amp installed, noise troubleshoot?

Just the facts: -1989 S10 Blazer, 4.3L V6 with standard alternator -all battery cables have been upgraded with 2-gauge welding cable. Crimped, silver-soldered, heatshrunk. -HU: older AIWA CDMP3 job. Only has 2 RCAs on the back. These have been jumpered via several "Y" cables to 3 RCAs - 2 for 4-channel seperates amp, 1 for mono sub amp. (I dislike using Y-cables, but when you have to, you have to. -All RCA are run to the HU, and run down the center of the vehicle- more than 18" away from power. -Seperates Amp: MTX TD75.4. Brand new, from Crutchfield on Friday. Installed today. -Power supply: 2-GA from the battery, through firewall, grommets and fuses in the obvious places. This lead goes to the rear of truck via driver's side near door. At the amp, a 18" stinger of 8-GA is soldered to the 2-GA to go supply the amp. 30A fuse on this lead. Soldered on a bifurcated terminal for the amp connection. -Ground: used the supplied 4-GA lead. Soldered on a bifurcated terminal for the amp connection. Soldered on a large-gauge ring terminal to the other end. As instructed in the install guide, I drilled a hole in the body (floorboard), sanded to bare metal, and through-bolted. I went one better, using 3/8-16 stainless bolt and nyloc, and using electrician's grease (Eezox? Can't recall the name- it's made for this task). Problem: Electrical noise with volume at "0" on the HU: -key in accessory, engine off (duh, and/or hola?): no noise, "0-bits" noise floor. The goal for all installs. -key in "run", engine not running: electrical noise. Obviously coupled from the running electrical system, not sure what circuit. Hard to describe it- obviously not alternator whine, more along the sound one might hear from a flourescent bulb with a bad ballast -key in "run", engine running: classic, monstrous alternator whine. I bought a couple of GLIs from Radio Shack for a "quick fix". They help but don't fix the problem. When I was testing the noise, I noticed that if I remove the white (left?) RCAs at the amp, as soon as the shield breaks contact, noise is gone- each channel carries some of the noise. If I remove both, the noise is completely gone. Haven't gotten to adjusting the gains yet, but the noise is there with the gains all the way down. Possible issue: I think the issue might be the 3 y cables at the HU. I need to test around that, but it's too late tonight. If this ends up being the issue I will replace the HU, as I am not married to it, it's 15+ years old, time for replacement anyway. I saw a Power Acoustix brand (may be mis-remembering) at Pep Boys for $100, with a DVD display. Yes, I know it's not up to competition vehicle use, or good enough to be put in your car. I don't care- this is a working/married man's truck, being built for mild expedition use and DD, kept inexpensive while keeping my hacker side busy when not at work. I have plans, but not thousands of dollars to waste on this like I did my car when I was 20... Also, might be that I need to run the ground to the battery. Along that line- have a 2-ga welding cable built to run from the grounding point of the amp (other side of the body, under the 3/8 bolt I installed today) to the ground terminal of the battery. Possible issue, but I dout it: I have heavy-gauge (2/0) disconnects for the battery fore and aft. These are for winch and jump-start use. There's a very remote chance they might be acting as an "antenna" to couple noise in, but I REALLY doubt it as they'd likely be damped by the battery. Likewise, I have the sub-amp RCA flaked out to the rear of the truck awaiting arrival/install of the sub amp... but I have the terminals insulated with electrical tape, highly doubtful this is the issue either).. Thougts?"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

Disconnect all speaker wires from the 4 channel amp, and using an ohm meter make sure none of those wires are shorted to ground. Grounding one of the Non-Bridged wires will result in problems just as you are having.

Alrighty, will try that. Tomorrow. Too darn late right now, and I still need to get the truck put together to drive tomorrow. See any problems with grounding the amp to the body without going to the battery, as presently built?"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

What is the HU? buy a sony, pioneer , kenwood or alpine HU. you will be better off in the long run.

cheap HU are usually the problem with ghosts and demons.

unhook rca cords from HU.

start car see if noise is still there. if it still is, it aint the HU.

if its still there, unhook rca cords from amp. it it still makes noise, it aint rca cords.

did you upgrade the "Big Thrree" as covered in this website.

I personally would run amp grounds to the frame.

if you end up suspecting the HU, try unplugging the antenna from the HU and see if that helps.

yuk

quiet rural missouri, near KC.

If your system moves you physically and not emotionally, you have wasted your money.

LOL... jusr read your post closer and saw you are using an Awia HU.

years I bought the original Aiwa head unit that was the first stereo on the market to play mp3 files.

it sounded ok untill i added amplifiers. then i was chasing the same gremlins you are. never again

if you dont have a quality head unit, all the amplifiers will do is amplify the problems.

yuk

quiet rural missouri, near KC.

If your system moves you physically and not emotionally, you have wasted your money.

You know, come to think- there's one wire I haven't upgraded- the ALT to BATT. Well, I should probably rephrase: I did replace the OEM bit with another cable, years ago. I made it with 8-GA, ring terminals on each end, crimped and soldered. Yes, that's probably just fine- but I will find a hunk of 4-GA and make a longer line so I can move it off of the battery to a Blue Sea terminal in accord with my battery relocation plans. (HU is a Aiwa CDC-x504MP, BTW)"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

Didn't feel like yanking the seat out tonight- it's 25 degrees outside, which considering I live in a semi-tropical climate, is friggin' COLD!!! (yeah, I used three !s there. Sue me. It's COLD, man!!!) Anywho- I did want to get some questions answered about this problem, so I donned my parka (again, don't laugh, Northerners, and don't ask why I own a parka...) and went outside with a headlight and a plan. .. see, the dash, I can sit in the passenger seat and close the door, and rip apart in something near comfort since I'm out of the wind. Found the problem- a really good example of what turned out to be a really bad idea. I bought my RCAs at Oreilly Auto parts, since they have a very liberal return policy since I am friends with the staff, plus they're close to home. Bought three RCAs, one of them having been out-of-package, loose on the rack. Guess which one was bad? Yup, that one. So, a good example of how occasionally being penny wise can be pound foolish. Honestly, that's no huge deal. I can do most of the run without pulling the carpet up. What will be difficult, however, is the next bit. A lesson I had to re-learn from my time half a lifetime ago as a pro installer: NEVER. Tape. The RCAs to the speaker leads. In fact, don't tape any of it together... because, you know- you're inviting Murphy to the party- and that guy's a dick! So now I have to "derun" for lack of a better word, all my signal: RCAs and output wires. At least I can tape a piece of paracord to it to enable this to go MUCH easier than the initial run. But since I had basically already made my speaker wires to length to tuck into the back of the radio cavity (because MAN, they didn't leave ANY extra room back there in 1989!), I am likely going to have to lengthen them a bit now. I'm only running 16GA wire from the amp to the speaker factory wires in the dash. While yes, I am sure I am going to lose a little street cred for not running new copper the entire way, I can live with that. There's no difference to be had in the final scheme of things to go that way for DD use... and the fact that I am DD'ing a truck I have built the entire drivetrain and suspension by hand more than makes up for it! (Especially once I have the Merc 5-cyl turbodiesel purring under the hood!)"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

[QUOTE=itsyuk]

What is the HU? buy a sony, pioneer , kenwood or alpine HU. you will be better off in the long run.

cheap HU are usually the problem with ghosts and demons.

unhook rca cords from HU.

start car see if noise is still there. if it still is, it aint the HU.

if its still there, unhook rca cords from amp. it it still makes noise, it aint rca cords.

did you upgrade the "Big Thrree" as covered in this website.

I personally would run amp grounds to the frame.

if you end up suspecting the HU, try unplugging the antenna from the HU and see if that helps.

[/QUOTT Thanks for refreshing me memory- I did as you suggested: -no change when ANT unplugged. -noise remained when RCA unplugged @ stereo -noise went away when RCA unplugged @ amp (as mentioned yesterday) Which obviously shows an RCA problem. Or possibly the Y problem I suspected. Remove them one at a time from the unplugged (@ stereo) RCA. No change. The future-expansion, 17' RCA was visibly different from the other two. Plugged it into the HU- no noise (as it's not plugged in at the other end this would have been peculiar indeed had the noise returned!) OK, still have the other two RCA plugged into the amp (via two RatShack GLIs). Plug in the one plugged into front channel- clear tunes issue forth. Check in all no/run conditions, no noise. Other one, noise is back bigtime. I did find when wrapping things up that one of the GLIs was pinched between the amp and the seat rail. However, the noise already existed yesterday before I installed said seat or the GLI. This points squarely at the RCA. ... Which gets into my last post. I will yank it and return it this weekend, weather permitting. While I am at this, might just go ahead and dropship 3 new quality RCA from Crutchfield and return all the ones I bought from Oreilly."Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"

sounds like your getting closer.

see if you can ditch the GLI units and progress toward making the system work without them.

try to make sure the rca cables arent running parallel to power wires of the stereo or anything else for that matter.

yuk

quiet rural missouri, near KC.

If your system moves you physically and not emotionally, you have wasted your money.

Progress? I have a noise floor of 0 near as I can tell now. GLI units are gone (thought I was clear above, sorry), and I know from my day job (computer network engineer) that signal should stay away from power, or if it must cross, it should do so at right angle and get away from the power ASAP. Merely "not being parallel" can still lead to inductive coupling if they're not seperated quickly. I ordered new RCAs from Crutchfield, they'll be here tomorrow. Of course, they're twice as long as I need, but better too long than too short!"Always listen to experts. They'll tell you what can't be done, and why. Then do it. - Robert A. Heinlein"