Need basic electronics help! (building VW Monsoon amp input)
There's at least a couple of other threads about this. I started this one so I didn't hijack the others.
The audio Monsoon amp in many Volkswagens expects a balanced signal biased to 6 volts. The line or headphone out from the carPC doesn't match that. Also the Monsoon amp doesn't have a separate turn-on lead, it uses the presence of 5-6V on the left front - line to turn on. A few people on here (R32 Juhl, colorless, and alimh, probably others) have figured out circuits to go from PC soundcard to Monsoon in. Here are two diagrams (from others):
- R32 Juhl -
- alimh -
I am so close to having a working system, but I need some help. I have little to no practical electronics-building experience. I've only recently begun soldering, I've done a bunch of reading on electronic components from this site (hey, I remember high-school science!), and I now understand exactly why the circuit above is needed. I even understand the diagram and why we need the voltage regulator. So, I'm not a total loss. But, it's all recently book learned and not hands-on. I need some advice on actually building the circuit above.
Here's what I have.
Things I have:
- 7805 voltage regulator
- Heatdsink for 7805, some thermal grease and a mounting screw. I'll be feeding the 7805 a 12V line from the M1-ATX power supply so the heatsink is needed.
- a mini PC board (http://www.radioshack.com/images/Pro...76/276-148.jpg)
- Some wire (18ga or 20ga)
- a 1/8" stereo plug (3 conductor, solder connections)
- A spare Monsoon input plug (the grey connector, part# 1J0-962-624-A), plus matching wires and pins (4 ea. of part# 000-979-131). I bought these from a VW dealer.
My plan is to follow R32 Juhl's diagram (the top one with a voltage regulator) and build four things:
1) Monsoon connector: Insert pins/wires into grey connector, group wires into three groups, front/rear left +, front/rear right +, common -. I'll crimp/solder male quick-connects to the other ends of these groups. One quick-connect each for L+ and R+, and two for common - (these are both connected to the same bunch in a Y configuration, you'll see why later). Now I have a Monsoon to L+/R+/common harness.
2) 1/8" plug: solder (practice makes perfect!) three wires to the conductors of the plug. Crimp/solder 3 female quick-connects to the other end of these three. Now I have a 1/8" to L+/R+/common harness. The L+ and R+ quick-connects go directly to their partners from step 1. The common goes to one of the common connects from step 1, leaving only one open.
3) PC power Molex 12V: I built this already, I have a 4-pin male molex -> 2 male quick connects (12V+/- only, I'm leaving the 5V alone) This will be my input to the voltage regulator.
4) The 5V circuit. I'm following R32 Juhl's diagram. So, I need a wire soldered to the input pin of the voltage regulator to my 12V+ quick connect (step 3). I'll solder another wire to the ground connector and connect it to the 12V- also from step 3. Finally I'll solder another wire to the output pin of the voltage regulator with and crimp a male quick connect. This connects to other common on the monsoon connector from step 1.
This sound good? Here are my questions:
- How do a phyisically wire up step 4? I have a PC board, and if I let the heatsink rest on the board, the pins of the 7805 go thru the holes a bit. If I bend and solder the pins here, it feels like it'll be pretty stable. Does the bent pins plus solder keep the 7805 in place? I know I'll have to solder my leads to the three pins on the 7805, but how don't I have to secure them physically first? Maybe I hook the wire lead and bend a pin around it? Do I even need a PC board, is there a better way?
- I've got 18ga wire, it clearly won't fit in the PC board holes, what should I use?
- On the PC board which way is the bottom? It looks like one side has a conductive ring around each hole.
- Can I see a picture of someone else's circuit?
- From the schematic, it looks like the common conductor of the 1/8" jack (and therefore my soundcard) will see 5V. Can I place something between the jack and the 7805 to keep that from happening? I want a one way valve). Would this be a a diode?
Thanks for any help.