Wednesday, July 05, 2006 - 11:35 pm, by: Blaine Hanson(Blaine)
Not directly related - but may help someone else ......I have a similar noise in my car. What I tracked it down to is the instrument panel dimmer switch. If the dimmer switch is on full brightness - there is no hmmmmmm in the stereo ( stock stereo system ), if I turn the dimmer switch onto any thing less than full brightness the hmmmmm begins through the stereo system.
Russell Rohde Tinkerer Queensland Soarer 1JZ 2.5L TT
Friday, July 07, 2006 - 08:39 am, by: Russell Rohde(Ax0n)
Easy fix - had same thing. Ground all your amps at one point in the boot then run a trailing wire (vers small wire will do) from the fram of the head unit to the amp grounding point. This will remove any "potential difference" in the ground between the amps and the head unit. Standard way of fixing. Has removed it in every stereo I have installed (10+ stereos)
Tuesday, July 11, 2006 - 10:12 am, by: Peter Bullman(Pete)
Have you tried seperating your RCA's from your Power cable..??
Do that first, then get yourself a good set of Twisted Pair RCA's.. I use Streetwires and they are excellent..!! Product code LN250. I used 3 sets in my car and they are perfect (used to have small whining..!) Cost about $30 a set
i have 2 head units, one is my tv unit and the other is my dvd. i also have a computer setup in the boot. all my audio signal to the amps is from my tv media center. both head units create the noise. Russel, thanks mate, iam going to try it out now.
Peter, yeah i did that the very first time i installed it, the only worry i have is that the RCA's iam using for the computer are 20m long which may cause interference. there al coiled up in the compartment where the fuel tank is. but that does not explain the noise from the head units
Russell Rohde Tinkerer Queensland Soarer 1JZ 2.5L TT
Saturday, July 15, 2006 - 07:44 am, by: Russell Rohde(Ax0n)
The whine is a result of the 'potential difference' in the grounds of the differing components in a car.
The chassy is the 'common or ground' (no •••• you all say). When the car is running, the altinator which incidently, runs somewhere in the vacinity of 10 to 11 volts AC (3 phase). With the use of several diodes (electrical 'one-way' gates), a rough DC supply can be obtained. Because no DC supply (with exception of a battery) is perfect, it adds 'noise' into the DC operation of the appliance which in this case is the car and stereo combined.
Alright, so, next... When the car is running, depending on your revs, the true supply voltage can be anywhere between about 13 and 15 volts. I'm not talking fluctuations over a 10, 20 or 30 second period, I'm talking over a .001 or .002 second period. As you accelerate, this fluctuiation time decreases. Revs increase, the speed of the altinator incresese, the generated AC frequency increases hence the fluctuation in the DC increases and the pitch of the whine gets highter because the frequency increases.
Making sense so far?
Now to what causes the 'ground loop'. There are a couple of 'rules' that are in place in electrical circuits. 1, Crrent and voltage are inversly proportional (higher thump from subs = dim in headlights cos current up, voltage down). 2, Voltage is the potential difference between 2 points (so, if you had a 100V dc supply, hooked up 4 25ohm resistors in series and connected them to the positice and negative terminals of the supply, 25v would be getting 'used' or 'dropped' by each resistor)
pos---[25ohm]---[25ohm]---[25ohm]---[25ohm]---neg
Alright, because, after installing extra parts in your stereo and grounding them at different points, the voltage each device is running off slightly differs. Head unit uses bugger all current, so the voltage to is remains relatively constant. Your great big 'mother of god' Class D Mono block feeding 2000wRMS into a 1ohm load is going full out scaring little kids and parting vain womens legs at 500metres. The voltage drop is in full sway as a result of your leg parting and kid crying amp/sub setup. The negative does not always stay at 0 and the positive not always 'pulls' down to the ground.
This means that the head unit may be running off 13.3v. the ground a +0.8v and the positive at +14.2v.
With amps grounded at different point, they do what's technically called by those in the loop as 'weird ••••••
Big bass, big current, big voltage drop. That same 2000wRMS amp may very well drop the voltage between it's ground and positive terminals to around 10 or 11v - maybe even lower. I know that with my last car, a big Big BIG bass hit would stall the engine at a set of lights.
This is what causes a potential voltage difference in the ground points of the stereo. That is why, no matter what, do everything and anything to ground all parts of you stereo in ONE place.
Running an extra ground wire from the head unit to the grounding point in the boot results in a 'short circuit' between these two points, so, the voltage difference between front and rear grounds is eliminated.
Hope this has shed some light - in some way. It is very had to explainin a way that is easily understood on a forum. To really allow people to understand how and why it is caused and how and why it is stopped would take a whiteboard, an array of different coloured markers and a dirty schoolgirl with pink panties and a short skirt sitting in the front row. Damn me and my fumbelling fingers - always dropping ny pens...
thanks russel, even though i only understood 1/3 of it i got the main idea of it though, i think. just wondering where the stock earth wire is mounted on the body? or is it easier to get the wire straight from the headunits
ok, today i went and tried grounding the units to the same place as the amps to create 0 potential. no difference. however i did not discconect the stock grounding.
Try disconnecting the stock ground point then, as this will have the least resistance to ground. IE the power will want to ground to the stock point as that is quicker and easier than running to the back of the car before hitting ground point.
Monday, July 17, 2006 - 07:30 pm, by: Mark Paddick(Sparks)
If it is alternator whine it could be being picked up by direct radiation. The most common point of entry to the audio system for electrical interference is speaker leads, followed by the power amp input leads. The 20m RCAs would be my first point to check and replace with shorter ones. In some cases using shielded speaker leads may help (if it does the the amp design is not the best...). Usually keeping them short and away from other wiring is enough.
ok i diccontected the stock earth, and still the same result. what iam missing here? the 20m RCA's are only used for the PC computer, and iam getting the same interference level from both dvd and computer use. i plan to take them out though, i think they vibrate against the tank when the subs go off
Russell Rohde Tinkerer Queensland Soarer 1JZ 2.5L TT
Friday, July 21, 2006 - 04:21 pm, by: Russell Rohde(Ax0n)
RCA's down the passenger side under/behind the trim furtherst to the outside of the car. Power from battery, across engine bay and down the drivers side. Drill a hole big enough to fit your RCA's through in the rear firewall. MAKE SURE YOU GET ALL BURRING OFF AND PUT SOMETHING AROUND THE HOLE TO PREVENT THE CABLES CUTTING ON THE NOW SHARP EDGES
RCAs ONLY down that side. all other cables down the drivers side in the exact same positions. If you really want to try this, run another ground (which you have already done aparently) and positive run from the boot - I'm assuming everything except the headunit is in the boot? Amps, Subs, PC etc...
Is your PC one with a 'viewing window'? PC's have a massive amount of electro magnetic interference (EMI). Seriously - a bull shizzle amount!! Full metal case and make sure all panels of the PC are going to grond. If this requires cables, lugs, nut and bolts to the side panels - so be it.
If you get sheilded cables for your RCA's, it could be of use to ground the sheild at both ends (ground of the AMP you are feeding and the frame of the headunit)
When you ran your new ground, did you also loop it from the back of the headunit where the cables joined to the frame of the player? Rarely, this could be a problem.
What brand is your headunit? I think it is Pioneer that is nutorious for having one of the ground 'tracks' on the circit boards inside it burn out - grounding the frame is a fix. Without this fix they can whine a huge amount. Not sure which models exactly it is that do it.
Apart from trying all this, I have nothing else I can really help you with. Not without seeing it - gutted - not installed.
one other point - how are you powering the PC? 12vDC to 230vAC inverters also put out a massive amount of EMI.}
Sunday, July 23, 2006 - 03:10 pm, by: Peter Bullman(Pete)
So I'm assuming the amps are the factory ones..??
Bizzare.. but as Russell has been saying, it more than definitely a grounding issue.. But, I still stand by what I said about the RCA's.. Get a GOOD set (if you havnt already..) and, as Mark said, SHORTEN them! more wire means more conducting..
One other method of trying to find the problem would be to 'dry run' the components out of the car.. ie. Separate the PC from the boot and run the RCA's OUTSIDE the car, as well as the Power cables.. See then if there is still any whine.. We've tried this at work a few times and found then that the issue may not be with the cables.. btw, we usually electrical tape up the individual wires for each component.. helps again to sheild against any 'unfriendly' earthing outs etc.. this includes speaker wire, power cable and RCA's.. just as an extra precaution..!!
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i got the main idea of it though, i think. just wondering where the stock earth wire is mounted on the body? or is it easier to get the wire straight from the headunits
