Add an iPod input to many Volvo radios for $0

Dazzler · Post by **Dazzler** » 01 Aug 2008, 14:39

Hi,

Has anyone tried adding an mp3 input to a CR-905?

Thanks

Post by **MadeInJapan** » 01 Aug 2008, 15:12

Don't know the answer- maybe someone else does.

squonk · Post by **squonk** » 08 Aug 2008, 17:36

mja850 wrote:I had a friend make good solder connections to the L/R/G on the circuit card using short wires. I then soldered these to a stripped headphone wire. The sound was alright from the iPod, but any loud music (like the Beatles) was noticeably distorted.

I just added 1K resistors to the L/R connections between the short wires and the headphone wire. I used a lot of solder and I think the connections are solid. I placed one piece of electrical tape under the connections and one piece over, to make a kind of sandwich and to keep all of the connections from touching. Some of the tape went over the resistors.

Problem is, the sound is almost all BASS and is much quieter! Is this some kind of grounding issue or are the resistors too strong/weak? Could it be the tape over the resistors? What could cause all of the high frequencies to be filtered out?

The reason you are getting all bass is because of where you have connected your wires.

A casette player employs the Dolby noise reduction system: tape players are inherantly susceptible to high frequency noise. To overcome this, during recording, the high frequencies of the audio signal are amplified to way above the noise level of the tape. In the tape player an equaliser circuit is used to attenuate the high frequncies back down in order to give a normal flat frequency response, thus reducing the noise to an inaudible level.

You have connected your mp3 player to the input of the equaliser and Dolby noise reduction chip, which is attenuating the high frequencies such that you hear only bass.

You need to inject your audio signal after this chip in order to get a normal frequency response: If you look at the edge connector on the circuit board you will see it marked LGR for left, ground and right. Cut the circuit board tracks to the L and R pins to disconnect the output of the equaliser chip and connect your wires to the LG and R pins.

You may need to capacitavely couple your input signal and use a potential divider to bias the signal to half supply voltage - i'm not sure yet, I am just about to do mine but haven't had time to study the circuit downstream of this point yet.

whoa · Post by **whoa** » 12 Aug 2008, 15:36

Thanks, squonk; I too patched into the tape-head connector (from the line out on the ipod dock connector, in my case) without thinking and was rewarded with awful tone and scary booms when plugging in the ipod. Patching in after the Dolby filter will help the first problem, and a high-pass interface should help with the second to some degree.

I detect a refreshing degree of actual competence, and I look forward to hearing of your discoveries!

Mark

bercy46 · Post by **bercy46** » 13 Aug 2008, 22:01

Does this $0 hack work on the 2002 XC-70 ?

I realize that buying a unit from USASPEC for example would give me the option of controlling the Ipod from the radio buttons, but all I really want is a better connection than those tape adapters or FM transmittors.

Thanks

Post by **MadeInJapan** » 14 Aug 2008, 04:51

No, it's a completely different unit....sorry.

EddieV · Post by **EddieV** » 30 Sep 2008, 11:08

I have an SC-816 and really woudl like to wire up a line input to the CD changer interface.

I understand that this $$$ USASpec device would provide an iPod interface and transport controls, but I really don't care about such frills -- I just want a clean line-in preferably without the tapping into the tape pre-amp signal and having to deal with a dummy tape to activate it.

I read in an earlier post that the CD changer interface expects some sort of signal handshake from the CD changer before it will activate the lines.

Could someone please clarify this? Is it possible to override this handshake just so I can wire up a connector with the correct pin-out to get a line input? If so, does anyone know the pin-out?

If that doesn't work, is there a point internally beyond this handshake control where I can tap into the CD changer pre-amp signal path (similar to the tape pre-amp trick, but somewhere along the CD changer signal path instead)?

Thanks folks!

whoa · Post by **whoa** » 30 Sep 2008, 11:19

This one is a bit cheaper and exactly what you seem to be looking for. I installed one and it sounds great (though there is engine-electrical noise on the fm radio if I don't unplug the ipod).

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0248656531

(In case the link fails, it's a "BlitzSafe" device that plugs into the changer interface and lets you use your ipod's own controls.)

Post by **MadeInJapan** » 30 Sep 2008, 14:37

Make sure the ground is good and the engine noise should go away or at least be considerably decreased. Same thing happened to my USASpec unit until I secured the ground to another area where there was bare metal.

EddieV · Post by **EddieV** » 02 Oct 2008, 07:20

Thanks for the suggestion Whoa, but I think that BlitzSafe device is still more overkill than I'm looking for. It looks like it has a iPod dock interface which I'm sure adds to the cost. All I really want is a way to enable the CD Changer inputs so I can wire in a headphone plug either directly or somewhere along its signal path.

I already wasted $$ on a Belkin 12V FM transmitter that doubles as a charging dock (their latest tech, but still an awful signal). It has a built-in headphone jack too for driving a car stereo aux input, so all I need is a way to hack that input. Preferably avoiding the tape pre-amp route.

Any suggestions appreciated!