Audio Interference Help


zackattack

Junior Member
Jan 20, 2016
3
0
Pennsylvania
Hello,

I have a 1996 Ford Bronco and I'm just about to the end with the stereo interference. I must have read every thread on the internet and I still can't get relief. My problem is unique in that I have no HU; I just use a bluetooth module plugged into my amp. I'll list my specs, troubleshooting I've already done and what the issue is. I hope I can get some help.

Specs:

- Front and Rear JL audo C3-650 components with tweeters mounted within 8" of midbass
- JL JX 400/4D powering the components
- 12 GA speaker wire to and from amp and x-overs
- JL MBT-RX bluetooth module plugged directly into amp input
- 120 amp powermaster alternator
- Optima red top starter battery (brand new)
- 2/0 cables to replace all engine and battery grounds
- 2/0 cables to replace battery + and alt cabling
- 4 - 8ga ground straps bolted to frame and car body to replace clip on straps
- 2/0 power wire from battery to 150 amp circuit breaker that feeds line to amplifier
- 2/0 power wire from circuit breaker to dist block and from block to amp
- Ground to amp rings directly to batt negative 0 ohm, and is secure; MBT-RX ground shares location
- Remote lead is from Ignition +
- Every set of speaker wires and power cables are ran in separate conduit

Troubleshooting:

- Alt output is clean DC
- Attached separate ground from alt housing to batt -
- Rang power cable to ground @ infinite resistance
- Rang all grounds and 0 ohms to batt -
- Rang ignition remote to ground @ infinite
- Amp RCA shield rings to ground 0 ohms
- AMP + to ground with amp hooked up but not powered rings thru but resistance rapidly increases until open circuit is reached (about 3 seconds)
- Swapping meter leads will do opposite (negative lead on power and positive lead on ground will start at open and decrease resistance to ring. Not sure the amp design as JL doesn't give a schematic so I can't tell where diodes are to test.

Issue:

- Amp getting power and remote signal but not connected to MBT-RX bluetooth module I'm getting alternator whine, this increases 10x when the electric fan turns on and is almost unbearable
- With BT connected and music playing I get zero alt whine but do get what I believe to be ignition interference; steady low ticking at zero volume that doesn't increase with volume. Due to my exhaust system I can't tell if it varies with throttle.
- With BT connected and volume up I get a distortion kind of similar to trying to tune a ham radio while music is playing. It is noticeable but not terrible and I cannot hear the ticking with volume up.
- If I trip the circuit breaker manually I get no alt whine, so I know it's coming thru the amplifier and not radiated into the speakers/wires
- If I remove the BT module by pulling power fuse or disconnecting RCA's there is no affect and Alt whine is still present as long as amp has power
- I am ordering an ignition capacitor as mine is original and I think may be failing due to age. It's 8$ so no big deal here to see if it can eliminate the distortion and ticking while music is playing.
- My biggest issue is that with no music, BT can be connected but without pressing play on my tablet, I get alt whine that sounds like a turbo spooling and when the fan kicks on it sounds like a diesel turbo. Sometimes I just want to drive without listening to anything and in order to do this I have to play a song and turn the vol all the way down which is kind of ridiculous.

Has anyone ran into an issue like this before? I would assume with Alt whine I should hear with music playing as well as without? What is causing the Alt whine? I have everything grounded, brand new cables secure with no paint or corrosion, used silver solder for all the lugs, brand new battery, 1 year old alt and no RCAs that run near anything that could induce RFI/EFI. There's only 2 grounds for Amp and BT module and they share it. The amp is mounted to the car body by rubber grommets and insulated screw holders, there is no 2nd case ground from the amp. I am lost, please help.
 
OP
Z

zackattack

Junior Member
Jan 20, 2016
3
0
Pennsylvania
Is there a way to test the Amp itself for a ground loop? Like the amp itself is defective and causing this? What If I put a diode on the supply, I know a lot of people use a cap as a filter but i don't have room nor do I want that. A diode would be smaller...
 

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