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Old 25th September 2012, 12:52 PM   #11
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I made a set of RCA mute plugs and connected them to the amp - no noise.. so that should rule out the amp. Also it is not the cross overs or the speakers/wiring because I took a extra full range speaker I had and connected a short run of wire to test each channel with the HU and RCAs connected - got noise in that speaker also. So I am looking at the HU as the problem at this point.

I have some more 0 gauge wire and a capacitor in the mail right now.. I will try a big 3 upgrade and installing a cap to quiet down the alternator this weekend.

Ill update soon.
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Old 27th September 2012, 10:14 PM   #12
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Here is something that did work, but I'm not sure if I like doing it this way..

When I tuned my amp I turned the EQ to flat (0s across the board) and turned the volume up to 27/35 and then increased my gains until I hit my 150v that I am sending to each component set. To get to this level I had to turn the gains up to about 7/10 and then tweeked my EQ down slightly. Never UP is what I was told.

Well today I turned the gains down until the noise went away. Then to get more volume I cranked up my EQs and guess what.. the noise is gone. So with the gains set on 3.5/10 the only way to get my power output is to turn the EQ settings up to about +9db on each EQ band and then adjust down from there.

Think this is ok? I dont know if cranking up the EQ like that is good for the sound quality or the amp.. then again I dont know if it will hurt anything.. might just be amping the signal before it gets to the amp.

I just got in a capacitor and some 0 gauge wire today so I am tempted to turn the gains back up and try a big 3 upgrade and a cap to see if that does anything.

What are your thoughts?

btw.. Gains = amp, volume = HU, EQ = HU
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Old 28th September 2012, 12:16 AM   #13
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150v to each component?

If it sounds OK, it's not doing any harm.

There is generally a fusible link or fuse between the battery and the alternator. If you upgrade and bypass that safety device, you could put the vehicle at risk for an electrical fire.
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Old 28th September 2012, 12:50 AM   #14
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I was getting 150v @4 ohm to each component set when I tuned my amp and was getting this noise.. I have not had a chance to see what it is putting out now.

The issue is.. Ive always been told the right way to tune an amp is turn the HU up with the EQs down and increase the gain until I hit the target voltage. That = noise

The way I have gotten around the noise is to turn the gain down and the EQ up.. which I have been told is not the right way. So not sure what to do.
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Old 28th September 2012, 01:28 AM   #15
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There is a problem with your meter if it read 150v AC at the speakers. The amp doesn't have enough rail voltage to produce 150v of AC.

The EQ is to correct for poor frequency response of the system as a whole. You only use it if you need to make corrections (most systems need corrections). The settings depend on where the corrections are needed.

JL amps are the only ones that I know of that have a target voltage. That's because they adjust the maximum output level depending on the load. This is not a feature of many other amps.

Even with JL amps, this generally doesn't work well for most users.

There is no foolproof way to set the gains for most systems because music varies so greatly. Ideally, you would set the gains so that the amplifiers are never driven into clipping. That requires huge amounts of power or a listener/user that doesn't require significant volume.

For most people, the gains are best set so that the amps don't clip on most music with the volume at about 75%. Again, this isn't fool-proof because increasing the bass boost or playing a track with a lot of bass could allow the amps to be driven to clipping at less than 75% of the volume.

When dealing with equipment that's not working properly (as it appears is the case with your head unit), you can't go by rules set for perfect systems.
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Old 28th September 2012, 01:40 AM   #16
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You are correct.. I did not mean 150v.. I mean 150w.

"When dealing with equipment that's not working properly (as it appears is the case with your head unit), you can't go by rules set for perfect systems"

^ this is the key for me it sounds like.. I think I have two options at this point: 1. live with the system the way it is with my work around (EQ boost/lower gains) or 2. continue to look for the REAL solution and tune the amp the "normal" way.

Thanks for your insight PB.
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Old 28th September 2012, 03:30 AM   #17
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When i run into headunits that have noisy RCA output, its usually a ground fuse on the headunit mainboard RCA plugs that pop.
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Old 28th September 2012, 01:49 PM   #18
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Quote:
Originally Posted by mbates14 View Post
When i run into headunits that have noisy RCA output, its usually a ground fuse on the headunit mainboard RCA plugs that pop.
as in, on the circuit board itself? I have soldering skills but I dont know how to read a board unless it is pretty obvious. Should I open up the case and see if I can spot any blown fuses on the board?
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Old 28th September 2012, 03:13 PM   #19
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Sorry if I missed this information, but what is it for a HU?
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Old 29th September 2012, 05:15 PM   #20
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Quote:
Originally Posted by mpednault View Post
Sorry if I missed this information, but what is it for a HU?
The head unit is a Kenwood DNX7140
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