help! alternator whine (and other electrical buzzing when boat is off) is making me crazy!

[justgary]

@shawndoggy- Please post a sketch of your sources, amps, and EQ including audio signal paths and power paths (plus the engine power).  I'm kind of confused about how everything is connected.  Nothing too elaborate, but seeing a block diagram would help.

Is your noise a simple hum, fuzz, or digital noise?  You called it alternator whine, but it can't be that with the engine off.  Can you post a short audio file that demonstrates it?

[shawndoggy]

1 hour ago, justgary said:

@shawndoggy- Please post a sketch of your sources, amps, and EQ including audio signal paths and power paths (plus the engine power).  I'm kind of confused about how everything is connected.  Nothing too elaborate, but seeing a block diagram would help.

Is your noise a simple hum, fuzz, or digital noise?  You called it alternator whine, but it can't be that with the engine off.  Can you post a short audio file that demonstrates it?

Gary,

I'm not a ee, so forgive my hacked out diagram:

I will post up a few clips of the noise later on tonight.

You are correct that my initial complaint was alt wine, but I've got a constant buzzing/hum/crackle/static too, the pitch of which changes when the blower (or other accessories) is turned on.

[justgary]

11 minutes ago, shawndoggy said:

Gary,

I'm not a ee, so forgive my hacked out diagram:

I will post up a few clips of the noise later on tonight.

You are correct that my initial complaint was alt wine, but I've got a constant buzzing/hum/crackle/static too, the pitch of which changes when the blower (or other accessories) is turned on.

Good job.

Pull each RCA plug one at a time and short pin and shield together to see if the sound changes.  Also try jumping the pin to the case ground on that item using a wire. Finally, jumper across your fuses one by one to make sure one isn't funky.  A needle nose plier will work.

[shawndoggy]

1 minute ago, justgary said:

Good job.

Pull each RCA plug one at a time and short pin and shield together to see if the sound changes.  Also try jumping the pin to the case ground on that item using a wire. Finally, jumper across your fuses one by one to make sure one isn't funky.  A needle nose plier will work.

"pin to the case ground on that item"... what is "that item"?

I.e. I pull RCA from EQ and then short the pin to the EQ (i.e. touch pin to EQ) or to the amp (jumper wire from pin back to amp)?

What am I trying to discover with this test?

[Slurpee]

2 minutes ago, justgary said:

 Finally, jumper across your fuses one by one to make sure one isn't funky.  A needle nose plier will work.

Be warned that fuses are there for a reason. Jumping them puts equipment and cable assemblies at risk. Better practice if possible is to use a multimeter to measure resistance across the fuse. Should be a short. 

[shawndoggy]

2 minutes ago, Slurpee said:

Be warned that fuses are there for a reason. Jumping them puts equipment and cable assemblies at risk. Better practice if possible is to use a multimeter to measure resistance across the fuse. Should be a short. 

That sounds smarter.

What do I set my free harbor freight mm to before I stick the probes in there, and what do I want the number to be?

[justgary]

5 minutes ago, shawndoggy said:

"pin to the case ground on that item"... what is "that item"?

I.e. I pull RCA from EQ and then short the pin to the EQ (i.e. touch pin to EQ) or to the amp (jumper wire from pin back to amp)?

What am I trying to discover with this test?

Yes, that.  You are trying to discover what is causing the noise.  Grounding inputs might help find it.

[justgary]

6 minutes ago, Slurpee said:

Be warned that fuses are there for a reason. Jumping them puts equipment and cable assemblies at risk. Better practice if possible is to use a multimeter to measure resistance across the fuse. Should be a short. 

Obviously, but he isn't having an issue with excess power draw, and he only needs to jump the fuse for a few seconds to listen.  An ohm meter will not find a dynamic problem.

[shawndoggy]

1 minute ago, justgary said:

Yes, that.  You are trying to discover what is causing the noise.  Grounding inputs might help find it.

so you are saying "both"?  I'm confused... 

[shawndoggy]

1 minute ago, justgary said:

Obviously, but he isn't having an issue with excess power draw, and he only needs to jump the fuse for a few seconds to listen.  An ohm meter will not find a dynamic problem.

Let's say (a) I'm cautious, and (b) I have an infinite number of fuses.  Would I achieve the same result by pulling all fuses and replacing with new ones?

[justgary]

8 minutes ago, shawndoggy said:

so you are saying "both"?  I'm confused... 

Left and right together or individually.

[shawndoggy]

Just now, justgary said:

Left and right together or individually.

No ... talk to me like a kindergartener....

I pull left RCA from eq, short to eq chassis.  I do same with right rca.  Then I take the end of the cable that I pulled from the eq and put a long jumper on it and short to the amp case too or no?  OR do I put the RCAs back in the EQ and pull from and short to amp case?

[Slurpee]

20 minutes ago, shawndoggy said:

That sounds smarter.

What do I set my free harbor freight mm to before I stick the probes in there, and what do I want the number to be?

Plug black into the bottom port. Red into the middle. Twist the dial to 200 just above the yellow on/off switch. You want to see something really close to zero. 

[justgary]

8 minutes ago, shawndoggy said:

Let's say (a) I'm cautious, and (b) I have an infinite number of fuses.  Would I achieve the same result by pulling all fuses and replacing with new ones?

Yes.  But a short jump across each fuse will not hurt.  You need to know that the fuse and holder aren't causing an issue.

[Slurpee]

I’ll also add that an easy test is get a nice quality long rca cable. Replace one of your installed cables with it. Unplug all the rest from the EQ. Unplug the second tower RCA from the amp and eq. We just want one shielded cable physically separated from everything sus connecting the Eq and amp. Drape it across the cabin. Don’t let it near any power cables. Does the one pair of amps getting a signal still him with the fan. 

My ‘01 Was wired like granddaddy’s. No noise. AFTER I moved my cheaper rca cables from running next to battery bus cables. 

[shawndoggy]

13 minutes ago, Slurpee said:

I’ll also add that an easy test is get a nice quality long rca cable. Replace one of your installed cables with it. Unplug all the rest from the EQ. Unplug the second tower RCA from the amp and eq. We just want one shielded cable physically separated from everything sus connecting the Eq and amp. Drape it across the cabin. Don’t let it near any power cables. Does the one pair of amps getting a signal still him with the fan. 

My ‘01 Was wired like granddaddy’s. No noise. AFTER I moved my cheaper rca cables from running next to battery bus cables. 

I have a brand new rca and will give this a shot. I’m 99% sure I tried this a couple of years ago, but worth running all the new tests. 

[shawndoggy]

Test 1: Remove MBT-RX inputs from EQ: noise still present (left unplugged for remainder of tests)

Test 2: Remove tower RCA from EQ: noise still present

Test 3: Remove tower RCA (still unplugged from EQ) from tower amp: noise gone(!)

Test 4: Remove all RCAs from EQ, drape one new rca from eq to tower amp through cabin, avoiding proximity to power sources to the extent possible: noise is back :-(

Test 5: plug SNI-1 ground loop isolator back into EQ, plug draped RCA to isolator: noise is back but significantly diminished.

Test 6: pull one of the draped rca plugs from back of eq, ground plug to eq chassis: noise is back, gets worse when I ground to a screw on the eq.

[shawndoggy]

Test 7: using Iphone lightning cable to headphone jack adapter, plug phone directly into tower amp: low level high pitch hum is back, however sound does not change when blower is turned on.

test 8: remove RCA from tower amp (confirm NO hum if no RCA input), plug one end of same RCA into each amp input: low level high pitch hum is back, sound does not change when blower is turned on.

[conclusion: tower amp must have some sort of signal sensing circuit in rcas?]

[shawndoggy]

Test 9: ground to shield side of rcas: sound gets worse when blower is running.

[shawndoggy]

this is the noise I'm dealing with.

[shawndoggy]

Test 10: pulled and replaced fuses with brand new never used spares in tower and cabin speaker amps.  No change in noise (it's still there)

[Slurpee]

1 hour ago, shawndoggy said:

[conclusion: tower amp must have some sort of signal sensing circuit in rcas?]

Kinda sorta. They are amplifiers. They sense signals and amplify them. I’m not being rude there. That is actually the high level explanation. I’m intrigued. What are the make and model of your rca cables?

I don’t know your amp well. Is there a signal range switch? Like high and low? What’s your Gain knob at as well. 

tests 7&8 are good info. 

Edited July 21, 2021 by Slurpee

[shawndoggy]

3 minutes ago, Slurpee said:

Kinda sorta. They are amplifiers. They sense signals and amplify them. I’m not being rude there. That is actually the high level explanation. I’m intrigued. What are the make and model of your rca cables?

The draped cable was an amazon basics.  

My main RCAs in the boat are Kicker KI46 (two sets, 8 rcas total. / two unused (were running to black box HU)).  These are new in the last two weeks.

I previously was running the wetsounds RCAs (prior to two weeks ago).

[shawndoggy]

Gains are set a tic above min.  The higher the gain the worse the sound.  crossover is set to high pass x1 about 90Hz

[shawndoggy]

out of desperation, would it be worth switching the KS300.2 to my sub and the HD750/1 to the towers?  My sub is 3ohm impedance so I'd give something up on the bass front, but right now I've been mostly leaving the stereo off because it's driving me crazy.