Mostly finished with my audio upgrade, weird behavior from sub amp

[rusty_shackleford]

Today, my t-harness arrived and I had to attach my own RCA ends because they were apparently out of stock when I ordered it. Been a while since I soldered, but I was pleased with the result after a few practice runs. Fished the wires and connected to the waiting amp, Kenwood X501-1, and sub, KFC-XW800F. I wanted to test everything without a sub box just to see if it lives, the box shipped late unfortunately and wont arrive until next Tuesday.

This is a second hand amp, everything else is brand new. Found it for $30 at a pawn shop. The amp powered on, before I connected the speaker I checked voltage at the amp to set the gain on a 50 Hz test tone, then connected the sub and played a few songs at about half volume. Not bad for no box, but when I turned off the ignition and opened the driver door, I started hearing a strange bump about 1 Hz. The screen and dash are turned off, I look behind at the sub on the back seat and I can see the cone of the sub bouncing with the thumping noise, I pulled the RCA plugs from the amp and it stopped, the power light went out. I plugged the red back and it started again, but with the white end it stayed off.

Any Ideas whats causing this? RCA cables were braided and foil shielded, ran from the amp to behind the glove box along the passenger door sills before the t-harness junction. I don't mind replacing this amp but concerned its an issue with the receiver.

I have also installed front door speakers and tweeters if it matters, Hertz k170 component set.

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[rallyshark]

Sounds like a case of noise in the RCAs combined with using signal sense turn on. NEVER use signal sensing turn on with these trucks. The truck sends voltage through the speaker wires, even when truck is off, which will then turn on the amps when it isn't supposed. Every time you open a door, or anything else will cause the amp to turn on. Not good for the battery either. You need to run a dedicated turn on wire to fuse 3 or 6. I used fuse 3 myself.

I'm not sure if the noise will go away when the dedicated turn on wire is used when the truck is actually on, but it will go away when it is off for sure. It won't make any noise, if the amp isn't on. That's my 2 cents.

 

[rusty_shackleford]

Sounds like a case of noise in the RCAs combined with using signal sense turn on. NEVER use signal sensing turn on with these trucks. The truck sends voltage through the speaker wires, even when truck is off, which will then turn on the amps when it isn't supposed. Every time you open a door, or anything else will cause the amp to turn on. Not good for the battery either. You need to run a dedicated turn on wire to fuse 3 or 6. I used fuse 3 myself.

I'm not sure if the noise will go away when the dedicated turn on wire is used when the truck is actually on, but it will go away when it is off for sure. It won't make any noise, if the amp isn't on. That's my 2 cents.

I have the supplies and planned to install the remote wire this weekend, but the amp doesn’t have a way to switch off signal sense. Is it just automatic with a signal wire on the terminal?

 

[rallyshark]

I have the supplies and planned to install the remote wire this weekend, but the amp doesn’t have a way to switch off signal sense. Is it just automatic with a signal wire on the terminal?

It's hard to say without knowing what amp you have. Some amps do switch automatically, but I would think there'd be a switch/setting somewhere on the amp?

 

[rusty_shackleford]

It's hard to say without knowing what amp you have. Some amps do switch automatically, but I would think there'd be a switch/setting somewhere on the amp?

It’s a Kenwood x501-1. No switches present, I would attempt to disable it permanently on the boards but I can’t find any source for a schematic of this thing. Just tried jumping 12v from batt+ to the remote and removing it, it stayed on anyway. Probably why the newer variants have a switch to turn it off lol

 

[rallyshark]

That's a bummer for sure. It might be worth it to change sub amp in your case. I know it's more money, but sometimes, that's what you have to do if you want things to be "right". Especially, given the hybrid's tendency to eat 12v batteries in many cases. FWIW, I've been running a fairly stout 5 channel with separate DSP for going on 2 years now, and still have the original battery with zero issues. I do have a dedicated turn on though.

 

[phoneguyinpgh]

You can block the DC signal from the factory amp with one of these.
https://www.amazon.com/Conext-Link-Channel-Isolator-Suppressor/dp/B082GV15Y1/ref=sr_1_1?sr=8-1

 

[rusty_shackleford]

You can block the DC signal from the factory amp with one of these.
https://www.amazon.com/Conext-Link-Channel-Isolator-Suppressor/dp/B082GV15Y1/ref=sr_1_1?sr=8-1

Thanks! I don’t have the b&o setup in my truck, but I can still see the value in these. I opted to order a LOC and I’ll power it off the fuse 6 tap, then it shouldn’t matter if my amp uses signal sense. May end up buying a 6 channel amp with built in DSP anyway, the more I read.

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