Using an Automotive Stereo to Play Mp3s on Older Home Stereo

Playing mp3 files on home stereo

I have downloaded or ripped roughly 5000 classic rock tunes over the last two decades and needed a simple way to play digital music files on an older home stereo. I have a home theatre computer (HTC) hooked up to the TV and my home stereo is connected to the TV, so I figured playing digital audio files would be fast and easy. Boy was I wrong, since I have to boot the HTC, turn on the TV, turn on the stereo, browse to a play list, (after creating the play list which is a lengthy process) and the control is with a computer mouse. The internet provided a few answers but most involved a Bluetooth device hooked up to the home stereo and the Graphic User Interface (GUI) along with the music files are on a cell phone or MP3 player with paired with the Bluetooth device. Another choice is to use a DVD player and put all the music files on a few DVDs, this method is a little better than the HTC but the GUI is still the TV. A couple of years ago I built a portable stereo using an inexpensive automobile media player that is powered by either an internal battery or an external DC power supply (maybe I’ll create its own Instructable). Also, I play music in my vehicle from a USB flash drive so why not use a car stereo in the home.

An automotive deck/head unit with mounting bracket and wiring harness $20

12 volt DC power supply $5-25 online

5.5mm x 2.1mm power jack (optional) $2

A set of RCA leads

Materials for a case

4 Rubber feet

Silicon adhesive

Soldering iron and solder

Volt/ohm meter

Heat shrink tubing (optional)

I decided to use an inexpensive, single DIN automotive deck or head unit from Wallyworld that fits the needs for this project. I am using a media player. A media player receiver(MPR) does not contain a drive to play CDs but does have a USB port, FM radio, a 1/8” auxiliary port and a Bluetooth connection. This MPR does not have a SD card slot but I’ve seen units that have both USB and an SD card slot. The MPR only recognizes audio files in the mp3 format; other MPR/CDR (media player receiver/compact disc receiver per the manufacturer’s terminology) units recognize other audio files with wma, flac, ogg and other common formats. And, most important, at least one set of RCA jacks for hooking up external amplifier(s). This project does not utilize the MPR speaker connections or the antennae for FM radio. The MPR connects to the home stereo with RCA leads only. When choosing a MPR or CDR assure RCA jacks are present on the back of the unit. I used the single DIN mounting sleeve that is included with a new unit to mount the MPR in the case. Also included with most new MPR/CDR is a remote controller, personally, I can’t see the need for remote control in a vehicle but for this application it’s great to have. You can use whatever MPR/CDR you choose, but it’s my experience that more expensive car stereos have lots of settings (the one year old K-wood in my truck has over 40 settings) while this MP has only five making it much easier to reset everything after a loss of power. Just a thought; why can’t modern, after market car audio system have an internal battery to hold

settings and saved radio stations the way computers, digital alarm clocks and even your digital heat/ac thermostats do. Resetting everything is a major pain in the butt, goes for the clock on the microwave too.

The supplied power needs to be 12-14 volts DC, check the manual with your MPR/CDR for the voltage requirements. The amperage (amps) draw is low because the MP/CDP’s internal amplifier and FM radio are not used. The power supply I’m using is 750 milliamps or 0.75 amps. A 500 milliamps or higher power supply of the correct voltage should be sufficient. Luckily, I have one so the cost is nothing. I’ve seen power supplies on line for less than $10. The power supply I’m using has a very common male jack, 5.5mm long and 2.1mm diameter. I purchased a matching female jack at a local electronic supply store for around $2. The jacks are not necessary if the power leads are connected to the wires from the MPR/CDR wire harness with wire nuts, butt splice crimped connectors or any other proper method to join wires. NOTE: Many online DIY sites with similar projects, the tinkerers utilize a computer power supply to fit the 12 volts DC requirement. I do not recommend this practice for a couple of reasons. A computer power supply usually has a fan which is noisy and increases electricity usage. They are physically large compared to other 12 volt sources, two or more leads on the motherboard connection have to be jumped, and look sloppy with a lot of loose wires and harnesses showing. A three prong, 120v receptacle is required, and, if the power switch is used all power to the MPR/CDR is lost. The MPR/CDR needs constant power so any audio settings and last played file are not reset to factory defaults. In other words, the power supply is always on.

I decided to
construct a metal and fiberglass case to house the MPR. I used materials I have on hand but you can use whatever you want, wood, MDF, sheet metal etc. Actually the case is optional if you don’t mind the look without a case or you might want to try the project first and build a case later. Another idea is to mount the MP/CDP directly to your stereo or home theater cabinet. Not a bad idea since the MPR is relatively small compared to standard sized home stereo components.

The case is mostly sheet metal scavenged from an old oven with ¼” thick fiberglass front or face plate. The face plate is 9” wide and approximately 4” tall. The opening for the DIN mounting bracket is centered on the face. I used the mounting bracket to mark the opening. I used a jigsaw with a fine toothed metal cutting blade. Pilot holes were drilled large enough to allow the jigsaw blade to go through the fiberglass. Take your time when cutting fiberglass or you will dull the blade since the imbedded glass fibers are harder than the teeth on the blade. I haven’t tried a carbide or diamond grit blades for tile cutting, if you have, let me know the result. The sides and top are a single piece of sheet metal with a ½” flange bent on the front and rear, the bottom has a 1 ½” flange providing rigidity and a mounting surface for four feet . I was able to bend/brake the sides and flanges with c-clamps and angle iron creating a makeshift sheet metal brake. Wish I had a real sheet metal brake, job done in two minutes. The rear is partially covered with two pieces of fiberglass mounted to the sheet metal flange. The bottom is open to provide easy access to the wire harness and RCA leads. I attached the front and rear panels with small pan head screws. Drill a proper sized hole in one of rear panels of the case to mount the female jack. Attach the rubber feet with silicone adhesive. Paint the case, I chose black to match the rest of my components. Allow the paint to dry thoroughly before handling the case.

The female jack has three connection points. Two of the connections will have continuity when no male jack is plugged in, these are the negative connections. Another way to determine the correct connections is to plug in the power supply to the female jack and check for voltage and polarity according to your multi-meter’s instruction manual. I do not know if you will damage your MP/CDP if the polarity is reversed. Keeping with the colors on the wire harness, a black wire for the negative pole and a red wire for the positive pole were soldered to the jack. The red (positive) lead from the jack is connected to the red and yellow wires on the wiring harness the black (negative) lead on the jack is connected with the black wire on the wiring harness. Both connections are spliced together with wire nuts. The unused wires on the harness are bundled together assuring no exposed wires are touching each other and secured with shrink tubing.

Mount the female jack/wire harness to the rear panel. Referring to the installation instructions enclosed with your MPR/CDR, insert the mounting sleeve in the front panel and bend the tabs to secure. Insert the head unit in to the mounting sleeve. Install the front bezel on the face of the head unit.

Connect one
end of the RCA leads to the jacks on the rear of the MPR/CDR, red lead to the red jack, white lead to white jack. Connect the other end to your home stereo receiver, pre-amp or power amplifier’s RCA jacks. My home stereo receiver has inputs for two tape decks, CD, auxiliary, and two videos. You can use any unused pair of jacks. Turn on your receiver. Plug the power supply into a wall socket then the 5.5x2.1mm male jack in the female jack on the MPC/CDR. Press the power button to turn the MPR/CDR on. Insert a USB flash drive containing music files encoded in the MP3 format. The unit will automatically start playing. Again, referring to the owner’s manual, check the operation of the remote controller. You can use a Bluetooth device or the auxiliary port as other sources of music.

This project was a fun, relatively easy to make and works exactly as intended. The case has a few imperfections but looks fine sitting in the stereo cabinet. I usually turn on the random feature and let it play. I figured out the simple remote control’s features quickly and can reset everything in less than 30 seconds after a power interruption. Music quality is generally good but variable due to inconsistencies in the quality of mp3 files. I was pleasantly surprised since there’s no hiss at all from the speakers when the player is not playing a file. I was expecting a little white noise like my CD player produced when not playing a disc. The blue display is a very pleasant but a bit too bright at night. I’m happy with the results for less than thirty dollars and a few hours in the shop.