highamperage

Hello,
I just installed a Car PC in my truck powered by an inverter connected to a secondary battery that is connected to the main battery/alternator for charging.

I am using a USB External Sound Card connected to a 4 channel amp and a another amp for the sub.

I previously used my laptop for this system (Temporarily) and the audio quality was excellent, but I just switched it out with my desktop and it's a different experience. In general, there is a buzzing sound coming through the speakers, and if I connect up my Sirius (USB-Serial) interface, I can hear the alternator whine strongly.

Since this was not a problem with the laptop, I am assuming it's because the inverter I am using is modified sine wave, and the laptops power supply was better able to filter it than the desktop's.

Here are the solutions I considering:
- Using Pure Sine Inverter
- Get DC power supply for computer
- Try Ground Loop Isolators
- Verify ground points are solid on amps. (But the inverter is hard wired to the battery)

What do you think would be best? Any suggestions? I'm leaning towards a pure sine wave inverter. What do you guys think?

I appreciate any help!

P.S. If the battery voltage is lower, can that increase the buzzing sound?

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highamperage

Was just thinking....I have an idea, I will plug the computer into my household power with an extension cord. If that solves the problem, I will consider the issue being with a modified sine inverter.

BUT... if I get a pure sine inverter, do you think alternator wine etc might still get through?

ClassicStyle

I'd probably start with verifying ALL of your grounds associated with the circuit. Tightening one loose ground is worth a weekend of frustration or hundreds of dollars in parts

If that fails, try a GLI. I know there is a reason people use them, but for the life of me I can't remember exactly why.

I'm not sure on the cost of the Sine Wave Inverter (or even technically how it works, though I have a general idea), but I'd imagine it's more expensive than a Ground Loop Isolator.

It seems to me that if it were in the AC circuit, you'd experience pulsating static, the kind a microwave oven causes on nearby stereos, rather than a whine per se. If the whine changes with RPM, it's almost certainly a loose ground or the need for a GLI.

::EDIT:: I just remembered the reason for GLIs, and I doubt it would change anything. It's used to keep one of the batteries from draining one of the one.

thewizard

A GLI simply isolates a possible ground loop. They are good for troubleshooting a ground loop, but they should not be left installed permantly. That would be a band-aid fix at best, as they will diminish your RCA signal quality, and ultimatley your overall sound quality. I keep one in my toolbox and use it to quickly determine if a ground loop is causing noise in new installations, then remove when it when the source of the loop is determined and corrected. I think that the other poster was confusing a GLI for a battery isolator that is used in a two battery system to direct the alternators charge between the two batteries, charging your starting battery first then switching to the aux battery second.

ClassicStyle

Ahh correct - my apologies, I was thinking the battery isolator. I'm not certain my understanding of a GLI is up to snuff. I'll have to google it later after work.

swiat34

Sounds like a grounding or even a posative-side connection problem. Try these easy fixes.

If you "made" your own grounds, double check them. I've seen people just use a screwdriver to scratch a little paint off the metal and thought they'd be ok. Pull those grounds and use 150 grit sandpaper or a dremel tool to clear all the paint away where the ground connector will contact. Then wipe some Vaseline on the metal, replace your ground wire tightly and cover with vaseline. The vaseline prevents corrosion resulting in bad connections.

If you're using "existing" (or factory) chassis ground points, remove your grounding connector and use a wire brush (toothbrush sized one or dremel attachment is best) to clear any corrosion. Wipe on some vaseline, reconnect and cover with more vaseline.

Check your posative connections especially where your inverter connects to the battery. Clean away corrosion and cover with (you guessed it!) vaseline.

Make sure all connections are tight, posative and ground sides. if you wrapped a wire around a screw, use a crimp-on loop end for the wire instead. If you still have problems get a DC power supply for your PC. I would have done that from the start.

Good luck!
Swat

ilyawizard

I had the exact same problem. Now I'm not an expert and it was my first instal, but I got it solved. I had my PC running of an inverter and had terrible buzzing sound. If I plugged it through extension cord from home it was working perfectly fine. And if I turned my inverter on without plugging PC power supply the buzzing was still there. Moving power cables and inverter away wouldn't help and all grounds were tripple checked. I did a small test and connected ground cable through PC chassis. It helped a little but you could still hear the buzzing. So I didn't risk anything else and bought M4-ATX which solved all of my problems. Sound is perfect now.

akwash79

*sigh* I still have this issue. I will try sanding more paint off but I don't think it will help much.

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