Thread: The alternator noise that won't die

I would say that converting AC to DC then AC back to DC has something to do with it....

First thing I would suggest would be to get a proper DC-DC power supply and do away with the 12vDC to 230VAC inverter.

If that does not make the noise go away you could try a capacitor in line to filter the ripple out of the 12vDC.

laters

Thanks for the reply.
DC-DC would be an expensive experiment just to see if it works, I'd like to pinpoint the problem first

As for putting a cap inline, I might have a big one stored away somewhere.. what capacity would I need? Should it just go in parallell between the battery and inverter?

As mentioned, the ground loop isolator removed the problem but mutilated the sound.. wouldn't that be an indicator that it's a ground loop problem, and not noise from the input power?

A ground loop isolator should not change the sound. What did you use and were did you get it?

Have you tried grounding the chassis of the invertor? Have you tried running the PSU connected to a wall outlet just to eliminate the invertor to see if that is what is causing the noise?

A ground loop isolator will take care of the issue if it's becuase the RCAs on the HU and another piece of equipment use the chassis ground as a reference for the ground on the RCAs.

The Isolator is removing power supply noise from your audio signal and should do the job for you, although it is not fixing the original source of the noise.

Ground Loop Isolator Explained

So the problem is still there, just the Isolator does that, Isolates it and should fix your problem without changing the audio signal???

As for the capacitor valuse, i believe you could use a very small value, a few MicroFarads, so if you have a power capacitor, .25 farad or so, it would work.. I am not saying it will work, but it may remove some of the AC ripple.

DC/DC power supplies are under $100, and they are made for your application, including built in shut down cotroller.

Laters

durwood;
The isolator was a "xitel" brand, looked like this:


It was borrowed from a renowned hi-fi store, although they primarily focus on home equipment, not cars. Is there a difference in the build of isolators?

I'll try both grounding the inverter and using 220v from the house, thanks for the tips! If the latter solves the problem, then what would be the solution for the car?


Felix;
thanks for the info on isolators, didn't really know what they did before now The one I tried -did- screw up the signal though, not just in an audiophile nitpick way, but majorly..

2nd poster got it in one, your transferring 12v power to 240v then back to 12v, this has a huge strain in an alternator not to mention a pointless process. Get a DC-DC psu.

Surely, someone must have got inverter-based solutions to work before? (I'm over budget, and hence very keen on putting what I already have to good use)

Here are ones maybe you can find in Norway.

PIE EIP-GLI

PAC SNI1

I have used the cheapo Audiovox ones without any problems of signal degradation. As Felix linked to, all it is transformer inside. The Xitel one is rather expensive and I have to wonder if it was doing more then isolating. It might have been trying to filter too (maybe to get rid of 50/60Hz hum from AC) since it used in home audio.

The ones I listed are under $10 and I bet you could find some even cheaper.

durwood;

thanks, DC-DC might be the last resort. As mentioned though, I'd like to establish whether the inverter is the problem or not.
I've tried running the inverter from in-house AC now, still getting alternator whine when the engine's running! Also tried grounding the inverter, no difference there.
Any suggestions?