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Hiss in stereo (suggestions?)


noquams

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I have three JL HD amps with a Audio Control Matrix and the stock Rockford Fosgate HU and remotes. At low volume I am getting a considerable amount of hissing from all the speakers. I initially thought it may be the bluetooth but even get the hiss with rca to 3.5 jack. I have tried low and high voltage settings on the amps with only minor differences between the setting. Any suggests and to what I should look into?

Thanks in advance

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Have you tried reducing the gains out of the matrix? Usually hiss (like steady background his that stays at a constant volume and can be overcome when the volume is turned up) is because the gains are too high somewhere.

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I have three JL HD amps with a Audio Control Matrix and the stock Rockford Fosgate HU and remotes. At low volume I am getting a considerable amount of hissing from all the speakers. I initially thought it may be the bluetooth but even get the hiss with rca to 3.5 jack. I have tried low and high voltage settings on the amps with only minor differences between the setting. Any suggests and to what I should look into?

Thanks in advance

You have a high and low voltage setting on your amplifiers. Given the high voltage line driver the amplifier input must be set to 'high' voltage. Then your gains are still going to be set very low in consideration of the amount of voltage this particular line driver delivers.

To determine where most of the hiss is originating from, first short the input of the amplifier and run it with the input gain set to the normal usage level. All hiss at that point is owned by the amplifier. Next, do the same with the line driver reconnected to the amplifier input and the input of the line driver shorted. Any added hiss is owned by the line driver. Then, move onto the source in the same manner, going backwards in the signal path.

To properly set the system gain structure you would work from the other direction beginning with the source unit and moving downstream in the signal path. You want the maximum gain at the beginning of the signal path without clipping the device's output or without over-driving/saturating the next input. This provides the maximum dynamic range and the minimum noise floor, which is exactly what you want. In this case, especially with this line driver, a sine wave oscillator/disc/file, and a distortion analyzer or ocilliscope, would eliminate all the guesswork out of the tuning process.

David

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David,

Thank you! Can you elaborate on what you mean by Short the input? I have the gain set to zero on the amps already. I ran the same set up but with a different head unit in my last boat so I doubt it the line driver or amps. since its on all of the speakers I am thinking it's coming from the HU. If that is the case is my only option to replace the HU? I must say that I am not a big fan of the unit. The next question is I wonder if the remotes for the Rockford Fosgate would work on any other HU's that way I could keep the factory look in the boat and use the remotes yet upgrade to a better HU.

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David,

Thank you! Can you elaborate on what you mean by Short the input? I have the gain set to zero on the amps already. I ran the same set up but with a different head unit in my last boat so I doubt it the line driver or amps. since its on all of the speakers I am thinking it's coming from the HU. If that is the case is my only option to replace the HU? I must say that I am not a big fan of the unit. The next question is I wonder if the remotes for the Rockford Fosgate would work on any other HU's that way I could keep the factory look in the boat and use the remotes yet upgrade to a better HU.

The factory BB is a dirty box, no question about it. The EQ from the same company as your line driver is the cleanest EQ around, has tons of voltage, and still gives you the triple discreet stereo outputs for control. It also has the Main/Aux provision that allows you to circumvent the HU when you want absolute SQ but still allows the redundancy of having the factory HU when control from the remotes is priority. This is the same approach many take in their vehicle where they keep the factory HU with navigation, steering wheel controls, etc., but when they want real SQ they input the Aux on a Cleansweep or Bit processor and often use an external DAC.

'Shorting the input' is simply taking a single RCA jumper from the left to right input so that neither is [open] allowing for another potential source of noise. Open inputs are not an issue when on a selector but for noise/hiss testing purposes should be shorted for accurate results.

David

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Running same setup....

For starters, what is the volume on the RFX Head unit...I have tested it and it clips at 38 - my suggestion would be to set it at 35 for a clean undistorted signal. Next set the voltage pod's to zero on the line driver and the gains in you amp to zero.

JL Audio amps can and should be set with a multimeter...look at you manual. I would hook up your multimeter to the amp speaker terminals and then adjust the gain on the line driver to get the voltage at the amp using the appropriate test tone. If you need to make adjust ment at the amp for a channel that runs 4 ohms versus 2 ohms...you can do that as well.

Per JL and I went round and round on this - try to get the voltage you need on the low setting...that means you gain on both the AC Matrix and the Amps are low. I was able to achieve this on my system with the low setting.

Why use more voltage when you don't need to. The Matrix is a really STOUT unit...I doubt those gains even get turned up over 3/8 of the way onthe mids and high...sub will take a little more love

The multimeter will give you the absolute max...then you can adjust gain down to blend system and eliminate distortion. I am happy to help , pm me - I have used all that equipment that you have and have made it all work!!!

Edited by Murphy8166
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Thank you for the suggestions

If I have the gain on the amps to zero and the gain on the line driver to zero and the voltage settings on the amp at high I should not have any static correct? If I still do have a static hiss coming out of all of my speakers what else can I do? David you said the RF is a Dirty unit. Would changing to the newer unit from RF help? I get the same volume of static from 1 as I do on 8 it does get a bit louder hiss above 8. I am pretty confident all the RCA's are connected red to red and white to white.

The sound coming out is not distorted. The issue is more between songs and when music is not playing. Maybe I am being too picky but It seems odd that there would be that much or a hiss. I do have a fair amount of power going to the speakers but suspect there is some other issue

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First off - flip this JL amp's to low. Call JL if you need reassurance that this is the preferred method.

The factory unit is dirty / due to the way that it wired from the factory. Couple minor changes and it can be fixed.

There is a power and ground on the unit....Have you cut the wires going into the BB and run the directly to the source where the amps are getting power and ground?

Everything must grab power and ground from the same source. So the BB, the Matrix - best place is to wire them to the dist. blocks on the amp. Start there.

Edited by Murphy8166
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Thank you for the suggestions

If I have the gain on the amps to zero and the gain on the line driver to zero and the voltage settings on the amp at high I should not have any static correct? If I still do have a static hiss coming out of all of my speakers what else can I do? David you said the RF is a Dirty unit. Would changing to the newer unit from RF help? I get the same volume of static from 1 as I do on 8 it does get a bit louder hiss above 8. I am pretty confident all the RCA's are connected red to red and white to white.

The sound coming out is not distorted. The issue is more between songs and when music is not playing. Maybe I am being too picky but It seems odd that there would be that much or a hiss. I do have a fair amount of power going to the speakers but suspect there is some other issue

noquams,

Above, I gave you a prescription to determine exactly where the noise is originating from. This will elinimate any speculation and confirm the source. Once you have done this you can then narrow your focus to the real cause.

David

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I would like to give thanks to David and especially Murphy. I followed your advice and the hiss was coming from the Matrix. The Audio Control was doing its job perfectly. It's owner is whom failed. I was applying the logic that I could not provide too much preamp power and was very wrong. I was giving the JL's soo much power they were screaming at me :) I lowered them and the hiss is all but gone. My next project is to actually tune the amps for now though I'm stoked that its not the head unit and I done even have to buy anything except for a new sub and box next year I am not a fan of the RF stock sub or enclosure.

Thanks again guys!!!

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I knew when you told me you had those gains on the Audiocontrol pegged that that was the problem. If you wire that black box right - noise is not an issue.

A little to easier to trouble shoot over phone than it is to do over the back and forth of the forum!!!

Glad we could help

Edited by Murphy8166
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I have the same problem on my sinister sd-4 and 4 rev 10 setup. I am running a ws 420 and the stock Rockford head unit. Gain ion the amp is about half. Any help would be appreciated. I also concur that earmark is awesome. That's where I bought my setup.

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Bob I'd betcha a dollar the gains on the amp are too high. Can you run us through the procedure you used to set them?

Not sure, I gave the tuning instructions from Earmark to my stereo installer. Not sure if he followed them.

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  • 2 weeks later...

Just for other people reading this thread, a charging iPod will introduce A LOT of hissing noise.

Yes, a charging ipod can create a voltage supply loop that causes DC voltage to travel down the signal cable shield that connects the ipod to the next audio component. Now the protecting shield becomes the direct noise transmitter into the center signal conductor. And boat noise in one form or another is always inherent in the DC. I don't like ground loop isolators, but in this case it often helps when using a charging ipod. You will have to convert back and forth to RCA connectors. Or, simply run the ipod on battery power.

David

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