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Too much hiss from speakers, what to do?


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hemanjoyman 
Copper - Posts: 77
Copper spacespace
Joined: August 18, 2006
Location: United States
Posted: November 10, 2006 at 10:39 AM / IP Logged  
When I had my Pioneer DEH-P9600MP which had 4V preouts, I was able to set the gain on my amps just fine, and when I turned the volume all the way down, there was no noise. Now, I have my Kenwood KVT-717DVD, which has 5V preouts, I have to turn the gain up a lot higher to get the right settings, but there is a lot of hiss coming from the speakers. What I had to do was turn the gains down and got rid of most of the hiss, but now I have to turn the deck volume up quite high to get good volume, and I'm not liking the sound too much. The thing is, now the RCA cables are a bit long, about 8-9ft too long, and I wrapped up around itself and set it on top of the brain unit under the passenger seat, I am wondering if that is what is causing the hiss??? Any Suggestions??? By the way, my amps are a JL Audio 500/1 and a JL Audio 300/4.
master5 
Silver - Posts: 1,123
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Joined: October 10, 2006
Location: United States
Posted: November 10, 2006 at 11:39 AM / IP Logged  

As far as the excessive rca cables causing hiss that is doubful, but it can pick up other kinds of inducted noise, you might want to move those cables around and listen for changes.

The odd part about your post is you are now using a unit with more preamp voltage but claim you need to set the gains higher. Kind of defeats the benifit of the higher voltage as that if anything should allow a better s/n ratio, as hiss is a byproduct of a poor (or lower) s/n ratio. However the output voltage rating is not the s/n rating. Without knowing the specific s/n ratings of each unit (which I don't) I can't say for certain that this is or is not the problem.

You might also be sensitive to certain frequecies that you didn't notice with the pionner, you could try adjusting the eq settings on the kenwood and lose or lower the hiss to an acceptable level without sacraficing too much SQ.

Best of luck.

hemanjoyman 
Copper - Posts: 77
Copper spacespace
Joined: August 18, 2006
Location: United States
Posted: November 10, 2006 at 12:18 PM / IP Logged  
Well, I looked at the specs. of both units, and the Pioneer has 4V/100Ω preouts, while the Kenwood unit has 5V/600Ω preouts. I'm guessing that could be the problem there. Do you think if I used a signal amplifier (having a brain fart right now, can't remember what they are called) before I go into the amp, then adjust the gain at the amp it would work?   
I think I'm just going to end up buying RCA cables anyway, the ones in there now are just regular unshielded and non-twisted pair....I am going to get shielded twisted pair RCA's that are shorter because the ones I have now are too long anyway.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: November 10, 2006 at 1:45 PM / IP Logged  

While the noise you hear could be caused through your RCA cables, this is unlikely.  Much more likely is improper gain setting or poor quality ground, or a poor ground inside the head unit.  Make sure your RCA cables are not damaged and are properly seated.  Read the ground stickies at the top of this forum and make sure you have good grounds for your amps.  Run a separate ground for the HU (do not use the factory wiring harness ground.)  In fact, some times the best results can be had if the HU and the amps are grounded at the same point.

It is also possible that the new HU is simply noisier than your old one.  If this is the case there's nothing you can do about it other than change the HU.

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hemanjoyman 
Copper - Posts: 77
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Joined: August 18, 2006
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Posted: November 10, 2006 at 2:02 PM / IP Logged  
I will try what you suggested DYohn, see if that helps any. Oh, by the way, I finally remembered it's called a "Line driver," do you think this would help me at all?? So I won't have to turn the amp gain so high??? I guess if the noise is really coming from the head unit, it won't help as the noise will be amplified anyway, right, but the noise does seem to go away when I lower the amp gain, but it has to be lowered quite a bit, almost all the way off?
I think the amp ground is fine because with my previous head, a Pioneer, which are notorious for causing noise, as I have recently found out, was dead silent.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: November 10, 2006 at 2:14 PM / IP Logged  

hemanjoyman wrote:
I will try what you suggested DYohn, see if that helps any. Oh, by the way, I finally remembered it's called a "Line driver," do you think this would help me at all?? So I won't have to turn the amp gain so high??? I guess if the noise is really coming from the head unit, it won't help as the noise will be amplified anyway, right, but the noise does seem to go away when I lower the amp gain, but it has to be lowered quite a bit, almost all the way off?
I think the amp ground is fine because with my previous head, a Pioneer, which are notorious for causing noise, as I have recently found out, was dead silent.

I doubt a line driver would help you at all.  It also sounds to me like your gain is way too high.  How did you set it?

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druidpagen 
Member - Posts: 13
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Joined: November 09, 2006
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Posted: November 10, 2006 at 2:34 PM / IP Logged  

many factors could be your problem.

"Much more likely is improper gain setting or poor quality ground, or a poor ground inside the head unit." Dyon is on the money, start there first.

i disagree with some ideas though through personal experiance. Rca's can pick up noise-and fairly easily.

" about 8-9ft too long, and I wrapped up around itself and set it on top of the brain unit under the passenger seat"  there is a couple "no no's" here. your rca's should never be longer than you need them. (i actually cut mine down and resolder and heak shrink to my cars length". since you wrapped them up and there so long they could be picking up inductance and acting like a coil (providing unwanted resistance). it's possible but not likely you could be picking up noise from your brain as well, but not likely. also make sure your RCA's are not running next to your power wire as this will pick up alot of noise as well.

hopefully if you take these easy steps it will clear up your problem. if not let us no and we can help you further. good luck.

hemanjoyman 
Copper - Posts: 77
Copper spacespace
Joined: August 18, 2006
Location: United States
Posted: November 10, 2006 at 3:55 PM / IP Logged  
Actually the gain is set pretty low, even lower than it was set with my previous head unit, and still some hiss. It is set about, let's say it goes from 1 to 10, it's set at 2 or 3. With my previous head unit it was set to about 5.
The first two things I am going to do is shorten the length of those RCA cables, and then I am going to put a better ground to the head unit, and see what happens.
The RCA's and the power wires run on opposite sides of the car.....the remote turn on wire does run on the side of the RCA's, but I don't think that will have much of an effect, if any.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: November 10, 2006 at 4:34 PM / IP Logged  

hemanjoyman wrote:
Actually the gain is set pretty low, even lower than it was set with my previous head unit, and still some hiss. It is set about, let's say it goes from 1 to 10, it's set at 2 or 3. With my previous head unit it was set to about 5.

The markings on the amplifiers are really meaningless.  Did you use test tones?  Did you set by ear?  Did you use a multimeter as JL Audio suggests?  Or did you just guess?  I really bet your gain is high and this is exaggerating any noise in your system, if not introducing it.  And I still bet your HU ground is bad.

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hemanjoyman 
Copper - Posts: 77
Copper spacespace
Joined: August 18, 2006
Location: United States
Posted: November 10, 2006 at 5:02 PM / IP Logged  
I actually did it using test tones and a multimeter like JL recommends, and that is the exact same way I did it to set up the Pioneer unit I had in there before. By the way, the amp gain doesn't have markings on it, I was just mentioned the numbers to give a reference point.
With the Pioneer, on the 500/1, to get the level to 44.7V on the DMM, I only had to turn the gain about half way, on the Kenwood unit, I have to turn the gain about 3/4, if not a little bit more. Same for the 300/4, to get it to 17.3V, I only had to set the gain to about 3/8 of the way with the Pioneer, with the Kenwood, I have to turn it about 5/8 to 3/4 of the way up.
It could very well be a bad HU ground.....by this you mean the ground to the HU harness, or internally???
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