Stereo Troubleshooting

[lindz34]

Hey Lads,

Having a bit of trouble with my stereo at the moment.

Stereo consists of:

Pioneer head unit

alpine type s splits

alpine type s 6"'s

audioline 4 channel amp

JL audio mono amp

2 x JL audio 12" subs.

Anyway, have been getting interference of sorts through the speakers, so i mixed and matched rca inputs on the channel amp to no effect.

Then i ran each channel on the channel amp one at a time & nailed it down to the rear right channel, where even with the other channels unplugged, would distribute this "interference" through the other speakers. I've checked the wiring for that rear right speaker & the rca for it which are fine.

Just to elimate the head unit, i connected my ipod directly to the amp & it still did it when it was plugged into that rear right channel.

So i came to the conclusion that it is the amp that is stuffed. (it's quite old so seems logical that it's met its maker )

But before i go out & spend a small fortune on a new channel amp, is there anything else i can try?

Was thinking about connecting a different speaker in place of the rear right just to 100% make sure it's not the speaker picking up noise.

Any pointers would be appreciated

Thanks guys

[Hadouken]

Are you running you're power cable next to you're audio cable? If so that could be causing the interference.

[lindz34]

nah nah, stereo has been in there for close to a year & I haven't made any of those n00bie mistakes haha

[Hadouken]

Ah, I see. Then youre right and it is most likely the amp. If youre mates have a amp you can always borrow one off of them. Thatll give you a indication whether youre right.

[Carbon 34]

dont overlook external crossovers , they can pick up noise as well

most likely a broken solder joint on the RCA to board connection . that audioline isnt the best and most likely not braced inside on the RCA jacks

is it a whine ?

depending on rpm ?

or just static ?

hiss ?

that can narrow it down faster?

could be a stray stand of wire off the speaker or tensel lead on the speaker as well. touching ground ever so slightly but sounds like you checked that already.

even dirty battery connections create noise

[lindz34]

The crossovers for my splits are behind the door trims & sealed off so dont think it would be them, plus the noise is only audible when the rear right channel is active.

Yeah the audioline amp is just something i picked up off a mate when i first did the stereo in my old commodore, always planned on upgrading it when i got the skyline but then that never happened haha

Do you think grounding the suspect rca channel would help? had to do a similar thing on my head unit as it succumbed to pioneers dreaded "pico fuse" blowing.

its just static, not constant, comes in and out randomly & is more noticable when there is "less" going on in the music if that makes sense?

(doesn't alter with rpm & doesnt changed whether the engine is on or off)

checked the speaker wire for that channel, literally runs off the rear right speaker straight to the amp & its fine so can't be that.

battery is pretty average but the noise isnt through all speakers/subs so i dont think it would be that?

at the moment i have all rca's plugged in but the fader on my head unit set to as far forward as possible so its only the front speakers that are active - no noise. (amp on 4 channel mode)

also tried it with the fader in the middle & the dodgy channel unplugged (as well as the one next to it for the other rear speaker) & there is no noise, but interestingly i flipped it to 2 channel mode & the noise was there, & when all 4 rca's are plugged in it is worse on 2 channel mode than 4 channel.

oh and the amp is "U.S audio" not audioline - sorry

doubt that makes a difference as it's still a dodgy brand haha

[Carbon 34]

its a blue and silver us audio amp, they have solder joint issues on the main boards for the RCA'S , i have 4 of them sitting here and had to fix a few already. the amp is a good one besides that , cheap and powerful for the price

the parts inside are actually a name brand design on the old ones they just went cheap on the solder joint.for the RCA they tended to crack , easy fix 2 min job once the cover is off

think you confirmed it by using the 2-4channel switch, and ipod direct if you used a new cable for that ?

its worth fixing , its a DYI job if you know how to solder and turn a screw , let me know if you get stuck I can open up my old amps to show you where to look if needed

And I have a spare parts board off another 4 channel US Audio if you need parts 55watts x 4 model the other 3 are 75x 4 and a 5 channel model all going up for sale soon, mine are custom painted and have spacers to make them a meter long as one amp

[lindz34]

yep, sure is the blue & silver one with a clear front section that shows the board !

its the 75rms x 4 version !

i'm fine using a soldering iron, just never cracked open an amp before, so if i have trouble locating where the joint is i'll shoot you a pm.

i'm going to guess it's right where the inputs are?

i'm not sure what you mean by ipod direct, but what i meant when i did the test plugging my ipod straight into the amp instead of through the head unit (like i would normally have it) is just using a 3.5mm (headphone jack) to red & white rca & plugged that into the rca inputs on the amp.

it is a pretty decent amp, matches my alpine speakers almost perfectly, it's just a tad on the big side so hard to find somewhere to mount it, it currently sits on that little step in the boot of r34's & hangs over quite a bit but is held there by the sub boxes haha

[Carbon 34]

yep thought so

unscrew the end bit that the rca is on, a few screws hold the rca, and speaker jacks to the steel bit. and a few hex heads hold the rest to the end of the heatsink, you will see the RCA solder joint , if you get a light and rock it gentle you will see the joint is cracked most likely and the pin /.solder moves. resolder any you think are broken , 1 pin is positive the other is ground on each RCA jack left and right.

dont overheat the board when soldering but its pretty robust in that area . and the bigger the glob the better the job doesnt apply here..lol

test the amp without the end cap just in case, works , fit end cap back on

fails, test jiggle RCA while the end is off, just use care not to touch anything inside ,

still no go then test jiggle the 2-4 channel switch as well ? might be dirty and need contact cleaner while amp is off power

let me know if you want a photo of the amp board , I have one out of the case completely since I cut/milled the case in 3 parts for spacers on the other amps to hide the wires

[lindz34]

Alright, sounds pretty straight forward, i take it i just have to be very careful & take my time.

A photo would help a lot actually, no rush as i'll probably have a go at fixing it on the weekend so just whenever you have some time to upload one, that'd be awesome !

Thanks so much for all your help & time mate, really appreciate it!

[Carbon 34]

the blue dots are the solder joints on the RCA, as you can see the black wire on this board, this amp fried and was returned for repair and I got it free from the distributor to cut the heat sink into wire cover end caps for my old amps. the black wire was soldered on by the repair center due to a burned trace its not there on yours . they have a few other jumper wires soldered on as well. it was a functional amp just repaired that I gutted if you need any parts off it

hope that helps, if not I'll be parting with my amps cheap when I get off my butt to sell them. mine look differenent now. 3 custom matching ones,, 4 x 75w , 990 watts max each total, they ran 1.3 ohms all day long bridged

and I have a unmolested 5 channel model, 1100 watts max I was saving for my garage but would sell cheap too.

Edited November 26, 2011 by Carbon 34