my subwoofer is picking up noise?

hi. my name is ben.

i have:

1997 ford escort sport
Kenwood KDC-MP5032
infinity reference 6 1/2
alpine type-r 5x7
kicker zr600 amp
2 4 ohm JL 12w3v3 in a sealed box
each sub gets around 1.5 cubic feet and they are wire to a 2 ohm load bridged on my amp

i have a major problem.
when i turn on my radio my subs do not hit but they do make a very soft low pitched sound that seems to mimic the engine but will not change with the rpms, and if i turn the gain up past the lowest it will go, it makes low short very loud bursts of sound or a very loud constant tone. i noticed if i move or touch the amp short loud bursts of noise occur as well. i tried mounting my amp to the box so it is not touching any metal or near any metal from the car. if i unplug the rca cables the noise will not occur at all. my amp is grounded to one of the large backseat bolts. my power cable is run on the opposite side of the car from my rca cables.

if there is something i am missing or something i can do to eliminate this problem i am very open to suggestions.

oh, and one last not i have not gotten this amp to work with these subs yet. my subs have worked fine with other less powerful amplifier. my other amplifier was a metrik max802

thank you for reading.
-ben-

Your amp is starved for power. You need to make a better ground. Sand away any paint and bolt the ground to the body with a dedicated bolt (not seat bolt). Check your power wire and fuse holder for questionable connections or corrosion. This is a common problem. I have no doubt in my mind that if you remedy your power (ground and power) wiring problems that you will no longer have noise in your subs. Be aware that running your amp as is will damage it.

thank you for your input.
that was what i was suspecting the entire time.
and i may be a novice at the moment, but i have an ear for music so if it doesnt sound good i wont listen to it.

ill try putting in another bolt strictly to the chassis like you said and ill have more info by tomorrow.

cool. let us know what happens.

There is no such thing as an "amp starved for power."  While I agree with the suggestion that a bad ground or other poor quality connection can exacerbate a noise issue, you cannot "starve" an amplifier for power.  The amplifier will draw whatever current it requires from the system.  If the voltage drops low it will simply draw more current until some limit is reached.  If there are bad connections these will heat up and draw more current.  But the amp will draw what it draws,  The ability of the vehicle electrical system to efficiently and effectively supply what it needs without adding noise, and without something breaking, burning up or blowing a fuse is the issue. 

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well i drilled a hole into on of the main chassis and sanded the paint off completely then i bolted the ground to that spot.

it did not change a thing.
i think i am going to try putting in a new set of rca cables to check if they were bad.

if anyone has any other suggestions im still open because i cant think of what could possibly be wrong.

Yes, make sure your RCA cables are good, and make sure you've set your gain properly.  Measure your ground return resistance, and you may also want to ground the head unit to the chassis directly, not using the OEM ground connection in the dash (if you did that.)

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How exactly you quantify the term “starved” is the question. It’s true that with a regulated power supply the out put will remain fairly stable as voltage drops, but this has its limitations. They have broader operating voltage ranges but none the less limited ranges. In the event that you drop below this voltage range the amplifier will stop producing its rated output. If you are dealing with a non regulated power supply then any fluctuation in voltage will affect the output. It is absolutely correct that a drop in voltage will render an increase in current draw coupled with a decrease in performance and efficiency. I wonder? At what point do you start to consider the amp starved for power. Maybe when the noise stops because the amp has gone up in smoke. Or maybe when the decreased performance and noise problem lead you to ask others for advice. You tell me.

You must think past Ohm’s law and realize Kirchhoff’s law.

thanks.

i am going to buy some rca cables tomorrow, and im going to pull out the head unit and ground it to the chassis like you suggested. i have a multimeter, but i need to buy/find some cables for it.

if all goes well ill post the ground return resistance and update how things are working out. (crosses fingers)

speakermakers, you are a smart guy and obviously educated, but please tell me how you think Kirchhoff's laws has anything to do with car audio amplifier noise generation?  I am very familiar with circuit theory.  In fact I used to teach it.  So please tell me how what I posted initially is incorrect, and how ideas like conservation of charge is relevant to noise induction in an amplifier.

Your post is completely out of left field in terms of addressing the OP's question about a noisy system.

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holy ****!

the resistance through my ground to the battery was 4 ohm.
i added a 4 gauge wire from my battery negative and bolted it directly to the chassis and preped the area before attaching it. now the resistance is around .2-.4 ohms.

this should help, but unfortunatly i broke one of the tips off of my current rca cables so i will have to go buy new ones to see if this helped with the noise.

i will let everyone know if it helped later today.

Yes, that should help.  With that high a return resistance you definitely had a ground loop happening.  Check the return resistance in your head unit as well.

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Well thank you for the compliment. Really. As voltage drops current will increase as you pointed out. My point is that the performance of the amplifier suffers as a result. Am I right? Will all types of amps perform the same at 11 or 9 volts as they will at 14.4 or 12volts? Maybe its just semantics, but if there is any change in the amplifiers performance due directly to voltage and or current drop then that amp is starved for power. If an amp can not be starved for power then we are all wasting money on large gauge power wire, right.

Amps with poor ground connections are prone to noise. I base this on 15 years of experience and a theory that I have. Of coarse I could be wrong. The theory that I have is that signal voltage is a direct result of difference in potential between the source and the amp. In the event that the amp or the source has an increased resistance to ground the potential for signal voltage will drop. This will also become worse as current (and therefore resistance) increases. This is exactly the reason that you suggested regrounding the head unit. The voltage drop that is a result of a poor ground to the head unit will cause a decreased signal voltage. This causes the RMS value of the musical content traveling across the RCAs to be too close to the noise floor, resulting in audible noise. On top of all of that an amp that is receiving insufficient voltage will clip with even a moderate input signal, adding to the noises. Ever see an amp that pulses the subs in and out at about one cycle per second because of a bad ground? In an effort to respond to your last post I found myself digging out my MECP advanced study guide (2004 I think) and came across page 24 (Power supply and distribution). If you have this guide sitting around please look this up. I think that by reading this page you will see exactly how I relate Kirchhoff’s laws of voltage and current to this topic. Not that I am absolutely right, but you will see my logic.

Like I said I could be wrong. And I have never taught circuit theory (beyond the bay). If I am wrong, I would be very interested in getting my hands on the documentation that can set me on the correct path.

well that did improve the sound quality of the subs, but there is still a lot of noise.

i guess ill go with regrounding the head unit next. if this doesnt work ill have my friends uncle, who has built and repaired amps for kicker for 10 or more years to take a look at the amp and make sure its working properly.

Unfortunately for you, Kicker (just like Pioneer does on their headunits) puts a fuse in the shield path of the RCA shields. If your ground wire comes loose while the amp is playing, it will cause the fuse to blow. You need to use your ohm meter and check the resistance from the RCA shields to one of the middle speaker connections. This should be 0 ohms. I am betting it is a lot higher than that.

well, my factory ground for the head unit is .2-.3 ohms so i should not have to reground that, unless it would help to reground it anyways?

i am an idiot wrote:

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Unfortunately for you, Kicker (just like Pioneer does on their headunits) puts a fuse in the shield path of the RCA shields. If your ground wire comes loose while the amp is playing, it will cause the fuse to blow. You need to use your ohm meter and check the resistance from the RCA shields to one of the middle speaker connections. This should be 0 ohms. I am betting it is a lot higher than that.

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well i checked that what you explained to me, but it did not give me a reading at all. i wonder if perhaps the connection inside the amp for the rca inputs it bad. if the connection is loose i would assume that would be the reason for all of the random noise, and it would explain the why when i tap or touch the amp the subs make noise.

can you tell me what are the info for the fuse. volts? amps?

or would it be perfectly ok to replace it with a resistor?

It will be perfectly OK to replace it with the resistor.  

great.

thanks for your help.
i hope this solves my problem :)

It will.   If you are removing the board and the transistors are stuck to the heatsink, you will need to use a pair of pliers to remove them.  Be careful that you do not damage the insulating tape that they are stuck to.  Grab a transistor with the pliers and rotate the transistor.  Do not rock the poiers you may cut through the tape.

ok well i now have the circuit board removed and in the process of taking this amp apart i noticed a couple things.

on of the capacitors looks kind of rough.


i found the fuse you were talking about.
instead of a TH on the top it just has a 1 and it is blue.

could you give me a link to a proper resistor so i can reference it. i do not want to put the wrong resistor

oops this was the picture i was trying to post.