Alternator Whine Vs Gain Vs Hu Volume

[Munkyb0y]

Hey guys, I'm a noob when it comes to car audio. So keep it simple please.

Pioneer 7950UB head unit + clarion 4 ch amp + 4 coax speakers (2 x front and 2 x rear).

I get alternator whine through my (mainly) rear speakers, audible when HU volume is low.

I can remove it entirely by turning down the gain on my amp to about 1/3 on F+R.

But setting the gain higher than that will bring it back on, and the higher the gain, the louder the whine.

That's all nice and good, but having my gain so low means HU volume needs to be up to almost max (45) for it to be decently loud.

Is this normal? Will increasing amp gain increase volume output through my speakers? ie require less volume at the head unit for same volume at speakers?

Or is this what I should expect of any amp?

And, is the whine a by-product of the higher gain settings, or am I just masking the actual problem? Possibly RCA noise, ground loops, etc?

I assumed you could turn the gain up till pretty much your speakers became unhappy. but since I know fk all about amps, I'm not sure it's the case.

For some background.

Amp is in the boot with the battery. Earthed directly to battery ground point (R33).

I have tried a couple of different earth cables. One thick muthrfker too.

I have removed the head unit more times than i care to remember. I have grounded the rca earths to the head unit chassis directly.

I have run the head unit ground wire to one of the bolts that holds the gear shift in place. I assume this is a decent earth?

I tried several other spots too with no change.

I also opened the head unit and soldered over the pico fuse which i'm sure was blown since i was getting excessive noise initially.

I swapped out the head unit for another one i had, and got the same whine.

My rca's and front speaker cables and remote wire run through the centre console, under the rear seat cushions, and into the boot.

thanks to anyone who can be bothered to read all that

[Carbon 34]

Your positive its alternator whine? , not fan or other induced noise?

Alternator whine speeds up as you rev the car ?

Run a cheap pair of rca outside the car to the amp ? even 2 dollar cheapies for test

Amp should be grounded to car not battery

Radio grounded to shifter bolts not a good ground , paint and grime tar , grounding the rca normally makes it worse , you need to break the ground loop not enhance it with yet another path

clean terminals on battery ? batttery at full charge ? alternator ripple can be tested for a/c leakage if its on the way out ?

A cap can filter a/c ripple from charging

Can you run another source ? Ipod or ? Instead of deck ?

Gain on the amp shouldnt exceed 3/4 in most cases , you can set the gains with tester or meter

if you need more gain buy a overdrive from audiocontrol or similar 13v preout with clip meter ? Or new headunit with 4-6v preouts

Prob the best source ever for engine noise And chasing it down

Lots of goodies this guy is one of the original gurus of car audio

And if you read this he is the original co guru lol

http://www.termpro.com/asp/pubs.asp?ID=121

http://www.davidnavone.com/heresHow/august2003.htm

[Munkyb0y]

Thanks for the reply.

So basically, i should be able to turn the gain up if all was good, and the only thing i would experience is too much distortion/volume to the speakers, but not whine?

And ideally i should not have to turn the radio volume all the way to 45 to get some decent volume? although this is about the limit of what my speakers can handle by the sounds of it.

Yeah I found that guide already. very informative.

basically i've tried everything besides re-routing the rca's. but i will be doing that next, and also trying a different amp.

I should prob try the external source like an ipod too. that would rule out the amp and speaker wiring.

- yes it's alternator whine. It increases pitch with revs.

- amp is grounded to the car at the same point the battery is grounded to the car. Is this not good?

- battery terminals are clean. battery is charged and fine.

- I have tried 3 or 4 different radio ground points, including an open bolt hole with clean metal under my console, and the frame/chassis behind the dash.

- the rca's entering the radio are grounded to the radio's chassis directly (not to an external ground), to ensure they have a good ground internally. It was recommended in that guide i think.

[Carbon 34]

It might be a bad rca easy fix?

You can get a groundloop isolator but thats a bandaid and if your alternator is stuffed it wont fix it, you can do a cap across the radio power to ground ( think jaycar sells a kit) or make your own

If your radio is culprit

Grounding the rca rarely fixes the problem unless the rca ground is bad inside the jacket it creates another ground plane/ path

is the amp close to battery power cable ? Maybe too close ?

Amp ground should be fine i thought it was direct to neg terminal not same bolt , you could move it it can pick up noise in some of the weirdest places

This is why installers hate used equipment on installs haha you can spend days chasing your tail

Even power antennas can cause it if the radio ground is better thru the antenna them ground wire

Floats ground thru antenna , or ground thru dash lights a common mistake

Edited July 23, 2012 by Carbon 34

[Munkyb0y]

Turns out it was the RCA's. I pulled my rear seat out and covered the rca's with conduit, and taped it all up, and used a more 'spacious' route to run them under the seat.

Noise is now gone at all gain levels, and i'm a happy camper!

Thanks for your help carbon.

Edited July 27, 2012 by Munkyb0y

[Carbon 34]

Turns out it was the RCA's. I pulled my rear seat out and covered the rca's with conduit, and taped it all up, and used a more 'spacious' route to run them under the seat.

Noise is now gone at all gain levels, and i'm a happy camper!

Thanks for your help carbon.

Good to here it wasnt a huge drama and cost

Your very welcome