Need help building VW Monsoon amp input - Page 2

kbyrd · 10-07-2005, 07:46 AM

I just re-read my explanation of the voltage regulator and something is bugging me. Is it really needed? Does the 5V rail from the power supply really vary? Using MBM5, I measured mine as something slightly less than 5V, but I didn't look at it over a long period of time.

agentloveless · 10-09-2005, 03:47 AM

Ok, So I am dedicated to the whole carputer deal. I prefer to get to use the current monsoon system but if I am unable I figure I will end up replacing it with an amp and new speakers. This attitude has led me to be less cautious than I otherwise would be. So here it goes.

I took a trip to frys today and bought myself some assoreted parts. Capacitors, resistors, diodes. didn't bother with the voltage regulator.

After verifying that the brown plug in the back of the head unit was indeed the inputs for the monsoon amp, I decided to employ the circuit diagramed in this forum. I used a 5v power supply and my iriver mp3 player. Unfotunately there were no results to report.

Worried I might have damaged the equipement I decided to hook up the original head unit. Luckily, there was no damage and the music played just as it used before i took the system apart. This is when i made an unexpected discovery. With music still playing I disconected the brown plug from the head unit. I then proceded to hook up the mp3 player only, without the 5 v supply to the brown plug. Music played over the speakers. I was fairly confused. I shut off my car and pulled out the key, and to my suprise the music didn't stop. Interesting I thought. I unpluged the mp3 player from the 1/8 jack, so at this point there was no signal going to the amp. I then pluged it back in. To my suprise once again the music started to play. I then connected the brown plug to the head unit and powered it down. Upon unpluging the brown plug and trying to play mp3s again it didn't work. I repeated this several times with the same results each time.

Also, while the head unit was on, I hooked up the multimeter to the back of the head unit where the brown plug conncets and got a 6v dc reading.

Conclusions:

It seems that some signal is passed from the head unit to the amp over the 8 wires that tells it to either power up or power down.

Although the 6v is there, it does not seem to effect the powering up or down of the head unit.

I am pretty lost for ideas as of what to do from this point. I only have a multimeter and this seems to be a much better job for an ociliscope. However, if anyone has any ideas please post then and i will give them a shot. The worst i can do is damage the monsoon amp, but if i can't get it to work i will have to replace it anyways.

BoraXP · 10-09-2005, 01:54 PM

ok...

i would recommend getting a new amp but the monsoon speakers are pretty good.

the only thing is, your gonna need at least a 4 channel amp to do power the eight speakers.

and run the tweaters with a highpass filter on two and the subs with out any filters on the other two

i dont know how loud you listen to your music but i have a five channel that runs i think like 60 watts a channel
and its loud

just have to rerun the speaker wire

BoraXP · 10-09-2005, 01:55 PM

ahhhhhh and to you vw owners...

it will be hard to get your car smogged or the engine checked

there is a (what i think is a ) myth that if the stock headunit isnt there, odb2 scanners will get fried

hasnt happend to me, but ive been denied service several times.

agentloveless · 10-09-2005, 02:00 PM

Do I have to rerun the wire because I will need sheilded wired now because the lines will be unbalanced?

alimh · 10-09-2005, 03:10 PM

Here is my thoughts on the voltage regulator and capacitor.

voltage regulator:
Why not?? Basically, the voltage regulator is designed to give a constant 5v output on a range of varying inputs (i think 6v-18v). Then, when you're dealing with the noise later, you can drop this out of the "what if" questions.

capacitor/diode:
You cannot use a diode because the audio signal that also passes through keeps switching from + to -. THe diode would block out all the -! Instead, the capacitor blocks out DC. Anyway, some soundcards (from what I read) do not use the computer ground so you could potentially hook it up wihtout a capacitor.

As far as the mp3 player staying on after you already turned on with the HU... R32 reported that the 5v turn-on voltage is just that... a turn-on! After you apply it, you can remove it and things should still work. I tried with mine, but it doesn't seem to work as well without it... the sound quality degrades... haven't figured it out yet.

But one more thought...
I am still hearing Hard-drive and engine noise on my speakers! And it's driving me crazy now. Anyone have any ideas on how to deal with this? I tried an RF choke, but that didn't do anything.

kbyrd · 10-09-2005, 04:00 PM

Quote: Originally Posted by alimh

Here is my thoughts on the voltage regulator and capacitor.

capacitor/diode:
You cannot use a diode because the audio signal that also passes through keeps switching from + to -. THe diode would block out all the -! Instead, the capacitor blocks out DC. Anyway, some soundcards (from what I read) do not use the computer ground so you could potentially hook it up wihtout a capacitor.

Does the one in your schematic say 0.1 microfarads? That is, 1/10th of one microfarad? I'm looking at several at RadioShack that match that:
272-109
272-1069
272-1053

They come in a variety of voltage and percentage ratings. As I understand it. The voltage rating only matters as a limit of the voltage I could run into given capacitor. That is, I'm putting my cap in a 5V-ish circuit so it'll always have 5V at it's terminals.

Also, there are smaller value capacitors, should I use those on the theory that even the smallest value will block DC and a lesser value will have a less chance of blocking the AC audio signal? Any other advice on the various types? (longer leads, etc.) ?

agentloveless · 10-09-2005, 07:29 PM

Ok, finally got this monsoon deal undercontrol. Here is what I got.

+12V to the FL- powers up the amp.

Gounding both the FL+ and FL- turns the amp off.

I found that removing he 12V after the amp turns on produces much cleaner sound, there is no noise because there is no source for it.

Here is my plan, I am going to build a circuit that utilizes a relay to turn the amp on and off. This will physicaly isolate the circuit which will ensure there is no noise with out having to worry about capacitors or diodes. I will post my plans. More to follow.

kbyrd · 10-09-2005, 10:21 PM

Wierd. I'm pretty sure I've read for vwvortex that the amp looks for 6V on - as the turn on. Removing the 12V provides cleaner sound because the amp is lookng for a signal ranging from 0-12V centered around 6V. 12V probably means max input to the amp.

alimh · 10-10-2005, 02:10 AM

kbyrd,

Any of those capacitors will work. The only thing that will be trouble are polarized (which those aren't). A smaller capacitor WILL work. I just picked this one because thats what they had at the engineer "store" (place for free electronics, hehe) at my school!

0.1micro (yeah, 1/10 of a micro) will block out any fluctuations from the voltage regulator, if for some reason there are any. Also, its small enough that it won't cut out any audible frequencies.

If you're interested, there is a program called PSpice. It is basically a circuit simulter. There is a free student version. Just google "pspice." Its what we used in our circuit classes.

Either way, if you have any specific questions about your circuit just let me know, I can even pspice-it for you. I wouldn't consider myself an expert by any means, but i have worked with this stuff before...

agentloveless,
What source isyour audio coming from? Your MP3 player? It still works when you take off the 12v? I tried it today, and if I take off the 5v then it will only work if the signal is loud enough... wierd. Let us know what else you find out.

kbyrd · 10-10-2005, 09:27 AM

alimh, thanks for the reply. I got a variety, I'll try them.

I have a couple of questions for whoever about the 5V added to the audio signal.
- Should we be adding 6V? Is it easy to find a 6V regulator?

- Regardless of 5V or 6V, shouldn't we be adding it to both + and - lines?

Here's what I'm getting at. The input signal expected by the monsoon is supposed to be a 6V on both lines for no sound and a varying 0-12 on both lines to generate an AC signal. What's the output of the PC soundcard? I assumed it was 0V at ground, and 0-5V (or some small number) on the + line for each of R and L. Does anyone have measurments on what the PC soundcard output is? I'm trying to figure out how to best match the expected 6V biased balanced signal I think the monsoon expects.

alimh · 10-10-2005, 04:38 PM

The output of the soundcard on my laptop is 1.2v maximum.

I think you should only apply 5v to the - channel. That is what I am doing and it works.

Let me know how it goes with those capacitors.

EDIT: Definately easier to find 5v regulators. I don't think they even make 6v...

agentloveless · 10-10-2005, 04:54 PM

What happens if you remove that 5V while the laptop is still on?

My big confusion is how you guys turn the amp off? To turn mine off i have to ground the + and - for the FL. I wonder if you guys are simply leaving your amp on the entire time.

alimh · 10-10-2005, 08:06 PM

I just tried this today:

I started the computer normally... with the 5v connected. While the music was playing, I disconnected the 5v.

Now, if the volume is loud enough, the sound still plays like normal.

As I decreased the volume, the sound would cut in and out at a medium volume level. I'm guessing this is because the volume of the song fluctuates a little.

When the volume goes below a threshold, the amp turns off and no sound. I knwo the amp turns off because if I increase the volume again there is no sound.

HOpe this helps.

agentloveless · 10-11-2005, 01:12 AM

Hmm that is really strange because I can even disconect my source, and as soon as I put it back it plays. Have you tried to use 12V to turn it on in the begining?