One seriously pissed off speaker whine

[JoshC 10+ year member]

So today i pulled my 750.1 from my f150 and installed an MTX 5ch. Now this amp has been repaired but it was done by a well know and skilled tech.

After install i had the whine, since then i have :

Ran new ground strait from HU to battery, no change

Tryed a 2nd know good set of RCA's (RF brand) on opposite side of power wire, no change

Grounded my RCA inputs to HU, no change

I looked at my amp ground earlier and it was fine, going to check it again though.(paint removed and tapped into body w/proper terminal)

Anyone have any other ideas? Its a mtx thunder 4405 on a sony HU, music sounds good threw speakers it just has the background whine. Whine does change pitch with RPMs if that matters.

The speakers have been on HU power there whole lives and sound fine no whine. First time on an amp, there infinity reference coaxials. Is it possible that there was a mistake made during the repair or is this strictly a install issue? I have no experience building amplifiers with input lines, just power supply's.

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[basswiigee2fix]

i dont know going through same thing....so far ive changed almost every wire, hu and amp trying to find my mysterious whine ... also installed ground loop isolators all to no avail....

 

[JoshC 10+ year member]

i dont know going through same thing....so far ive changed almost every wire, hu and amp trying to find my mysterious whine ... also installed ground loop isolators all to no avail....

Im starting to believe its the amp itself, going to try a 2ch tomorrow on my highs and see what i come up with.

 

[wew lad 5,000+ posts]

you have two amps? it is very possible for one amps bad ground, or bad board, to induce noise through backfeed into your system

 

[JoshC 10+ year member]

you have two amps? it is very possible for one amps bad ground, or bad board, to induce noise through backfeed into your system

No its a single 5ch amp setup, the sub sounded great and the speakers honestly sounded really good just a mild whine in the background. Im going to remove the 5ch amp and install a 2ch in its place. Just to see if its the wiring on the speakers causing the issue or the amp itself.

 

[wew lad 5,000+ posts]

No its a single 5ch amp setup, the sub sounded great and the speakers honestly sounded really good just a mild whine in the background. Im going to remove the 5ch amp and install a 2ch in its place. Just to see if its the wiring on the speakers causing the issue or the amp itself.

how long is your ground and where is it located? does the hiss still happen with the front, rear, or sub RCAs unplugged? if the rca's are unplugged and you still get noise it is a problem with the amp or its wiring.

could be a bad alternator but it isnt usually.

 

[JoshC 10+ year member]

how long is your ground and where is it located? does the hiss still happen with the front, rear, or sub RCAs unplugged? if the rca's are unplugged and you still get noise it is a problem with the amp or its wiring.

Trucks only had an amp for ~3 months and it was only bass until today. I never had a single issue with my sub, using the same amp location and wiring for the 5ch. But no the hiss is only on the ch.1&2(no 3 or 4) but sub was playing, and the whine goes away when you unplugg the RCAs. Again when i pull the RCA on either ch. 1 or 2 the whine goes away. This means its an install complication not my amp?

 

[wew lad 5,000+ posts]

Trucks only had an amp for ~3 months and it was only bass until today. I never had a single issue with my sub, using the same amp location and wiring for the 5ch. But no the hiss is only on the ch.1&2(no 3 or 4) but sub was playing, and the whine goes away when you unplugg the RCAs. Again when i pull the RCA on either ch. 1 or 2 the whine goes away. This means its an install complication not my amp?

means a couple things, you could be getting negative power running through your rca's to your headunit, but grounding the RCA shield at the amp to a good ground would make a difference in the hiss.

you wont generally hear hiss through subs because its a higher frequency, unless you have really bad noise in the system then you can definitely get sub 'hiss/hum.'

the amp could still be bad, it may have an open ground to rca shield in the amp. its kinda complicated at that point but yes it could be the amp.

i would still verify the ground, and its length. if moving the ground makes no difference you can rule usually rule it out at the amp side - your negative ground from body to battery and alternator should be checked and ruled out as well.

 

[JoshC 10+ year member]

means a couple things, you could be getting negative power running through your rca's to your headunit, but grounding the RCA shield at the amp to a good ground would make a difference in the hiss.
you wont generally hear hiss through subs because its a higher frequency, unless you have really bad noise in the system then you can definitely get sub 'hiss/hum.'

the amp could still be bad, it may have an open ground to rca shield in the amp. its kinda complicated at that point but yes it could be the amp.

i would still verify the ground, and its length. if moving the ground makes no difference you can rule usually rule it out at the amp side - your negative ground from body to battery and alternator should be checked and ruled out as well.

So i moved the ground wire over a bit, noise remains. This is after i grounded the HU inputs again and then grounded the amp inputs to the amps NEG terminal. Even with both grounded the noise remains. I have not verified any wiring under the hood though, thats my next check.

 

[wew lad 5,000+ posts]

where exactly is your ground in relation to the chassis of your car? the first pic looks like its actually on a seat, ideally you want to get it grounded to a large piece of the main chassis of the car that has the least amount of bends, joining of metals, etc.

grounding the rca shields will usually make a difference in the case of a ground loop, it could be a bad headunit or amp at this point although it could be a ground loop still. it's a long process but you'll figure it out by elimination eventually.

how long is your amp ground wire? that wire terminal looks pretty oxidized, you probably know this but be sure to sand the bottom of the terminal as well if it gets like that

 

[hispls 5,000+ posts]

I've auditioned some low end head units that are noisy once you amp them. Sometimes that sort of noise can be caused by weak/failing battery or alternator. I'd suspect the heat unit myself. If you unplug the RCA's from the back of the head unit and still hear the noise it's likely that is the problem. Lastly, Have you tried to lower the gain on the amp? Sometimes just turning down the gain will make that sort of thing inaudible/harmless.

 

[JoshC 10+ year member]

I've auditioned some low end head units that are noisy once you amp them. Sometimes that sort of noise can be caused by weak/failing battery or alternator. I'd suspect the heat unit myself. If you unplug the RCA's from the back of the head unit and still hear the noise it's likely that is the problem. Lastly, Have you tried to lower the gain on the amp? Sometimes just turning down the gain will make that sort of thing inaudible/harmless.

No the whine goes away when the RCA is pulled, i just played with all over gain/crossover settings. No change, whine is still very much so present.

The battery is new, i can get the alternator checked.

 

[hispls 5,000+ posts]

No the whine goes away when the RCA is pulled, i just played with all over gain/crossover settings. No change, whine is still very much so present.
The battery is new, i can get the alternator checked.

I'd bet a new HU would fix you up. Go down to Best Buy, buy one, test it and then return it after you've tested.

 

[JoshC 10+ year member]

I'd bet a new HU would fix you up. Go down to Best Buy, buy one, test it and then return it after you've tested.

That's pretty much were in at with it, although my neighbor stopped by last night and dropped off a rf t600-4 to use as a tester. If it's still whining with that amp too I'll be looking into new hu

 

[wew lad 5,000+ posts]

i have an old broken headunit (well it works just usb is broken) laying around just to test with, its handy to have because the plugs are the same so its not difficult to swap it in and out.

definitely leaning more towards a faulty piece of equipment at this point.