could p1900 introduce noise in the system?

natedawgg · 03-08-2009, 06:02 PM

i have a p1900 that is running my mac mini. anytime i have the car turned on ( not even started yet ) i get this horrible humming noise through the system. the p1900 and mac mini are side by side in the glove box, but i can move the mini out and set it on my seat with no difference in the hum. could there be some sort of wiring problem that is letting the noise into the system?

PaulF · 03-08-2009, 06:32 PM

Try hooking up the mini to its normal power supply and hook it up to a standard wall outlet. If the noise persists, the problem is not the p1900.

natedawgg · 03-08-2009, 09:38 PM

yeah i have done that. the problem is that i have several different components in my setup, and i am just trying to narrow down the source. Essentially the setup is the p1900 powers the mac mini and the monitor, while i have a intermediate amp that pumps the signal to send to the car's factory amp (factory amp has to have a speaker level input in order to work). It seems though that it is the combination of all the components, because if i remove any one of them, as far as i can tell, the noise is not present. i tried hooking my iphone directly to my amp and there was no noise whatsoever. however, i need all the components in order to get the sound loud enough. i am just trying to determine if their is anyway that the p1900 could be the source.

PaulF · 03-08-2009, 09:40 PM

without the p1900 was there noise?

natedawgg · 03-09-2009, 12:46 AM

no. when hooked up inside the house using factory power supply there is no noise.

also if i am in the car and plug in headphones instead of the plug to the amp, there is no noise. very weird.

PaulF · 03-09-2009, 06:20 AM

Keep the mini inside the car, but plug it into its indoor power supply.

It seems like the problem is going to end up being that there is an RCA cable run too close to a power line.

natedawgg · 03-09-2009, 03:39 PM

good idea! I will try this out tonight and see how it works.

itsasony · 03-09-2009, 05:26 PM

Does anyone have the power specs for the new March 2009 MacMini that uses less power?

PaulF · 03-09-2009, 05:43 PM

While you're at it, also check to see if this only happens while the engine is running or if it happens when the car is in accessory mode also.

PaulF · 03-09-2009, 07:15 PM

Quote: Originally Posted by itsasony

Does anyone have the power specs for the new March 2009 MacMini that uses less power?

That's a bit off topic. Next time, post in a new thread. A quick google turned up this page: http://forums.dealmac.com/read.php?4...820758,quote=1
I'm not sure how reliable that is though.

natedawgg · 03-11-2009, 03:06 PM

Quote: Originally Posted by PaulF

Keep the mini inside the car, but plug it into its indoor power supply. It seems like the problem is going to end up being that there is an RCA cable run too close to a power line.

so i tried this but my inverter is not strong enough to power the mini. im not entirely sure that it is an RCA cable because i have moved all of them the as far away from any power source as possible. I did do some re-wiring to make sure i wasn't getting any cross-talk in the wires. the funny thing is i noticed just last night is that if i turn my AC fan on high i get an extra high pitched buzzing sound. so i don't know what that means. it only happens when the fan is on full ( at 3/4 you don't hear it). my theory now is that there is some interference coming through the power system somehow into the mini that is then amplified later down the line before heading into the car's factory amp.

Quote:

While you're at it, also check to see if this only happens while the engine is running or if it happens when the car is in accessory mode also.

the noise is always there. even when you just turn the key to the accessory position, as soon as the mini boots up, you hear the noise. it is directly related to the mini. for instance if all the components are running except for the mini you will hear no noise, it is as soon as the internal components are running (hard drive, cpu, etc) that you get all of the static like noise.

PaulF · 03-11-2009, 03:15 PM

Quote:

so i tried this but my inverter is not strong enough to power the mini.

Nailed it. Inverters introduce noise into the system. What do you have running off of the inverter? Try taking the inverter out of the system entirely. I bet your problems will disappear.

natedawgg · 03-11-2009, 06:01 PM

well, i was only using the inverter ( i may have made reference to the wrong thing here, i am trying to refer to a device that essentially gives me a standard plug in my car ) to test the mini in the car without requiring the p1900 for power. sorry for the confusion.

PaulF · 03-11-2009, 07:52 PM

That's exactly what the inverter is. They convert a car's 12 vold dc power into a standard home's 110 volt ac power.

So you were only using it for testing purposes?

Not what you want to use for a test. It will cause its own noise and not help us at all.

Just run an extension cord to your car from inside your house.

natedawgg · 03-12-2009, 02:06 AM

i will see what i can do. i live in an apartment so it is not very easy to find an outdoor outlet near my car. i will see what i can find though. i must say though thank you for all of your help and suggestions on this. you have been very helpful.

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