CF-29+Car audio= alternator whine

When my 29 is plugged into the stereo, I get an alternator whine. I also get another bad buzz (pwm/ccfl inverter) (through audio) when the screen brightness is at anything but max.
I know what it is, I just want to know the best way to kill these noises, please....

My setup is as follows:
car battery to 8gauge stranded wire (~15ft/4m) feeding a distribution block
From the dist block, I have
200watt amplifier off 8g wire
12 gauge stranded wire supplying my stereo (~10ft/3m)
Lind car adapter plugged into dc lighter jack fed by 12 gauge stranded wire (6in/15cm) plugged into my dock
dock plugged into car stereo front input (3.5mm audio type)
I did fabricate the cables for my lind, they are not shielded.

i've done what i can to eliminate ground loops, and my connections are fairly clean (I turn them frequently to reduce noise(s)). Is there some sort of compound I can use on the plugs to help stop them from getting dirty/making poor connection (that won't short center/ground)?

I don't want to use a ground loop isolator (1:1 transformer/balun) becuase it kills the volume too bad

What size cap can I put on to kill the alternator whine/electrical noise? should I put one on the dock power, or the 12v to the lind?

I also plan on installing a 4amp SLA (sealed lead acid) battery at the distribution block, supplying the lind, so it will be fed power %100 of the time (relay disconnecting the SLA when the engine is started). I know that will help absorb some of the noise.

To add to it, I also am about to install an 800w inverter to drive my ml2010 laser printer. That will also be hooked up to the SLA to maintain constant power.

As always, thanks ya'll!

 

First, are we sure it's alternator noise?

If the noise doesn't vary in pitch when the engine speed changes, it's not alternator noise; it's from another source. Ignition noise will vary in pitch too but it's usually sharper, more staticky sounding and only present in the radio portion.

My experience with laptops (particularly ones using the RealTek AC97 audio like the ToughBooks have) is that they tend to have a truly CR@PTACULAR audio amplifier subsystem; they will carry noise from the CCFL inverter, the Switch-mode power systems on the mainboard, and even data bus noise from the processor, etc. In most cases, these noises will be much less noticeable using headphones or cheap desktop speakers; but plug that output into a good quality amp and speakers and it will drive you starkers.

I would first try plugging the output from your laptop, running on battery power, into a decent home stereo. If you have noise there, you're not going to get rid of it with any kind of power filters you have because it's present in the source signal. Your potential solutions include:

Try a USB audio card. It often helps to isolate your audio output from the rest of your computer.

Catapult the Toughbook and get a one of the hoity-toity models with designer-name (Polk Audio, Bose) audio subsystem. They ARE BETTER at the audio reproduction thing; remember, Panasonic didn't design these things to be a Home Entertainment rig.

Use your ToughBook to control an iPod; use the output from THAT to feed your stereo.

Most modern high-end car audio is designed around a 5V P-P input signal standard rather than the typical 200mV P-P as we are familiar with from home audio; this is SPECIFICALLY to combat these kinds of noise issues. Unfortunately, most laptop speaker outputs are LUCKY if they can produce 500mV P-P; so you're kindof stuck there.

Another idea - You can try feeding your signal from the ToughBook directly into the amp; it may help you determine where your noise is coming from. The guys at TermPro have a lot of good reference; start here:

Noise Prevention

Moving on to the power subsystem:

The first thing I would do is get into a SuperCap (Audio Capacitor, Amplifier Capacitor) at the distribution block; for the draw you have, a 1/2 FARAD cap will be plenty, so any $30-$40 cap you get from AutoZone or WalMart or online will do. Yeah, they'll be rated between 1.5-2 FARAD, but those ratings are usually complete BS; you'll still get an honest 1/2 - 3/4 F out of them anyways. The nice part is most of them will add a nice, digital voltmeter right at your distribution block. Handy.

To feed an 800W inverter, you'll need to get into a larger SLA; probably a 12AH one or at least a 7AH. That inverter will suck a 4AH battery dry in less than an hour just idling, especially if it's true sine-wave output. Also, you have the isolation relay backwards; you want it ON while the car is running, or you won't charge the SLA. Remember to ONLY isolate the SLA & power loads; we don't want that SuperCap & amplifier on the switched side of our distribution block.

Another option is to get a cheap 750VA or so UPS like this one:

apc es 750 - Google Product Search

& keep the battery charged from your alternator; it adds a whole host of power protection features, plus when you get home you can plug it in and it should keep your car battery trickle charged; or, if you use the isolation relay (probably a better idea), or a solid-state battery isolator it will keep its internal SLA charged. They will typically contain a 7AH battery which will be good for approx 30 minutes at a 200W draw.

You don't want to use a regular 20-30A relay for this like you'd get from AutoZone for foglights; you need something heavier-duty like this:

PAC PAC-80 80 Amp Power Relay/Battery Isolator

The contact resistance from the smaller relay can introduce voltage fluctuations which will drive you nuts.

Either way ( SLA/Inverter or UPS), you may want to try eliminating the Lind and power up via a 120V adapter (make sure it's one with the grounded AC plug) plugged in; they include a ground filtering circuit which may help eliminate the noise you're looking to fight. At least it would help locate the source of the noise.


Good hunting,

mnem
Herding electrons...

 

Don't forget grounding straps; OEM-installed on most police cruisers.

 

Jeez... Someone is always "whining" about something around here!

How about an isolation circuit? You used to have to build those years ago when you added a newer stereo to your older vehicle.

 

mnem, awesome, as always. not trying to be rude, but to make sure I cover all of it, I'm just gonna spit it out

yes, it's alternator whine (Unfortunately, it's wine, which would be good!)
and everything sounds awesome, when i unplug the lind from the dock.
The usb or ipod would work, but dern it, I want it my way (all self contained and what not)
On my buddies $5k home theater, it sounds great (same 3.5mm connection)
First, are we sure it's alternator noise?
Hottie tottie notebooks are not as good as my toughbook! At least, that's what i think...
I want to feed it directly to my amp, but that means it would only be pumping out through my 12" sub. my other speakers are driven 60w each off the built in from the head unit. I just can't spend that kind of money on my work van; I'd like to, but can't till I at least get a trailer.
supercap=explosion. i have way too many random things/tools that get chucked in there... it will get punctured or shorted; which austensibly seems cool, but not so much in applilcation.

I do like your ups idea, I'm gonna sit and think on that for a minute. Are you saying to shoot car 12v right to the sla in the ups, and then when I plug the ups ac in at home, it'll trickle the whole system?
I got the ml2010 monochrome printer for a whopping $10. I also have a line on an 800w inverter for $20, so the I might do the ups, but the inverter is cheaper.

I had actually planned on a 20 amp relay, between the sla and the supply. The sla would be for my laptop and printer, only for a 10 minutes if I ran into the store, and my thought was to keep those items powered when the vehicle was beging started (and all the available juice goes to the starter, undervolting everything else). I hadn't thought of the relay generating noise.... we'll see.

I hate the idea of ditching the lind. The thought of adding links in a chain for only 1 purpose kills me (IE alternator ac to dc to ac inverter to power supply dc).

I was really hoping a small cap put on the input of the dock would help tremendously. Kind of like putting a cap on your car speaker to eliminate low freq....

@TOPCOP
I hadn't thought about that. My mount/dock is not grounded except through the power supply. I have it bolted to my sub woofer box, not to anything grounded.... I'll try that for sure!

Dunno. I'll try some cheap stuff first, and then move up if I have to.

Thanks again, as always!

 

Well... you really SHOULD have the supercap there for your amp; even a 200W amp (If it's an honest 200W, not some BOSS or Phase Linear IC Finals POS) can pull an alternator down and beat up the rectifiers, causing junction leakage and alternator whine (In other words, you may have already done the damage). This is especially true when serving sub duty.

You need to build an enclosure for the rest of your electrical equipment for safety's sake anyway; if things are hazardous enough to puncture a cap, there's just as much likelihood of you puncturing/cutting/shorting your power wiring or violating the hull integrity of your amp.

If you're running an AC inverter anyhow, who cares if you're adding a link in the chain with the AC adapter? The real-world current draw won't be great just to keep the laptop powered as long as your laptop battery is healthy and charged; and if the Lind is creating noise, it needs to go.

I've done the UPS thing myself before; yes, it does charge its internal battery when plugged in at home; but I DID have it on the other side of an isolation relay so that it connected to the car 12V charging system only when the car was running. I don't know if the internal charging circuitry would be adequate to charge a LLA starting battery; I conjecture that it would probably be adequate to trickle charge, but it may take days to make an appreciable difference.

I have no doubt that the dock already has considerable ripple filtering (capacitors) at the input connector; however, you could TRY a 2200-4700 uf 16V cap there just for grins - you may get lucky.

Oh... and get your mount bolted somewhere OTHER than the sub enclosure; the vibration from that will beat your laptop to death, Toughbook or not. This will also make sure your mount chassis is properly grounded.

mnem
You and your BoomBox car...

 

I would try and ground the lind power supply at the back of the radio or the same ground as the amp. and only have one ground.

I have a CF-M34 under my seat in my car for my mps and sat nav I also had the wine you are talking about.

I grounded the lind power supply to the same ground as my radio as my audio for the dock went in to the radio this stopped my wine.

try this leave the audio cable in place and lift the ground wire from the lind power supply to see if the wine goes, if so the I would say you will have to keep the ground wire as short as posable to lind.

 

I have a cf-28 (mk2) i keep in my truck (2005 dodge quad cab) for the kids to watch movies on and play games on trips. I have the same thing some time happen with the alternator wine. I noticed the more i try to "boot" or "amp" the signal the worse it is as expected. I have got most of it out. I use "vlc" video player and i went to there control panel and played with the equalizer setting. The noise is still there but it is not as nearly as bad as it once was.

Try another input device into the amp and make sure it is coming from the computer and it is not affecting the amp directly.

(For reference my setup, cf-28 mk2, cheap o car power adapter off ebay with no dock, jumper cable off the sound output to a FM mp3 player to put the sound through the radio)

 

I found an easy solution for this problem. I bought a 3.5mm audio cable with a built in filter from griffin. Works great, gets rid of the irritating noise when using an audio device in the car and it is also plugged in for power, works with my zune hd, cf-29, cf-30 etc.

FRYS.com | GRIFFIN 3028-NRACBL

 

This is a POSSIBLE solution; but I've tried MANY such adapters and the effectiveness varies greatly, and it usually comes at a noticeable loss of frequency range and signal volume.

Hey; it's easy, and cheap. Worst case you're out $10 if it doesn't work.

mnem
Whine, whine, whine... :wink:

 

TUrns out it was indeed my heapchit head unit. I ended up throwing in my old head unit that I thought had a fried channel (turned out to be my amp).

So yeah, make sure if you have this problem, that it isn't a crappy head unit in your car!

FWIW.

 

Shielded input cable.

 

I don't have time to read this entire thread right now but i can say from experience what the OP is experiencing is MOST DEF an alternator wine! This can be mitigated by a few ways:

1) Be sure that the power cord powering the toughbook and the aux audio cable are AT LEAST 1' apart.
2) Don't plug the power into the toughbook whilst in the vehicle and only run on the battery (doesn't work for long trips though).

I have this problem to some extent in ALL the vehicles I've owned over the last 8 years (which has been A LOT OF VEHICLES). In ALL of these vehicles the wine will vary in pitch when accelerating & de-accelerating (when the RPM's are changing)

 

I would like to try this product, however the link doesn't work...

 

Most alternator whine is usually a mistaken a ground loop (or a lag in positive feed)

in a ground loop: remember, you are using the vehicle body as the negative conductor. As a result of environmental variables, the path that the "negative" electricity is taking is constantly changing, and the result is an audible whine in the stereo

A similar problem can exist if your positive feeds aren't correct. I almost always try to run all my grounds and positive feeds from a distribution block, so I know I'm not relying on some crappy OEM PDC problem.

The ground loop isolators (as last mentioned by kd8npb) is a matching transformer (a 1:1 transformer) that electrically isolates either end of the audio cable. In my experience they cause a volume drop that isn't worth it: EG, I have to turn up the volume even more, which makes the regular background hiss even louder. IMHO, I personally kind of see a ground loop isolator as a cheap fix/bandaid. But they are appropriate for certain circumstances.

Thanks ya'll! I i figured I should have made the previous post, in case any one else is suffering from their own cheapness (like I said, it was a cheap head unit that was doin it to me). The head unit I have in now, with everything else the same, has NO NOISE at all from my setup.

Good Luck!