vw mk4 monson amp and another amp - Page 2

R32 JUhl · 08-16-2005, 07:30 PM

Quote: Originally Posted by alimh

I need some advice now...

This is my setup:
I have a 1/8'' connector (regular stereo) that has 3 pins (left, right, and common). The left wire connects to the LF+ and LR+ of the monsoon. The right signal from the 1/8'' connets to the RF+ and RR+ of the monsoon. The common from the 1/8'' connects to the LF-, LR-, RF-, and RR- of the monsoon as well as a 5v signal from the m1-atx power supply (red wire).

The amp turns on and I hear a little bit of static to confirm... The computer turns on fine... but when I plug the speaker 1/8'' plug into the computer, everything shuts off! This only happens when both the speaker 1/8'' plug AND the 5v turn on are on. Any ideas?

Also, I used the 5v from the m1-atx but plugged the 1/8'' connector to the output of my laptop sound card and it works perfect!

I think it might be a grounding issue... maybe the 5v is going back to the soundcard (which is grounded?) so there is a short. Also, somebody in the thread mentioned that their setup was getting really hot... maybe mine shuts off but theirs is still shorting but instead of turnng off just getting really hot. I guess I need to put a capacitor to block out the DC from coming back into the soundcard, but I don't understand exactly where to put it...

Any help would be much appreciated!

Test this: Install a 10k ohm resistor in series from the power supply to the amp.

+5v-----10kresistor-----amp left channel common

Let me know if that changes anything. I tried my work-around on two different sound cards and did not have any trouble. And I believe you're saying that you can hear your laptop perfectly through the audio system, but your carputer doesn't like the 5V coming in. Let's see what this does.

alimh · 08-17-2005, 03:57 AM

All right! Good news from the desert:

I was playing around and got my setup to work. I have a m1-atx power supply, and a on-board soundcard (on my mini-atx motherboard) hooked up directly to my Monsoon amp. It works and sounds awesome! There is some slight audible noise but nothing too bad (could just be the quality of the mp3...?). I am posting a picture of my wiring diagram. Hope this helps to all you dubber's trying to hook up directly to the Monsoon amp.

kbyrd · 08-17-2005, 08:14 AM

I would be great if this info could make it into the FAQ, there seems to be a lot of vw owners here.

vdoubleu · 08-17-2005, 05:40 PM

I GOT MY PROBLEM FIXED!!!

in case anyone else runs into the same problem....my setup basically looks like alimh's diagram but i used a diode where he used a capacitor.

I still have a little noise when the computer is on.

But my biggest problem is that I have a LOT of noise when the computer is on, the amp is on, but the lilliput is unplugged. Anyone know what the problem might be?

colorless · 08-17-2005, 08:50 PM

try only putting the 5v to the left front speaker common.. alos make the cap bigger to 1000uf or more then place another cap inline so the negatives are tied together... when the caps are tied together like that it makes a dc filter and since you are entering dc into the speakers it is what you are hearing.. also when the caps are tied together like that is it like a 500uF cap so bigger is better but i found 1000uf to 2200uf works good.

R32 JUhl · 08-17-2005, 09:32 PM

Quote: Originally Posted by vdoubleu

I GOT MY PROBLEM FIXED!!!

in case anyone else runs into the same problem....my setup basically looks like alimh's diagram but i used a diode where he used a capacitor.

I still have a little noise when the computer is on.

But my biggest problem is that I have a LOT of noise when the computer is on, the amp is on, but the lilliput is unplugged. Anyone know what the problem might be?

You need to determine where the noise is coming from. Make sure you are not introducing it directly from the audio output of the carputer. Test this by plugging headphones into your sound card to see if you still hear the noise. If the noise is present in the headphones, your computer is making the noise and you need to resolve the ground issue, most likely (in other words, your mother board or PSU is not properly grounded). If the noise is not present in the headphones, then you are introducing the noise on the 5V signal. Follow colorless' advice to clean out the DC signal you're putting into the amp.

Let us know how it turns out, too!

NeckPayne · 08-17-2005, 10:51 PM

Thank you guys for all your info on this...I'm very excited to finally start this project now that so many are reporting success!!

kbyrd · 09-07-2005, 08:48 AM

I'm a bit confused on the wire hanrnes you used. I'd like to do this without taping into existing wiring. I'm ditching my HU, so I though I would just buy a replacement for the "input" harness at the monsoon. That is, I want a duplicate of the plug that goes into the monsoon from the HU, that way I don't have to tap or cut existing wires. Any idea where I can find one? (Or, a series of aftermarket harnesses I can buy that will do the same thing?)

After thinking about this, I realized I could buy an aftermarket HU harness and connect it to the HU end of this moonsoon input wire, but then I'd have to run my audio out from the PC all the way from the hatch to the dash. Seems lame when the PC is right next to the monsoon.

R32 JUhl · 09-07-2005, 03:53 PM

Quote: Originally Posted by kbyrd

I'm a bit confused on the wire hanrnes you used. I'd like to do this without taping into existing wiring. I'm ditching my HU, so I though I would just buy a replacement for the "input" harness at the monsoon. That is, I want a duplicate of the plug that goes into the monsoon from the HU, that way I don't have to tap or cut existing wires. Any idea where I can find one? (Or, a series of aftermarket harnesses I can buy that will do the same thing?)

After thinking about this, I realized I could buy an aftermarket HU harness and connect it to the HU end of this moonsoon input wire, but then I'd have to run my audio out from the PC all the way from the hatch to the dash. Seems lame when the PC is right next to the monsoon.

Make your own harness. Your dealer can hook you up with the terminals and connector. Don't repeat my mistake, though - use shielded wire for your audio out and make sure the shield is grounded but is does not share the audio ground/common.

kbyrd · 09-07-2005, 05:09 PM

Quote: Originally Posted by R32 JUhl

Make your own harness. Your dealer can hook you up with the terminals and connector.

Cool, I'll start asking around here.

Quote: Originally Posted by R32 JUhl

Don't repeat my mistake, though - use shielded wire for your audio out and make sure the shield is grounded but is does not share the audio ground/common.p

What do you mean by "shielded wire for audio out"? I was going to just use speaker wire like I would use for wiring up a home theater system. It's just standed 18ga (or something). Where to I get this stuff and where/how do I ground it?

Bugbyte · 09-07-2005, 05:25 PM

He means for wires carrying the audio signal from the soundcard to the amp you should use wire like they use in RCA cables. This is because the signal is relatively low voltage and interference can easily distort the audio signal.

There are core wires (say white and red) and they are wrapped usually with strands of wire or a metal jacket that are the ground. The wires form a shield around the core wires that helps block interference.

You can buy shielded audio speaker wire pretty commonly. It should say so right on the package.

I don't think you need shielded wire for the output of the amp to the speakers. Those are relatively high power.

kbyrd · 09-07-2005, 05:33 PM

Quote: Originally Posted by Bugbyte

I don't think you need shielded wire for the output of the amp to the speakers. Those are relatively high power.

Great, one more thing to buy. Well, better I found out from the forum then bang my head against the wall trying to solve some noise problem myself. At least it'll be a short run, the pc and the monsoon amp both in the hatch. Do I need to ground this like you do stuff that connects to the car's battery? (Short, large wire, unpainted metal on the car) Or, can I somehow connect it to a ground near the PC (my power supply?). Or, maybe the negative wire my power supply takes as input? I understand I can't connect this ground to the audio signal '-' wires.

R32 JUhl · 09-08-2005, 10:22 AM

Thanks Bugbyte!

[QUOTE=kbyrd]Great, one more thing to buy. Well, better I found out from the forum then bang my head against the wall trying to solve some noise problem myself. Kbyrd, my understanding of electronics says you want to use the same ground

Yeah - like I have been!

Quote: Originally Posted by kbyrd

Do I need to ground this like you do stuff that connects to the car's battery? (Short, large wire, unpainted metal on the car) Or, can I somehow connect it to a ground near the PC (my power supply?). Or, maybe the negative wire my power supply takes as input? I understand I can't connect this ground to the audio signal '-' wires.

Kbyrd, my understanding of electronics says you want to use the same ground as your carputer to eliminate a ground loop. So whereever you ground your power supply, also ground your shield wire - then again it may not matter where's it's grounded as long as it is dispersing its energy to ground, but I'm taking the "better safe than sorry approach".

kbyrd · 09-26-2005, 09:03 AM

I just ran across this thread on vwvortex:
http://forums.vwvortex.com/zerothread?id=2122749

Assuming the posted knows his stuff (I'm not in a position to tell), it looks like the monsoon amp expects a BTL load swinging around 6V on all inputs 4 inputs. Also, there's this talk of BTL a single input being out of phase on + and -. Do the diagrams here or in R32 JUhl's post do this? Clearly they work people have heard pretty good sound coming out out their speakers, but are they correct?

I'm wondering if we can find a pre-packages part that converts either speaker level or line level output from a soundcard into this BTL signal. Somthing like this:
http://store.qkits.com/moreinfo.cfm/fk608
maybe?

The little bit of searching I did didn't turn up any pre-packaged car audio amps that had BTL output

kbyrd · 09-26-2005, 04:11 PM

Quote: Originally Posted by kbyrd

The little bit of searching I did didn't turn up any pre-packaged car audio amps that had BTL output

I've learned a tiny bit more about car audio amps, and it appears many/some are bridgeable. A two channel amp would have a signal on the left + and the right - terminals. I seems like using two low powered bridgeable amps (feed one channel of the output from soundcard into each) would be exactly what the monsoon amp expects. Someone please chime in on how this differs from the circuit from this thread or R32_JUhl's install thread.

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