Remove Tape deck and interface MP3 ???

[Guest]

I just took out the tape deck section of the radio and trying to interface an MP3 player to the existing electronics ...
getting sound but have to keep level very low so it won't overload the preamp ..
any one have any sugestions ????

Thanks

[SIR tricky]

Presumably you do have the schematics

I dont know enough about electronics to muck about, are you trying to do the same as they do with the 1500, that is install a 1/8 stereo jack into the preamp section?

[Guest]

Yes that would be more or less what I want to do ... I'm also going to install a USB power jack so I can power the player ... just need some kind of interface to the preamp ... been years since I played with this stuff ... just rusty now

LOL

[SIR tricky]

Can you not add some kind of resistance to the mp3 input?

I had a look at the schematic but dont know enough about it to warrant a try, preferring to play it safe and use an FM modulator, I have a cheap one presently but plan to go to an inline atenna model like the audiovox.

[Guest]

I hope no one minds if I jump in here and try to help some...
Please ignore this if so.

The reason you have that problem is that your impedence and input levels between the old and new systems are way different.
As was mentioned above some resistance may be necessary but it may be that you also need a voltage divider made out of two or more resistors. That way you can get a ratio out of the higher level MP3 player output and still approximate the input impedance needs of the input circuit. An easy way to accomplish this, at least for measurement and testing is to use a 20k to 50k pot.
Tie one end of the three leads of the pot to ground. Feed the MP3 output to the other end of the pot. Then feed the center or wiper terminal of the pot to the input circuit through a 10uf capacitor.
You will only use one channel of the MP3 circuit while you find out what resistors you need.
Set the MP3 player at a level somewhat above what you listen to it with ear buds. My earbuds run about level 13 and about 23 for feeding to the amp if I use it that way. You will have a different setting scale but it gives you a reference to go by.
Then set your bike amp to about mid amplitude or where you have your volume set when listening to other things.
Then turn your pot up and down until you get the right volume and low distortion.
If you have distortion anyway, back down the output of the MP3 player until you don't and then take note of that level setting.
Once you find the right place for your pot settings, avoid moving the setting while you disconnect it from everything, then using an ohm meter, measure reading from the ground end to the center terminal. This will be the value of your low resistor. Then repeat measurement between the MP3 feed side terminal to the center terminal on the pot. This value will be the feed resistor side.
These readings don't have to be exact when you go get resistors to replace the pot with.
In the end you will need two feed resistors of the same value (one for each channel of stereo), two low resistors and two 10 uf caps.

Connect thusly...

MP3_Out_left >>> one side of Feed resistor >>> other side of feed resistor to one side of low resistor >>> other side of low resistor to ground, Additionally, One side of cap to center point of two resistors >>>. other side to Left input circuit of radio.

Repeat for Right side.

It is easier to add the wired in FM modulator that was mentioned above, at least for me it is.
Here is a link to some options you can explore, including the wired in modulator. It is for the 1500 but a radio is a radio.
<!-- m --><a class="postlink" href="http://goldwingtech.info/auxradio/">http://goldwingtech.info/auxradio/</a><!-- m -->

HTH

[SIR tricky]

Anyone is welcome to join in and add their comments

[roscoepc]

Yeah!! They even let me comment!! :mrgreen: :mrgreen:





Sometimes....... =)) =)) =))

[Guest]

Hmmm ... thats the way I was working ... just have to look through my parts bin ..LOL ..

I'll keep working on it and let you know how it all works out ...

bought USB power unit that will be mounted inside the radio where the cassette unit was ...


STILL Working on it ... almost there ...