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Thread: FAQ: Connecting your soundcard to a Volkswagen Monsoon Amp

  1. #51
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    Quote Originally Posted by qkslvr View Post
    Did you take the key out of the ignition after you turned the car off? I know in stock form the music won't turn off until the key is removed from the ignition.
    Yes, I did remove the key. Music still goes... and even if I shut off the music, obviously, the amp remains on.

  2. #52
    Constant Bitrate Lazyflip's Avatar
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    I was wondering how a regular head unit turns on the monsoon amp. I currently have a head unit right now but the remote turn on isn't connected. Can someone explain?

  3. #53
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    I connected an isolated power supply to my left front speaker - and ground, then I found the amp turns on at +3V and off at -.5V. Current draw was less then 10ma. I suspect the -.5V may be caused by some voltage on the ground wires, perhaps increased as age increases resistance, ect. Any one experimented with a means of putting a slightly negative signal on the wire to make sure the amp turns off? The ground loop isolator may offer a means of doing that with an inductive spike.

    2001 Jetta 1.8T AWW

  4. #54
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    I guess I'll reply to myself. It appears that my problem is that when I turn off the radio, my radio goes from driving the speaker lines, to floating, rather then driving them to ground. When they float, some times, but not always, the lines end up at around 2-3V or higher. When this happens the Monsoon doesn't fully turn off. Causing a dead battery.

    So my solution, which is under test now and has had good results so far, is to put a 1K ohm resistor between gnd and the left front - line. Here's the reasoning for using a 1K resistor. My radio claims 50W output for 4 speakers each with 4 ohms, or say 12.5 watts per speaker. I'll assume that's RMS not peak, even thought the real power is probably closer to 8-9 watts RMS. With P = V X I and I = V / R plus a little algebra we get P = V^2 / R or (P X R)^.5 = V = (12.5 X 4)^.5 = 7.07V. Resistors typically come in 1/8 watt or 1/4 watt so I'll choose look to drive it to ground with an 1/8th watt resistor. So we do V^2 / R = P --> R = V^2 / P = (7.07^2) / .125 = 39 ohms. But lets say it can do up to 12V we get (12 X 12) / .125 = 1152 or about 1K. So I chose 1K because you don't have to worry about the power rating of the resistor.

  5. #55
    Maximum Bitrate kbyrd's Avatar
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    Quote Originally Posted by Lazyflip View Post
    I was wondering how a regular head unit turns on the monsoon amp. I currently have a head unit right now but the remote turn on isn't connected. Can someone explain?
    Did you read this thread? The OEM head unit applies 5V to the speaker signal, that acts as the amp on/off switch.
    My worklog.
    Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

  6. #56
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    Quote Originally Posted by kb1gtt View Post
    So my solution, which is under test now and has had good results so far, is to put a 1K ohm resistor between gnd and the left front - line.
    Well it's been about 2 weeks now and no dead battery. Appears to have worked.

  7. #57
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    Still can't turn off the monsoon amp

    I've been reading this thread and working on my golf for the passed few months (very little time).

    I have succesfully turned on the amp with my 5v injected into the audio system, but can not for the life of me turn it off.

    if I leave the car running, and physically take off the positive wire running into the regulator - nothing happens. if I take out the key, nothing happens.

    does anyone have an idea about this?

  8. #58
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    Yes I've had the same problem. Ground the LF- line and the amp will turn off. I found a 1kohm resistor from LF- to GND works well as a permanent fix. The resistor won't affect your speaker level audio signal but will pull the line to 0V and turn the amp off when the radio doesn't drive the LF- hard enough.

    Your problem is that some voltage is getting on the LF- line keeping it above about 3V. This can be caused by radio signals and long wires picking up the voltage out of the air, it can be caused by small amounts of leakage current from a number of electrical devices, or it can happen because it wasn't given a chance to go somewhere else. A meter is basically a resistor with a meter across it, so if you put a volt meter across LF- and GND, the meter will probably cause enough of a pull to ground to make the amp turn off.

    It's now been several weeks, and we have had no problems with a dead battery.

  9. #59
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    Thanks very much for this. this has helped extremely. I've been able to avoid having to put in the resistor, and the amp shuts off - albeit, with a 3 second delay. I believe it is as you said, a small amount of current left over from the other devices and is leaking back into the 12v+ line of the amp turn on wire. I don't care if the music plays for 3 seconds after I remove the key. The amp is turning off, and the delay is kind of cool actually.


    Thanks for the reply,

    regards, Jay

  10. #60
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    I'd like to raise some caution about the 3 second thing. I had the same sequence when I originally installed my head unit. What I found is that once in a while, usually once a week, it would last longer then 3 seconds. When it lasted longer it generally didn't turn off until the battery was dead. At first we avoided a dead battery by pulling the fuse. The fuse how, ever is not intended to be a switch and can wear out. If it does wear out, what a bear that can be. In the end we needed the resistor to make for a consistent turn off, as well as a permanent fix.

    Good luck.

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