Sticky?

Credit goes to minivanman over on mobilesoundscience

I don't know if this falls in the low cost necessarily, but it is high value. Here is a complete module that operates as a line output converter (LOC), and a digital sound processor (DSP)

The goal of this project was to build a unit that could convert the speaker level outputs of my stock head unit and supply a line level signal to a miniDSP module.

http://www.minidsp.com/onlinestore/c...7/minidsp-kits

http://www.mobilesoundscience.com/f4...-work-you-257/

Typical car audio branded LOCs generally have a limited bandwidth, and even within that bandwidth, the signal isn't very flat. All an LOC is is a group of small transformers that step down the voltage to a line level, and provide ground isolation. Since consumer car audio LOCs utilize such small, and inexpensive transformers, you'll get the limited bandwidth I was talking about. For example, David Navone brags that his LOCs exhibit bandwidth extending down to 80 hz. Roll off after that occurs at 12 db/oct, so by 20 hz, you're 24 db down in output. Usable, but we can do better, albeit with a considerably higher cost.

Now in come the pro grade transformers. These are not cheap, but they exhibit a full audio bandwidth between 20-20khz, and the signal is flat. The most respected, and popular are made by a company called Jensen (not to be confused with Jensen Car Audio).

http://www.jensen-transformers.com/

I decided to use a JT-10KB-D transformer for this project based on a very simple schematic that Jensen provides on their website for a LOC. The schematic is listed under application AS068.

http://www.jensen-transformers.com/apps_sc.html

Since the power being supplied in this application is fairly small, it was very easy build. In fact, technically, you could just run this transformer without any additional resistors. I put some on the back purely for protection sake.



Here are the transformers. You can fit about 4 transformers from a car audio branded LOC into one of these.



Here's the input plug. Simply two runs of speaker wire, and a 12 volt power, and a ground wire.


Output side.


Total this project costs about $225.00. With another DSP module this could easily run a full 4-way setup for under $350.00.