Low fluctuating hum?

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Mar 21, 2021 | 10:23 PM

Jamesvan

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From: Iowa

Low fluctuating hum?

I need some help. 2007 Electra glide.I just got done installing a Sony HU ss pn4.1000d amp on top of HU and a ss pn2.350 on a hogtunes 2ch inner faring bracket. I’m running the rear tour pak speakers off the 2.350 and running the fairing and lowers of the 4.1000 with y splitters(running 6 Polk mm652s).I’m running two sets of 8awg wire to the amps grounding to the battery. I’m getting a low fluctuating hum at low volume. I’m also getting a pop when I turn volume from 0 to 1, if I turn the HU off or the volume to 0 the hum goes away. I’ve also tried to disconnect the rca’s and move the amps away from each other and off the HU but get no change. Thoughts?

Mar 22, 2021 | 12:02 AM

hamah

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From: Vancouver, BC

What do you mean by "fluctuating hum"? Do you mean the hum increases/decreases in pitch as the motor RPMs increase/decrease or does the noise also happen with the motor off? If it only happens with the motor running that sounds like alternator whine and it's likely due to poor grounds or a ground loop. There are a few other threads ongoing right now on that issue here and here although neither has been resolved (or at least the OP hasn't updated us on the resolution).

With the RCAs disconnected you say you still get the hum? That's a bit confusing to me as you also say the hum goes away with the HU off or volume set to zero. Are the RCAs disconnected at the amps or at the HU when you are still getting this hum? Or did you just disconnect the RCAs to move the amps and they are always connected when you get the hum?

A few things to try:

1 why are you grounding the amps at the battery? Try grounding the amps to the frame (use as short a ground lead as possible) and see if there is any difference.
2 keep the RCA cables and speaker leads as far from the power leads as possible
3 try isolating the noise source by disconnecting 1 amp at a time by removing the RCA preamp out on the HU (also remove the fuse on the amp you have disconnected). See if you still get the noise with both amps individually.

Last edited by hamah; Mar 22, 2021 at 03:13 AM.

Mar 22, 2021 | 03:29 PM

Jamesvan

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From: Iowa

The hum sounds like it’s coming through the speakers at low volume and it fades in and out with no volume change. I can’t really hear it with the bike running just when its off. After getting home from work I completely disconnected the rca’s from the HU and amps and the hum stops. Could it possibly be cheap rca cables?

Mar 22, 2021 | 05:28 PM

hamah

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From: Vancouver, BC

It sounds like ground noise to me and if you're getting it through both amps it's likely not both RCA cables. Still, it's possible, try swapping at least 1 of them out and see. Did you try moving the amp grounds from the battery to the frame? It's worth trying and the safe/correct way to ground the amps anyway. You could also try a ground loop isolator (GLI) of the type Bates recommended in this thread. None of these are expensive options to try.

EDIT: I know you mentioned the hum goes away when you turn the volume to zero, turn the HU off, or remove the RCA cables and that the hum is not audible with the engine running. Does the hum always stay at a low volume (while fading in and out) or does it get louder as you increase the volume?

Last edited by hamah; Mar 22, 2021 at 06:01 PM.

Mar 23, 2021 | 09:18 AM

Jamesvan

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From: Iowa

I can only hear the hum at low volume when the bike is off. When I start to increase the volume I can’t hear it anymore. I haven’t tried to move the ground wires yet I’ve got them ram under the tank. Maybe I could extend them to reach a good chassis ground?

Mar 23, 2021 | 10:35 AM

teedoff65

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Joined: Jul 2017

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From: High Point, NC.

Quote:

Originally Posted by Jamesvan

Ground to the battery isn't the root cause. 90%of the guys here run their grounds to the battery, myself included and I dont have a hum. If you want to take the time to rule that out, no harm, but I would check all my other connections first. Speaker wires coming in and out of the amp, RCA's as well. Make sure nothing is touching other metal parts.

Also check your fuse in the wiring to the battery. There is anther post of a similar issue here the last couple days. His wires going into the fuse was frayed or something.

Mar 23, 2021 | 04:10 PM

BlackPearl#1

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From: Black River Falls, WI.

Leave your ground at the battery.
My bet is you will fix this by spending some time swapping rca’s to a good set.
If you have a quality set, put them in place of the others one at a time to find your weakest link. Or simply plug and unplug them one set at a time. Cheap RCAs are quite often the culprit. Good luck, hope this helps.
Kris