Help with DB651 or blown amp not sure..

Odin2347

Hey guys I bought 2 pairs of polk db651 from crutchfield and they sounded great hooked up to my 4 ch JVC amp(50 watts rms x4) but I feel like an idiot after what happened last night. I noticed one pair of speaker connections from the amp came undone and I thought my car was off but my GF had put the key in without telling me as I was trying to screw the pair of speaker wires back in. There was a loud noise that came from all 4 speakers and now it makes a mess of terrible static and whine that goes away and they sound normal when I turn the volume up. It makes the noise even with the volume off! any ideas? thanks

Odin2347

yep its the same amp and it changes with the engine rpm. i also noticed it makes no noise with the key turned to accessory but if i turn it again it makes noise and it also makes noise with the engine on

catch22atplay

Sounds like the rca plugs or cable maybe. Unplug them then plug em back in. Just make sure the power is off this time. And since you were rehooking up wires ensure the rca cables are away from the power wire and ground. I'd start with that.

Odin2347

i tried plugging the rcas in and out and it still makes the whine. hmm I had this amp installed at a local shop and they ran the rcas along with the power on the same side

catch22atplay

Power and rca's on the same side eew.

I'm just hoping it's not the amp or some other expensive part. I would assume you're using balanced rca cables ie twisted wire pairs. If you got an mulimeter i'd disconnect them and check ohms from center pin to outer. See if they're both the same. That can at least eliminate a faulty rca cable. Cause it almost sounds like the outer wire may be broken or partially broken at the plug. A very common occurrence. Other than that i'm out of ideas. Except to say make sure all speaker wires are in or on the terminal and no loose strands are touching anything else.

All the above i've caused or have had happen before. And it's a good thing i work on electronics and can solder quite well.

Odin2347

with the RCA's to the amp disconnected theres no whine/noise. So i assume its the amp that's messed up?

catch22atplay

No it could mean a bad rca cable/plug as well. Try 1 rca by itself. Then try the other by itself. See if the noise goes away. Make sure the one not hooked up is isolated from anything else. Still hoping it's an rca issue here. If there's no noise with one of the left or the right connected by itself it may be the rca cable where it's soldered to the plug. See what results you get by trying that. Last check i can think of before hitting up an installer.

Since there was no noise with rca's disconnected it's either the rca's or the input stage of the amp i'd think. If you find an offending plug, say it's the right one. You could try the left rca in the right rca in of the amp. That would test the input stage of the amp. Basically process of elimination.

Odin2347

Thanks i appreciate your help:cool:! I just tried powering it on with 1 RCA connected and then powering off trying another etc..and they all seem to make noise

Odin2347

now that i think about it..there's been a slight whine at different RPM ever since I got my 2nd amp put in. but it was very slight and only noticeable when the volume was low so i didn't really think anything of it. but now it's 100x worse

Odin2347

it's a pioneer AVIC F700BT. I was just reading about the "pico" fuse on them and how when i plugged the speaker wire into the amp i could've blown this fuse? apparently its $85 to fix

arun1963

I'm not an expert but I think its probably alternator noise. Just change the RCA's. You don't have to go expensive here.

Pio hu's are known to be susceptible to noise issues. I don't think you'd blow the pico fuse by connecting the speakers. You'd have to be hot swapping the rca's to do this. That's connecting or disconnecting the rca cables while the hu is on.

Odin2347

well i'm pretty sure it was the pico fuse i wrapped some wire around the RCA shields by the headunit and then grounded it to a screw on the headunit...NO MORE NOISE! thanks for your help guys

catch22atplay

Damn just read about that pico fuse on the pioneer unit. They sound like a **** to replace. So you either hot swapped an rca or when you redid the speaker wire 1 stray strand hit the rca plug and pop went the fuse. Figured it might be an rca issue. Didn't know about those rca fuses though.

I think i'll be taping up all my rca connections from now on. Especially as my HU probably has the exact same thing. And no more hot swapping rca plugs for me.