amp whine question
 

Hi All,

just want to see if anyone have any thoughts on helping me identify potential cause of my issue.

my ap2 has a pioneer head unit, alpine amp and alpine speaker set up. (installed by previous owner so i dont know the details behind the install, when i first got the caught both amp and speaker fuse were blown lol)

i noticed a whine as the RPM climbs, if it's idle in non radio mode (aux/cd...etc), it gives a slight hum as well through the speaker

i did some research it seems like it's a grounding issue but im having a hard time trying to find out where they grounded the amp (amp is located in back of passenger seat), there's a cable that runs to the battery positive terminal but i dont see where they mounted the negative ground, what are some common spots where people mount the amp grounds?

Thanks!

I'd check the grounding points on the engine and chassis, first. Tight and clean. One is behind the head.

You'll prolly need to remove the radio from the console, to find where the radio/amp is grounded.

Good luck!

Audible whine changing pitch with RPM is usually caused by a ground loop. Wouldn't hurt to find out where the amp is grounded so you know it's solidly connected to a point of the car with no other grounds.

If nothing else a ground loop isolator might help, assuming the amp input is part of the ground loop. This thing goes between the amp and headunit and should block any ground loop noise on the amp input:
https://cimg7.ibsrv.net/gimg/www.s2k...27819f24f4.png

There's apparently a tiny fuse ("pico fuse") in Pioneer headunits that is famous for causing this problem:
See this thread.

ahh i have a feeling this is exactly what's causing my issue , i searched pico fuse on youtube same noise. just wondering if i just get that RCA filter posted by @mikeyds would solve the issue?

looks like the pico fuse would require me to take apart the headunit to resolder shiet, thats just too much work, i probably rather just buy a new deck


edit: ok it is the pico fuse that was blown, causes for it to blow can be someone hot swapping RCAs without powering down the amp and Head unit first. it's a common pioneer deck problem.

i worked around the issue by following this video
in case this video ever goes offline for some reason, here's the work around

1. wrap the RCA inputs behind your head unit with speaker wire , (wrap it on the outer ring so when you plug it in it's not inside the hole, it's outside but will be secured
2. ground the other end of the wire
​​​​​​​3. Test to see if issue is fixed

This is the first I've heard of any audio unit using this "fuse" arrangement on their RCA connections. Car, home, or studio. Did you "hot swap" your RCA lines? Or did the fuse pop on its own?

Off course this fix bypasses the pico fuse's function. Not sure why Pioneer added this feature to its units. What risks do you run bypassing it?

Thanks!

bought the car used , when i first got it, head unit and amp fuse was already blown so something happened there, not sure how previous owner blew the pico fuse or if it just went out on its own. just wanted to call out you will blow the pico fuse if you hot swap rca connections so people dont make that mistake

definitely lots of complain of people about pioneer using the pico fuse, for anyone that's interested, you can google and find a ton of results

in terms of the risk of doing the work around, maybe someone more knowledgeable can chime in , i did read it in the youtube comment but cant recall. the pico fuse acted as the ground when that blew, you start getting all the whines , the bypass basically grounds it again hence removing the whine.

Makes sense, now. The "fuse" is the connection from the amp's output to the RCA connector's outer ground. So, when the fuse pops, you lose the connection to this ground point --- thus making a huge ground loop (via some other path to ground). Which prolly has resistance, due to longer electrical path length.

Problem is... I've never heard of a unit (car or home) which was damaged --- when its pre-amp output or input were not connected to a source load or the connections removed with unit turned on. Only when the amplifier's output is not connected to a load. Even high-end, old-school Class "A," hi-fi pre-amps, like Perreaux.

:ponder:

Wow! would've never guessed it could've been a fuse on the RCA output. How cool! ....well not for OP...

The isolator I posted wouldn't have worked, I'd guess nothing would come out of the channel with the blown fuse, there'd have been no path to ground for the signal.

Just worth a mention, make sure your power wires are not run right next to the RCAs. This has been known to cause the whine as well.