Hissing Sound After Amp Install
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=71015
Printed Date: April 28, 2024 at 8:46 AM
Topic: Hissing Sound After Amp Install
Posted By: deeve2
Subject: Hissing Sound After Amp Install
Date Posted: January 17, 2006 at 11:06 PM
I have a Kenwood Ecelon KDC-X689 head unit with a MTX Thunder 895 5 channel amp. When I ran the speaker wire I tapped into the stock wiring from the amp to the speakers by the head unit because the doors of my 05 F150 have an actual large plug instead of just a rubber boot and I did not want to drill holes in the doors. I noticed after the install that I can hear a slight hissing sound from the speakers. It gets a little louder if I turn the gain on the amp up, but engine speed and all that have no effect. The head unit has settings for CD, Tuner, Aux and Stand-By. I hear the hissing on everything except for the Stand-By mode. I am thinking that it is from the head unit and not the amp since the noise goes away when I switch it to Stand-By. I figuire if it was coming from the amp I would hear it all the time the amp was powered. Could it be the ground on the head unit? It is grounded through the factory wiring with an adapter. Also, if it makes a difference I have the head unit internal amp shut off and am using shielded RCA's from KnuKonceptz and they are run about 3 feet away from the amp power line. Thanks! Dave
Replies:
Posted By: 99 mondeo
Date Posted: January 18, 2006 at 8:11 AM
Hello I had a simular problem a few years ago and found it was an earth loop, When you turn the headunit onto standby does it actually switch the amp off through the remote wire? if so this is probly why the noise stops when the head untis off. here are a few things you could try to find the fault. Try removing the rca leads and remote wire from the amp but not the speaker cables and connect the remote terminal to a live wire so the amp is actually on and ready to make sound and not in standby, Is the noise still there? if not then the noise is coming from the head unit direction so reconnect the rca cables one by one and take note to see if the noise returns as each one is plugged in. if the noise returns when the rca's are plugged back in then you will probly find theres a problem with them or an earth loop in which case tere are plenty of earth loop proctors out there and there not expensive so go get one and try it and report back on your progress. I'm not an expert on this subject but I have come across this problem before and found it to be solved quite simply by doing the process above.
Posted By: haemphyst
Date Posted: January 18, 2006 at 9:56 AM
Most likely, it's from the head unit. It is called Signal to Noise Ratio, and, Kenwood, (not being really high on my list for SQ; even their "good decks" suck AFAIAC) probably does not have a really high one. (The higher the better) You are forever stuck with it - it'll never "go away".
Upon digging deeper, the 90dB S/N ratio on the amplifier is not too spectacular, either... Here's the spec sheet for that amp... The specs are listed in TINY print, on the lower right of the second page.
Kenwood is SO proud of their gear, that I couldn't find even ONE specification for S/N on even ONE piece of their eqipment - even on the amplifiers, where this is QUITE an important specification... I hate to break it to you this way, but there ya are... ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: deeve2
Date Posted: January 18, 2006 at 3:56 PM
Well, I followed 99 mondeo suggestions and found that when I powered the amp up to turn on by jumping the remote from a different source (the amp power lead) and disconnect the RCA's then the noise is there, so it is not coming from the head unit. It is in the amp. The ground is on bare metal and is about 3 feet long. I tune the amp gain all the way up and really hear it. Is it a ground issue or just the amp quality? If it is the amp, how can I best reduce it?
Thanks!
Dave
Posted By: 04coupe
Date Posted: January 18, 2006 at 4:03 PM
I have this same problem with my infinity 7541. I found that ground loop isolators band aided the problem for now. ------------- Derek
Posted By: furflier
Date Posted: January 18, 2006 at 4:39 PM
deeve2 wrote:
I tune the amp gain all the way up and really hear it. Is it a ground issue or just the amp quality? If it is the amp, how can I best reduce it?
Dave
You need to set your gain properly. -------------
Posted By: deeve2
Date Posted: January 18, 2006 at 4:46 PM
I am working on setting the gain correctly. Someone thought the 3 foot ground was too long and it should be shorter, which I can do. I also have Audio Tool Box onmy ipod I can use to set the gain, but what tones would be best and exactly what does "clipping" sound like. I cannot find an example of that anywhere. From whatI have read, once you hear it you know what it is for sure.
Thanks
Dave
Posted By: OCURIEL
Date Posted: January 18, 2006 at 5:57 PM
What is your amp mounted on? I've ran into this following scenerio twice - amp housing grounds to the frame of the vehicle & causes this noise. most likely not this but worth to check off.
Posted By: deeve2
Date Posted: January 19, 2006 at 5:07 AM
It's screwed to MDF that is screwed to the truck,so Idont think that would be it. I am going to mess with the ground some more and see if that helps.
Dave
Posted By: stevdart
Date Posted: January 19, 2006 at 5:58 AM
Here's a link to https://www.timo.esser.dsl.pipex.com/ttg.htm which is a test tone generator. Load this program, and you can listen to what a square wave (clipped signal) sounds like. This is the program I use to make test CDs. You can get by with using the eval version for your test CD but I paid the people the $26 because I think it's worth it. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: deeve2
Date Posted: January 19, 2006 at 2:03 PM
That program is great. I guess I have never heard the clipping from my amp.
Thanks!
Dave
Posted By: stevdart
Date Posted: January 19, 2006 at 5:47 PM
It's very pronounced when you hear such a flattened wave like the program has. What I've noticed is this: when adjusting gain (volume on the deck, too), the clipping sound is just slight when it appears. This is due to the fact that the gain control is moved very slowly. A full flat wave isn't really reached. But the difference in sound from the pure sine wave is distinctly noticeable. It will sound like it has a staccato ticking within the tone, and the tone frequency seems to change to lower somewhat. When adjusting gains on your system, you should particularly try to find the point of clipping and then move back off of it just enough to reach the pure sine wave sound again. This will ensure that you've reached maximum signal-to-noise ratio and you'll be provided with the best sound your equipment can make. Glad you can use the program. I've referred it many times but usually don't hear whether it was put to use or not. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: deeve2
Date Posted: January 21, 2006 at 1:11 PM
Looks like it was a gain issue. I set it using a DMM per JLAUDIO's site and all is well. Thanks!
Dave
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