# Alternator whine in tweeters - I'm running out of ideas - please help



## mechatron (Sep 26, 2013)

Hi guys, I really need your help as I'm all out of ideas. I'm getting alternator whine through my tweeters. It's more noticeable when the alternator loads up especially when the air con is on or in the upper rev range. Strange thing the noise is intermittent. 

Basically my setup is:
Front battery: Deka intimidator in engine bay
Head unit: Alpine ICS-X8
Processor: Arc Audio PS8
3-way front stage consists of Focal TN53K tweeters, Audible Physics NZ3A midrange drivers & Stereo integrity TM65 midbass.
Sub Amp (in boot): Mosconi AS300.2
Midrange and midbass amp (in boot): Mosconi AS200.4
Tweeter amp (under front passenger seat): Mosconi One 120.2
Rear battery inside sub box: Deka Intimidator

Basically the front battery runs the car's main accessories, the head unit and the sound processor, whereas the rear battery powers the 3 amps. The rear battery is run in parallel to the front battery (with just the positive power cable). The front battery is grounded to the chassis in the engine bay and the rear battery is grounded to the chassis behind the rear seat. 

Strange thing is....when I only had two amps in my car (Mosconi AS300.2 and AS200.4) the AS200.4 was running a set of 2-way KRX2 speakers actively and I had alternator whine as well (in the tweeters) . I was really hoping that in this 3way upgrade I would have eliminated this noise after re-running all the cables neatly and also the fact that the tweeters are now run off a totally different amp ( Mosconi One 120.2 under the front passenger seat).

Things I've tried (and still had whine):
- re-ran & re-routed new speaker cables from Mosconi One 120.2 amp on top of the carpet & over the front seats to the tweeters.
- re-ran & re-routed a new RCA cable from the Mosconi One 120.2 amp on top of carpet to PS8 under the drivers seat.
- ran a thin cable from the negative terminal of the rear battery to the ground terminal on the PS8 sound processor. This earth was also connected to the earth between the PS8 and the Alpine Head unit.
- checked all RCAs were all tight on the head unit, PS8 and all amps.
- all power cables are going down the left hand side of the car. 
- all speaker cables are at least 2-3 inches away from the power cables and where this was not possible they were crossed at right angles.
The rest of the speaker cables and RCAs were run down the right hand side of the car.

Also know that the gain settings on all amps are quite low 

Any help or ideas would be greatly appreciated. Thanks guys


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## ninetysix (Dec 6, 2009)

Tried running the head unit and processor off the same battery/ground as the amps? Even if that means temporarily setting the head unit and processor up in the boot. Running the head unit and processor off one battery and the amps off another is asking for trouble, can you ditch one and try it as a single battery setup?

If still noisy the next step would be to isolate where the noise comes into the picture, try a 3.5mm-rca cable from a phone/dac or laptop, either into the processor or straight into the tweeter amp. Remove as much complexity from the system as you can, if you connect just the tweeter amp into the front battery and a good ground with a source not powered by the cars 12v you should be clean as a whistle. Start adding components (head unit, processor) from there and use the same 12v and ground for all of them.


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## mechatron (Sep 26, 2013)

ninetysix said:


> Tried running the head unit and processor off the same battery/ground as the amps? Even if that means temporarily setting the head unit and processor up in the boot. Running the head unit and processor off one battery and the amps off another is asking for trouble, can you ditch one and try it as a single battery setup?
> 
> If still noisy the next step would be to isolate where the noise comes into the picture, try a 3.5mm-rca cable from a phone/dac or laptop, either into the processor or straight into the tweeter amp. Remove as much complexity from the system as you can, if you connect just the tweeter amp into the front battery and a good ground with a source not powered by the cars 12v you should be clean as a whistle. Start adding components (head unit, processor) from there and use the same 12v and ground for all of them.



That's some great ideas bud. From what you've said, it really does sound like a physical earth/grounding issue. Since my two batteries are powered up in parallel, do you think I should firstly just try running an earth cable from the front battery directly to the tweeter amp (and still have the power cable coming from the rear battery)? Also I didn't install my head unit originally but I'm pretty sure the head unit is powered off some harness somewhere that obviously eventually goes back to the main battery


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## ninetysix (Dec 6, 2009)

Even tho the two batteries are the same type, there's going to be a slight difference in potential between them. Normally a dual battery setup would have an isolator AFAIK. 

I would suggest disconnect the rear battery completely (+ & -) and use the power cable that links the front battery to the rear to power everything in the boot direct from the front battery. And I would start with just one amp (the tweeter amp) hooked up and no DSP, and if it's still noisy I would eliminate the head unit by using a phone/iPod/laptop. If it's still noisy you might need to check your ground is good in the boot, extra long multimeter leads come in handy. You could even pull the amp and set it up on a stool up front with a set of jumper leads off the front battery and temporary RCA's/speaker wire. If that doesn't clean it up I'm not sure what will! But work backwards from there towards the original setup until the noise returns.


Cheers


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## SkizeR (Apr 19, 2011)

ninetysix said:


> Even tho the two batteries are the same type, there's going to be a slight difference in potential between them. Normally a dual battery setup would have an isolator AFAIK.
> 
> I would suggest disconnect the rear battery completely (+ & -) and use the power cable that links the front battery to the rear to power everything in the boot direct from the front battery. And I would start with just one amp (the tweeter amp) hooked up and no DSP, and if it's still noisy I would eliminate the head unit by using a phone/iPod/laptop. If it's still noisy you might need to check your ground is good in the boot, extra long multimeter leads come in handy. You could even pull the amp and set it up on a stool up front with a set of jumper leads off the front battery and temporary RCA's/speaker wire. If that doesn't clean it up I'm not sure what will! But work backwards from there towards the original setup until the noise returns.
> 
> ...


isolators arent needed or preferred. on paper they sound good, but it was explained to me a while back by someone who i trust heavily with the subject that you do not want to bother with them. my suggestion is the same as your first one though


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## Sine Swept (Sep 3, 2010)

Nailed it on the head about the different potential voltages. I had some noise in one tweeter and it was just a bad shield on an RCA. Once I wiggled the cable in the right spot all excess noise was gone.


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## ninetysix (Dec 6, 2009)

SkizeR said:


> isolators arent needed or preferred. on paper they sound good, but it was explained to me a while back by someone who i trust heavily with the subject that you do not want to bother with them. my suggestion is the same as your first one though


Fair enough, I'm no dual battery expert. But if I had such a setup, I would power and ground everything (hu DSP and amps) from just the one battery, in this case the rear


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## SkizeR (Apr 19, 2011)

ninetysix said:


> Fair enough, I'm no dual battery expert. But if I had such a setup, I would power and ground everything (hu DSP and amps) from just the one battery, in this case the rear


i see why one could think that, but ive had a few dual battery, and one 3 battery setup. no noise from them. actually yesterday when i was tuning my car my one battery was definitely lower than the other, and still no noise. im pretty sure once you put them together thy even out. not positive though


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## mechatron (Sep 26, 2013)

Awesome info ninetysix. I have a lot of good ideas to try. I'll report back within the next few weeks...hopefully with good news


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## mechatron (Sep 26, 2013)

Thanks heaps for your input SkizeR about the dual batteries. Since the batteries are in parallel hopefully they should even out. 

I do have an earthing kit under my bonnet that goes from the main battery to multiple earthing points in the engine bay. I'm thinking of running an earth cable from this earthing kit into a new distro block inside the cabin connecting this to the tweeter amp and the head unit. I'm hoping this gives me positive results


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## mechatron (Sep 26, 2013)

Sine Swept said:


> Nailed it on the head about the different potential voltages. I had some noise in one tweeter and it was just a bad shield on an RCA. Once I wiggled the cable in the right spot all excess noise was gone.



I was hoping that the problem was just an RCA, as I found a broken RCA going to the sub amp (AS300.2), then replaced the whole RCA cable and still whine. I'm now using a different RCA cable to the tweeter amp due to a shorter run (i.e. Amp under the front seat instead of going to the amp in the boot) and still noise


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## SkizeR (Apr 19, 2011)

just try grounding the head unit and dsp with the amps first


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## mechatron (Sep 26, 2013)

SkizeR said:


> just try grounding the head unit and dsp with the amps first



I did run a thin earth cable from the negative of the rear battery to the PS8 processor and I still got noise. And the PS8 has the same ground as the head unit


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## mechatron (Sep 26, 2013)

Thanks heaps for the ideas/suggestions guys. I've got a few things to try now. I'll let you know what I find


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## gumbeelee (Jan 3, 2011)

mechatron said:


> Thanks heaps for your input SkizeR about the dual batteries. Since the batteries are in parallel hopefully they should even out.
> 
> I do have an earthing kit under my bonnet that goes from the main battery to multiple earthing points in the engine bay. I'm thinking of running an earth cable from this earthing kit into a new distro block inside the cabin connecting this to the tweeter amp and the head unit. I'm hoping this gives me positive results


Wow, nice clean wiring!! I hope u figure the noise issues out, I have chased the dragon before, It will literally drive u crazy trying to figure it out. Good Luck!!


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## mechatron (Sep 26, 2013)

gumbeelee said:


> Wow, nice clean wiring!! I hope u figure the noise issues out, I have chased the dragon before, It will literally drive u crazy trying to figure it out. Good Luck!!



Thanks buddy. Yes FHRX did that nice artwork under the bonnet. And yep we've spent soooo many hours chasing this evil noise...lol....it will be such a relief once we find the cause of it


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## kyheng (Jan 31, 2007)

If you don't know what is the actual problem, you add till each amp/DSP with a battery also won't help at all.
What you need to do is start measuring voltage on each and every equipment when they are power on with engine running. 
Rightfully the voltage should be maintaining at 13-13.8V on all equipment.
Next is to check for continuity of the RCAs, male to male, female to female and male to female. This is top cross check to confirm the RCAs are at good condition.
Once this is done, check out the amp, DSP gains. Proper way is HU's volume as master volume, DSP and amp's gain should be at minimum as this can reduce noise pickup.
Happy troubleshooting, I've been all this last time and the main reason for noise is dirty terminations on battery which causing low vaoltage.


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## mechatron (Sep 26, 2013)

Thanks Kyeng the only things I've established so far are:
- noise is a lot more noticeable when the alternator loads up
- and when the RCA lead between the PS8 and the tweeter amp is removed the alternative whine completely disappears. In saying this I have my other amp (AS200.4) playing my midbass' from 60 to 400hz and and midrange drivers from 400 to 5000hz at the moment. I'm not sure if I would get the alternator noise through my midrange drivers if I extended them up to 16khz


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## ninetysix (Dec 6, 2009)

I could hear pretty nasty alternator noise thru my alpine 8 midbass drivers, turned out to be a dodgy amp


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## kyheng (Jan 31, 2007)

Looks like the problem is isolated on PS8 and the amp, simple way to check it now, set you midrange from 3000-6000Hz, put the RCA to the tweeter amp and see how it goes and the tweeter output to midrange amp.
If no noise, then it could be the RCA giving problems.


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## mechatron (Sep 26, 2013)

ninetysix said:


> I could hear pretty nasty alternator noise thru my alpine 8 midbass drivers, turned out to be a dodgy amp



What frequency range were you running your midbass drivers?


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## mechatron (Sep 26, 2013)

kyheng said:


> Looks like the problem is isolated on PS8 and the amp, simple way to check it now, set you midrange from 3000-6000Hz, put the RCA to the tweeter amp and see how it goes and the tweeter output to midrange amp.
> If no noise, then it could be the RCA giving problems.


Thanks for the reply bud.
I don't think the cause of the noise can be a faulty amp since I've used two different amps for the tweeters now (AS200.4 when running 2way active & now the One 120.2 solely running the tweeters in my new 3way setup) and I still get alternator whine.

I also don't think the head unit or processor could be the cause as there was a time (2yrs ago) when my system was noise free. The whine only started when the AS300.2 amp and the 2nd battery went in the boot. I'm really starting to think that the problem is either a bad RCA cable (from the head unit to the processor... As I've replaced the rest of the RCA cables) or an earthing problem.

I'm also going to run an RCA cable directly from the head unit to the tweeter amp (i.e. Bypass the processor) to see if the whine disappears.


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## ninetysix (Dec 6, 2009)

mechatron said:


> What frequency range were you running your midbass drivers?


Pretty narrow, about 60-250ish. But the crossover setting didn't matter, the noise got thru all the same, tho with RCA's disconnected I think the amp muted itself. Was a nice amp too, Boston GT-2200. Did 350x2 2ohm, replaced it with a pair of soundstream Picasso nano 450w monoblocs, very cheap very small very powerful and no noise at all. I still have a Boston GT-4100 for my midrange and tweeters, it's about the size of a skate board but it's awesome and no noise issues


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## mechatron (Sep 26, 2013)

ninetysix said:


> Pretty narrow, about 60-250ish. But the crossover setting didn't matter, the noise got thru all the same, tho with RCA's disconnected I think the amp muted itself. Was a nice amp too, Boston GT-2200. Did 350x2 2ohm, replaced it with a pair of soundstream Picasso nano 450w monoblocs, very cheap very small very powerful and no noise at all. I still have a Boston GT-4100 for my midrange and tweeters, it's about the size of a skate board but it's awesome and no noise issues



Damn that's a very narrow frequency band hey. And I've never ever heard of anyone who had alternator noise go through their midbass drivers until I read your post...only the tweeters.

And that's a shame about the Boston amp as they're very nice amps. Did you always have a noise issue with this Boston amp or did it occur over time as the amp got older?


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## kyheng (Jan 31, 2007)

mechatron said:


> Thanks for the reply bud.
> I don't think the cause of the noise can be a faulty amp since I've used two different amps for the tweeters now (AS200.4 when running 2way active & now the One 120.2 solely running the tweeters in my new 3way setup) and I still get alternator whine.
> 
> I also don't think the head unit or processor could be the cause as there was a time (2yrs ago) when my system was noise free. The whine only started when the AS300.2 amp and the 2nd battery went in the boot. I'm really starting to think that the problem is either a bad RCA cable (from the head unit to the processor... As I've replaced the rest of the RCA cables) or an earthing problem.
> ...


Not that a good idea if you were to use another RCA cable bypassing the DSP to Hu direct. Fastest I still think do like what I say(increasing the HPF for midrange to protect tweeter and plug it to the tweeter amp).
Wait, you say you got another battery, I think maybe that's the cause.


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## ninetysix (Dec 6, 2009)

I'm pretty sure it was clean when I first bought it, my ears are a lot better now than they were then, tho an audiologist may disagree. I actually had to replace a few burnt out resistors on both the 2200 and the 4100, but the 4100 never had a problem before or after.

Got it dirt cheap from the US back when the AUD was about $1.12, it was about au$200 shipped.

My 8s are actually subs and not true midbass, but they work very well in sealed boxes on the floor up front. For a while they were my only subs, but I've added a alpine type R 12" since in a sealed 0.9ft³ box, sealed from the boot thru the ski pass in a 04 astra. The 8s are not real good above 300hz, but my 6" Boston spz mids are good well below there. Planning to replace them with scanspeak revelators in 5.25".

I think noise from a bad ground or rca might normally be a lot less less likely to show up thru a 8", but the amp playing up made it a special circumstance.


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## mechatron (Sep 26, 2013)

kyheng said:


> Not that a good idea if you were to use another RCA cable bypassing the DSP to Hu direct. Fastest I still think do like what I say(increasing the HPF for midrange to protect tweeter and plug it to the tweeter amp).
> 
> Wait, you say you got another battery, I think maybe that's the cause.



I will indeed try what you have said with the midranges. Another thing I tried not long ago was disconnect the rear battery completely as the front battery is actually connected to the rear battery with a distro block in between. The distro block is underneath the amps in the boot. So two 4 gauge power cables go from the main battery to the distro block in the boot. Then there are 3 additional power cables connected to this rear distro: two 4 gauge cables for the two amps (AS200.4 and AS300.2) and a 0 gauge power cable going to the rear battery. After we tried disconnecting the rear battery, the alternator whine was still there 

Note that the earthing point for the rear battery is behind the rear seat...and hence the earthing points for the AS200.4 and AS300.2 amps. I'm going to check if the earthing bolt is zinc plated and if it is, I'll replace it


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## mechatron (Sep 26, 2013)

ninetysix said:


> I'm pretty sure it was clean when I first bought it, my ears are a lot better now than they were then, tho an audiologist may disagree. I actually had to replace a few burnt out resistors on both the 2200 and the 4100, but the 4100 never had a problem before or after.
> 
> 
> 
> ...



Thanks mate for clarifying that. Also I notice you're from VIC. Are you on the Aussie car audio forum at all?


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## ninetysix (Dec 6, 2009)

mechatron said:


> Thanks mate for clarifying that. Also I notice you're from VIC. Are you on the Aussie car audio forum at all?


About 15 years ago I was on car audio Australia, which I think became MEA and now for some reason road.com.au ? Cyberpunky lived around the corner from me and supplied me with a set of Hertz 8" energy midbass drivers, and juice-e knocked me up a set of 8" pods for my EF falcon that replaced the map pockets. Great days


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## mechatron (Sep 26, 2013)

ninetysix said:


> About 15 years ago I was on car audio Australia, which I think became MEA and now for some reason road.com.au ? Cyberpunky lived around the corner from me and supplied me with a set of Hertz 8" energy midbass drivers, and juice-e knocked me up a set of 8" pods for my EF falcon that replaced the map pockets. Great days



Boy that was a long time ago. The road forum actually shut down not that long ago due to very little activity but it's back alive again and it's a lot more active...however it's definitely not as happening as what it used to be or what this forum is like


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## kyheng (Jan 31, 2007)

mechatron said:


> I will indeed try what you have said with the midranges. Another thing I tried not long ago was disconnect the rear battery completely as the front battery is actually connected to the rear battery with a distro block in between. The distro block is underneath the amps in the boot. So two 4 gauge power cables go from the main battery to the distro block in the boot. Then there are 3 additional power cables connected to this rear distro: two 4 gauge cables for the two amps (AS200.4 and AS300.2) and a 0 gauge power cable going to the rear battery. After we tried disconnecting the rear battery, the alternator whine was still there
> 
> Note that the earthing point for the rear battery is behind the rear seat...and hence the earthing points for the AS200.4 and AS300.2 amps. I'm going to check if the earthing bolt is zinc plated and if it is, I'll replace it


Head to hardware shop and get your self a silicone dielectric grease.


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## mechatron (Sep 26, 2013)

kyheng said:


> Head to hardware shop and get your self a silicone dielectric grease.



Thanks mate, is the silicone dielectric grease for the zinc plated bolt?


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## Sine Swept (Sep 3, 2010)

Do you have any way to test what is coming out of your alternator? Perhaps you've got too much AC ripple in your DC voltage.


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## mechatron (Sep 26, 2013)

Sine Swept said:


> Do you have any way to test what is coming out of your alternator? Perhaps you've got too much AC ripple in your DC voltage.



Unfortunately I don't, but this whole time I've been wondering if my alternator has had a problem with the rectifier.

Might have to take a trip to an auto electrician just to be sure


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## ninetysix (Dec 6, 2009)

If you can get clean sound with the amp connected to the battery with jumper leads and the engine running, and say a set of bookshelf speakers wired to the amp playing full range, would that not prove your alternator is putting out clean DC? If it was still noisy there even with an iPod as a source, it would almost certainly be the DC supply or the amp itself


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## mechatron (Sep 26, 2013)

ninetysix said:


> If you can get clean sound with the amp connected to the battery with jumper leads and the engine running, and say a set of bookshelf speakers wired to the amp playing full range, would that not prove your alternator is putting out clean DC? If it was still noisy there even with an iPod as a source, it would almost certainly be the DC supply or the amp itself



Definitely something to try. I'm will try an iPod, but I want to download an equalizer to keep the frequencies high enough for the tweeters


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## ninetysix (Dec 6, 2009)

mechatron said:


> Definitely something to try. I'm will try an iPod, but I want to download an equalizer to keep the frequencies high enough for the tweeters


Not sure an EQ would be enough to protect a tweeter. Does the amp have a built in crossover? If it can go up around 1k you should be fairly safe, depending on slope and tweeter of course. Could always use a capacitor too. You could also set the DSP up along side the amp, and that would also confirm that the DSP, amp and alternator are not the problem if it's clean.

That's where a bookshelf speaker comes in handy as it already has a passive crossover.


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## ninetysix (Dec 6, 2009)

Another thing, do you have a multimeter? An o-scope would be better but this should raise a red flag without having to pull the system apart.

See this video for more: https://youtu.be/Nhc5VqlUrY0


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## kyheng (Jan 31, 2007)

mechatron said:


> Thanks mate, is the silicone dielectric grease for the zinc plated bolt?


Yes, and for all terminations also especially on the battery side


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## mechatron (Sep 26, 2013)

Thanks guys I was doing some tuning with the PS8 and noticed this:




































The RCA signal going into input 3 on the PS8 isn't working. I swapped the RCA heads around (i.e. Red to input 4 and white to input 3) and input 4 didn't work. Now to trial run another RCA cable to see if it's the RCA cable or the head unit sub pre-outs.

Note it was originally input channel 4 that wasn't working but I didn't take a photo of when the suspected faulty RCA was plugged into that input (4 into the PS8)


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## mechatron (Sep 26, 2013)

ninetysix said:


> Not sure an EQ would be enough to protect a tweeter. Does the amp have a built in crossover? If it can go up around 1k you should be fairly safe, depending on slope and tweeter of course. Could always use a capacitor too. You could also set the DSP up along side the amp, and that would also confirm that the DSP, amp and alternator are not the problem if it's clean.
> 
> 
> 
> That's where a bookshelf speaker comes in handy as it already has a passive crossover.



Yes the amp has a high pass filter so that should help protect the tweeters. And yes so true about the bookshelf speakers


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## mechatron (Sep 26, 2013)

ninetysix said:


> Another thing, do you have a multimeter? An o-scope would be better but this should raise a red flag without having to pull the system apart.
> 
> 
> 
> See this video for more: https://youtu.be/Nhc5VqlUrY0



Great link, thanks mate.


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## mechatron (Sep 26, 2013)

kyheng said:


> Yes, and for all terminations also especially on the battery side



Awesome thanks buddy


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## kyheng (Jan 31, 2007)

mechatron said:


> Awesome thanks buddy


No problem mate, this is what I had last time. So now the grease will be always in my storeroom.


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## mechatron (Sep 26, 2013)

I just did a diode check as per the video link above. I measured the AC and DC voltages with & without the Aircon on:

Without Air con:
- DC voltage = 13.99V
- AC voltage = 0.01V
With Air con:
- DC voltage = 13.66V
- AC voltage = 0.01V & times it measured 0.02V

I checked a few things with the sub pre-outs....and wiggling the pre-out harness brings both subs pre-outs on as per the PS8 input monitoring graph. The problem isn't the RCA cable it's the harness from the Alpine head unit. Although I don't think it's the main cause of the alternator whine as I disconnected the sub RCA lead and still had alternator noise through the tweeters.

Still more testing to go


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## ninetysix (Dec 6, 2009)

Well at least your diodes are good


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## mechatron (Sep 26, 2013)

ninetysix said:


> Well at least your diodes are good



Yeah that's right


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## mechatron (Sep 26, 2013)

Hi guys, we have made a bit more progress with this whine issue. We've found a few things last week that when rectified reduced the sound of the whine but it's still there. Last weekend we did the following:
- grounded the head unit and processor at the same point underneath the dash. We measured the continuity from the earthing kit (connected to the negative terminal of the battery under the bonnet) to this new freshly sanded spot under the dash and we also measured a resistance of 0.2 ohms. The head units 12V supply is coming from the harness that that factory head unit 

- behind the head unit was a birds nest of wiring and we found that the aerial connection wasn't that tight so we rectified that.

- We then completely bypassed the head unit by putting another source (tried iPhone and laptop) straight into the PS8 processor and the whine was still there. We then put an iPhone (as a source) into the tweeter amp and had no noise. So then we were thinking the cause of the source was the PS8. 

- But then we bench tested the PS8 out of the car with head phones and there was no noise or problems. We then reinstalled the PS8 under the driver's seat and powered it by an external battery then started up the car with the air con on and we still had whine.

- We also changed the RCA leads (between the PS8 and tweeter amp) and no change which indicates there's a still grounding issue somewhere.

We also found that the grounding point that the rear battery was connected to was actually a black bracket (for the rear middle fold down seat thing) and had bad conductivity so we sanded back another part on the car chassis (on the rear upright in a sedan)...and after this we measured a resistance 0.2 ohms from the earthing kit in the engine bay to the new spot...started the car and this really reduced the whine, but it's still there.

One thing that did completely remove the whine was to put a ground loop isolator between the 2 channels going from the PS8 to the tweeter amp...however I really don't want to use this as it really effects SQ and I don't exactly have a cheap setup.

Now...the things I'm worried about (however I'm not sure if they're affecting anything):

- are the length of the ground cable from the tweeter amp (under the front seat) to the negative of the rear battery. As this ground cable would be about 4m long

- the fact that the tweeter amp is grounded directly to the negative of the rear battery

- and the ground cables of the other two amps are connected to the rear battery (via distro block) before going to a good solid earth.

I'm thinking of grounding the tweeter amp (under the front passenger seat) to the seat itself or somewhere very close to it as I'm thinking a 4m ground cable could incur noise. I've also read something that an amp shouldn't be directly grounded to the negative post of a battery...but then again I've read sooo much info of dos and donts and there's so many different opinions on every topic...lol.

I looked at the positive lead going from the battery to the alternator and it does look decent. I am however going to install an 8 or 4 gauge cable from the body of the alternator to the chassis of the car in hope to get the charging voltage a little higher.

Is there anything you guys can suggest that I try? 

Have anyone ever heard of anyone having noise issues when the ground cable was too long or when an amp was directly grounded to a battery? Or has anyone found that they're PS8 was the root cause of dreaded alternator whine? Thanks guys. Here's a schematic of my layout excluding the head unit & processor


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## gumbeelee (Jan 3, 2011)

Man, brother all i can say is i feel bad for you. You are working your ass of to find the damn problem, believe me I have been there. You are right i would not use ground loop isolator unless its the last option. As bad as i hate to say u might have to end up using one, but I hope it does not come to that point. GOOD LUCK!!


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## mechatron (Sep 26, 2013)

gumbeelee said:


> Man, brother all i can say is i feel bad for you. You are working your ass of to find the damn problem, believe me I have been there. You are right i would not use ground loop isolator unless its the last option. As bad as i hate to say u might have to end up using one, but I hope it does not come to that point. GOOD LUCK!!



Thanks buddy...you're not wrong about working our asses off. We are going to try the things I suggested above but I have a strong feeling that I may need to use a ground loop isolator


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## ninetysix (Dec 6, 2009)

Did you ever try using the digital inputs on the DSP?


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## mechatron (Sep 26, 2013)

ninetysix said:


> Did you ever try using the digital inputs on the DSP?



No unfortunately not as we ran out of time. We also need to find a digital source to use


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## ninetysix (Dec 6, 2009)

Perhaps an old DVD player? Lots of cheap usb DACs also have optical or digital out. I'm using a $7 pcm2704 usb sound card from my phone to DSP as a source


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## mechatron (Sep 26, 2013)

ninetysix said:


> Perhaps an old DVD player? Lots of cheap usb DACs also have optical or digital out. I'm using a $7 pcm2704 usb sound card from my phone to DSP as a source



Yeah good call thanks bud


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## ninetysix (Dec 6, 2009)

And another thing, did you ever try running your tweeters off a different amp? Like your midrange or midbass amp?

I started to notice some pretty nasty alternator whine today, thought it was my diy RCA's but nope... switching out my beloved Boston GT-4100 amp for a cheap and cheerful pioneer GM-D8604 fixed it immediately. RIP. Oh well, lots more room for amps now


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## mechatron (Sep 26, 2013)

ninetysix said:


> And another thing, did you ever try running your tweeters off a different amp? Like your midrange or midbass amp?
> 
> I started to notice some pretty nasty alternator whine today, thought it was my diy RCA's but nope... switching out my beloved Boston GT-4100 amp for a cheap and cheerful pioneer GM-D8604 fixed it immediately. RIP. Oh well, lots more room for amps now



Yes, when I only had a 2way front stage with 2 amps (AS200.4 and AS300.2), the AS200.4 powered the tweeters and the mids and I had whine then as well. I do feel like we have reduced the whine quite a bit as the tweeters are now in the sail panels (so pretty much in your face) and the whine is slightly less when the tweeters were far away in the dash pointing near the windscreen...so we are making progress...slowly

And that sucks about your Boston amp...do you think you have a capacitor problem inside that amp?


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## ninetysix (Dec 6, 2009)

mechatron said:


> Yes, when I only had a 2way front stage with 2 amps (AS200.4 and AS300.2), the AS200.4 powered the tweeters and the mids and I had whine then as well. I do feel like we have reduced the whine quite a bit as the tweeters are now in the sail panels (so pretty much in your face) and the whine is slightly less when the tweeters were far away in the dash pointing near the windscreen...so we are making progress...slowly
> 
> And that sucks about your Boston amp...do you think you have a capacitor problem inside that amp?


Possibly, it did have a few burnt out resistors that I replaced, and I think I got it for less than $200 about 4 years ago when we were above parity. She was a behemoth in my tiny Astras boot, I need some class D action


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## mechatron (Sep 26, 2013)

ninetysix said:


> Possibly, it did have a few burnt out resistors that I replaced, and I think I got it for less than $200 about 4 years ago when we were above parity. She was a behemoth in my tiny Astras boot, I need some class D action



That's a shame...at least it didn't cost you that much...annoying none the less


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## mechatron (Sep 26, 2013)

Has anyone on here experienced alternator whine due to a low voltage produced by the alternator? The thing that I always forget to tell people is that my LS1 engine has a 25% underdriven pulley which in turn gives me a bit more horsepower but as a consequence the alternator spins slower meaning less charging voltage at a lower rpm. Also the whine is only really noticeable with the air con on and when the voltage drops to about 13.7V.

I'm going to replace this underdriven pulley with a standard OEM replacement harmonic balancer in hope to increase the charging voltage and hopefully reduce whine . What are other people's thoughts?


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## mechatron (Sep 26, 2013)

Hey guys, a bit of success finally..we managed to get rid of about 90% of the whine, volume wise...the whine only happens when I'm accelerating hard with the A/C on and the volume of my stereo is down very low, although you really have to be listening for it to know its there....or just turn the music up more 

So on top of everything we've done so far, we also grounded the head unit and ps8 to the chassis instead of the factory harness...we earthed the alternator to the chassis with 4 gauge cabling and we swapped the cabling between the starter motor and the alternator around as the alternator was on the distro block and the starter motor was on the battery...we were thinking that the battery has some sort of filtering properties so we connected the alternator directly to the battery...by earthing the alternator and connecting it directly to the battery this actually gave us the biggest improvement. If only we had done this first ...o well it was a great learning experience


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## michael92 (Apr 7, 2015)

I had this problem..drive me batty man. Drop thousands on equipment....you turn it on expecting to be blown away. AHHH. 

I ended up grounding all the amp/dsp/and head unit to the body inside the car. Alt noise is 100% gone. I do have a hiss in the tweeters but I determined it's the cheap apline amp. 

Also on newer cars they are loaded with tech. Makes it REALLY hard to trace stuff.


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## ninetysix (Dec 6, 2009)

Well done mate, hopefully that last 10% doesn't gnaw at you too much  are we talking flooring it with a tweeter against your ear (tricky to do!) or audible from normal listening position?

Maybe a PD supercharger or a snail will disguise the noise


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## mechatron (Sep 26, 2013)

michael92 said:


> I had this problem..drive me batty man. Drop thousands on equipment....you turn it on expecting to be blown away. AHHH.
> 
> I ended up grounding all the amp/dsp/and head unit to the body inside the car. Alt noise is 100% gone. I do have a hiss in the tweeters but I determined it's the cheap apline amp.
> 
> Also on newer cars they are loaded with tech. Makes it REALLY hard to trace stuff.



Great work bud. The thing that I didn't expect to do much...actually did the most...ie earthing the alternator and connecting the positive cable directly to the battery...everything else only gave very slight improvements even where we improved grounding where the resistance was reduced from 24 ohms to 0.5 ohms on certain grounds


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## mechatron (Sep 26, 2013)

ninetysix said:


> Well done mate, hopefully that last 10% doesn't gnaw at you too much  are we talking flooring it with a tweeter against your ear (tricky to do!) or audible from normal listening position?
> 
> Maybe a PD supercharger or a snail will disguise the noise



Thanks buddy, it's definitely livable now. Before when I turned the car on with the a/c on there was instant whine and even slight taps of the accelerator gave some wicked whine. But now all that is gone and it only happens on hard acceleration when the music volume is very low...but the volume is only low when I'm testing for whine..lol....and its when I'm tilting my head towards the tweeter.

And yes forced induction is definitely on the list of things to do...but it is a bit of pipe dream at the moment....but then again if I did supercharge my LS1 then I'd never know where the whine was really coming from ...lol


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## ninetysix (Dec 6, 2009)

mechatron said:


> Thanks buddy, it's definitely livable now. Before when I turned the car on with the a/c on there was instant whine and even slight taps of the accelerator gave some wicked whine. But now all that is gone and it only happens on hard acceleration when the music volume is very low...but the volume is only low when I'm testing for whine..lol....and its when I'm tilting my head towards the tweeter.
> 
> And yes forced induction is definitely on the list of things to do...but it is a bit of pipe dream at the moment....but then again if I did supercharge my LS1 then I'd never know where the whine was really coming from ...lol


Exactly! Though you might also struggle to hear any police sirens too... Keep an eye out for blue and red lights  tho I'm sure any LS1 with a few bolt ons could get you in trouble quick


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## mechatron (Sep 26, 2013)

ninetysix said:


> Exactly! Though you might also struggle to hear any police sirens too... Keep an eye out for blue and red lights  tho I'm sure any LS1 with a few bolt ons could get you in trouble quick



Hahaha that's funny as


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## wizzsb (Mar 16, 2016)

Hi All,
I’m new here and I create account here because of this really annoying problem.
I installed my new setup 2 weeks ago and in general is sounds according my expectations but I can’t get rid of the *alternator noise in speakers*.
I had some old Ground zero Amps but in good condition and Alpine DSP, so I bought some speakers, cables... so really cheap but nice playing setup.

my setup:
- car is BMW 320d e91 (2009) with *only battery in trunk*. Amps and DSP as well as capacitor is located on left side of trunk (hidden underneath upholstery)
- HU unit bmw CIC with Hi level output and flat characteristic (Hifi coded CIC)
- signal cables - 4x industrial twisted pair 1mm2 (17 AWG), double shielded, connected from HU to DSP
- DSP (Alpine PXE H650) 
- RCA cables HQaudio 1,5m from DSP to Amps
- Amps: Old but good Ground zero GZHA 2250X for Subs (2x KICKER CWRT81 under seat) + GZHA 4150X for main speakers (HERTZ EMV100.5 + HT20.4 front and Hertz ECX100.5 back).
- feeding route is 50mm2 (2 AWG) cables (Cable length is 1.5m / 5 feet) to 1F V-cap (HiEnd custom made capacitor) with distribution block, than 25mm2 (4 AWG) cables (Cable length is 0.3m / 1 feet) to amps and 2.5mm (13 AWG) for DSP. 
- Grounded to ground screw near amp, of course precise cleaned and sanded. (Ground cable length is 1m / 3.28 feet)


till now I try this:

disconnect signal cables between HU to DSP - still noise
disconnect RCA cables between DSP to Amps - no noise
connect external player to Amps - no noise
connect headphones to DSP and listen - no noise
try to reground DSP and Amps to different position - still noise but with different level

So I assume that problem should be:

RCA cables, which using ground wire as shield
Another possibility is that I need to filter DC voltage for DSP
Or Amps is to old and capacitors inside is damaged? (but there’s no noise if external device connected)
Look to alternator grounding and battery grounding


is there some recommendation from you guys?
Thank you very much from Slovakia.


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