Designing an imaginary car CD project..

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For a Commerce uni assignment we have to come up with an original product (or at least no "that already exists comments!! :) ) and come up with a business plan etc.

Its a group assignment and I, being the EE of the group have been allocated to R&D.

FWIW, im a 4th year student.

For those who care of the background, our "product" is a portable car stereo system. Basically its a discman which has a "slot" in the car stereo, so you can essentially remove the cd player from the car, leaving the "console" in which it sits in behind. The console will also consist of a radio.

By having a product which acts as a car stereo AND a discman, we hope it will appeal to students etc. Adding perhaps mp3's etc etc...either way, whether it would sell or not is beside the point, what I need your guys help for is a few starting tips :)

The removable cd player (discman) will contain rechargable batteries, fed off a car battery.

I need to break up the "discman" component into transport, DAC and headphone stage.

I need to break the "console" part into the preamp, radio, and power amp.

The problem is keeping the costs down. Seeing as you can get a "4x50W" head unit, which has a cdp and radio for about $AU500...building a $AU2000 car stereo setup isnt exactly going to work.

Price is more of a factor than sonic quality. I like to pay for good sound, but for this assignment...I have to go the other way :)

I think retail price should be around $ assume parts cost has to be $AU200-300, at the most. Less is better.


I am pretty sure I can handle the DAC section myself (using a 12V car battery source).

I am pretty sure I can handle the headphone stage myself, and their are enough projects out there for me to copy/modify one.

The problem is the transport. I cant seem to find anything either suitable for a "discman" style implementation, not anything thats even remotely close to the price range. Realistically this thing should cost about $AU50 when buying in mass quantities, otherwise the budget is going to blow out. Any ideas?


For the radio section I can probably buy an off-the-shelf ready to go "module". Anyone know a decent, but cheap one?

The preamp can also probably be either passive (just a pot), or somthing pretty minimalistic.

The power amp. I am sure there are some efficient IC based amps out there. Has anyone got any suggestions?

Thanks for any opinions out there. Basically I dont have to come up with a working design..just something that gives the idea that it "could be done". Its a Commerce assignment, not an engineering one :)

Lots of tricky looking schematics/datasheets go down well with people who have absolutely no idea what they mean..
One thing I wanted to ask..

Is that most IC's I would like to use for the power amps need higher Supply voltages than 12V to obtain more than about 10W (usually less) output.

I read something about a switching supply, but its beyond my expertise, and I have never studying anything alone those lines.

Anyone know how car amps get more than about how they boost the rail voltage cheaply??
As far as IC amps check this link for Nationals offerings.,1850,695,00.html

They have several that require significantly less than 12 V rails. You could likely use one of those. You could also use a Step-Up Switching regulator from a company such as Maxim to boost your ~12V in from the battery. These regulators are very simple to use, and maxim has lots of information on them on their website.
Why bother with a CD mech?

I would guess that a cd mech is going to need to be custom made for you application, what about using a laptop hard disc and making it an incar MP3 player and a portable MP3 player at the same time.

It would probably have more appeal to your target market than a cd player and (as far as i know) would also be unique (the traxdata mstation is the only commercial in car player i know of and it's not portable afterwards).

best of luck with your project
Thanks for the help.

I would love to use an existing portable transport, I just cant find anything..including a price and moderate information about one..

Our "future options" include an mp3 or minidisc etc player. Using an mp3 option initially is an option...but I think CD is just as important/accessible.
OK, I've had a bit of a look around.

I like the looks of the LM3886 Power IC. It will provide 68W @ 4ohms off +/-28V. According to the datasheet, I am going to need to get over 6A from this power source to meet this requirement.

What's the best way to get the +/-28V from a 12V battery? I find heaps of them capable of meeting the +/-28V on the maxim website, but none I see are cable of the current, and the voltage delivery required (or anything close for that matter).

Any help will be appreciated.
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