My Factory AM Radio is now mp3 Compatible!

[Frizzle Fry]

I’m the type that likes the look of a stock dash and radio but wants a modern sound system. A few weeks ago I bought a Rockford Fosgate Omnifi mp3 player. It’s basically a 20gig hard drive based system (easily upgradeable to 120gig) that allows you to transfer mp3s from your computer to your car via USB or optional wireless (which I have).

I had planned to run it stand-alone directly to my cross-over/amps, but I soon found out that it has no built in pre-amp, so no volume control. My existing 10+ year old CD player had no audio inputs either (the way the Omnifi was designed to be installed). I looked at the USA-1thru6 options, but didn’t really want a new deck.

I decided that all really needed to run this thing stand-alone was some sort of volume control capability and power antenna signal. So I did a little google’ing and found info on in-line RCA volume control. A trip to Radio Shack and I was ready to do a little radio surgery.

I picked up some 0-10k ohm potentiometers and surface-mountable RCA jacks. I later discovered that 0-10k was insufficient and went to 0-1M ohm. The 0-10k pots only adjusted volume from 100% down to about 90%. The 0-1M pots adjust volume from 100% down to about 5% (plenty low). A further improvement may be possible using this configuration. My setup works just fine, though it does get a little touchy/sensitive near full volume, meaning a little adjustment goes a long way in volume. But it's not enough to be an issue.



When you remove the covers from the radio you can see there is plenty of room to do this. Just take out a few components behind the volume knob. I didn’t use nor did I plan to use the radio as an actual AM radio.





The existing volume/tone knob has two pots (two are required for stereo volume control) so at first glance I thought this was going to be easier than expected. But they are not matched and are the wrong specs for the job. But the amazing thing is that the annulus (resistive disc - more info here), is nearly identical in size/shape from stock to new. A little clearancing on the new ones and they fit perfectly.

[Frizzle Fry]

Now, the other thing I learned is that the stock sweepers don’t work very well with the new annuluses. They look like they will but when I tested them in this configuration there were open spots in the volume range. So, tried gluing the new sweepers onto the stock sweeper discs. That seemed to work ok, but when I went to the 1M pots I decided to use the new sweepers AND their plastic discs. I did this because the centering of the sweeper on the annulus and shaft is critical. I just drilled holes in the center of the black plastic sweeper discs to fit them over the shafts.

[Frizzle Fry]

Drilled holes and mounted the RCA jacks. I would move them forward or to the bottom of the deck if I had it to do over because they are pretty close to the wiper motor as is.




Another great thing about the stock pot housing is that it has a built in switch. This was the main reason I chose to stick with the stock pot housing instead of trying to find a compatible dual-gang pot. I wired the switch up to the existing power jack in the back of the radio. So two of the spades in that jack are now used for power antenna (on/off signal to the crossover, amps, and mp3 player), and the other spade is now connected to the internal light. I later wired the radio light to the dash light circuit so it will be on/off/dim with those. You could wire it to the knob switch if you want it to switch on/off with your system, but I like the back lighting on and dimmable even when the system is off.

[SactoJim]

Holy Crap....what are you..a rocket scientist!

That's impressive and a little (way) beyond me!

[Frizzle Fry]

I left the tuning mechanism alone so the kids can sill push the preset buttons and watch the needle move all day long. But you could build a balance/fader knob on that side if you wanted using the same technique and simply wiring one pot inversely as is also explained here.

I installed a new bulb while I was in there (also put all new bulbs in the rest of the dash).

This set-up would work for any audio device that is designed to be run through AUX inputs in a deck and has its own control interface.

Here it is installed. The faceplate is pretty thin and could be mounted anywhere, but it's going here for now (hot glued on so it's easily reversible).




Next install; my new covered fiberglass kick panels thanks to this FAQ

[67arch]

Nice post!! That is exactly what I would like to do.

[sdkid]

That is so cool. I'm not sure I'm that smart for this though. It also needs to be moved to the FAQ forum.

[jaros44sr]

I'm alittle old, well make that a lot old, but what is mp3. Your work is impressive even tho I don't know what you said. I'll have to go back and reread it. That is awesome to see it look stock. Congrats on your success... J.

[jimmydean]

Nice work indeed!

I was going to get the OmniFi setup until I saw the limitations and the price. One thing let to another and I am now planning a system around a Mac Mini. I will do it in stages, I still need to modify the dash to accommodate the screen,

[special-K]

You`re a frickin`genius Frizzle Fry.Shoot me your address.I`m sending 1/2 dozen radios your way. That`s great!

[Frizzle Fry]

Thanks guys. The basic idea was pretty simple, but making it work the way I wanted it to using some of the factory parts took a little trial and error. Now that it's all figured out it would be cake to do again. I just wired up the radio back light today so I went outside a few minutes ago to check it out after sun down and it looks great

I think I'll move the Omnifi face-plate somewhere else in the future and put the ashtray back, but for now this works.

You could run a stand-alone CD changer or HD-Radio unit this way too.

Here's a link for jaros http://en.wikipedia.org/wiki/Mp3

[cdowns]

will it play 8-tracks??

[flatheadnut0]

That's the coolest thing I ever saw. How the hell did you come up with that?

[IvelDesigns]

that's awesome.

[724x4a/cchevy]

holy crap man!! this is awsome!!

[Draggn66]

[jaros44sr]

Originally Posted by Frizzle Fry

Thanks guys. The basic idea was pretty simple,

Here's a link for jaros http://en.wikipedia.org/wiki/Mp3

Thanks Fry, but that was way to much info. Are you saying it plays CD's? Your work is way too cooool! Wish I knew what you were talking about.... J.

[oj70chevy]

Originally Posted by SactoJim

Holy Crap....what are you..a rocket scientist!

That's impressive and a little (way) beyond me!

that is awsome. I see this going to the FAQ!

[Yukon Jack]

Incredible . . . just incredible. You could surely make some money marketing these conversions!

[gmc1969custom]

Very, Very Impressive!!!!

[Orange]

Very impressive. I have a factory AM radio. I may do something with it someday.

DLB

[PanelDeland]

Frizzle,you do realize this is a great mod but probably only a few on here are 'lectronically literate.This is a great write up and pics for a FAQ,maybe it should be used as a template for them.You should look at posting it on an audio forum or maybe selling it to them as a mod from stockers.

BTW my TV wont work do you do house calls.

[grant's72]

could I plug a i-pod in to that and have it work

[Frizzle Fry]

Yep, with the iPod RCA adapter. All this mod does is give you the ability to adjust line level into your amp or crossover (and on/off). So anything that puts out an analog audio signal can be run through it. The best iPod RCA adapter is the one that runs from the bottom port, not the headphone jack. You can get this type with RCA out and charge capability.

[oldgold70c10]

My setup works just fine, though it does get a little touchy/sensitive near full volume, meaning a little adjustment goes a long way in volume. But it's not enough to be an issue.

You should try using audio or log tapered pots for volume controls, instead of linear. This will give you the "normal" control you expect from a volume control.

Neat setup. A lot of AA5 tube radios in the 60's had a "fader" arrangement for plugging in a phono; with nothing plugged in, the volume control worked as normal, but, with a audio sourse plugged in, and the radio tuned to an empty spot on the dial, the knob was used opposite of normal (full clockwise was min. volume). I have thought of modifiying my truck's stock radio this way so I can still use it as an AM radio. I know it wouldn't be stereo, but I could mix both channels together with two 1K resistors and get true mono from any stereo source. It wouldn't be hifi, either, but that's why I got a nice amp at home.

Anyway, nice job!!!!