background noise linked to rpms
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=106508
Printed Date: May 20, 2024 at 1:50 PM
Topic: background noise linked to rpms
Posted By: grant2207
Subject: background noise linked to rpms
Date Posted: August 01, 2008 at 12:27 PM
I know this is in here somewhere but i cant find it...sorry for the over coverage of this topic. i just installed two subs (pioneer 10' 1000 watt) and an amplifier (crunch 1400 2-channel) in my jeep grand cherokee with the amp under the rear seats. the subs will be in a sealed enclosure but i just have them sitting on my trunk space floor right now to test the connections. when i turned my car on i hear a buzz coming from the subs, and it adjusts with my rps, more rpms = higher pitch buzz. i have the rca and power cables running on opposite sides, BUT the power cable is run over the top of my engine (zip tied to some hoses) and it crosses the rca cable when it comes threw the firewall near my gas pedal. the rca goes to the left side and the power cable runs to the right. they are not in too close of contact so i dont think that is my problem. i have a feeling it is because the power cable is running over the engine. if anyone has a suggestion of why my problems are occuring please help me out. im no physics major......
Replies:
Posted By: i am an idiot
Date Posted: August 01, 2008 at 1:28 PM
Posted By: grant2207
Date Posted: August 01, 2008 at 2:04 PM
i also have the remote wire running to the head unit directly along side the rca cable. could this effect the buzz? also, i was fiddling with the amp and also noticed that when i turn up the level control from the 2 volts to the max (5 volts) the noise was greatly decreased, but did not go away. I thought it should be at 2 volts because the manual of my sony head unit said that the pre-amp put out 2 volts.
Posted By: DYohn
Date Posted: August 01, 2008 at 2:25 PM
1. Check the link kindly posted above and see if it might apply in your case. 2. Engine whine is commonly cause by bad grounds. Read the grounding sticky posts and measure your ground return resistance. 3. Your gain is set improperly. Read the "How to set your gain" post and follow those instructions. ------------- Support the12volt.com
Posted By: grant2207
Date Posted: August 01, 2008 at 2:44 PM
i checked the setup on that link you gave me. the ohms matched so i dont think that is the cause of my trouble.
Posted By: haemphyst
Date Posted: August 01, 2008 at 8:47 PM
Crap amp. Does the noise go away when you disconnect either end of the RCA cables? If not, then it is a crap amp, and you need a big, fat noise filter. In THIS case, a cap may help, but not for power supply stiffening, as they are often sold for.
If it does go away, then you have a ground loop, and you need to better ground all of your components, from the alternator back... ALL devices, including alternator ground, battery ground, engine ground (this is the big three...) deck, and amplifier. Is your amp grounded to a seat bolt? Bad mojo, there. Find a better place. Check the condition of your battery; go to your local autoparts store and have it load tested. A bad cell can reduce the filtering efficacy of the battery.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: i am an idiot
Date Posted: August 01, 2008 at 8:53 PM
Please describe in detail, "The ohms matched" And just being curious, what kind of radio are you using?
Posted By: twistedp
Date Posted: August 01, 2008 at 9:17 PM
i agree with haemphyst. crap amp. you shouldn't be hearing such pronounced alternator whine from a subwoofer that's made to produce low frequencies regardless of where or how you routed the wires. the only exception i could see are defective power wires, bad ground, or bad rca cables. perform the tests prescribed above to rule everything else out. ------------- Twisted Performance
Posted By: i am an idiot
Date Posted: August 01, 2008 at 9:30 PM
I would move the power cable so it is not running over your engine.
Posted By: haemphyst
Date Posted: August 01, 2008 at 11:17 PM
I might add that if the amplifer has the low-pass crossover inside it, and you are using that low-pass crossover, as the frequency of the whine goes up, it will be more and more effectively filtered. (Meaning you'll hear less and less noise as the engine RPMs go up.) This makes me believe even a bit more that the issue is within the amplifer, not the RCAs.
While moving the power wire from the route you are presently using is not necessarily a BAD idea, I cannot believe that the issue lies there. The current within the power cable FAR exceeds any magnetic interference that might be induced into the power cable from it's present route. Even if there were, the power supply would very effectively filter it out.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: grant2207
Date Posted: August 02, 2008 at 5:50 PM
haemphyst wrote:
Crap amp. Does the noise go away when you disconnect either end of the RCA cables? If not, then it is a crap amp, and you need a big, fat noise filter. In THIS case, a cap may help, but not for power supply stiffening, as they are often sold for.
If it does go away, then you have a ground loop, and you need to better ground all of your components, from the alternator back... ALL devices, including alternator ground, battery ground, engine ground (this is the big three...) deck, and amplifier. Is your amp grounded to a seat bolt? Bad mojo, there. Find a better place. Check the condition of your battery; go to your local autoparts store and have it load tested. A bad cell can reduce the filtering efficacy of the battery.
just like to say that this post made me feel very confident that i wasnt wasting my time trying to find a better ground spot. thank you. the whine goes away when i disconnect the rca from the amp itself. my ground was the connection between the back of the seat hinge and the floor (the seats fold down so there is a large metal plate, for stabilities sake i would assume). i think the problem lies in the paint that is lightly sprayed over the body of the car that is keeping the seat metal from being in direct contact with the body. i think i found a spot BUT, it is not a direct contact, it is a piece welded to the car body. My next question is wether the weld would alow proper electrical travel? i used the stock radio grounding, and i have not changed anything as far as the big three... for those who asked, i am using a sony head unit, i forget the model but it is the cheapest ($75) one with the aux connection. and by the ohms matching, i followed the tutorial for checking the rca ground and it said to touch the headunit case and the rca sheeth and see if the ohm output matched and it did, at about .5 ohms i believe... also, i was showing my dad the sound it made to see if he had anything to add to my research (he has a somewhat random wealth of knowlege, so it never hurts to ask) and it didnt happen. i tried a few times and the sound wasnt there.....but this morning when i went to work it was. idk
Posted By: DYohn
Date Posted: August 02, 2008 at 6:02 PM
Check the return resistance at your proposed ground spot. ------------- Support the12volt.com
Posted By: i am an idiot
Date Posted: August 02, 2008 at 7:21 PM
Have you tried turning the gains of the amp all the way down?
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