I'm getting high pitch hum (upper midrange freq) and a warble sound coming from the sub when everything is on.

1. Amp is a Zed Mini

2. front stage amp is a sundown 100.4

3. Sven LOC for the stock H/U

The high pitch hiss comes on when the amps turn on. I don't get any distortion from the speaker run by the sundown. When I turn the music up, the sub still has the high pitch noise and a warble sound that kinda goes with the music. I've check the RCA and have used two different sets to make sure. I even connected another sub to the system and get the same horrible distortion. Is this an amp problem or is there something wrong with the electrical system trying to run this amp off the stock H/U? Does the stock H/U lack the ability to run a sub? This OEM system came with an amp and sub. I did not use the wires on the back of the H/U that are assigned to the sub stage. I connected the front and rear channels to the LOC to get the signal to the Zed amp. I need some serious help. I want to get this done correctly ASAP and I'm running out of ideas. Thanks guys.

Check the ground.

I've moved the ground twice and had the same result. I actually have the sundown and and the Zed on the same ground right now. No noise from the Sundown, but noise from the Zed.

Does the sound go away if you unplug the RCAs from the sub amp? If it does.. trace the source backwards.

No noise with the RCA's out. NOw what. Not sure how to go backwards from here.

It is either your headunit or rca's. Most likely the headunit and most likely it has a shit ground.

*just remembered you are using a LOC.

unplug the rca's from the loc and see if the noise goes away. If it does it is LOC or upstream. I would reground the LOC as well and see if that helps, a temporary ground straight to the battery would tell you. If it is neither of those, unplug the speaker leads from the LOC and see if it is generating the noise on its own.

Well, After much work, I figured out the problem. The Amp is bad. I switch it with another Mini and everything worked great. We will have to send the amp back to see what the problem is.

I DID have noise even after I unplugged the RCA's. I was wrong on my previous post. Anyone know what the problem with the amp might be? Thanks.

Could be lots of things, I would guess a shorted trace on the power supply though.

I dont mean to jack, but my amp has pretty much the same problem the OP described. Except, when I unplug the Rca's the sound remains. Ive moved the ground 3 times and went straight to the battery before with no change. Is it just a defect in the amp. It a hifonics, 1606d, and I realize that may be part of the problem. Its not a big issue, because its not audible when the car is on, unless youre outside and the trunk is popped.

Bad component in the amp. I've got issues with my PG Son of Frank right now that are quite similar. Noise with the RCAs unplugged. Gonna send it to PG for a refurb in the next couple months.