View Single Post
Jehannum's Avatar
Moved on to a "get some tunes in the car" project.

The stock radio is AM, powers one speaker (to the tune of 4W), has a weird-ass rocker switch in the dash to raise and lower the antenna, isn't built to any sort of DIN standard, and is super duper expensive. Mine works perfectly, and it's a nice visual piece in the dash, so I wanted to keep it, and keep it working.

So, with that in mind, I set out to make a stealth setup for the car. It will stream bluetooth from the phone, will be on when the radio is off, will add a right speaker in addition to a decent left, and won't be visible externally.

It's kind of a tight set of conditions, and it made for a couple tradeoffs that compromise sound quality a little bit. The biggest tradeoff is that the stock brackets only have room for a 5.25" speaker, and a maximum depth of a little over 2". So, I bought Match MS5x speakers.

I bought a Sure bluetooth module to match up to a small class D amp that I bought from gee, which is a basic 2x50W unit that has a little 12-24V stepup circuit in front of it.

Here's the initial "will it work" board:

I didn't want to modify the radio, because like I said, it's super expensive, but I really needed a radio-switched 12V. So, I looked at the service manual (which included a complete circuit diagram), took a deep breath, and heated up the soldering iron.

I added the blue wire in the picture:

Fortunately, there was a spare output in the bulkhead, so I didn't even have to mod the case.

I repurposed the antenna harness, so that i could get ignition and radio-switched power to the hatch without having to run new wires, which had the added bonus of allowing me to use a modern power antenna.

I bodged up a schematic, that used one more relay than necessary, but I was a little worried about drawing too much through the radio +12V. Two constraints that you don't normally have to deal with that I did are: 1) backfeeding the amp usually doesn't do anything, but it has a history of blowing up the Hitachi radios, so I needed to switch speaker outputs according to which is on. Also, the amp I got doesn't like being on without having a load on the speaker terminals, so when the radio is on, the amp must be off.

Then I started assembling.


Right speaker, installed in all the mess of hoses that Nissan decided was necessary to handle slosh and vapor in the fuel tank. This is just a spare left bracket, with the studs pounded out and new screws installed:

Amp in place, in the compartment behind the Driver's seat.

Test! Because the amp is from a Canadian, I had to make its first play Tom Sawyer.
+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
Your powers are useless! I'm wearing my tin foil underwear!

1992 300ZX: Not stock, 433 RWHP
1971 240Z: Toyota front brakes, 123 RWHP
1967 Pontiac GTO: not stock.
Old 12-18-2016, 11:56 AM Jehannum is offline  
Reply With Quote