Hi there. I'm fairly new to the DIY scene especially with the electronics side.
My problem here is car audio related, but i figured the viewers of this thread would know the most.
I'm getting engine noise in my car due to poor ground isolation in my amplifier. I'd like to add differential inputs to the amp, or at least just outside of it.
What is happening is I have a potential from the rear of the car to the front and current flows through the RCA shield. This dirty, ripple filled current makes noise in the signal and is amplified as whine.
Transformers filter this fairly good, but result in very bad frequency response.
My problem is most articles i've found are for balanced inputs. Understanding the CMRR in those is fairly straight forward and all the noise rejection that comes with it.
I however don't know how to make one for an unbalanced source.
The output signal ground of the differencial circuit must have a very high impedance to stop any current flow.
Any help, links, direction on this subject would be sooo very much appreciated. Thanks to all who contribute.
Sincerely,
new Diy'er Mark Nickel
My problem here is car audio related, but i figured the viewers of this thread would know the most.
I'm getting engine noise in my car due to poor ground isolation in my amplifier. I'd like to add differential inputs to the amp, or at least just outside of it.
What is happening is I have a potential from the rear of the car to the front and current flows through the RCA shield. This dirty, ripple filled current makes noise in the signal and is amplified as whine.
Transformers filter this fairly good, but result in very bad frequency response.
My problem is most articles i've found are for balanced inputs. Understanding the CMRR in those is fairly straight forward and all the noise rejection that comes with it.
I however don't know how to make one for an unbalanced source.
The output signal ground of the differencial circuit must have a very high impedance to stop any current flow.
Any help, links, direction on this subject would be sooo very much appreciated. Thanks to all who contribute.
Sincerely,
new Diy'er Mark Nickel
Possible Solution
Okay...after looking around the posts here for a while, i've come up with a possible solution...
A Burr DRV134 unbalanced to balanced line driver, straight into a INA134 which is a balanced to unbalanced converter. The INA134 states it has ground loop isolation. So i think this sort of thing may work.
I'm like a true beginner with this, so bare with me.
The Vcc and V-, can this be my 12-15 VDC source in the car? Or do i need actual -5 v and +5 v minimum. I'm worried about the cleanliness of my DC source too. perhaps a cheap DC-DC converter with 12v+/- outputs would be in order.
If anyone could give a beginner a hand here, it'd be greatly appreciated.
Also, what would be a good online dealer to supply small quantities of these IC's.
Thanks alot guys.
Mark
Okay...after looking around the posts here for a while, i've come up with a possible solution...
A Burr DRV134 unbalanced to balanced line driver, straight into a INA134 which is a balanced to unbalanced converter. The INA134 states it has ground loop isolation. So i think this sort of thing may work.
I'm like a true beginner with this, so bare with me.
The Vcc and V-, can this be my 12-15 VDC source in the car? Or do i need actual -5 v and +5 v minimum. I'm worried about the cleanliness of my DC source too. perhaps a cheap DC-DC converter with 12v+/- outputs would be in order.
If anyone could give a beginner a hand here, it'd be greatly appreciated.
Also, what would be a good online dealer to supply small quantities of these IC's.
Thanks alot guys.
Mark
The common approach to prevent groung loops in these circumstances is to use a floating SMPS on the amplifier [or at least partially floating], this forces the speaker/signal ground and the chasis ground to be no longer coupled
Currently almost all amplifiers use this cheap approach
In the other hand, almost all amplifiers not having a SMPS are powered directly from +12V and thus rated at 15Wrms@4 ohms per channel so they are useless nowadays. Special class H ICs [50W@4 ohms] designed to be powered from +12V like TDA1562Q also include differential inputs internally
Currently almost all amplifiers use this cheap approach
In the other hand, almost all amplifiers not having a SMPS are powered directly from +12V and thus rated at 15Wrms@4 ohms per channel so they are useless nowadays. Special class H ICs [50W@4 ohms] designed to be powered from +12V like TDA1562Q also include differential inputs internally
Don't knock balanced.......
The cable isn't going to be any longer if it is balanced, and even if it was.......it would sound better. Period.
OK.....another way........if you have a source of +/- 12 volts.....a lot of this car audio stuuf does, with all those SMPS inside.......
Analog Devices makes some parts called.......SSM-2142/3, etc. for this. Don't sound too bad, a little rolled off in the top, but I don't think that will be a hinderance in this application.
Yeah....you could buy some cheap DC-DC converters......cheaper still if you can find them surplus..........
I know.....another overkill solution form an engineer. Hey, that is what we do best. Sometimes.
Jocko
The cable isn't going to be any longer if it is balanced, and even if it was.......it would sound better. Period.
OK.....another way........if you have a source of +/- 12 volts.....a lot of this car audio stuuf does, with all those SMPS inside.......
Analog Devices makes some parts called.......SSM-2142/3, etc. for this. Don't sound too bad, a little rolled off in the top, but I don't think that will be a hinderance in this application.
Yeah....you could buy some cheap DC-DC converters......cheaper still if you can find them surplus..........
I know.....another overkill solution form an engineer. Hey, that is what we do best. Sometimes.
Jocko
Re: Don't knock balanced.......
I'm sure the amp has SMPS. I'm quite a beginner here, but what I can tell you is there is about 10Kohms between the RCA ground and chassis ground. This is not big enough and DC current flows...
The amp ground is 4 gauge and very short. To assure best connection, i welded a bolt right to the frame and secured the ground ring with a nut. There are no long wires to pick up EMF. The noise is not induced. It comes from the very bad ripple in the DC supply. The RCA sees this ripple because of the slight potential difference in the car. If i power the head unit with an isolated power source, the noise is completely eliminated. A DC-DC 12v-12v isoloted converter is not cheap and not very common for the size of one i'd need to run the Head unit.
I'm not worried about powering long cable runs. I've got 4V rms output into a 600ohm load from my alpine deck.
How is your solution different than mine aside from the IC's? Isn't that the same as what i thought i could do. You're right about the +/- 12v source though...i'm sure i could open up a component and find a good regulated supply. If i can, i will attempt to put this entire circuit inside my amp. That'd be pretty cool i think.
The only requirement I have for solution is...
Take an unbalanced source, and remove it's ground. harder than it sounds beacuse the ground carries the signal. This would happen if i used the Burr chips, wouldn't it?
Thanks for the quick responses guys.
Perhaps with my added facts, you guys will know more of what i'm talking about (not likely, cuz i don't even know what i'm talking about!
)
Mark
Eva said:
I'm sure the amp has SMPS. I'm quite a beginner here, but what I can tell you is there is about 10Kohms between the RCA ground and chassis ground. This is not big enough and DC current flows...
Konrad said:
Naaaa I belive it's lack of gnd. Short wire too gnd/chassi is the common way, why use a lot of cable when not nessy? A long wire or two to pick up more noise, like an antenna?
The amp ground is 4 gauge and very short. To assure best connection, i welded a bolt right to the frame and secured the ground ring with a nut. There are no long wires to pick up EMF. The noise is not induced. It comes from the very bad ripple in the DC supply. The RCA sees this ripple because of the slight potential difference in the car. If i power the head unit with an isolated power source, the noise is completely eliminated. A DC-DC 12v-12v isoloted converter is not cheap and not very common for the size of one i'd need to run the Head unit.
Jocko Homo said:
I'm not worried about powering long cable runs. I've got 4V rms output into a 600ohm load from my alpine deck.
How is your solution different than mine aside from the IC's? Isn't that the same as what i thought i could do. You're right about the +/- 12v source though...i'm sure i could open up a component and find a good regulated supply. If i can, i will attempt to put this entire circuit inside my amp. That'd be pretty cool i think.
The only requirement I have for solution is...
Take an unbalanced source, and remove it's ground. harder than it sounds beacuse the ground carries the signal. This would happen if i used the Burr chips, wouldn't it?
Thanks for the quick responses guys.
Perhaps with my added facts, you guys will know more of what i'm talking about (not likely, cuz i don't even know what i'm talking about!
)Mark
10K isolation between RCA/speaker ground and +12V ground should be more than enough, even values as low as 220 ohms work quite right
Now I'm almost sure that your noise pickup problem does not come from a ground loop
I would check that the RCA ground is the same as the speaker ground of the amplifier to discard some quite common problems like fused ground tracks on the amplifier [RCA connectors touching 12V by accident]
I would also check that the RCA ground of the head unit is the same as the chasis ground to discard fused tracks inside the head unit [again RCA connectors touching 12V by accident]
Then, I would look for magnetically induced noise. This happens usually with 4 channel amplifiers when there are two stereo RCA wires between the head unit and the amplifier and each follows a different path.
I suggest checking if you get noise with none, 1, 2, 3, etc... RCAs connected
In case of fused tracks on the amplifier you may get noise even with no RCAs connected
In case of ground loop or fused tracks on the head unit, you should get no noise with no RCAs and noise with one or more RCAs
In case of magnetic couplig you should get no noise with one or no RCA connected and noise with two or more
Dont panic, I've faced that problem many times and there is allways a simple clever way to solve it
Now I'm almost sure that your noise pickup problem does not come from a ground loop
I would check that the RCA ground is the same as the speaker ground of the amplifier to discard some quite common problems like fused ground tracks on the amplifier [RCA connectors touching 12V by accident]
I would also check that the RCA ground of the head unit is the same as the chasis ground to discard fused tracks inside the head unit [again RCA connectors touching 12V by accident]
Then, I would look for magnetically induced noise. This happens usually with 4 channel amplifiers when there are two stereo RCA wires between the head unit and the amplifier and each follows a different path.
I suggest checking if you get noise with none, 1, 2, 3, etc... RCAs connected
In case of fused tracks on the amplifier you may get noise even with no RCAs connected
In case of ground loop or fused tracks on the head unit, you should get no noise with no RCAs and noise with one or more RCAs
In case of magnetic couplig you should get no noise with one or no RCA connected and noise with two or more
Dont panic, I've faced that problem many times and there is allways a simple clever way to solve it
>I would check that the RCA ground is the same as the speaker >ground of the amplifier to discard some quite common problems >ike fused ground tracks on the amplifier [RCA connectors >touching 12V by accident]
The RCA ground to spaeker ground of the amp is 500ohms.
The RCA Left to right is 1000ohms.
The RCA Ground to chassis ground is 10Kohms.
>I would also check that the RCA ground of the head unit is the >same as the chasis ground to discard fused tracks inside the >head unit [again RCA connectors touching 12V by accident]
0 ohms, a direct short.
>Then, I would look for magnetically induced noise. This happens >usually with 4 channel amplifiers when there are two stereo >RCA wires between the head unit and the amplifier and each >follows a different path.
>I suggest checking if you get noise with none, 1, 2, 3, etc... >RCAs connected
With only 1 RCA connected, Noise results.
>In case of fused tracks on the amplifier you may get noise even >with no RCAs connected
Absolutely NO noise.
>In case of ground loop or fused tracks on the head unit, you >should get no noise with no RCAs and noise with one or more >RCAs
This is where I have noise.
>In case of magnetic couplig you should get no noise with one or >no RCA connected and noise with two or more
No different with 2.
I've read and talked to Jason Cuadra (maker of elyptic crossover, electrical engineer)...
He diagnosed some other guys and posted all the steps. Seems to be the most knowledgable guy in noise in electrical systems i know. Posts i read from... http://members.fortunecity.com/jasoncuadra/audio/noisehunt.html
However...he did not mention any fused tracks...so maybe you are the one to talk to
Anyways, but the results i've found thus far, somehow a ground loop is resulting.
I have a fealing it is a very dirty alternator. With my dads car turned on and jumped to my car, there is no noise. This led me to believe it was completely ground loop/alternator sourced.
The only thing i do to help minimize the noise is run an 8 gauge from head unit ground to amp ground. This effectively reduces the potential. However, there is still noise. Using a transformer removed it, but there were super cheap and not shielded. I cannot afford the Jensen ones
So this is the solution i've come to...differential inputs.
I initially thought it would work as well, becuase i used to have a rockford fosgate with differential inputs and there was no noise in my system. However, i think the potential was too great and in 2 weeks, the circuit blew and there was a direct short from chasis to amp rca ground...extreme noise.
Anyways, any further info would be great. Thanks for the trouble shoot Eva.
mark
The RCA ground to spaeker ground of the amp is 500ohms.
The RCA Left to right is 1000ohms.
The RCA Ground to chassis ground is 10Kohms.
>I would also check that the RCA ground of the head unit is the >same as the chasis ground to discard fused tracks inside the >head unit [again RCA connectors touching 12V by accident]
0 ohms, a direct short.
>Then, I would look for magnetically induced noise. This happens >usually with 4 channel amplifiers when there are two stereo >RCA wires between the head unit and the amplifier and each >follows a different path.
>I suggest checking if you get noise with none, 1, 2, 3, etc... >RCAs connected
With only 1 RCA connected, Noise results.
>In case of fused tracks on the amplifier you may get noise even >with no RCAs connected
Absolutely NO noise.
>In case of ground loop or fused tracks on the head unit, you >should get no noise with no RCAs and noise with one or more >RCAs
This is where I have noise.
>In case of magnetic couplig you should get no noise with one or >no RCA connected and noise with two or more
No different with 2.
I've read and talked to Jason Cuadra (maker of elyptic crossover, electrical engineer)...
He diagnosed some other guys and posted all the steps. Seems to be the most knowledgable guy in noise in electrical systems i know. Posts i read from... http://members.fortunecity.com/jasoncuadra/audio/noisehunt.html
However...he did not mention any fused tracks...so maybe you are the one to talk to
Anyways, but the results i've found thus far, somehow a ground loop is resulting.
I have a fealing it is a very dirty alternator. With my dads car turned on and jumped to my car, there is no noise. This led me to believe it was completely ground loop/alternator sourced.
The only thing i do to help minimize the noise is run an 8 gauge from head unit ground to amp ground. This effectively reduces the potential. However, there is still noise. Using a transformer removed it, but there were super cheap and not shielded. I cannot afford the Jensen ones
So this is the solution i've come to...differential inputs.
I initially thought it would work as well, becuase i used to have a rockford fosgate with differential inputs and there was no noise in my system. However, i think the potential was too great and in 2 weeks, the circuit blew and there was a direct short from chasis to amp rca ground...extreme noise.
Anyways, any further info would be great. Thanks for the trouble shoot Eva.
mark
These measurements suggest that your amplifier already has diferential inputs with 500 ohms input impedance on the RCA ground [inverting input], but those 500 ohms may be also due to a fused ground track
To test the input of the amplifier :
Try shorting the tip and the ring of a test RCA connector and plug it to the amplifier. Does it produce noise? [It shouldn't]
Then try connecting both the tip and the ring of the test RCA connector to chasis ground or head unit ground and plug it to the amplifier. Does it produce noise now? [It shouldn't]
Some amplifiers use two diodes in paralell, placed back-to-back, to force speaker/RCA ground potential to be within +-0.7V of 12V ground potential. This usually works as expected but in some cars potentials higher than +-0.7V are reached due to bad grounding on the head unit or the amplfier [or excessive chasis/ground wiring impedance] and the diodes blow. Then a dead short between RCA ground and 12V ground appears and it causes lots of noise. It's very easy to repair though [I've seen also PCB traces blown in extreme cases]
Your car is probably suffering from such excessive potentials and the amplifier may be internally protected and simply clamping them [and causing noise too]
I would test the system with the head unit powered directly from the +12V and GND binding posts of the amplifier through long enough wires. This makes still a ground loop but the potential difference should be low enough to be handled by any amplifier [except in case it's broken]
Testing 1, 2, 3
>These measurements suggest that your amplifier already has >diferential inputs with 500 ohms input impedance on the RCA >ground [inverting input], but those 500 ohms may be also due >to a fused ground track
This impendance from input to output ground could be the "Controlled Electronic Noise Suppression "Cens" " circuitry that is supposed to eliminate noise. It in fact does change the noise from a moderate level to a softer one, but never eliminates it.
I'm not sure if they are differential...perhaps we can find out.
>Try shorting the tip and the ring of a test RCA connector and >plug it to the amplifier. Does it produce noise? [It shouldn't]
With this done, there is no noise.
>Then try connecting both the tip and the ring of the test RCA >connector to chasis ground or head unit ground and plug it to >the amplifier. Does it produce noise now? [It shouldn't]
I have not tried this and am at school now without my car, but seems like an interesting test. I'll definately try this when i get home. My thoughts are that there is noise with this setup simply because the chassis ground now has a link to amplifier RCA ground. This is just speculation and I'll let you know in about 12-13hours.
>Some amplifiers use two diodes in paralell, placed back-to-back, >to force speaker/RCA ground potential to be within +-0.7V of >12V ground potential. This usually works as expected but in >some cars potentials higher than +-0.7V are reached due to >bad grounding on the head unit or the amplfier [or excessive >chasis/ground wiring impedance] and the diodes blow. Then a >dead short between RCA ground and 12V ground appears and >it causes lots of noise. It's very easy to repair though [I've seen >also PCB traces blown in extreme cases]
I think you are dead on with this one....as i remember, i was moving the deck or playing with it or something and probably had a bad if not completely disconnected ground while everything was on. I wish I had known it was so easy to repair. I sold the amp as a dedicated sub amp with the LPF on so that no High freq noise would be heard. Is such a solution possible with my amp?
>I would test the system with the head unit powered directly >from the +12V and GND binding posts of the amplifier through >long enough wires. This makes still a ground loop but the >potential difference should be low enough to be handled by any >amplifier [except in case it's broken] [/B][/QUOTE]
This is where i was a little mistified. I tried this recently with the deck nearly on top of the amp. I connected power and ground right to the amp with 3ft test leads (14 gauge). Signal through a spare RCA (not through car). I still had Noise!
This can only lead me to believe that the it's when the RCA input ground of the amp sees a chassis ground, it somehow amplifies noise. So I'm still a little lost as to the actual cause.
All in all, would these differential converted inputs I would make be isolated from ground completely? Would it work as a solution. I would like to find the right solution however. But it is taking some time. I will probably take my car in to have the alternator tested to see if it is excessively dirty. I'm sure it's original, car has 110k miles. And i have ran a heavy duty stereo for a year and a half now. I usually just lowered the gains as far as completely possible. I now have speakers that will take alot of power and need to have the gains higher as to get very loud.
Anyways, your help Eva, has been the best so far. Thanks
Mark
>These measurements suggest that your amplifier already has >diferential inputs with 500 ohms input impedance on the RCA >ground [inverting input], but those 500 ohms may be also due >to a fused ground track
This impendance from input to output ground could be the "Controlled Electronic Noise Suppression "Cens" " circuitry that is supposed to eliminate noise. It in fact does change the noise from a moderate level to a softer one, but never eliminates it.
I'm not sure if they are differential...perhaps we can find out.
>Try shorting the tip and the ring of a test RCA connector and >plug it to the amplifier. Does it produce noise? [It shouldn't]
With this done, there is no noise.
>Then try connecting both the tip and the ring of the test RCA >connector to chasis ground or head unit ground and plug it to >the amplifier. Does it produce noise now? [It shouldn't]
I have not tried this and am at school now without my car, but seems like an interesting test. I'll definately try this when i get home. My thoughts are that there is noise with this setup simply because the chassis ground now has a link to amplifier RCA ground. This is just speculation and I'll let you know in about 12-13hours.
>Some amplifiers use two diodes in paralell, placed back-to-back, >to force speaker/RCA ground potential to be within +-0.7V of >12V ground potential. This usually works as expected but in >some cars potentials higher than +-0.7V are reached due to >bad grounding on the head unit or the amplfier [or excessive >chasis/ground wiring impedance] and the diodes blow. Then a >dead short between RCA ground and 12V ground appears and >it causes lots of noise. It's very easy to repair though [I've seen >also PCB traces blown in extreme cases]
I think you are dead on with this one....as i remember, i was moving the deck or playing with it or something and probably had a bad if not completely disconnected ground while everything was on. I wish I had known it was so easy to repair. I sold the amp as a dedicated sub amp with the LPF on so that no High freq noise would be heard. Is such a solution possible with my amp?
>I would test the system with the head unit powered directly >from the +12V and GND binding posts of the amplifier through >long enough wires. This makes still a ground loop but the >potential difference should be low enough to be handled by any >amplifier [except in case it's broken] [/B][/QUOTE]
This is where i was a little mistified. I tried this recently with the deck nearly on top of the amp. I connected power and ground right to the amp with 3ft test leads (14 gauge). Signal through a spare RCA (not through car). I still had Noise!
This can only lead me to believe that the it's when the RCA input ground of the amp sees a chassis ground, it somehow amplifies noise. So I'm still a little lost as to the actual cause.
All in all, would these differential converted inputs I would make be isolated from ground completely? Would it work as a solution. I would like to find the right solution however. But it is taking some time. I will probably take my car in to have the alternator tested to see if it is excessively dirty. I'm sure it's original, car has 110k miles. And i have ran a heavy duty stereo for a year and a half now. I usually just lowered the gains as far as completely possible. I now have speakers that will take alot of power and need to have the gains higher as to get very loud
. Anyways, your help Eva, has been the best so far. Thanks
Mark
Hi Mark!
...looks for me like a simple solution could work.
I would try to change the ground connection of the power amp
in the back of your car. Instead of your short connection to the frame in the rear of the car, you could try to get the ground of the amplifier from the head unit.
You already noticed that a ground wire between amp in the back and the head unit reduces the noise. For a simple test put this wire again and remove the ground connection to the frame in the back.
If this works, then you can be sure that your issues are caused by
a ground loop (ground delivered through shield of RCA cable and frame of car).
Is there a reason why you don't want to pick the ground for the amp in the back from the head unit? ...just a single thick wire could be the solution of all your trouble...
Good Luck
Markus
...looks for me like a simple solution could work.
I would try to change the ground connection of the power amp
in the back of your car. Instead of your short connection to the frame in the rear of the car, you could try to get the ground of the amplifier from the head unit.
You already noticed that a ground wire between amp in the back and the head unit reduces the noise. For a simple test put this wire again and remove the ground connection to the frame in the back.
If this works, then you can be sure that your issues are caused by
a ground loop (ground delivered through shield of RCA cable and frame of car).
Is there a reason why you don't want to pick the ground for the amp in the back from the head unit? ...just a single thick wire could be the solution of all your trouble...
Good Luck
Markus
This suggests that the noise actually comes with the signal out of the head unit or that the input circuit of the amplifier is malfunctioning
The amplifier would definitely be the cause if noise appears just by connecting both input tip and input ring of any channel to chasis ground or any other grounds
Chocoholic : car-audio amplifiers may draw in excess of 100A peak and 20A to 50A average at high volumes. Head unit power wiring is usually 0.75mm^2 to 1,5mm^2 and is intended for about 5A average current consumption. It shares fuses and ground points with the rest of the electrical system of the car. Amplifiers must be connected to the chasis or to the battery through a reasonable gauge wire. Powering them from the head unit may even cause disastrous results like smoked wires, altough the usual result is amplifiers and head units shutting down due to excessive voltage drop
Testing
Ya...This is why i was so mistified. But...think about this.
If i power the head unit from an external source...ie my computer power supply, and isolate the ground. Then there is no noise (except 60hz hum from very bad PS). Also powered the head unit again yesterday from our 90 Ranger. With the ranger running, there was no noise whatsover...i doubt the ranger has a great alternator too.
HOWEVER, if i then ground the chassis of the head unit to the car's chassis, then the full noise returns. This shere fact alone tells me that noise comes from grounding the shield of the RCA's to chassis ground. unless the noise is induced into the head unit because it's grounded.
Like i said before. Isolators (transformers) eliminate alot of the noise too. So if the deck had poor power filtering then it should show up regardless of isolators because it would be in the hot signal. Right?
I'll have to check this for sure when i get home. Also, my test setup for the Deck right on amp could have been better. I'm not sure how good the ali clips were on...and a 3ft rca could be used as opposed to a 15ft one. I'll also try another amp too and see what sort of noise i'm getting. I have a soundstream Lil' wonder i could use. I really don't think it is the amp however because every amp i've put in...aside from the Rockford with differential inputs...has made noise.
Soundstream Reference 644s
Soundstream Lil' Wonder
JL e6450 - 6 channel
MTX 6304
MTX 4244
All have made noise...except the Rockford.
I have changed the grounds several times too depending on where the amp was mounted...so it was not that i've used the same bad ground everytime.
I've always dealt with it as best i could by turning gains down and wiring deck ground to Amp ground. This has been enough to make it almost unnoticable with accessories off, but when a load is applied to the alternator (lights, defroster, fan), the ripple increases a fair bit and the noise is very audible at night with the stereo at a lower volume.
Today I will try an alternate grounding point in the trunk for the amp. I have a second amp in the trunk, but it is basically disconnected as i'm troubleshooting this amp alone. It is a class D sub amp. Both amps are grounded at the same point, and also, a single 8 gauge is grounded at the same point too which goes up to my head unit. Perhaps the ground is not good enough with all 3 ring terminals on top of each other. Or...i'll disconnect the wire going to the head unit as it may be picking up noise somehow. I'm quite meticulous with my grounds however and it would be the last thing i'd worry about, but alas, that sort of thing could be exactly the problem. I'll check the battery terminal ground too, which i've done several times.
Is there anyways this could be related to a bad alternator? Bad alternator connections? I noticed the alternator 12v supply line is only like an 8 gauge wire that runs about 6 ft. Should i beef this up to help.
I can't tell you Eva how much I appreciate your knowledge and direction. This board is awesome with so many kind people willing to help. I myself am only 20 but have had a huge passion for electronics, computers and audio since i was about 16. In time hopefully Ill be a veteran like you guys
I hope these posts aren't too lengthy. Anyways, thanks again and i'll figure more stuff out tonight.
Mark
Ya...This is why i was so mistified. But...think about this.
If i power the head unit from an external source...ie my computer power supply, and isolate the ground. Then there is no noise (except 60hz hum from very bad PS). Also powered the head unit again yesterday from our 90 Ranger. With the ranger running, there was no noise whatsover...i doubt the ranger has a great alternator too.
HOWEVER, if i then ground the chassis of the head unit to the car's chassis, then the full noise returns. This shere fact alone tells me that noise comes from grounding the shield of the RCA's to chassis ground. unless the noise is induced into the head unit because it's grounded.
Like i said before. Isolators (transformers) eliminate alot of the noise too. So if the deck had poor power filtering then it should show up regardless of isolators because it would be in the hot signal. Right?
I'll have to check this for sure when i get home. Also, my test setup for the Deck right on amp could have been better. I'm not sure how good the ali clips were on...and a 3ft rca could be used as opposed to a 15ft one. I'll also try another amp too and see what sort of noise i'm getting. I have a soundstream Lil' wonder i could use. I really don't think it is the amp however because every amp i've put in...aside from the Rockford with differential inputs...has made noise.
Soundstream Reference 644s
Soundstream Lil' Wonder
JL e6450 - 6 channel
MTX 6304
MTX 4244
All have made noise...except the Rockford.
I have changed the grounds several times too depending on where the amp was mounted...so it was not that i've used the same bad ground everytime.
I've always dealt with it as best i could by turning gains down and wiring deck ground to Amp ground. This has been enough to make it almost unnoticable with accessories off, but when a load is applied to the alternator (lights, defroster, fan), the ripple increases a fair bit and the noise is very audible at night with the stereo at a lower volume.
Today I will try an alternate grounding point in the trunk for the amp. I have a second amp in the trunk, but it is basically disconnected as i'm troubleshooting this amp alone. It is a class D sub amp. Both amps are grounded at the same point, and also, a single 8 gauge is grounded at the same point too which goes up to my head unit. Perhaps the ground is not good enough with all 3 ring terminals on top of each other. Or...i'll disconnect the wire going to the head unit as it may be picking up noise somehow. I'm quite meticulous with my grounds however and it would be the last thing i'd worry about, but alas, that sort of thing could be exactly the problem. I'll check the battery terminal ground too, which i've done several times.
Is there anyways this could be related to a bad alternator? Bad alternator connections? I noticed the alternator 12v supply line is only like an 8 gauge wire that runs about 6 ft. Should i beef this up to help.
I can't tell you Eva how much I appreciate your knowledge and direction. This board is awesome with so many kind people willing to help. I myself am only 20 but have had a huge passion for electronics, computers and audio since i was about 16. In time hopefully Ill be a veteran like you guys
I hope these posts aren't too lengthy. Anyways, thanks again and i'll figure more stuff out tonight.
Mark
Eva said:
DING DING DING DING!!!
We have a winner. When i connect tip and ground of rca to chassis ground, i get pretty bad noise.
And a very applicable note here. That Noise Rejection circuit i was talking about...it directly adjusts how loud the noise is. Sooo, if i turn it all the way to the left, the noise is lower, and when i turn it the other way, it gets very loud. So this noise rejection system is crap. Not sure how it works.
So what do you suggest? Selling the amp for an alternative is not a problem. I don't mind taking a loss on it. It would still work great for someones subs i think.
This may be my best solution. Or the differential box i speak of, but i'd rather have an amp that works good. Or i can attempt to open the amp, trace the circuit, remove it, and create differential inputs for it. This may be the funnest route, or most troublesome.
It was the amp afterall! I would never of thought a noise rejection system would introduce NOISE!
Thanks EVA and i look forward to your conclusion on this matter.
Find two speaker terminals [2ch amp, or more for 4ch amp] giving a dead short between them. These terminals are the internal ground of the amplifier. Be careful, this works only for non-internally-bridged standard designs [ie: most amplifiers]
Then repeat the test [both tip and ring of the RCA connected to chasis ground] but connect the tip and the ring also to the internal ground. This effectively bypasses any 'noise cancellation' circuit
Is there noise now?
Warning: Results may be a bit catastrophic [oscillation or latching] if you mistake the internal ground of the amplifier and any speaker 'hot' connection. Be aware that speaker 'hot' is not allways the '+' terminal, but the one that does not give a dead short to other terminals
And finally this is a silly question : Have you checked that none of your speaker wires is touching ground permanently or intermitently anywhere in the car?. This not only would produce noise but may be the cause for blown input circuits, clamping diodes or PCB traces. Check that before doing the test. You may also try disconnecting all speaker wires and use an external test speaker [ie: from some home stereo...]. If noise disappears ...
PS: Don't thank me, I have to practice my english
Then repeat the test [both tip and ring of the RCA connected to chasis ground] but connect the tip and the ring also to the internal ground. This effectively bypasses any 'noise cancellation' circuit
Is there noise now?
Warning: Results may be a bit catastrophic [oscillation or latching] if you mistake the internal ground of the amplifier and any speaker 'hot' connection. Be aware that speaker 'hot' is not allways the '+' terminal, but the one that does not give a dead short to other terminals
And finally this is a silly question : Have you checked that none of your speaker wires is touching ground permanently or intermitently anywhere in the car?. This not only would produce noise but may be the cause for blown input circuits, clamping diodes or PCB traces. Check that before doing the test. You may also try disconnecting all speaker wires and use an external test speaker [ie: from some home stereo...]. If noise disappears ...
PS: Don't thank me, I have to practice my english
Hi,
Simplest test for your alternator would seem to be, run the amp off the battery alone, engine off.
What's your head unit grounded to?
I've experienced the stock car head unit "ground" wire having some resistance on it.. 10 or 100 ohm.. can't recall, ground it to chassis as well.
Also if it's alternator induced noise, the pitch of the whine will increase when you step on the gas, usually from having the power cable of your amp too close to it.
Seems to me the simplest test of all, power and ground everything (head unit and amp) directly to a battery, if that works well why doubt the equipment?
Does your battery have a good ground to chassis which isn't the alternator?
Make sure the ground from the battery to the chassis is high grade, consider upgrading that, the 8 gauge from the atlernator to the battery is fine.
Make sure the braided ground strap from the engine block to the chassis is OK as well, could possibly double it up too.
Since it works fine when you jumper it to the ranger, I suspect something along those mentioned lines.
Hope that helps.
Chris
Simplest test for your alternator would seem to be, run the amp off the battery alone, engine off.
What's your head unit grounded to?
I've experienced the stock car head unit "ground" wire having some resistance on it.. 10 or 100 ohm.. can't recall, ground it to chassis as well.
Also if it's alternator induced noise, the pitch of the whine will increase when you step on the gas, usually from having the power cable of your amp too close to it.
Seems to me the simplest test of all, power and ground everything (head unit and amp) directly to a battery, if that works well why doubt the equipment?
Does your battery have a good ground to chassis which isn't the alternator?
Make sure the ground from the battery to the chassis is high grade, consider upgrading that, the 8 gauge from the atlernator to the battery is fine.
Make sure the braided ground strap from the engine block to the chassis is OK as well, could possibly double it up too.
Since it works fine when you jumper it to the ranger, I suspect something along those mentioned lines.
Hope that helps.
Chris
>>Simplest test for your alternator would seem to be, run the amp off the battery alone, engine off.
I'm not really sure what you mean by this, or what it accomplishes.
>>What's your head unit grounded to?
Chassis with 14 gauge ground, also amplifier chassis ground with 8 gauge.
>>Also if it's alternator induced noise, the pitch of the whine will increase when you step on the gas, usually from having the power cable of your amp too close to it.
You can't have the power cable close to the amp? I've never heard this before. The power cable goes into the amp, and is routed there from the bottom sort of. I'm fairly certain it's not induced noise.
>>Seems to me the simplest test of all, power and ground everything (head unit and amp) directly to a battery, if that works well why doubt the equipment?
This should not be required and is usually not recommended. You almost always want to run the amplifier power ground as close as possible. I know the amp is not doing its job. I tried a soundstream amp with the same test eva recommened (short hot and ground of rca and touch to chassis) and there was much much less noise, if any at all.
>>>Does your battery have a good ground to chassis which isn't
the alternator?
Ahhh, the "big three".
I used big 0 gauge massive ground. This could be overkill. I however used welding cable as it was cheaper. Perhaps the quality of the cable is not good enough (the gauge definately is though). I plan on getting 4 gauge and rewiring most of the engine bay.
>>>>Make sure the ground from the battery to the chassis is high grade, consider upgrading that, the 8 gauge from the atlernator to the battery is fine.
Will do.
>>Make sure the braided ground strap from the engine block to the chassis is OK as well, could possibly double it up too.
I redid this one already...good quality 4 gauge connection.
>>>Since it works fine when you jumper it to the ranger, I suspect something along those mentioned lines.
Not sure how you come to this conclusion.
From the diagnosis done by Eva, I believe him and would say that there is something in face wrong with the design of the amp. These things you recommened may help a little, but not to the degree of the noise i'm getting. Thanks for the advice though.
Anyways, thanks.
mark
I'm not really sure what you mean by this, or what it accomplishes.
>>What's your head unit grounded to?
Chassis with 14 gauge ground, also amplifier chassis ground with 8 gauge.
>>Also if it's alternator induced noise, the pitch of the whine will increase when you step on the gas, usually from having the power cable of your amp too close to it.
You can't have the power cable close to the amp? I've never heard this before. The power cable goes into the amp, and is routed there from the bottom sort of. I'm fairly certain it's not induced noise.
>>Seems to me the simplest test of all, power and ground everything (head unit and amp) directly to a battery, if that works well why doubt the equipment?
This should not be required and is usually not recommended. You almost always want to run the amplifier power ground as close as possible. I know the amp is not doing its job. I tried a soundstream amp with the same test eva recommened (short hot and ground of rca and touch to chassis) and there was much much less noise, if any at all.
>>>Does your battery have a good ground to chassis which isn't
the alternator?
Ahhh, the "big three".
I used big 0 gauge massive ground. This could be overkill. I however used welding cable as it was cheaper. Perhaps the quality of the cable is not good enough (the gauge definately is though). I plan on getting 4 gauge and rewiring most of the engine bay.
>>>>Make sure the ground from the battery to the chassis is high grade, consider upgrading that, the 8 gauge from the atlernator to the battery is fine.
Will do.
>>Make sure the braided ground strap from the engine block to the chassis is OK as well, could possibly double it up too.
I redid this one already...good quality 4 gauge connection.
>>>Since it works fine when you jumper it to the ranger, I suspect something along those mentioned lines.
Not sure how you come to this conclusion.
From the diagnosis done by Eva, I believe him and would say that there is something in face wrong with the design of the amp. These things you recommened may help a little, but not to the degree of the noise i'm getting. Thanks for the advice though.
Anyways, thanks.
mark
K I mentioned that as you questioned the alternator being a source of noise a few times. If you run the stereo without the engine running, you eliminate it as a possible source of noise, quick and easy.
Nah I meant close to the alternator, or say spark plug wires, distributor coil, etc. Gotta keep the monster gauge power wire you run from the battery to the amp away from all that, as it's a big source of noise, but it will be in step with the engine rpm if that is the problem.
For the very same noise induction reasons, also have to keep signal wires away from power wires. Cross em if you have to but dont' run them parallel to each other at all. I know you know this though.
You're right about that of course but, it's a means of eliminating any possible ground loops, for a very temporary, low power (no music playing even) test.
You mentioned something about smoking a rockford because of the same problem before? Still get noise on a soundstream.. three amps with the same problem? Makes me wonder..
Lemme get right to the point. I think your'e in denial after not having found the problem yet and are all set to blame the electronics but that's unlikely.
Look what you said here:
"Soundstream Reference 644s
Soundstream Lil' Wonder
JL e6450 - 6 channel
MTX 6304
MTX 4244
All have made noise...except the Rockford."
Is that the same Rockford you sold broken? Kind of hard to smoke a Rockford, something IS wrong and it's not all those amps.
While I've little doubt Eva knows his stuff, I think Eva will agree with me here, He's only giving you a few means of testing to see if it is your amp, but we don't know the internals of your amp. If your chassis has voltage riding on it.... yeah maybe it will buzz when you short the input to it? He also isn't yet satisfied it is the amp, as he's given you another test to perform, but the shear number of amps that have made noise and the smoked rockford tells me right away it just isn't the amp. Not to say whatever is actually the cause of the noise hasn't smoked an input or something either.
I can't say that for sure, but the odds of 4+ amps having the same problem tell me you havent' yet found the cause, so before any more amps burn out from it..
Here's what seems like an excellent link, give it a good read and go from there I think it could put you on the right path.
http://www.termpro.com/articles/noise.html
Also be sure to do both a continuity test from your grounds directly to the negative terminal on the battery, as well as a voltage test between the same points. Try the voltage test with the amp off and then on, you said it's worse with the more things you have turned on, lights, defroster, so turn those on too and do the same test. You could have a short somewhere totally unrelated to the audio system.
Let us know how that went.
I have ran the stereo without the car on. Funny thing, I do get noise. It is very very minimal with no accessories on, but turning the lights on/defroster on/ and heater fan add a decent amount of noise to the stereo. Especially the Rear defrost, possible because it's ground is in the rear.
I do however have the gains maxed...but only to be able to hear drastic changes in noise amounts.
I could try to run all power connections straight to the battery, it would be quite troublesome to just test, but i plan to work on it today for a few hours, so i'll unistall the amp, and try that.
All those amps i listed had noise i think mostly because of ground loops. I had not run a good ground from deck ground to amp ground yet. Doing so in this system has proven quite effective, but not effective enough for this amp. I think had i done it in the other amps, i would've been fine.
I never "smoked" the rockfrod. Eva mentioned that they have diodes to equalize the potential of rca ground to chassis ground. I however ungrounded the deck while the amp was plugged in. This caused the deck to get all it's ground from the amp. This current overflow in the diode simple blew it. It still worked fine, however there was now a direct short from Chassis ground to RCA ground on the amp.
Perhaps the noise is somewhere else. I'm having a helluva time finding it though. I think a solid alternator test may be in order. I think i'll stop at a shop on my way home.
I've read that article as well. Probably several times. I do in fact have the grounds over the bolt. I'll change this today. I never have the problem listed, but regardless...having the best ground for the amp is essential. I'll let you guys know how things turn out today.
I do however have the gains maxed...but only to be able to hear drastic changes in noise amounts.
I could try to run all power connections straight to the battery, it would be quite troublesome to just test, but i plan to work on it today for a few hours, so i'll unistall the amp, and try that.
All those amps i listed had noise i think mostly because of ground loops. I had not run a good ground from deck ground to amp ground yet. Doing so in this system has proven quite effective, but not effective enough for this amp. I think had i done it in the other amps, i would've been fine.
I never "smoked" the rockfrod. Eva mentioned that they have diodes to equalize the potential of rca ground to chassis ground. I however ungrounded the deck while the amp was plugged in. This caused the deck to get all it's ground from the amp. This current overflow in the diode simple blew it. It still worked fine, however there was now a direct short from Chassis ground to RCA ground on the amp.
Perhaps the noise is somewhere else. I'm having a helluva time finding it though. I think a solid alternator test may be in order. I think i'll stop at a shop on my way home.
I've read that article as well. Probably several times. I do in fact have the grounds over the bolt. I'll change this today. I never have the problem listed, but regardless...having the best ground for the amp is essential. I'll let you guys know how things turn out today.
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