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Discussion Starter · #1 ·
so, here's a tutorial for those who want an aux-input, but aren't willing to pay a sh*tload of money for a volvo premium sound system
(model years 2005 to 2007)

1. the amplifier is located at the left side of the trunk. in order to access, you'll have to dismental some of the trunk lining (? not sure if this is the correct term)...







2. locate capacitors C625 and C626 somewhere at the center bottom of the mainboard. Audio signals coming from the radio & CD player can be detected at this point.



3. Connect two 10 Ohms resistors to each of the capacitors (Just solder two SMD chips next to the C62X capacitors.)



4. From here, you'll have to wire your 3.5mm Socket / Jack, which can be placed somewhere on the center console (I've used the "button" aside to the DSTC switch)



I must admit, that this is a somewhat peculiar way of an aux-input, but without really understanding the complete circuit...
anyway, it works just fine with my samsung mp3-player. once you plug-in the player, audio from the radio / CD player is muted. all the controls (volume, sound tuning etc) can still be used. honestly, I don't quite understand why audio from the radio is muted once you connect your mp3 player, most likely the impedance of the original circuit at this point is rather high compared to the rather low output impedance of the mp3 player.

so, hope some of you guys 'n girls can use that and spend your money on something else than a dension gateway or a volvo premium sound system


if there are any questions, feel free to ask


cheers
crossie
 

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Awesome! I've been seriously considering shelling out for a better sound system if/when Volvo replaces my broken cd player. This might be a nice alternative...

Assuming it's applicable to an S40 of course. I don't see why it wouldn't be though.
 

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Sweet! Is the quality top notch? and for those with no electronic experience what items do i need and where can i get them? thanks in advance!
 

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Discussion Starter · #6 ·
@ mofolicious: I'm sure it would work in an S40 - pretty sure that the amp is the same!

@ PasS40ion: the quality (compared to an audio CD) is a little bit better (had it tested with a 192kbit/sec mp3-file, and a 128 kbit/sec audio CD) - so I'm satisfied with it

all you need is some solder, two 10 ohms SMD resistors (I got mine from an onlineshop here in germany), some wiring/cable and about 2 to 4 hours for getting the work done.

@ turboah: that'll be an expensive beer
from canada to germany - about 4000 miles


@ Vash13: the procedure is pretty simple - if you manage to get the trunk lining off, there's not much work left


thanks @ all for the positive feedback!!
 

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Martin, you are the new Hero of Swedespeed!

We have been waiting for someone with enough knowledge of circuits to figure out where to hook an AUX jack! You have done it my friend, we are all forever grateful.

I will be installing my AUX jack this week!
 

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Crossie: Can you keep us updated on how well it works as you use it? I really like this idea but I have heard of a lot of problems (such as the Passenger Airbag warning coming on) when people tried messing with the audio system. I want to do this but want to make sure it won't mess up anything in the future. Thanks for taking the time to figure this out!
 

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Discussion Starter · #9 ·
Re: (carreragt7)

sure, no problem... I don't think that this should mess up my airbags or anything of the car's other electronics...

but still - IF anything happens, I'll inform you
 

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Just to confirm, When you plug in an ipod, mp3 player etc.... the audio system will automatically shift the radio/cd player to the aux in? What does the screen display?
 

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Discussion Starter · #13 ·
Re: (Vash13)

Quote, originally posted by Vash13 »
Just to confirm, When you plug in an ipod, mp3 player etc.... the audio system will automatically shift the radio/cd player to the aux in? What does the screen display?

haven't tried it with anything else than my mp3 player yet... will test it out tomorrow with my GPS...

the display still shows your current radio station / CD title etc...

sure, it would be great if the display would also show the mp3 title information... but hey, for this little effort - what do you expect ?
 

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Re: (Vash13)

Excuse the non-knowledge of wiring and circuits, but on each of those two wires connected to the circuit board, what are the two connections to the board? One to the resistor and one grounded to the board?

Thanks. Also, what exactly are those wires...? The back end of a auxiliary jack?

Do you have any full pictures of the cable you used?
 

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Re: HOWTO: AUX-in for your V50, basic sound system. (crossie)

I figured that this must be possible since at some point the digital fiber optic signal gets translated into analog and that that would be a good point for injecting a signal. How did you figure it out?

Stan
 

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Re: (turboah)

This is awesome! I'm glad that someone took the time and figured this out. I'm in Germany right now, but will be back home in 2 weeks and will try to accomplish this feat. Thanks again! http://********************/smile/emthup.gif
 

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Re: (turboah)

Guys, even though this connection seems to be working and the OP clearly has found the correct line level input to the amp circuitry (good work btw), the source impedances do play a rather large role here.

Now what happens is the headphone output of the authors MP3 has much lower impedance than the amp stage coming from the optical interface. This is the reason why the MP3 output overrides the other signal sources (which I guess can be heard if listened carefully). There are two drawbacks:

1) If the MP3 or whatever source that is connected has much higher than a couple of ohms source impedance, the CD or radio does not mute totally but can be heard in the background.

2) If the source has insufficient audio coupling capacitors the sound quality may be worse than optimal especially for bass frequencies since it needs to fight with the CD/radio source. It is possible that this sort of weird matching causes distortion etc. as well. I don't think you could destroy anything by trying this though.

The circuit could be improved if the traces from optical interface can be located (should be rather easy at this point since the coupling capacitors/points have been found). You need one dual pole relay to switch over from the factory input to the new AUX input and some sort of control for the relay. I bet the relay control can be tied to the AUX jack somehow so that when the AUX is plugged in, the relay switches over.
 

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Discussion Starter · #19 ·
Re: (FinnSpeed)

Quote, originally posted by cicatrizdare »
Excuse the non-knowledge of wiring and circuits, but on each of those two wires connected to the circuit board, what are the two connections to the board? One to the resistor and one grounded to the board?

Thanks. Also, what exactly are those wires...? The back end of a auxiliary jack?

Do you have any full pictures of the cable you used?

you are absolutely right. the cables are for left and right channel, they are screened audio cables, with the screen connected to ground. the groundlanes are just next to the 2 capacitors, as you can see in the picture.
you can check ground with an ohm-meter - there is no resistance between the case of the amp and the corresponding ground lane.

wires are in fact the back end of an aux jack. if you cannot find screened microphone cable you can also use coax RG174. which you can probably find at a local radio store.

Quote, originally posted by AutoGeek »
I figured that this must be possible since at some point the digital fiber optic signal gets translated into analog and that that would be a good point for injecting a signal. How did you figure it out?

Stan
hey stan,

I found out by searching for an audio signal on the circuit board, as close to the digital fiber optics. this is the one that seemed to be allright for an aux connection. I used a scope to detect audio (oscilloscope).

Quote, originally posted by FinnSpeed »
Guys, even though this connection seems to be working and the OP clearly has found the correct line level input to the amp circuitry (good work btw), the source impedances do play a rather large role here.

Now what happens is the headphone output of the authors MP3 has much lower impedance than the amp stage coming from the optical interface. This is the reason why the MP3 output overrides the other signal sources (which I guess can be heard if listened carefully). There are two drawbacks:

1) If the MP3 or whatever source that is connected has much higher than a couple of ohms source impedance, the CD or radio does not mute totally but can be heard in the background.

2) If the source has insufficient audio coupling capacitors the sound quality may be worse than optimal especially for bass frequencies since it needs to fight with the CD/radio source. It is possible that this sort of weird matching causes distortion etc. as well. I don't think you could destroy anything by trying this though.

The circuit could be improved if the traces from optical interface can be located (should be rather easy at this point since the coupling capacitors/points have been found). You need one dual pole relay to switch over from the factory input to the new AUX input and some sort of control for the relay. I bet the relay control can be tied to the AUX jack somehow so that when the AUX is plugged in, the relay switches over.

good suggestion! I myself thought of adding a relay at this point - but audio quality was excellent and muting of the radio/CD signal was really good so that the radio could not be heard anymore, even at full volume.
but as you said, it could be worse with any other audio source.
(first I tried with different resistors; 63 ohms was still to high and you could hear the radio then...)
so I came up to 10 ohms.

cheers
crossie

Modified by crossie at 2:52 AM 9-22-2008
 

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Discussion Starter · #20 ·
I just had the problem that, after disconnecting the mp3 player, my radio/CD stayed mute, so I'll have to adopt FinnSpeeds solution with a relay, to be on the safe side!

disconnecting the audio cable with the mp3player switched on, solved the problem - radio worked again. (static charge?!)
 
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