# What causes static hiss?



## Mless5 (Aug 21, 2006)

From the moment I turn on my sound, I get constant hiss through my speakers. Not too bad, but rather not have it. I was very careful in routing cables, even separated power and the rest to different door sills. Is it my equipment or installation issues?

Thanks!


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## MarkZ (Dec 5, 2005)

Could be a little of both.

Unhook the RCAs from the amplifier. See if the hiss is still there. If so, try terminating the RCA inputs on the amp. See if it's still there. That would indicate the amp is at fault.

Try muting the head unit. Still there? Is it there for all input selections (tuner, CD, AUX, etc)? If it appears to be source-related, play with HU grounds. Even try grounding the chassis (or ungrounding it, if it's touching metal).

Sometimes it's even in the recording. Make sure it's present for all your CDs.

It's probably not a wiring issue. Running the power wire alongside signal wires rarely has an adverse effect, and if it did, it wouldn't sound like hiss. Bad cables, screws through cables, etc don't typically result in hiss either.

Worst case scenario, try swapping out equipment. Some equipment in some vehicles is just hard as hell to get rid of noise issues.


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## Mless5 (Aug 21, 2006)

SO I went and unplugged RCAs on the amp and it became dead silent. Could somewhat long grounds cause this?


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## MarkZ (Dec 5, 2005)

Have you ever upgraded your head unit's ground?

Also, what happens when you short the RCA input shield to the center of the RCA input _on the amp_ (without the HU hooked up!)? 

How about when you hook one of the RCA's back up and short the shield to the amp's ground?

I assume you also checked to make sure the amp was staying powered on even when the RCA inputs were disconnected, right?


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## ryan s (Dec 19, 2006)

im having this same problem...it sounds like a cassette tape is playing at low volumes or when there is no music but the track plays. i even have some whine lower in the RPMs. im going to give these tips a shot...its annoying me lol. (i was about to start a new thread too  )

im suspecting the amp or the rcas, since both were introduced into the system at the same time with new front speakers.

could a speaker wire run near the ecu cause the noise as well?


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## atoz350 (Aug 31, 2006)

I believe it has to do with your processor. Most processors add a bit of noise to the system due to the D/A, A/D conversion. My Audiocontrol does the same thing. The only way rid this is to use an analog processor to rid the conversion.


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## stryke23x (Jun 22, 2007)

Since you don't get noise when your RCA's are unplugged you know it is a signal being amplified. Turn down your gains all the way on the amp and see if the hiss goes away. If it does, you need to find a way to get stronger signal to your amplifier. What kind of headunit do you have and what kind of output levels does it put out to the rCA's?

John


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## spag_bace (Aug 24, 2006)

Most likely it's ur amp that cause the hissing. I have the same problem. My amp is a zapco AG360.4. It's one of the older version. I had no noise/hiss using previous amps. But once I put the ag360.4 in, the hissing started. The loudness level of the hissing varies/dependent upon the gain level. It is explained at zapco that some of the older version of the AG series has internal ground issues that causes the hissing. So there's nothing that I can do but to set the gain at lower level. Your amp might have the same problem too. I would suggest you swap another amp in to see if the hiss still there. 

I don't think the hiss is introduced by the RCA getting noise from the power lines. I believe the power lines usually introduce alternator whines, not hiss. 

I strongly suggest swap the amp to see. If it's not the amp, then it's gotta be processor or headunit. It's probably equipment related, not installation, nor power lines/cables.


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## Diru (May 23, 2006)

Sounds gain related to the amp input level to me. 

Do you have your inputs tacked out?

Some amp inputs can reach max output with only 200mv of input with the gains tacked out. Hence pissing away the possible S/N ratio of having a 4 or 8 volt line level HU.

Work on your gain structure.


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## chad (Jun 30, 2005)

Diru said:


> Sounds gain related to the amp input level to me.
> 
> Do you have your inputs tacked out?
> 
> ...



Best advice yet IMHO..... Sounds totally gain structure related to me. But look at it this way (bright side) if it IS a gain issue and your only complaint is hiss then you are ****ting in tall cotton! Because once you get rid of that (pulling gains back) it will be silent with no other noises.

Often times I will in-properly set gains for a bit on purpose to see if I'm going to be battling any other noises caused by the vehicle. After I'm certain that the whines/pops/ etc are out I'll back the gains back..... good for preemptive troubleshooting for me


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## shado (Jan 18, 2007)

i had a question on topic for this thread.
i have that slight static noise on my front stage (white noise, i believe)

now, the static is NOT always there, i think it might be recording of the songs because I have played a few songs without noticing any static (might be at a minimal volume tho).... for most songs the static is there, but when u turn up the volume it is not THAT noticeable (unless you know it's there).... 
the radio plays pretty clear, but i think any static from radio must just be the reception from the antenna

my head unit is a jensen 9410 dvd player, so it only has like 2v pre-amps.
the gain on the amp has ALWAYS been set to about 25%, i haven't set it any higher than this point yet.

i will see how it sounds when i pull out the RCA's from the amp later today.... but so far i'm thinking:

- the recording of the actual song
- low voltage pre-amps 
- bad RCA's
- bad ground
- gain??? (but it is set really low at like 25% which is the factory RMS rating of the speaker)


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## Whiterabbit (May 26, 2006)

Mless5 said:


> SO I went and unplugged RCAs on the amp and it became dead silent. Could somewhat long grounds cause this?


Woah guys, woah! Right here he proves the amp isnt causing the hiss! Post after post of advice to screw with the amp..... :blush: 

follow the signal back. Plug the RCA's back in but unplug the OTHER end of the RCAs. hiss came back? RCAs are a problem. (Might need a shorting plug for this? I don't know. open naturally harms nothing)

still noiseless? plug those back in and unplug the next item in the signal chain. thats a processor? noise is gone? present? you will eventually find your contributor.


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## Abmolech (Nov 2, 2006)

> Woah guys, woah! Right here he proves the amp isnt causing the hiss! Post after post of advice to screw with the amp.....


Incorrect, a power amplifier requires an input signal to verify if is at fault. Unless you think the female RCA input terminators are acting as an antenna (unlikely) then there is no signal to amplify. Read Marks original post.

You need to short the input terminals to give it a unity signal. Simplest way is to make mute plugs.


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## Whiterabbit (May 26, 2006)

shorting plug....mute plug.... got it. thanks for the clarification!


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## dbiegel (Oct 15, 2006)

I had a very similar issue and tried everything, new RCA's, signal wires run separately, etc etc... heres what finally fixed it for me:

http://www.diymobileaudio.com/forum/showthread.php?t=8520

I'll try to explain the second fix in more detail... I took some bare copper wire (basically just stripped some wire and cut it) and wrapped it around screws on the amp case, and around the RCA's. The screws hold it in place. I'm not sure exactly why this worked, but I haven't had a problem ever since. Seems similar to what people have to do with 880 PRS's to prevent noise issues. Probably some sort of internal grounding issue due to poor quality control or design.


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## ezdollarz (Aug 5, 2020)

Mless5 said:


> From the moment I turn on my sound, I get constant hiss through my speakers. Not too bad, but rather not have it. I was very careful in routing cables, even separated power and the rest to different door sills. Is it my equipment or installation issues?
> 
> Thanks!


Your amp is experiencing ground noise between the head unit and the amp through the RCA connections which is also known as dead air and is usually a result of the gain on the amp being set to high causing dead air when the volume is turned completely down .... The best solution for this is to turn your gain on the amp all the way down and turn you head unit all the way up and the adjusted amp gain until it starts to distort the it is properly adjusted ..... if this does not solve the issue then purchase a ground isolator and connect it to ground and place it between head unit and amp and this will correct the issue.

I hope this helps ..... Good Luck!


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