background noise linked to rpms

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grant2207

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Joined: July 08, 2008

Location: United States

Posted: August 01, 2008 at 12:27 PM / IP Logged

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......

i am an idiot

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Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 01, 2008 at 1:28 PM / IP Logged

http://bcae1.com/images/rca/temporaryrcashieldrepair.html

grant2207

Member - Posts: 24

Joined: July 08, 2008

Location: United States

Posted: August 01, 2008 at 2:04 PM / IP Logged

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.

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: August 01, 2008 at 2:25 PM / IP Logged

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.

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grant2207

Member - Posts: 24

Joined: July 08, 2008

Location: United States

Posted: August 01, 2008 at 2:44 PM / IP Logged

i checked the setup on that link you gave me. the ohms matched so i dont think that is the cause of my trouble.

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: August 01, 2008 at 8:47 PM / IP Logged

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.

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."

i am an idiot

Platinum - Posts: 13,670

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 01, 2008 at 8:53 PM / IP Logged

Please describe in detail, "The ohms matched" And just being curious, what kind of radio are you using?

twistedp

Member - Posts: 38

Joined: July 10, 2008

Location: Texas, United States

Posted: August 01, 2008 at 9:17 PM / IP Logged

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

i am an idiot

Platinum - Posts: 13,670

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 01, 2008 at 9:30 PM / IP Logged

I would move the power cable so it is not running over your engine.

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: August 01, 2008 at 11:17 PM / IP Logged

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.

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."

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