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Project: convert radio/CD player into an mp3 jukebox

Discussion in 'Audio' started by Qualcomm_inside!, Mar 12, 2017.

  1. Qualcomm_inside!

    Qualcomm_inside!

    17
    1
    Jan 27, 2017
    I have an interesting project I'd like some advice on; I have a couple of old boombox stereos I would like to convert to an mp3 player/ recorder.

    Essentially, what I want to do is install a CODEC board into my the case of my radio and solder the audio line Out and line In ( tape monitor ) lines to the mp3 device.
    I want to use a mp3 codec that has both an SD card and a USB host that will allow me to play files on a USB stick, as well as be able to RECORD line out from, say the radio or the CD player and store that record as mp3 on my jump drive.
    Is this possible?

    The radio I will experiment with is a Jensen SCR-415A, AM/FM stereo cassette recorder. Also I have a Sony AM/FM CD boombox I could try..
    For wiring the mp3 player into the stereo I was thinking of using the cassette deck wires because A, that would give a direct line-level IN and OUT to the amplifier.
    The tape deck has record/ monitor circuit,
    Was thinking of removing the tape deck and mounting my mp3 in this space, wiring it to the appropriate lines on the amp..

    1: where can I find a single board mp3 player that does both playback & record, has USB host port, and has analog I/O that can solder directly to an amp/ receiver?

    2: is my idea of wiring in place of the cassette recorder a good idea?
    Is the output monitor circuit of a cassette recorder line level? or is it amplified/ powered?

    3: what would I need to wire power to the mp3 player? Assuming the device operates at 5V, and my radio operates on 6V ( 4 D batteries ), what would I need to regulate voltage to get what I need ( 3.3 or 5 volt ) from the radios power supply?
     
  2. dave9

    dave9

    795
    186
    Mar 5, 2017
    Can't help with a board recommendation, would just crawl the eBay listings to find one at the price point and feature set you want.

    Since you want USB connectivity it should have 5.0V input to power that, or within a few tenths of a volt. You could get lazy and wire a silicone diode in series for about 0.6V drop to 5.4V peak input, or just settle for one of the popular LDO, low dropout regulators like LM1086-5. It has a dropout voltage under 1.0V for the low current such an MP3 module would use so it will work. See the datasheet, it needs nothing more than a 10uF capacitor (or whatever, lol) on its input and output.

    http://www.linear.com/product/LT1086

    I mentioned the diode in series only because you're doing this cheap and dirty. For a long lasting result I would not use some very old radio, instead starting with a relatively new one, and ideally one that uses 18650 Li-Ion or (n)* AA NiMH cells.

    How a cassette deck is set up depends on how modular it is. A complete drop in module would have its own preamp. A proprietary deck may not. You can measure the signal level yourself to see what you're dealing with before you tear it apart. You could use an opamp buffer to adjust level or just a resistor divider to pull the signal down if you need to... we're not talking about great quality audio I mean, from an ancient 4 x D boom box.

    However I noticed that Jenson SCR-415A appears to be 6 x D cell powered, which is enough voltage headroom that you could use a LM7805 regulator to the MP3 module instead, but the same LM1086-5 would also work.
     
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