Hacking Car Radio / Cassette for iPod / Smartphone

[bsuttie]

Just thought I'd share my experience of hacking a Volvo CR-902 radio / cassette to give it an aux in.

I've been meaning to get round to this for some time, but finally got round to it last weekend.

I had thought about replacing the unit with a new one, but as the old unit would probably be going in the bin there was nothing to lose by giving it a go.

So, pulled the radio out and started taking it to bits which was very straightforward. As I was basically looking to tap into the top end of the volume control I was delighted to see that the control was actually mounted on a separate PCB which came out easily.

Traced the PCB back from the volume control and found a couple of capacitors which the audio was going through. Ideal I thought - no chance of any DC to damage the source if I connect in there. So I cut the tracks, fed a 3.5mm stereo cable in through the cassette slot, tagged the wires on and put the radio back in the car.

Hooked up an ipod and couldn't believe how good the sound was! Far better than the FM radio, wider response, unbelievable bass like I've never heard from this system. And if you pause the iPod and turn up the volume you hear nothing - absolutely nothing, it is so clean!

So, time to take the radio back inside and formalise the mod. My first thought was to blank off the cassette slot with a switch and 3.5mm jack, and I got quite a long way down the road when I had an even better idea. There was plenty room beside the volume control so I added a small bit of veroboard with a relay on it.

The normally closed contacts have the original feed from the radio cassette on them, the normally open contacts are connected to a flying lead out the back of the radio terminating in a 3.5mm jack, and the commons go to those capacitors and then to the volume control.

I fed another wire out the back to activate the relay, found a nice switch with a blue LED in Maplins to turn it on or off and hey presto - off we go!

I am now using this with my SPV 3100 smartphone to listen to music and can also take phone calls with much better clarity than the Bluetooth adaptor I was using.

Only slight issue is that the point I tapped into is after the tone controls so they don't function, but the audio quality really is so good I wouldn't want to change it.

So if you're handy with a soldering iron I would have no hesitation in recommending this option.

regards

Brian

[davepuma]

Pics?

[bsuttie]

Originally Posted by davepuma

Pics?

Ahh well, stupidly didn't take any at the time. I'll take one of the finished setup tonight and if there's any interest I'll pull it out and take some of the innards at the weekend.

regards

Brian

[bsuttie]

OK, here's a photo to give you the idea. The small ABS box and the wiring would normally be tidied away.