#1704582 - 09/12/09 08:26 AM
Tips on tackling ALT whine
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LanBlau
Optidriven
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Registered: 02/21/01
Posts: 3377
Loc: Lawrence, KS USA
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So I replaced my old Lanzar Opti100.4 (Zed) with a new Korean Opti4x400d. Both amps bridged to run my fronts. Old amp 180x2, new one 360x2 gain limited to 250x2 (gains are pretty low).
Old amp was quiet - new amp has alt noise - relatively loud coming from the tweeters. Nothing else changed about the install. I just pulled the old and put in the new.
The noise is always the same volume, ie when I'm playing it loud I don't really notice the noise, but at low-moderate volumes it is obvious. And it changes frequency with the RPM's.
It's a little bit of a task to pull my enclosure so I can get to the amp so I'd like to have a laundry list of possible fixes when I take the time to tear into it.
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#1705362 - 09/14/09 11:05 AM
Re: Tips on tackling ALT whine
[Re: LanBlau]
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keep_hope_alive
in another life, i'm a serial killer
SD I Power Bombed the Undertaker
Registered: 04/24/07
Posts: 13370
Loc: Quad Cities, IL
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old != new
zed amps != korean amps
the new amp will have more distortion and more noise than the older version. it also has cheaper parts and poorer quality.
what that means is that the old amp was designed to eliminate the ground loop that already existed, and the new amp is not.
start with grounds. head unit ground, processor grounds, amp grounds. try grounding RCA shields, and cases. etc.
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#1705555 - 09/14/09 04:28 PM
Re: Tips on tackling ALT whine
[Re: keep_hope_alive]
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BillK1002
SD Ralph Wiggum
Registered: 03/29/09
Posts: 78
Loc: Baltimore
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I read the sticky on grounding multiple amps, It states that the amps should be grounded 1/2 to 1 in apart.
Should you not ground multiple amps to the same bolt??????
How important is the length of the amplifiers ground wire?
When grounding the RCA shields on the back of a head unit.
Can you tie this ground to the chassis ground for the head unit? I'm using the rear mounting bolt for the head unit in the middle of the heat sink for a chassis ground along with the black ground wire and still have alternator wine.
Do I need to ground all 6 of my RCA outputs, or are they usually tied together??
Thanks
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#1705754 - 09/15/09 07:13 AM
Re: Tips on tackling ALT whine
[Re: BillK1002]
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imtfox
Ban Stick Swinga
Registered: 08/05/99
Posts: 25777
Loc: Omaha, NE
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The problem with grounding amps at the same spot occurs when you have a very high draw amp and a much smaller draw amp connected to the same ground point. The large draw amplifier can cause interference with the smaller amp by modulating the ground through that point.
This usually only occurs on a ground point that is the minimum sufficiency for both connections. If this type of problem is present, it can be easily solved simply by unstacking the grounds and moving them about 2-3" apart.
When solving alternator whine, you have to remember that you want the ground potential to be equal throughout the system to avoid ground current flowing where it shouldn't be (the RCA shields). You can have the greatest head unit ground and a crummy amp ground and have noise. You can have a great amp ground but a crummy head unit ground and have noise. Oddly enough, you can have a crappy head unit ground and a crappy amp ground and have NO noise at all.
If you get through all of the troubleshooting steps (including running a temporary set of RCAs) and you still think you need to ground the RCA shields (or you have a Pioneer head unit with the micro fuse issue), you should only need to ground one RCA shield in the bunch. The signal grounds should already be tied together internally.
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