't bemoan me for trying to be helpful. This technique could be achieved using multiple methods including electronic signal detecting equipment but I write this for people who want an easy and safe way to play their mp3's in their Volvo.

Instructions:

Step one is go to Maplin (other retailers are available) if you come to the Preston one you can see me!
You will need:
1. 3m - 5m 3.5mm Jack to twin phono cable.
2. 1m twin phono to twin phono cable.
3. Multimeter
4. 2 10k resistos.
5. Soldering iron.
6. Ground Loop Isolator.
7. Lots of Electrical / Insulation Tape.
8. Patience.

First get into your boot and carefully pull back the lining. Then remove the four screws holding in the amp (DO NOT DROP THE SCREWS DOWN THE BACK OR THEY SHALL BE GONE FOREVER) as such I now only have 3 screws holding the amp in place lol.

The next part is a ball ache to do. There is a silly connector into the amp which is only available via a cramped hand space and sharp metal. You must try to grip the connector hard and press and pull to release it without grazzing or slitting you hand on the exposed metal work.

In your raw and bloodied hands you should now hold your amp. Take a screwdriver to it and remove all the screws leaving only the board. There are at least two different designs of board but don't worry they all do the same job. (At this stage it is a good idea to take a picture of the board and print it on plain paper or produce a good drawing of the board and solder joints.)

What you do now is remove the amp casing and cover the area the amp lived in in electrical tape. The reason for this is that you are now going to plug the amp back into the connector and work with a LIVE board and some high voltages. Therefore it is important that you insulate any exposed metal work the board could *accidentally* touch. It is also quite important to put some electrical tape on clear areas of the board front and back so that you may safely hold onto it.

For the next step I advise having a friend to help you - Working spaces are confined and there will be a lack of light so I advise a work lamp or very good torch. Also have your multimeter and printed picture

Ask your helper to turn the ignition to pos 1 whilst you support the board in the boot using only the areas you have covered in insulation tape. Carefully pass the board to your helper whilst you turn on appropriate lighting, prepare your multimeter and consult your diagram.

If you are not sure on how to use a multimeter or are unsure of the basic components of a PCB I would ask someone for some help as this could be dangerous.

Carefully with your multimeter, work around the board looking for any high voltages (30v or more really). (The board should be roughly split into several sections) Any time you find a high voltage or you see a large capacitor or transformer, cross off that solder or component from your printed picture. Repeat this process until you have isolated all areas on the board of high voltage. You should notice more clearly now how the board is split up and you should have big cross marks on one section of the board.

Remove the key from the ignition and take a deep breath. The hardest part is over. Head inside and make a cup of tea to calm your nerves and steady your hands - It's time to crack open the soldering iron.

Take your 1m twin phono to twin phono cable and cut the phono plugs off one end - the same end! Peel back the outer plastic sheathing about 3cm and you should see a braided copper outer core. Pinch the copper to one side and twist it together and tug into a right angle from the cable. (it is ESSENTIAL that this shielding does not touch the centre core of the cable - not even a strand) Now remove the inner plastic sheath by 2.5 cm revealing the inner copper core, depending on the cable you use this could be a thick single core or many thin cores of cable. Now do the same with the second cable. Take your time with this step and get it right. Just one snapped cable or the braided cable touching the centre core could spell ruin!

Turn on your soldering iron first and leave for at least 5 minutes to ensure you are using a hot iron. Take one resistor and wrap the inner copper core of your cable around one leg. It doesn't matter which leg as resistors aren't directional. Then place a small amount of solder onto the copper core to secure it onto the resistor. When you have a good connection cover the centre core and your solder in electrical tape so that the braided sheath can not ground against it.

Take your time to get the best connection you can to the resistor! Repeat with the second cable. Being half arsed here could set you back hours in the end!

You should now have:

1. Picture of the amp board with crosses designating where the high voltage spots are.

2. A twin phono cable with two ends removed and replaced with resistors.


Good, next step. Plug the 1m phono cable with resistors into the ground loop isolator and then plug the 3m jack to twin phono cable into the other end of the ground loop isolator resulting in one long cable starting in a Jack plug and ending in two resistors.

You will now need a cheap device that can play sounds with a jack socket. When I did this I read up that Ipods and Iphones have a higher impedance than most other devices and so would suggest using something else. I used an old Nintendo DS and the mario 64 home screen sounds turned down quite low.

Return with your assistant to the car. Turn the ignition to pos 1 and turn the radio ON but reduce the volume. Plug the long cable you have made into your device and turn the device on but at about 25% volume.

What you will do now is place the leg of one resistor (or the resistor leg and also the braided sheath) on solder joints on parts of the board you know to be *safe* (no high voltage).

At the volumes and voltages there should be no real risk of damaging any components due to the low volume being used, the two resistors, the ground loop and also the device you are plugging in.

If you are unsuccessful with a particular solder then cross it off your picture in pencil and move on to the next. What you are aiming to hear is crackling from one side of car (close) or the sound coming from your device. There will be a total of 4 different solder sections on the board which produce sound. Front and Back LEFT and Front and Back RIGHT. These solder joints will all be on a similar part of the board and when you find them you should highlight them on your picture and label which speakers they operated.

You should now have a picture which shows the exact solder joints able to input your aux sound. Remove the amp board one last time and return indoors and turn on the soldering iron again. Perhaps retire with a brew and a biscuit for half an hour before turning the soldering iron on again and starting up one last time.

Home stretch now I promise! Using 4 pieces of single core speaker cable about 6cm long (not the cheap thin stuff but not the huge stuff either) solder onto the four different solder joints.

Bridge the 2 pieces of speaker cable together which match the same side with another dab of solder resulting in a Y-shape going to either fL + bL or fR + bR. You should now have a board with four pieces of cable soldered on which come together to make a Left side (front and back) and a Right side (front and back).
Think carefully about this next step! You now need to solder on to the Y-Bridges your resistors which are attached to your cable and using more electrical tape make sure everything is insolated. Some helpful tips here are:
1. Remove the 1m cable from the ground loop so that you can feed it through the amp casing as you may struggle after you have soldered the wire to the board.
2. Your 1m cable will end in a red and white phono plug. If you can tell which resistor is connected to which colour plug you are fine if not use the continuity test on your multimeter (arrow with line through). Make sure to solder the correct resistor to the correct side on the amp. (This can easily be changed by swapping the plugs over going in to the ground loop if you **** up - but we've done a good job this far let's keep it up!) The simple rule for audio leads is LEFT - White ... RED - Right. Sing it to yourself a few times and you are good to go!

The very last job is to earth this new cable you have created using the braided sheath from both cables. The easiest way to do this is to solder both braids together and attach another piece of speaker wire. You can then solder onto an earth connection on the amp PCB or you can solder onto the negative power terminal or you can extend the earth lead and later wire it to an earthing point in the boot. Whichever option you choose should be fine.

Finally, you can turn off your soldering iron and admire your handy work. You will have an amp PCB with four leads coming off of it which form a Y-bridge and connect to 2 resistors attached to a 1m phono lead through the case of the amp. You should also have both braided cores connected together and soldered onto the board or ending in a long wire you will earth when you return to the car.

Top tip....Go out to the car before putting everything back together and test it! Turn the stereo off and start with the music on your mp3 player low but gradually turn it up. If you've cocked up you've rushed...welcome to step 1! If you hear music Well Done! You've done it! You have saved yourself a small fortune and improved the time you spend in your car vastly!

Rebuild the amp case ensuring that you are careful! It would suck if you broke a solder or tugged a wire free! Then take the amp to the car and plug the amp back in to the car before securing the amp in place.

I connected the ground loop isolator to the 1m cable coming from the amp and placed it in the body panel above the amp. I then ran my 3m cable from the ground loop up down towards the bottom and back of the boot lining where it emerged only to pass under the back seat. I then looped the cable a few times under the back bench and passed it from under the bench down by the centre console to the cup holders next to the handbrake where I keep my phone. If you want a longer or shorter cable change how much is stored under the rear bench.


And finally, there you have it. You should now have your own 3.5mm jack aux socket wired in to your Volvo S40 / V50!


Top Tip: I would really recommend, from my experience, Power Amp from the Android market as it's built in EQ is fantastic and it allows you to control the preamp built in to your android phone. For an extra few quid I think it really makes this project complete.




This project took me and my friend a few solid days of trial and hard work to discover and build but I am very proud of what I have accomplished. I would appreciate people not ripping off my guide and passing it off as their own work. This guide has taken me a long time to write accurately and well and I would be very grateful if people were appreciative.
I am a newly qualified teacher and frightfully busy but I will try my hardest to answer any questions you may have.

Thanks Guys,

Kane.

[kane]

Here are some picture of the Amp board and the wires I've soldered onto it.

If your amp is similar use the area as an easy reference for where to test.

[Bendolfc]

Nice one. Will have a look on a doing This on a sunny day.

[JIMBOfred]

I'm thinking of having a go. Has anyone done this just from these instructions successfully?

[JIMBOfred]

Bit optimistic this as I've not had a reply on this thread before. Getting closer to having a go (possibly over easter). Just have a few q's. Is the idea just to find the speaker connections and wire straight into them? I would have thought that this would bypass the amp and so just have the weak headphone signal coming through the speakers. Also it doesn't say how you would set up the system to listen to it. Do you just have it on cd mode but with no cd in or something? Obviosly I'm not having a go or anything. The instructions look excellent. I just want to be sure before I do anything drastic.

[mattievrs]

Originally Posted by JIMBOfred

Bit optimistic this as I've not had a reply on this thread before. Getting closer to having a go (possibly over easter). Just have a few q's. Is the idea just to find the speaker connections and wire straight into them? I would have thought that this would bypass the amp and so just have the weak headphone signal coming through the speakers. Also it doesn't say how you would set up the system to listen to it. Do you just have it on cd mode but with no cd in or something? Obviosly I'm not having a go or anything. The instructions look excellent. I just want to be sure before I do anything drastic.

Read the first post again, it tells you how to listen to the aux input and what mode the radio is in to do so.

[gdmllr]

Kane, You da man! Gonna give this a go. Can't put up with analogue radio and CDs in my C30 - Why the hell did they take out the aux?