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August 17, 2006 AT 2:11 am

Bike Stereo

Sometimes its really important to have a stereo system for your bike. SCUL has a ‘standard’ method by which they use a 12V SLA hooked up to a car stereo which is then wired to some car speakers. It’s cheap and easy but I’m never one to leave well enough alone. Thus my ultra-light/ultra-efficient pimped-out bike stereo system:

  • 2 x 7.4V 4Ah Lithium Ion Camcorder batteries = 15V at 4A = 60W of power! ($20 each)
  • Class D amp. I use the TPA3001D1 you can get kits for this, I made my own PCBs cause I wanted to make at least 4 amps. Either is A-OK. up to 20W output! Is TSSOP so a pain to solder.
  • Cheap MP3 player (this one was ~$10, uses MMC cards and a AAA battery) You dont want to get your iPod all dusty. Requires an MMC card, a 256M is like $25 or something.
  • Speaker(s)! I recommend old car speakers. Making an enclosure for them will make them sound better but they’re sort of engineered for poor enclosure design. Cheap/thin cookpots work great and come with an attachment point even!


Because I’m using lithium ion batteries (twice the power per lb) and a class D amp (twice the efficiency, and also no heatsink to make it superheavy), the whole system (minus speakers) is 1lb. A speaker in a cheap pot as above is about 5lbs more.
Took it out of storage and tested it on a $2 speaker which promptly died from overdriving it :(

OK well, now to hook them up to the big speaker. Lookin’ good!

Here is a closeup of the board

And the files for the PCBs, make sure to read the datasheet to see what is up with the parts, this is otherwise undocumented

Notes:

  • I used MOLEX Micro-fit 3.0 connectors for the wiring harness. These are awesome!
  • Solder directly to the camcorder plugs to avoid having to get the wierd micro-banana plugs but then…
  • Wires go through a lot of stress here so use zipties for strainrelief as shown.
  • You’ll need a 7.4V battery charger for LiIons. I made one using the BQ2057 chipset, or buy from your favorite online battery store. Or just give it 1/4C 8.4V with some power supply. I’ve seen people use LM317s…hey whatever works for you
  • Be careful, I overdrove the two cambridge soundworks speakers (they lasted 6 days tho!). Bring extra speakers or just use big speakers so you’re safe
  • Bass response sucks…thats just what you get for having a system like this.

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6 Comments

  1. Cool — Go Class D amps!!

    Hey, get some sleep already…
    :)

  2. Where did you find that cheapo mp3 player?
    I’d like to get me one.

  3. what was the name of the software that you used to design the PCB for the TPA3001d1?

  4. hi ur project is ok
    but u can chose a new one
    have alook at this

    http://groups.google.com/group/class-d-amp/web/100w-mhz-class-d-amp-mcd-v100

    if u like ,mailme pls

    best rg
    fumac

  5. […] Related: Ultra-light/ultra-efficient pimped-out bike stereo system – Link. […]

  6. Great Project. If you can’t take the party with you why would you leave?

    I have a similar monster on my bike, but I used:
    – A Motorcycle Sized SLA Battery
    – & The 41hz AMP 3 http://www.41hz.com/main.aspx?pageID=105

    41hz also has the AMP6 that features all thru hole components (for people like me that curse the Surface Mount Movement)

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